Coupe Stereo Upgrade

November 1, 2002

By: Douglas Lindqvist

1.9 Sound System Upgrade

I’ve wanted to upgrade my Z3 sound system for a while. I found that the stock system simply wasn’t good enough to support a convertible. I started looking around and came to MZ3.net and looked at Robert’s 1.9 (Non-HK) Stereo Upgrade. This article helped me A LOT during my search for a better sound system. Now was the time to see where I should get it done. The first place I went to was Audio Excellence. It looked very professional and some of my friends suggested it. I also went to Audio Extreme and Sound Advice but out of the three Audio Excellence was at the top.

I wanted to upgrade the front speakers first. I looked at JL Audio and was impressed by their clarity. I also wanted to get larger speakers and I ended up with 6 ½” JL Audio XR650-CS (with tweeters and crossovers).

I realized that I needed a much better amplifier because the stock amp (non HK) was pushing around 20-25 watts per channel. I decided to go with the Orion Cobalt CS200.4 (Which later changed to the CS500.5) I was also looking at the Alpine V12 models but their prices were too high.

Audio Excellence told me that I might be able to put 5 ½” in the rear to replace the 4″ speakers. This luckily didn’t work out and I got a free pair of 4″ speakers.

Installation

The installation took around 7 hours. I took it in at 9 am at brought it home at about 4 pm. I was very happy with this installation because everything seemed to go my way. First they tried fitting the 5 ½” in the rear. These didn’t fit so they decided to leave the stock 3 ½” in there. The install for the tweeters and XR650-CS went fine but the amp didn’t. They put the CS200.4 in and it blew my rear speakers due to a short. They gave me a CS500.5 instead and replaced my rear speakers with JL Audio XR400-CX.

So the price of the JL Audio XR525-CX was cut from the bill and I upgraded to 4″ rear speakers and a 5-channel amp for free! Total cost was about $750.

Turning up the new system loud would guarantee to make your ears bleed. All that was coming out of it was highs. There was more bass than stock but it wasn’t enough. I decided to get a subwoofer.

The first place I wanted to put one was in the trunk. I planned on putting a 10″ sub opposite the side of the trunk with the CD Changer. Audio Excellence told me that in front of the trunk was a metal wall separating the cabin from it. Porting to the cabin would have to go through the boot of the convertible and with the top down bass would be nonexistent. I also wasn’t too happy with the idea of cutting a whole in my BMW.

My other idea was to put an 8″ or a 10″ in the spot where the HK Sub is. My idea was similar to where the Dodge Viper has its subwoofer. Audio Excellence looked at the area (where my storage compartments are) and told me that it would mess with the structural integrity of the car because the roll bars came down into there. I decided this idea was a no-go also.

They came up with an idea that I was trying to avoid. They wanted to put the sub below the dash on the passenger side. They did this to a member of N’Sync’s Superformance Shelby Cobra. Even though I was disappointed because doing this would take up legroom I decided to go along with this idea.

They ended up making a custom box and putting a JL Audio 8W3 subwoofer in my car. This ended up costing $350 and took about 13 hours (11 hours one day, 2 hours the next). It turned out well and sounds amazing!

Is it worth it?

Yes, I think that it was worth it. I love being able to hear music without distortion at 60mph with the top down. It turned out to be much cheaper than I thought and sound better than I imagined. Even though the subwoofer installation took forever I think that having that extra bass really makes the sound fuller.

Pros – Awesome Sound, Not very expensive

Cons – Lost passenger legroom, No more stock look

Cost – About $1,100

4 Inch Rear Speakers

In the continuing quest for better sound in a Z3, I decided to replace the stock rear 3″ speakers in my 99 2.3 with 4″ speakers, or possibly 4×6″. Model year 2000 and newer have 4″ speakers, so I knew that in theory at least, I should be able to fit a decent set of 4″ co-ax’s back there. The stock 3″ speakers are pitiful single paper cone drivers, “designed” for “filtered” midrange sound from the factory amp. I found their sound lacking, even annoying. They did not add anything to my audio experience. I am cheap, …..let’s say cost conscience,…… so I am always looking for more bang for the buck and aftermarket speakers have always provided more satisfying sound over stock OEM drivers. The first step was to see what kind of volume and interferences I had to work with. I popped out the little hatch, shown in first photo, but even with a flashlight it was difficult to get a clear view. The 3″ speakers are held in place by a threaded collar, essentially a giant knurled nut. If you take a large screwdriver and tap the knurls through the little hatch counter clockwise with a rubber mallet to start, it then unscrews easily. The speaker pulls out to reveal a circular hole with a chord (flat spot), that is supposed to prevent the speaker from spinning. This allowed a better view and some discouraging news as well.

There’s a bunch of stuff in there…the seat belt retractor, the structural steel for the roll hoop and the re-enforcing cross member that goes across the vehicle. The steel is a problem because it is so close to the plastic trim housing. This limits where the speaker can be placed, because either the driver basket or magnet will hit something. Depth is about 2 ½”, but variable because the housing slopes. In addition, the 3″ speaker opening is located far to the outside, because the tiny magnet does not interfere with anything. It is actually easier to install a new speaker if you have NO rear speakers; ie. you can cut a new hole farther inboard without worrying about the existing hole showing beyond the coverage of the speaker trim/grill.

Luckily, 4″ speakers are strange creatures, many appear to have grills with trim that increases the coverage area. This was critical in this case; if the trim were any smaller, it would not have been possible to mount the speakers and avoid interference, and still cover the existing opening. The last photo shows the grill coverage outline (courtesy of dirt sticking to Armorall……will stop using that stuff!). I looked at installing a 4×6 speaker, but quickly found that only Blaupunkt 4×6 seemed to come with grills! The other manufacturers assume you are replacing an OEM installation and do not include them. I was not impressed with the Blau 4×6 specs, so I decided to go 4″.. Based on listening and a car audio store recommendation, the speakers I installed were Pioneer TS-A1086. They had nice plain black grills, and once I dremeled off the Pioneer name and made a P-touch label that spelled “BMW” to put in its place, it really looked stock. They have a cut out requirement of 4 1/16″, and a magnet diameter of 2 3/4″ . The trim and grill actually covers a diameter of about 6″.. I also looked into installing Infinity 452i speakers which are a “plus one” 4 inch size; ie the cone is 30% larger for the same cutout. It has a magnet that is ½” larger in diameter and ½” deeper, so it would be trickier to fit, but has a rubber surround, silk tweeter, and higher power handling capability. It would be easier to install the 452i, if there had not been any rear speakers. And since they were out of stock at the time, I went with the Pioneers. My cutout (from the outside edge of the hole, closest to the measuring point) ended up being 3/8″ vertical down from the upper trim piece end that starts the groove (leaves about 1/8″ left in bottom trim piece TO the groove) and 1 5/8″ horizontal from the center trim piece. This allowed the magnet to clear (actually JUSTS touches the carpet over the cross member), the speaker trim to cover the old opening, and still contain the plastic cut within the lower trim piece. I was afraid that cutting into the upper trim piece would cause the assembly to be too flimsy and buzz or rattle. There are also some interference issues, if you feel up under and into that area. The upper and lower trim pieces snap together, and I wanted to try to avoid breaking that connection for aesthetic and structural reasons. The plastic is thick, about 1/8 to 3/16″ and is ribbed on the backside for more support. I used a Dremel tool with a cutting blade that resembles a tiny circular saw. It cut through the plastic like butter, but it is CRITICAL that you tape the surrounding area, as it is VERY easy for the saw to jump and instantly mar the surface for good. It is easier to work the saw with the seats removed but I actually only removed the driver side; once I had my measurements I did the passenger side with the seat moved all the way forward, but then I also have a flexible extension that really helps…YMMV.

The pictures are pretty self- explanatory. There was a very noticeable increase in clarity and volume with the new speakers, even hooked up to the stock amp. I ended up running dedicated, unfiltered speaker wires directly from my Toronto head unit under the center console to get full range (for a 4″, anyway) sound, which sounded MUCH better than the stock amp connection. Even firing into the back of the seats, they are so close to you that they provide significant “top down” midrange and high sound. I find the stereo sound similar to that of wearing headphones; it is as if you are “in” the sound, not “in front” of it. Some people don’t care for that…I like it. Another idea to try instead of the Infinity co-ax’s, would be to use a 4″ component set and locate the tweeters up and outboard in the upper trim unit for better separation and directionality. I found the Pioneers to be a significant upgrade to the sound system for very few dollars. Now if I can just find a way to put in a powered subwoofer and lose no legroom or storage space……..

Sound System Upgrade for a ’98 HK Equipped Z3 Roadster

Pros: Unimaginable sound improvement, Maintains factory look
Cons: Limitations in sub woofer design is prevalent in terms of frequency response
Cost: Professionally Installed at $1500

Anyone who has visited the Z3 message board has come across many discussions and complaints about the stereo system in the Z3. One would think that for the money (and the fact that its a convertible) it would have a decent sound system. My ’98 roadster came equipped with the Harmon Kardon upgrade which offers a few more speakers and the infamous sub-woofer system. I like having the BMW head as it has a proper fit and finish to the rest of the interior, and helps keep an untouched look to curious passers-by.

Upon reference of a good buddy of mine who is an absolute nut when it comes to auto and home theater systems, I went to CAPS Audio which is an operation run by two brothers, Danny and Frank. They exclusively handle car audio for the Ferrari dealership down the road. (check out pg. 3 of their photo gallery!) After a preliminary visit, Danny gave me the plan of action: We are going to open up the car and see how the stereo is arranged, I offered Robert’s “A stereo upgrade to learn from” which seemed to spell it out to me, but that was not sufficient. “I’ll tell you what you have, then we can figure out what we can do.” Hey, what can I say, the man is thorough and I don’t pretend I could do their work. He explained in great detail about how proprietary the BMW systems were and that if the project either became too costly for me, he promised to reassemble the system to a level that BMW would not know anyone had touched it.

The design constraints were as such:

* Keep the factory head unit as I like the matched looks to the rest of the dash and provides a “stealthy” approach towards the stereo upgrade. Since I separately purchased the CD unit, I felt even more committed to this. If I could have started all over, I would consider an alternate head unit that would match up nicely.

* Minimal trunk (what trunk?) obtrusion. I actually attempt to use it.

* Keep the factory speakers, but drive them with clean power. I felt that the sound system was acceptable for almost all driving, the speakers are fine (with the exception of the sub). The only time where I was dissatisfied with the performance of the stereo was when driving at highway speeds with the top down. I could hear the amplifier weaken after 20 minutes down the highway as the factory amp would start warming up, and the bass became easily distorted. Notably absent was a full range of sound under these driving conditions.

* Some sort of flexibility towards future applications, in case I should want to redo the entire car. (Not for a long while)

After some time they had figgered it out and offered to install the following (You can see that I obviously went with it.) The installation of two amps as such:

# The red one is a Sony Xplod which drives everything but the subs. 40Wx4 Ch, 4 Ohms at 0.04% THD, 5 Band ±12dB Adjustable Equalizer, 50/200/800/3.2k/12.8kHz Frequency Centers, Level Indicator LED’s, Regulated MOSFET Power Supply, F & R 50-200Hz Variable Hi/Lo CROSSOVER, Recessed Control Panel with Clear Cover, Separate RCA & Speaker Inputs, Peak Power 80W X4Ch, Signal to Noise Ratio 100 dB, Fan Cooled, Gold Plated Terminals and RCA connectors and a power level meter.

# The Silver is an Alpine Flex4 which drives the subs exclusively. MAX POWER (EIAJ), 75W x 4 (4 Ohm Stereo), 180W x 2 (Bridged 4 Ohm), RMS Continuous Power (Watt) (at 14.4V, 20-20 kHz): 4 Ohm Stereo (0.08% THD) 30W x 4; 2 Ohm Stereo (0.3% THD) 40W x 4; Bridged 4 Ohm (0.3% THD) 80W x 2, S/N Ratio 100dBA, Frequency Response (+0, -1dB) 10-50kHz, 4/3/2 Channel Operation, MOSFET Power Supply, DC-DC PWM Power Supply, Double Buffered Pre-Amp Input Circuitry, Discrete Pre-Amp Stage, Darlington Bi-Polar Outputs, STAR Circuitry, Duo (Beta) Feedback Circuit, Solid Copper Bus Bars, MultiMode, Top Mounted LED Power Indicator, Fixed Crossover (HP/LP), Continuously Adjustable Gain Control, Both sides Terminal Layout, Gold Plated RCA Input Connectors, Speaker Level Inputs, Gold Plated Power Screw Terminals, Gold Plated Speaker Screw Terminals, Noise Elimination Coil, Non-Fading Pre-Amp Output

As well, I required a few crossovers and the infinity Kappa crossovers were suggested. I have heard the Kappa series for home audio, so I felt confident in their suggestion. The crossovers were installed in the tower section where the original amplifier lived.

The installation took almost 10 hours from end-to-end. They cranked it out! I would walk back and check on the car on occasion to see the progress of the install. Danny was a little nervous about me looking over their shoulder, mentioning something about people being nervous about seeing someone rip apart the car, well hey if I could, I would have installed it myself! I did my best to stay out of their way so that they could complete their job.

Of course, this installation was quite timely and thus costly, as they spent quite a bit of time adjusting and tweaking to the oddities of the BMW system. It was pointed out that to me that I was taking a more expensive route in terms of my installation due to this, but they were both willing and capable of building to my wishes. Also the quality in their work is quite impressive.

Here’s a close-up of the wiring work.

Result: WOW! I had some expectations on how the system would sound, but DAMN! I never expected it to sound so great! This baby behaves like a Z3 should, with plenty of clean power for your entertainment.

The Test: Two days later, I put the car to the test with a trip to Syracuse and back (about 600 miles altogether) to add to it, I crammed every last inch of trunk space with stuff for the weekend journey.

Outcome: No Problem! It was wonderful to be able to hear the music so well while driving with the top down! I notice that I spend more time adjusting the bass & treble since the amps are capable of overdriving the subs if I don’t pay attention. The other thing I notice is that the speed sensitive volume has different nuances to it, as it seems to be adjusting the bass amplifier only – which probably has a lot to do with why I keep adjusting so much. I pulled from the instructions from Message Board Archive on adjusting the sensitivity of the amplifier will make that adjustment. Notably, the limitations of frequency response in the sub-woofer is present, but what it does handle is amazing. I’m sure that one-day, its day shall come for replacement.

Overall, I am excited with the outcome and performance of the stereo. If you have the opportunity to catch up to me on a cruise, you’ll be able to hear it for yourself. You won’t believe its the OEM speakers!

The Harman Kardon Affair

One of the reasons I got a 2.8 instead of a 2.3 was the “premium” Harman Kardon stereo system with “upgraded” speakers. Granted, it wasn’t the ONLY reason, nor was it the PRIMARY reason, but it was A reason. I have to admit that as far as stock sound systems go, I’ve heard worse. But I’ve heard better, as recently as the day I got my Z3, which is when I turned in my 1998 Ford Expedition Eddie Bauer with a Mach 460 stereo system. Without getting too much into an acoustics argument, the Harman Kardon system, well, how can I put it….. SUCKED.

I am not an audiophile. I am not a music hardware nut. However, I do enjoy my music, and I like it loud and I like it distortion free. The first clue that the HK was a POS was the rattling of the subwoofer enclosure. However, through my “investigation”, I found out that the HK amp was “tweaked” to produce 10% harmonic distortion. Now, I am not an audio engineer, but for something that is usually measured in FRACTIONS of ONE PERCENT, 10% cannot be good. Cranking the volume up supported this conclusion. The distortion was there, and life sucked.

The Amp has GOT to GO

In one of those fits I am famous for (hey, the car cost me quite a bundle with all the stuff I put in it, so I WAS frustrated), I took it to the folks at Tampa Bay Audio Sound, and they hooked me up with a couple of brand spanking new Alpine amps — an MRP-F306 and a MRP-F406.

Alpine MRP-F306 4 channel amp

MAX POWER (EIAJ)

75W x 4 (4 Ohm Stereo) 180W x 2 (Bridged 4 Ohm)

FEATURES

RMS Continuous Power (Watt) (at 14.4V, 20-20 kHz): 4 Ohm Stereo (0.08% THD) 30W x 4; 2 Ohm Stereo (0.3% THD) 40W x 4; Bridged 4 Ohm (0.3% THD) 80W x 2

Alpine MRP-F406 2 channel amp

MAX POWER (EIAJ)

90W x 2 (4 Ohm Stereo) 240W x 1 (Bridged 4 Ohm)

FEATURES

RMS Continuous Power (Watt) (at 14.4V, 20-20 kHz): 4 Ohm Stereo (0.08% THD) 40W x 2; 2 Ohm Stereo (0.3% THD) 60W x 2; Bridged 4 Ohm (0.3% THD) 120W x 1

Why two? Trunk space was a prime concern (or lack thereof), so any of the premium solutions that ate up trunk space were unacceptable to me. No 1000 watt amps for me. I wasn’t looking to win a BOOM BOOM competition, just clean, distortion free, loud music. Simple.

The Alpine MRP-F356, a 5 channel amp, would have sufficed, but it was BIG. The F406 fit nicely into the space the HK POS amp fit (marked by the red circle in the middle picture below), and the F306 was fitted vertically neat and tidy on an L board on the other side of the trunk with virtually no loss in trunk space.

The guys at Tampa Bay Audio Sound configured the F306 to supply only highs and mids, and the F406 to supply the bass (using a simple switch on the amps themselves).

Now, with this came some good news and some bad news. The good news was that the highs and mids sounded better, cleaner and crisper at high volumes. The HK amp was clearly very deficient in this regard. The bad news? The subwoofer popped, Bad. Of course you genius!!! A subwoofer rated at 30W was getting juice from the F406 which can pump up to 240W!!! Ok, so of I went into the quest for a new subwoofer.

The Quest for a Subwoofer

Putting a subwoofer in a Z3 is like trying to fit an elephant into a Jetta. Reading some more articles at MZ3.net and the Z3 message board I learned of many options, including custom enclosures and Bazooka tubes. None of these options sounded good to me (literally and figuratively) since the Z3 trunk is sealed and the lack of air put a serious cramp in the boom of the subs. Drilling holes in my brand new Z3 was DEFINITELY not an option for me, so on I went trying to find another solution.

I took apart the subwoofer enclosure (thanks to Robert Leidy and his article on Dissecting the HK Subwoofer) and took it to the folks at Sound Advice. They hooked me up with a couple of Boston Acoustics 5.5 ProSeries woofers (I had to pay for two whole kits which included tweeters and crossovers, which sucked) and installed just the woofers it into the Z3 subwoofer enclosure.

Something tells me that I could have gotten off a LOT cheaper than $400, but at that point all I wanted was a functional subwoofer that would fit in the stock enclosure. Money was not an issue (never is until the bill gets here… 🙂 I plugged the enclosure back into my Z3 and… Voila!

Ahhhhh, nice, neat tidy bass. Cool. I cranked up the volume all the way and it was now the tweeters and midranges distorting — the sub was cool as a cucumber. It was a good thing I padded all the contact points as specified in the Z3Bimmer.com Subwoofer Rattle article, since the extra bass would have certainly worsened the rattle problem. Once the proper insulation was installed, the rattling disappeared.

I cranked down the gain on the F306 a notch (to NOM setting) since I don’t listen to music that loud anyway (it was really hurting my ears at that point) and I reached a happy compromise — $1,000 later. 🙁

Upgrading the Front Speakers

With new amps and a new sub, the remaining speakers started to get on my nerves. Having seen the poor quality of the speakers I removed, I wanted the rest of those POS speakers out of my Z3 pronto!!! After reading several messages in the Z3 Message Board, I learned that to remove the tweeters on the doors, I had to remove the door panels. All of a sudden, the tweeters started to sound good to me. Nahhh, I didn’t need to replace THEM (wimp).

So I turned my attention to the kick panels in the front. An article in MZ3.net showed how easy it was to do, so I did the logical thing… took it to the folks at Tampa Bay Autosound to do it for me. 🙂

They replaced the front speakers with a couple of Rockford Fosgate 5.25″ coaxial 2-way speakers. Yes, I know, the stock speakers were component speakers and had no tweeter. However, I am the guy who turns the treble all the way up anyway, so a pair of extra tweeters didn’t bother me. And since I am not an audiophile, I had no clue what this would do to the sound balance in my car (ignorance is bliss…)

Actually, they sound pretty good to me. I can crank the sound up more, but the tweeters in the doors pop a little bit at the highest volume. Darn. I guess I’ll have to remove those door panels after all. Maybe some other day, but not today… 🙂

Upgrading the Rear Speakers

Turning my attention to some easy-to-replace items, I focused on the rear speakers. Removing the covers revealed a couple of 4″ component speakers (again, no tweeters here). Removing the covers was relatively easy. On the Y2K 2.8, the speaker grills and covers are held by five plastic tabs. You can pop a little door on the base of the roll hoops and you will see the top tab holding the cover to the plastic wall of the car. With a long screwdriver you can push down on that tab and pop the cover off.

WARNING: Do this at your own risk. I broke the little tab on one of my covers, although it didn’t seem to mind too much when I put it back. Don’t blame me if you brake your precious little Z3…. 🙂

I took my car over the folks at Tampa Bay Autosound and they hooked me up with a pair of Sony Xplode XS-F1020 4″ two-way speakers. We tried some SAS and some Alpines, but the tweeters wouldn’t allow the grills to be put back on. The Sony’s were a good choice since they had recessed tweeters which did not add anything to the size of the speakers themselves. No drilling or cutting of any kind was a goal of mine, not to mention a depleting budget made the Sony’s a good choice at $85 for the pair, installed. WOW!

Leave the Door Panels Alone

Which brings me back to the “popping tweeters” in the door panels. The folks at Tampa Bay Autosound put in some other kind of crossover that filtered out more of the mids and lows, sending more of the highs to the door panel speaker to address the popping sound. Seem like it took care of most of it. Only when I crank it ALLLLL the way up (and my ears start to bleed) do I hear some popping, but even at the loudest level I use it (which is doing 90Mph with the top down) they sound great. Besides, leaving those door panels alone is worth a lot to me… 🙂

Upgrade Summary

BMW’s “premium” sound system is, in my humble opinion, disappointing. They could have done better.

However, this is the ONLY thing that I can find fault with in an otherwise very, very, very cool car.

In summary, this is what I did:

Replaced Harman Kardon amplifier with a pair of Alpine amps

Replaced stock subwoofer speakers with a pair of Boston Acoustic Pro Series 5.5 woofers

Replaced front footpanel speakers with a pair of Rockford Fosgate 5.25 two-way speakers

Replaced the rear speakers with a pair of Sony Xplode XSF1020 two-way speakers

Filtered out all mids and bass going to the doorpanel speakers

The choices in speaker brands were mostly driven by price and fit into the car. The Rockford Fosgate speakers cost me $85 for the pair plus $20 install fee, and the Sony Xplode cost me $85 for the pair, installation included. For that price, you can’t go wrong! The Boston Acoustics Pro 5.5, on the other hand, cost me $400. Too pricey.

The system as a whole sounds good to me. No, I will not be competing in any auto shows, but it sounds a heck of a lot better than the stock system, virtually no modifications to the car at all, and 99% of my trunk space is still available.

Mikky’s M Coupe Stereo

Mikky’s 99 M Coupe has a JL Audio 10W3 Subwoofer with a Precision Power 6600 amplifier built in on the top.

You can see the blaupunkt toronto with the remote control mounted on the steering wheel.

HK Amp Swap

Pros: Easy Upgrade, Maintain Warranty
Cons: Just a moderate upgrade
Cost: About $40 (price depends on seller)

The Environmentally Correct Stereo Upgrade

Or

Please don’t throw those HK amps in the dumpster!!

I’m not certain how it came up, I think it was Robert’s idea. He wondered if there was a way to use the vast number of Harmon Kardon amplifiers that have been removed during the stereo upgrades by members of the Message Board. The idea was to replace the stock amplifier with the HK amp. I volunteered to use my 3/96 production 1.9 Z3, one of the very early production cars. It does not have rear speakers or a sub woofer. The only stereo upgrade that has been performed on my Z is a set of MB Quart QM130TX3 5¼ in. front kick panel speakers. The improvement that these speakers made is chronicled by Carter Lee in his column here on MZ3 Net.

You will need a few hand tools to perform the swap:

10 mm socket

short extension

ratchet

large flat tip screw driver or

trim panel plug removal tool

You remove the carpet trim from the front of trunk by removing the black trim plugs. Locate your amp: on early cars its located in the upper left front of trunk, on later cars it’s in the upper right front. Using the 10mm socket, extension, and ratchet remove the three nuts that hold the mounting bracket to the body. You then unplug the two connectors from the back of the amp. There are three 10mm nuts that hold the amp to the mounting bracket, remove these. Place the amp in a safe place. The installation of the HK amp is the reverse of the removal. This is an exact bolt for bolt swap, nothing to modify! Total time for this upgrade 30 min., a complete no-brainer! There is one remaining plug on the HK amp that remains unused, I am told this is for EQ changes related to the speed sensitive volume. But the amp works just fine without this connection (which is a good thing since older stereo setups don’t have this wire).

Now the results. Bass is much better, feels about 30% better. Measurement done by the bass-o-meter (my left foot on dead pedal). Highs are about the same. Tried increasing the treble but not much different from original amp. The most noticeable change is the lack of distortion in the upper volume ranges. The original setup would flake out at volume levels required at 70mph. The HK amp allows distortion free sound at speeds up to 85mph.

Is it worth it? In a word, YES! For those of us who are not the audiophiles this is a very cost efficient upgrade. In my case the hardest thing to do was empty the trunk. At the 1999 Homecoming there will be a new contest to go with the autocross, the POS Amp Toss, you can use it there. Now all you true audiophiles who have upgraded to an aftermarket system now have a market for your old amps, and we will have enough of the old amps for the POS Amp Toss at 99 Homecoming.

In an attempt to match HK buyers up to HK sellers, I recommend you post on the BMW roadster message board, Robert and I agreed upon a $40 price for the HK amp so I recommend you start the buying/selling negotiations there.

A Stereo Upgrade to Learn From

In 1994 I made a very costly mistake, I had some extra money burning a hole in my pocket and decided to buy myself an in-dash CD player and Polk speakers for my Ford Explorer. As I was picking out the CD player the salesman made me an offer I couldn’t refuse on a Polk subwoofer that was about to be discontinued. I left the vehicle with them and it was ready later that afternoon. The system sounded awesome but now I recognize what a costly mistake that stereo system was because it forever changed my appreciation for car audio.

In 1996 I found myself with a hard decision to make, I had just driven a Z3 for about a week (dealer loaner) and I really wanted one. While struggling with the decision if I should stick with the Explorer or go for the Z3, the upgraded stereo system almost kept me in that Explorer. However the allure of the BMW Z3 was just too much for me, so in October of 1996 I took delivery of a 1.9 liter BMW Z3.

The stock stereo lasted until February of 1997, with spring weather approaching I decided it was time to upgrade it. Once I had upgraded/fixed the stereo in that Z3 I was pleased with the sound. It didn’t have the deep bass my Explorer had, but the system was very powerful and clean. It could be heard with the top down at highway speed and always sounded great.

In 1998 I had another decision to make, BMW had just released the new 3.2 liter M roadster and the allure of a new muscle bound version of my Z3 was just too much to pass up. I sold my 1.9 Z3 to a friend and purchased the new 3.2 M roadster. The M roadster came with a much better stock stereo system than the original 1.9 Z3 came with. This new HK (Harmon Karmon) stereo was much cleaner and better sounding, in fact I had actually decided that it was “good enough” and didn’t need to be upgraded. I drove around with the stock HK system for three months and never even added a CD player to it.

However the stock HK system suffered a set back when I got to hear my old 1.9 Z3’s stereo system again (I see the current owner about once a month at a poker game). I had forgotten how much better and cleaner the stereo could sound. Top up or top down it didn’t matter because that system had enough power to be heard. The desire for a better stereo and a CD player in my 3.2 M roadster had infected me.

As fate would have it another M owner that I keep in touch with on a regular basis got a deal with a stereo manufacturer to be a show car for a/d/s/ stereo equipment. On almost a daily basis I got to hear the ongoing saga of what they were doing to his car, what kind of equipment they were using, what speakers sizes were fitting into the various locations. This was just too much for me to bare, I decided to start looking into upgrading/fixing the stock HK stereo system. The first step was to figure out as many details as I could about the stock HK stereo system.

Researching the stock HK stereo system

For the 1996, 1997 and 1998 model years every BMW Z3 came stock with the same head unit, regardless if it was an HK stereo upgrade or the base stereo (starting with the 1999 model year BMW started using a different head unit which will not be covered in this article). This common head unit is an Alpine made AM/FM/WB/Cassette unit. It has some nice features like weather band radio, built in theft deterrent system, speed sensitive volume, and the ability to control a trunk mounted BMW CD changer. The stock radio is pretty plain to look at but it blends in to the dash well and shares the same common orange lighting as the rest of the dash. On the downside, the FM reception on the unit is well below average and the tape player ranks right up there with names like Kraco.

Z3’s that have the HK stereo have 10 separate speakers hidden around the cockpit in various locations.

In each of the side door panels there are two speakers, a 1″ 4 ohm tweeter and a 2″ 4 ohm mid-tweeter. These two speakers are running on the same 25 watt, electronically crossed over, amplifier channel that provides a 1.5Khz to 20Khz signal. Some inline crossovers further split and control that signal so that a 1.5Khz to 3.5KHz signal drives the 2″ speaker and 3.5KHz to 20Khz signal drives the 1″ speaker.

On each side of the Z3, down by the driver’s and passenger’s feet there is a single 5 1/4″ 2 ohm speaker in the kick-panel. Each 5 1/4″ speaker is driven by its own 25 watt, electronically crossed over, 100Hz to 1.5KHz signal.

Directly behind each seat is a 3″ speaker that receives its own electronically crossed over 25 watt, 200Hz to 1.6Khz channel.

And lastly there are a pair of 5 1/4″ speakers in a subwoofer enclosure in the center of the console behind the driver. Each speaker in that subwoofer enclosure is receiving an 40 watt, electronically crossed over, 80Hz to 100Hz signal.

The HK amplifier is an eight channel amp that BMW claims is (6×25 and 2×40). However to reach those power ratings BMW had to overdrive the amp to an outrageous 10% Total Harmonic Distortion (THD). To benchmark this amp using aftermarket amp rating standards would probably reveal less than half the power that BMW is claiming. The amplifier is hidden in the trunk behind the lump on the passenger side towards the back.

HK Amp Wiring

M Roadster, 3/98 build date

J1 12-pin AMP connector

Pin Function Wire Color

1 12V red/white

2 on/off white

3 ground brown

4 ground brown

5 RBLO+ blue/purple

6 RBLO- blue/gray

7 LFLO+ yellow/red

8 LFLO- yellow/brown

9 RFLO+ blue/red

10 RFLO- blue/brown

11 LBLO+ yellow/gray

12 LBLO- yellow/blue

J2 26-pin Siemens connector

Pin Function Wire color

1 RB- IN blue/gray

2 RB+ IN blue/purple

3 LB+ IN blue/black

4 LB- IN yellow/brown

5-7 n/c n/c

8 RFHI+ yellow/red (LTwtr)

9 RFHI- brown/orange (LTwtr)

10 LBHI+ yellow

11 LBHI- brown

12 RBHI+ blue

13 RBHI- brown

14 RF- IN blue/brown

15 RF+ IN brown/black

16 LF+ IN yellow/red

17 LF- IN yellow/brown

18-20 n/c n/c

21 LFHI+ yellow/green (STwtr)

22 LFHI- yellow/brown (STwtr)

23 RFHI+ blue/brown (STwtr)

24 RFHI- blue/green (STwtr)

25 LFHI+ yellow/blue (LTwtr)

26 LFHI- yellow/gray (LTwtr)

J3 6-pin AMP connector

Pin Function Wire color

1 GAL IN black/white

2 SPATIAL n/c

3 SUB LO n/c

4 GAL OUT n/c

5 SUB OW n/c

6 SUB HI n/c

Notes:

J1 connector has the thick gauge wires

pin numbers are labeled on the connectors

Function is as labeled on the HK Amp circuit board;

RBLO+: Right Back Low-freq speaker positive

n/c: not connected;

STwtr: small tweeter;

red/white: red wire with white stripe

Knowing these details about the HK stereo system helped me in planning a better stereo system. Figuring out what to keep and what to replace is like putting a jigsaw puzzle together. You have to identify each piece of the puzzle and make sure they fit with the other pieces. Putting this puzzle together is more difficult than most cars, because BMW uses some non-standard equipment. The trouble starts with the stock head unit. It would appear that BMW knew what they were doing when they had Alpine make both the head unit and CD changer. Both units are only compatible with the other, so if you want to use the BMW CD Changer, you have to use the BMW head unit. Or if you want to keep the BMW head unit and play CDs, your only option is the BMW CD Changer. The other “non-standard” part of the radio is that it sends a 5 volt signal from the Alpine head unit to the amplifier. Not very many aftermarket amplifiers can accept inputs in this range forcing upgraders to either limit their choices on a replacement amplifier or to use a line leveling device (also referred to step-down converters).

So when you are planning your upgrade, consider the BMW head unit and BMW CD changer one unit. You either use both or neither. On top of that, if you’re going to stick with the stock head unit then you have to limit your aftermarket amplifier to ones that can accept 5 volt input, or budget for a couple line levelers as part of your upgrade. See why I say this is like putting a jigsaw puzzle together?

Putting the Puzzle Pieces together

Certain parts of my new stereo system puzzle fell into place quickly. In my previous Z3 I had used Boston Pro series 6.4 component speakers. They worked so well with the odd acoustics inside the Z3 that they were the first piece of the puzzle to be locked into place. At the time I was shopping for stereo equipment Boston Acoustics was starting to place advertisements for their new 6.5 component speakers. They weren’t available yet but plenty of stereo places were putting the 6.4 component speakers on sale to clear the shelves and get ready for the new 6.5 models. I have no idea what the new 6.5 speakers will sell for but the 6.4 speakers were normally in the $400 range, on sale you can find them in the sub $300 range.

The Boston Pro Series 6.4 speakers almost fit without modification. However the speakers did come in contact with the plastic kick panel that installs over the speaker. The solution proved to be simple, a protruding plastic ring was sanded down on the back side of the kickpanel. This provided the extra room necessary to properly install the 6.5 inch speakers.

The next piece of the puzzle involved a new device that I had no experience with. Alpine had a product they were calling Bass Shakers. Alpine was saying that these Bass Shakers could be installed under the seat and they would trick you into thinking you were hearing low bass sounds when what it was really doing was just creating the vibrations associated with low frequency bass sounds. It sounded pretty far fetched to me, but the local stereo shop set up a demo with one of these shaker things mounted to a wood box. The demonstration let you listen to a stereo and step on and off the wooden box to “feel” the difference. It was very strange to be tricked like that but sure enough, when I stepped on the box it really did seem like someone turned on a subwoofer somewhere. I still wasn’t fully convinced of this products capabilities inside a Z3, so I posted my Z3 Bass Shaker question on the BMW roadster message board. It turned out several had not only felt the Bass Shakers before, a few had even felt them inside a Z3. Once I got the virtual thumbs up from a few individuals I started shopping prices on the internet.

After a little research I found out there are a few different Bass Shaker models available. A company by the name of Aura actually makes these devices and offers two different models, the Bass Shaker, and the Bass Shaker Pro. The pro model is physically bigger, heavier, and handles more power which results in more “shake”. I believe that Aura also makes Bass Shaker Pros under the Alpine brand name. Down deep I think the Aura Bass Shaker Pro and the Alpine Bass Shaker are actually the same product, but the Alpine salesman was telling me his version was slightly larger when I was trying to get him to price match on the Aura Bass Shaker Pro. However I think I basically just paid extra for the Alpine name. On the internet I found the Aura Bass Shaker Pros for $180, but I ended up paying just over $200 for the Alpine brand.

To install the bass shakers, the seats needed to be removed. Initially the installer said I would need to take the Z3 back to BMW after the installation because removing the seats would set off the SRS light on the dash. However Larry Nissen (BMW Certified Tech) told me how to remove the seat without setting off the SRS light on the dash. The secret is to never put the key in the ignition. Every time the key gets put in the ignition it triggers a self test that will notice the seat is missing and turn on the light.

My attention then turned to the stock BMW subwoofer. Under the stock conditions the subwoofer seemed to do well up to a point but then it started buzzing and thumping. I removed and dissected the HK subwoofer to see how the thing worked and what could be done to improve it. It was too hot to be working out in the garage so once it was removed I took the subwoofer inside and using some old crossovers I had hooked it up to my home stereo system. (Note: one of the speakers gets wired backwards, reversing the positive and negative wires so the two speakers will work together by pushing in the same direction at the same time even though one is facing the opposite direction).

I was actually quite shocked at what happened, suddenly the bass got much cleaner at high volume, the muffled-buzzy sound was gone. What I learned is that the HK sub still has its limits, but if you give it a good clean power source it actually does pretty well. I could tell that this upgrade was going to get expensive so I decided to stick with the stock subwoofer. As long as I can get a good, clean, power source for the sub it was going to be fine for now (but maybe the subject of a future upgrade). Vibration was really my only concern with the stock BMW sub, especially if I was going to start sending it even more power. I had already found a fault with the rubber porting tube, so I knew I would have to secure it better. But I also suspected that I should invest $20 into some vibration dampening material in an attempt to cut down on the amount of buzzing and rattling the plastic components make as a result of the subwoofer.

I then started looking at those tiny speakers behind the seats, I just wasn’t sure what to do here. It was obvious the current speakers were not worthy of being part of this new stereo system, but what could replace them. I had seen what a/d/s/ did in their show car in regard to rear speakers and liked that solution. But one quick check of the rapidly depleting budget made this decision a little easier. I decided to physically leave the stock speakers in place, but they would not be hooked up to anything. The budget played a big part in this decision, I decided to give up rear speaker sound fill in order to save some money right now. If the desire for rear speaker sound hits me in the future I will deal with it then. However if possible, I should attempt to plan my amplifier selection so I could add rear speakers at a later date if I choose to do so.

There were two pieces left to the puzzle, the CD player and the amp. I went back and forth on the CD player. On one hand I could spend $500 on the BMW CD changer, mount it in the trunk and stick with the stock head unit. This option has many advantages such as retaining the speed sensitive volume, and weather band features on the stock head unit. It also would maintain a totally stock look to the stereo system which is practically a stealth mode shield against car stereo thieves. On the other hand spending the same $500 could get you a much better in dash CD player installed which would probably sound better and offer tremendously better FM reception. The hangup on the in dash option that eventually led me to choose the overpriced changer route was purely cosmetic. It seems the trend on aftermarket stereos now is to add lots of flashy multi-colored light displays. But what I really liked is how that constant simple orange display lights up the dash at night. I didn’t want to break up that look so I choose to purchase the BMW trunk mounted CD Changer. I’m not sure if I made the right decision here, but I figured I could sell the changer at a later date and install an in-dash CD without loosing too much money.

About a week after taking delivery of the CD Changer one additional fact came to light that might have led me to choose an in-dash player if I would have know about it ahead of time. The BMW CD Changer now has two different mounting location possibilities. I had only seen the side mounting location in the Z3 and assumed that is where the CD Changer would be mounted in the M roadster. However now there are some rumors that BMW is mailing me an M Mobility system that will fit in roughly the same area as the side mounting location making me either relocate the CD to a less desirable location (pictured) or remove the nice gray flannel cover around the CD changer. If the M Mobility kit ever shows up I’m probably going to wish I would have gone the in-dash route.

So now the only part of the puzzle left to put in place was the amplifier. A quick count of speakers tells me I need to power 6 separate channels

Boston Pro series 6.4 Component Speaker Set (Left – Front)

Boston Pro series 6.4 Component Speaker Set (Right – Front)

Alpine Bass Shaker (Left – Front)

Alpine Bass Shaker (Right – Front)

BMW Subwoofer (Left – Rear)

BMW Subwoofer (Right – Rear)

Picking the Amplifier

Choosing the right amplifier proved to be the most difficult part of this upgrade. Initially I choose a pair of amplifiers from Phoenix Gold new line of amps that were all chrome. The salesman showed me how Phoenix Gold’s QX4150 4 channel amp and the QX2100 2 channel amp could be mounted together and joined using this cosmetic piece to make them look like one big amp. We took the amps out and laid them in the trunk to see if they would fit. Sure enough they fit just perfectly, almost the entire width of the trunk. The band of all chrome across the back of the trunk looked really good too so I decided these amps were going to be the ones.

The Phoenix Gold amplifiers sounded really good, however they started overheating and shutting down after only 30 minutes of hard use. The stereo shop that installed the amplifiers diagnosed the fault to be the amplifiers and suggested trying a different brand.

The salesman suggested a more expensive Rockford Fosgate 360.6 six channel amp with the promise that it would not only run cooler but it would also sound better. This single unit six channel amplifier delivered 30 watts per channel so the overall output was lower however the salesman promised it would run cooler.

After the new amplifier was installed I found that the bass sound had improved (probably due to the rockford bass EQ feature) but the Boston Pros were not as clear and couldn’t get nearly as loud before distorting. It still sounded pretty good, but not as good as with the previous pair of Phoenix Gold amplifiers. The lower power of this amp didn’t sit well with me especially considering the additional cost and poorer sound quality, but I had resigned myself to accept it as long as this one didn’t overheat.

However after putting the Rockford Fosgate amplifier through a road test this amplifier overheated as well. After talking with Rockford Fosgate’s customer service they suggested that something was wrong with the installation. I returned to stereo shop to question the installer but they didn’t find anything wrong with the installation, and suggested I choose another amplifier. Since I wasn’t happy with the sound quality with the Rockford Fosgate anyway I started looking for another replacement.

At this point I was getting very frustrated and confused. Alan’s a/d/s/ show car was running nearly twice the power with his a/d/s/ P840 amplifier that I was with the Rockford Fosgate. And he was telling me his amps were cool enough to rest your hand on. I really wanted to just give up and retreat back to the stock stereo, but even this option had additional costs. In the end I decided to stop listening to advice from the shop that was installing the equipment. I did my own research and decided to try the same a/d/s/ P840 amplifier that Alan was using in the a/d/s/ showcar. This amplifier has 8 separate channels rated at 40 watts per channel. The amplifier also had full crossover control over each channel. With this much power and flexibility the new amplifier required a lot of thought and planning on how everything would be set up. I ended up setting the new amplifier up in the following configuration.

Channel 1&2 bridged: Source should be the front, left channel with the high pass crossover set at the lowest point of 45Hz. This signal would deliver 120 watts from 45Hz to 20kHz to the driver side (left) boston pro series 6.4 component speaker set via the boston crossover.

Channel 3&4 bridged: Source should be the front, right channel with the high pass crossover set at the lowest point of 45Hz. This signal would deliver 120 watts from 45Hz to 20kHz to the passenger side (right) boston pro series 6.4 component speaker set via the boston crossover.

Channel 5: Source should be the rear left channel with the band pass crossover set to drive the range between 80Hz and 100Hz. This signal would deliver 40 watts from 80Hz to 100Hz to the front facing driver in the BMW subwoofer.

Channel 6: Source should be the rear right channel with the band pass crossover set to drive the range between 80Hz and 100Hz. This signal would deliver 40 watts from 80Hz to 100Hz to the rear facing driver in the BMW subwoofer.

Channel 7: Source should be the rear left channel with the low pass crossover set to drive the range below 100Hz. This signal would deliver 40 watts from 20Hz to 100Hz to the driver’s side (left) alpine bass shaker.

Channel 8: Source should be the rear right channel with the low pass crossover set to drive the range below 100Hz. This signal would deliver 40 watts from 20Hz to 100Hz to the passenger’s side (right) alpine bass shaker.

Fighting Amplifier Heat

After installing the a/d/s/ P840 amplifier I was still having some amplifier heat problems. After discussing the trouble I was having with other people and with a/d/s/ I decided to give up on stereo shop that had been working on my Z3 *Earmark Car Audio in Dallas). Several other Z3 owners as well as a/d/s/ recommended I talk to Custom Sounds in Austin Texas. I eventually gave into my frustration and paid Custom Sounds to fix the problem.

What they discovered was that a couple of the speakers were wired out of phase, some line leveling (or signal knockdown) devices that were not appropriate for use with the a/d/s/ amplifier were installed, and in general the wiring was in their opinion “messy”. Custom Sounds cleaned everything up, wired the speakers correctly, removed the signal knockdown devices and also suggested installing some fans just for “overkill” to make sure I wouldn’t have any heat related problems. Taking their advice I had them wire a power source for the fans, however they were out of the particular Radio Shack fans they wanted to use so they took the time to show me how to add the fans myself.

On the way home I stopped by Radio shack. The fans were only $9.99 each and I picked up a plug as well so the fans and cover could be unplugged and removed if the need should ever arise. With four fans there is quite a bit of air flow directly over the amp. The fans are attached under the facade but blow air through the groves in the heat sink. It is a very productive setup, the fans are quiet and do not affect the sound quality.

While at Radio shack I also picked up a fancy digital thermometer that has two separate temperature sensors. I used this device to measure the temperature directly over the amp as well as in the corner of the trunk. After comparing these temperatures to those I took from other Z3s I’m ready to declare the heat problem resolved.

Six Month Update


Over six months have passed since this stereo upgrade initially began, and there are several things that have happened so I felt the need for a “six month update”. I will go into detail one issue at a time below but basically I’m happier with the stereo, but even more upset with Earmark Car Audio, the stereo shop that initially installed everything. At this point there is not much of the upgrade that was initially installed that hasn’t been uninstalled and reinstalled by someone else.

Amplifier Heat

This is no longer a concern for me, the a/d/s/ amp is running relatively cool with the help of the four additional fans. When I compared the temperature in my trunk to the temperature in other Z3 trunks during the homecoming convoy, I discovered that I am well within the norm. Most (stock stereo) trunks were cooler than mine but not by much, and any Z3 (with the exception of Alan’s) that had an upgraded amplifier were actually running hotter. I am happy to report that the a/d/s/ amplifier has never shut itself off even with extended high-volume stereo listening. The radio shack digital thermometer was very handy, during the homecoming convoy I was able to toss it into a different Z3 trunk every time we stopped for fuel. By the end of the trip I had a very accurate representation of what was acceptable and I was within that range.

Boston Pro 6.4 Speakers

I was disturbed to discover that the passenger side tweeter stopped working one day. It took nearly two months but a replacement was delivered at no cost. The speakers still sound great, but a recommendation is worthless at this point since the 6.4 model has been discontinued.

Alpine Bass Shakers

While my M roadster was on the lift at BMW one day I asked the Tech “what are those sheet metal screws”. He smiled at me and said “those are holding down your bass shakers”. I could feel my blood pressure rise as I looked at these inch long sheet metal screws ripped through the bottom of my M roadster. One of the screws had been bent (probably from a speed bump) and the installer hadn’t even put any kind of sealant around them to stop water/rust. The BMW Tech cut the screws off so they didn’t stick down quite so far and added some sealant but the damage had already been done. About a month later that bent screw finally gave up and the drivers side bass shaker shook itself loose and was now a bass rattler.

One weekend I ended up taking out both of the M roadster’s seats and then removed the bass shakers. I reinstalled the bass shakers using nuts and bolts and a generous amount of sealant. Once everything was reinstalled the bass shakers were working as good as they had ever worked, however my opinion of them has gone way down over the last six months. Their shaking affect is quite impressive when the car isn’t moving. However once the car is moving at more that 30mph the slight vibrations from normal driving seem to cancel out the bass shaker affect. Maybe they work better in other cars, but the sports car (stiff) suspension in my Z3 appears to make the bass shakers a poor decision.

BMW subwoofer

Finally some good news, for several months a/d/s/ has been using my BMW HK subwoofer to develop a upgrade kit. I haven’t received the finished product yet but they are telling me they have made some improvements to the stock enclosure and are now using two new drivers. I can’t wait to hear it in my car.

Rear Speakers

The desire for rear speaker fill has hit me, I’m going to hold off until I get the a/d/s/ subwoofer installed but I suspect I will be adding some rear speakers (myself) sometime this summer. I will probably work them into the same channel as the bass shakers or a/d/s/ sub via some external crossovers.

BMW CD Changer

The rumors about the M mobility kit and its interference with the side mounted CD changer were correct. To get them to fit in that location the gray flannel cover must be removed. It might be my imagination but the CD Changer also seems to be skipping more frequently. I’m starting to second guess my decision to keep the BMW equipment rather than get an indash CD player.

a/d/s/ Subwoofer

My HK subwoofer was rebuilt by a/d/s/ as a development project while they were evaluating the possibility of making a speciality kit. The product they created works very well, however it was determined that the stock HK amp was not powerful enough to truly drive the (now) a/d/s/ subwoofer with enough power to audibly tell the difference between the stock sub and the much improved a/d/s/ subwoofer. As a result of this, a/d/s/ canceled the project.

The individual within a/d/s/ that had done the research and development of the prototype replacement subwoofer got permission from a/d/s/ to build the subwoofers on his own for those HK owners that had also replaced the stock amplifier. However even that project was canceled with the news that BMW had a new HK subwoofer with the model year 2000 Z3.

So as it stands I have the one and only a/d/s/ prototype subwoofer. I do not have any details about the drivers, they were specifically unmarked so I can’t tell you anything about them from looking at them. All I can add is that they sound very good and its a shame the way things worked out.

DC’s Stereo Upgrade

Pros: Improved sound quality, increased power let you hear the stereo over the hi-way speed wind and road noise
Cons: Some trunk space is lost to the amp, permanent modification to the kick panels
Cost: $900 to $1000

So, thinking about upgrading that stereo huh? Well, you’re not alone. As factory systems go, the Roadster’s isn’t too bad. In fact, it would probably sound great if it wasn’t in a ragtop. Unfortunately, it is. Most people who buy this car will be satisfied with this stereo. Some will perform a minor upgrade such as a speaker swap, etc. The rest of us are looking for something a little bit more substantial. So, where do we begin? Well, if you’ve ever read “The Art of War” you know that the very first rule in conflict resolution is “Know your enemy”. So let’s take a look at the factory system in the M Roadster.

M Roadster Factory Sound System

AM/FM/Cassette/CD Changer Controller Head Unit (made by Alpine)

6 Disc CD Changer (made by Alpine also)

Factory amplifier

5.25″ speakers in the kick panels

2″ midranges in the doors

1’ tweeters in the doors

3″ midranges behind the seats

Two 5.25″ “subwoofers”

The major shortcomings of this system (in my humble opinion) are as follows:

With the top down and the car moving the stereo is pretty much useless.

The sound is muddy (lack of highs).

The maximum volume is inadequate.

The low frequency response is non-existent.

Having said that, let’s look at what the factory system has going for it:

The head unit and changer although labeled as HK are actually made by Alpine.

The head unit has SSV and a weather band.

The factory equipment looks “stock”, a great theft deterrent.

The front factory speaker locations are quite good (in terms of sound stage).

Okay, so what do we do about it?

Upgrade #1 – The front speakers

GOOD – Replace the factory 5.25″ midrange with an aftermarket 5.25″ midrange. This size speaker is a drop-in replacement for the factory speaker – no modifications necessary. The MB QUART QM 130-TX3 are an excellent choice.

Parts $130 – $150 for the pair

Labor $25 – $40

Benefit You will experience a cleaner, brighter sound with more usable volume.

BETTER – Replace the factory 5.25″ midrange and the factory 1″ tweeter with a good quality 5.25″ component speaker set including crossover. The 5.25″ speaker is a drop-in replacement as is the 1″ tweeter. You will not use the crossover included with the speakers unless you are adding an aftermarket amplifier (see Best). The factory 2″ midrange is left alone.

Parts $175 – $225

Labor $40 – $75

Benefit More highs, better sound stage.

BEST – Replace the factory 5.25″ midrange and the factory 1″ tweeter with a good quality 6.5″ component speaker set including crossover. I used Boston Acoustics 6.4 Pro’s. ($299, reg. $450)

The 6.5″ Mid/Woofer will require minor modification of the kick panel to get it to fit. You’ve got 2 choices here. You can remove the plastic ring on the backside of the kick panel and mount the entire speaker behind it.

Or you can cut a round hole in the kick panel and mount the speaker through it.

The factory tweeter should be left in the factory location and disconnected. The factory 2″ midrange should be removed and the aftermarket tweeter installed in its place using a simple bracket.

I suggest doing it this way rather than placing the tweeter in the factory tweeter location because you will experience better stereo imaging this way. It is kind of hard to explain why but I’ll try. You all probably know that the “sweet spot” is in the absolute middle of 2 speakers as opposed to being closer to one or the other. If the left speaker is 1 foot away from you and the right speaker is 3 feet away – that’s not so great because the right speaker is 3 times the distance away. But if the left speaker is 1.5 feet away and the right speaker is 3 feet away – that is much better because now the right speaker is only twice as far away. See what I mean? This is why I suggest using the factory location for the 2″ midrange – it eats up some of the disparity. Finally, you will be using an aftermarket amplifier with this upgrade (see next section) and you will be using the passive crossovers supplied with the component speaker system.

Parts $250 and up

Labor $100 and up

Benefit Excellent clarity and imaging, low end much improved over stock system by use of dual 6.5″ mid/woofers instead of 5.25″ midranges. HUGE IMPROVEMENT!!

Upgrade #2 – Aftermarket amplifier.

Note regarding any of the following options. Installing an aftermarket amplifier is pretty easy in this car. The battery is located in the trunk and so is the factory amplifier. I stuck the crossovers that came with my Boston 6.4’s in the factory amp location.

I temporarily mounted the ADS P840 amp to the carpet with Velcro pending my decision regarding subwoofers in the trunk.

GOOD – Use a decent 2-channel amplifier to feed your new front speakers. I recommend a minimum of 40 to 50 watts a channel – remember…this is a ragtop. This amp should be able to accept “high level” inputs from your factory head unit.

Parts $199 and up

Labor $50.

Benefit Vastly improved volume and dynamic range.

BETTER – Use a multi channel (at least 5 or 6) to amplify your entire systems and bypass your factory amp entirely. 2 channels to your new front speakers, 2 channels to your factory rear speakers and 1 or 2 channels to the factory subs.

Parts $249 and up

Labor $50 – $75

Benefit Increased rear fill and improved low end. BE CAREFUL not to overpower your subs!! While most speakers fail due to too small of an amplifier being driven into distortion (and the distorted signal destroying the speaker’s voice coil), speakers reproducing low frequencies can be “overdriven” with too much power, clean or otherwise.

BEST – High current/high power multichannel amplifier (or multiple amplifiers). I used the ADS p840 amplifier ($565, reg. $699 or so). This is an 8-channel amplifier with built-in electronic, adjustable crossovers rated at 8 x 40 watts.

I bridged 4 channels to create 2 channels at 120 watts/channel for my Boston Acoustic 6.4’s in the front. Using the electronic crossovers in the amp (as well as the passive crossovers supplied with the speakers) I restrict the frequency response of these speakers to 65HZ to 20KHZ. By removing the lowest frequencies from these speakers, I prevent damage to these speakers due to overdriving. This basically means I can crank the volume up to ear piercing levels without worrying about damaging the speakers. 2 channels (at 40 watts per channel) go to the factory rear speakers and the remaining 2 channels (at 40 watts per channel) go to the factory subs. The factory amplifier is being used as a paperweight on my workbench.

Parts $399 and up

Labor $75 and up

Benefit With this combo (amp and front speakers) the sound stage and imaging is excellent and the volume is awesome. The only downside is that the fronts are so good that it makes the lack of real bass (20 HZ to 60HZ) all the more noticeable. Sighhhhhhhhhh…….

Upgrade #3 – How low can you go……

GOOD – Live with the improved low end from your new 6.5″ front speakers.

Parts $0

Labor $0

Benefit N/A

BETTER – A custom fiberglass enclosure in the passenger footwell with an 8″ subwoofer. This will improve the low end substantially (if properly designed) but will obviously effect legroom for your passenger. JL AUDIO makes some very nice subwoofers, as does KICKER.

Parts $150 – $200

Labor $250 – $300

Benefit Improved low frequency response. Your car won’t BOOM but you should have usable bass down to about 30 HZ.

BEST – Custom enclosure in the trunk firing into the cabin. This is the only way you will get truly mind-numbing bass response in the vehicle short of MAJOR reconstruction (i.e., modify kick panel to take 8″ woofer, etc.). Be prepared to have your baby out of commission for a few days (minimum), tolerate moderate cutting to port the sound into the cabin (probably not a good idea for those who lease), the loss of half of your trunk and a hefty bill at the end (at least $800, more like $1200). If you can live with these costs, you will enjoy the BASS that the rest of us can only wish for.

Parts $500 – $700

Labor $300 – $500

Benefit Truly awesome Bass!!

To be covered next time

Upgrade #4 – Rear Speakers

Upgrade #5 – Aftermarket Head Units

Upgrade #6 – Misc. (Stereo FAQ?)

Did You Know Your ’96 Roadster HAD a Stereo?

Let me preface this entire article by admitting I’m no audio-maven…far from it. The true audiophiles out there can save themselves from wasting any time by skipping this article. I have a good grasp on what you expect, and it’s far different than where my meager goals will lead you. I would HIGHLY recommend following the efforts of gutsier enthusiasts like Robert Leidy, Alan Riley, Phil Ehlen, and Brian Powell.

Now that they’ve left, I suspect there are a number of you out there who, like me, have this overpowering preference to live with what you have…to make lemons out of lemonade, to accentuate the positives and ignore the negatives. Maybe it’s due to hearing of the horror stories of audio freaks who’ve ripped out their entire stock system only to be saddled with untraceable audio whine, botched installations, and the multi-thousand dollar price tags for a system that could be better spent on a fancy home theater. Maybe the the idea of letting some unfamiliar shop monkey rip into the interior cutting, testing, and sparking all sorts of wires makes you far nauseous than any weak stereo. I have owned my ’96 1.9L since September and have avoided cutting into it in any way. My audio needs were enough where having an audible stereo with the top up was sufficient. My system is full factory stock with consists of a speed-sensitive/theft-deterrent head unit, door panel tweeters, kick-panel mid-woofers and factory amp in the trunk. The HK upgrade wasn’t available at the time of my order and even if it were I’m not sure I would have ordered it without having heard the difference. In fact, I still haven’t spent any appreciable time evaluating a HK-equipped Z3. (All you HK comparison seekers can leave now too) Although upgrades like the CD Changer and rear speaker upgrade became available at better prices than the dealer, I still opted to stay stock.

After all this time, I think I can sum up the existing ’96 setup. The system sounds fine (to my amateur ears) when the volume is moderate and the car is quietly parked. The moment the car’s in motion, the sound is drowned when competing with wind noise. Cranking up the volume when tooling around town can only be done to the point at which 25% of the music peaks are legible. Any higher and all that’s being turned up is mud as the speakers begin distorting…a likely testament of the grossly inefficient amplifier and speakers. In addition, the ’96 setup presents the driver with a wall of sound from the front. Without rear speakers, there can be no immersion of sound. At highway speeds with the top and windows down, there’s no reason to expect any sound from the stereo. At best, I can distinguish a legible 5% of music peaks. Any more volume cranking and it’s all garbage from thereon. The whirr of tires from highway traffic was a death blow to any hope of legibility. There wasn’t much point to pursue the factory upgrades under these conditions.

This didn’t faze me much as most of my driving was off the highway. Once on the highways, I’d be preoccupied visually scanning for state troopers in the horizon anyway.

During a recent road trip with the top up, a friend attached a portable CD via cassette adapter to the roadster’s head unit. Until now, I knew the BMW CD Changer was supposed to be an improvement to the overall system, but couldn’t imagine by how much. The portable CD showed me that the system COULD sound better than it did…and that part of the blame rested squarely on the crappy FM tuner. Yes, I know that CD offers better sound, but I could hardly believe the fidelity I had been missing all this time in listening only to the FM tuner. I would equate this sound to enjoying music in your living room with throw pillows pressed against each ear. The tuner simply did a horrible job at detailing the highs and lows. I now knew that there was room for improvement without confronting my aftermarket concerns. It definitely involved adding the CD Changer as I was willing to abandon FM radio, but the full potential of that $523 investment wouldn’t be realized without also improving the speakers.

Calvin Jennings had mentioned the improvement he got when replacing the kick-panel speakers with ones from a company called MB Quart. I checked out their website and brochure. This Obrigheim, Germany company’s mobile speakers have won the majority of IASCA World Finals since their US arrival in 1987. Even more appealing was how their brochure mentions specific applications, like BMW, and how certain MB Quarts “can drop right into the existing speaker cut-outs…” Physical fit was one thing, but I knew nothing about the OHM (resistance) rating, how changing it affected the system, and whether doing so was foolish. Nonetheless, Calvin mentioned they dropped right in, so I investigated further.

Speakers 101. The gap between the audiophiles and no-nothings is a wide one. I was clearly in the latter category as I immediately came across vaguely familiar terms like coaxial and component. In speaker design, sounds do not come from one single speaker. In a two-way setup, highs come from tweeters and the rest from the woofer. With a three-way setup, there are tweeters, midrange and woofer speakers all working in unison. Coaxial speakers have tweeter and woofer mounted on a single unit. You can see how the tweeter is often suspended above the woofer. In a Component setup, the tweeters, midrange and woofer are separated and installed in different locations according to the car’s design. Your ears can distinguish where tweeter highs come from directionally, but woofer sounds are vague and thus can be located anywhere.

The ’96 Z3’s design has a woofer (or mid-woofer) in the kick panels and the tweeter/midrange located in the door grills near the side mirrors. This is clearly a component setup. Removing the door panels to access these tweeters has been known as a major pain. I reasoned that typically, volume-cranking distortion was heard on the low sounds, so let’s see what replacing just the kickpanels would do.

This meant sticking coaxials (woofer AND tweeter) down there was inappropriate. Trying to do so would mean we don the cap of stereo design engineer, and based on who should be reading this it’s out of our expertise! I needed to look into buying the large speaker from a component setup. Luckily, MB Quart does sell things separately, and what I needed in the Z3’s kickpanel was the MB Quart QM 130 TX3. This is listed as a 5¼” (130mm) component midrange loudspeaker.

Calvin mentioned the QM 130 TX3 cost $89 each. I stopped by a local electronics/appliance store and salesman Mike Blanchard offered them for $74 apiece. Their new mobile electronics room is a gee-whiz experience. I’d recommend stopping by if you get the chance. Check out their PC-controlled switching and price quote system. After waiting nearly a week for a special order, I was ready to proceed with installation.

For no particular reason, I chose to start at the passenger’s side kickpanel first. Each panel is held in place by a plastic cam. Use a simple flathead screwdriver to turn this 90° in either direction.

With the panel now unlocked, wriggle it out by first undoing the catch area shown by the arrow. There is a plastic extrusion that’s held by the door sill cover. The rest of the edges are simply wedged in place. Pay attention to which edges come out first though, as you’ll probably need to reinsert it in reverse order when you’re done.

Meet the factory stock kickpanel speakers. These are held in place by four screws. Use a 5/16th socket to remove the bolthead screws.

Remove the four screws and the speaker simply drops loose. As King has indicated in the past, the wires from the amplifier to this speaker are coded blue/red and blue/brown. The positive wire is held in place by a 5mm connector. The negative by a 3mm connector. Disconnect them to complete the removal.

A visual inspection of both speakers clearly show the reason why decent speakers cost what they do. The factory stock unit is manufactured in Germany by Nokia Audio Electronics. In addition to computer monitors, Nokia has been known to supply Mercedes Benz with speakers. Looking at this unit, I find it appalling that BMW gave these things the thumbs up. The cone looks to be composed of cloth laminated with some sort of slightly-tacky material. Other markings indicate 4 ohms and 40 watts. The MB Quart’s cone is smooth and feels stiffer. Its markings say 4 ohms and 40-100w. The depth of each unit is noticeable. At this point I decided that even if there was ZERO sound improvement, I’d never reinstall the factory ones.

A small hiccup arose when I saw the MB Quart tabs were each one size higher than the factory tabs. After an hour of weighing out what to do, I decided to cut and replace the factory connectors. The reasoning was that moving the connectors up from 3mm & 5mm to 5mm & 6mm respectively would STILL allow the factory speaker to be reinstalled for whatever reason, and more importantly, bring the connector sizes up to aftermarket norms. (a presumption) Luckily, I had the salesman throw in a handful of 5mm and 6mm connectors.

This was a MUCH simpler process than I figured it to be. Cut off the old connectors and stripped ¼” of jacket material to re-expose the wire, slipped on new connectors and crimped their collars to the wire. No soldering was necessary, but I did it anyway to obtain a gorilla-strength connection. I also slipped a piece of heat-shrink tubing over each crimp area to prevent excess moisture and corrosion. To be on the safe side, attach the uncrimped new connectors to the MB Quart tabs to check their fit.

The MB Quart’s bracket ring can ingeniously be flipped to provide two mounting depths. I chose the depth that positioned it deepest. I connected the freshly-prepared factory wires to the MB Quart tabs and mounted it into place using the old factory screws.

Replace the kickpanel by working it back into place. It might be easier to remove that plastic cam and reinsert it after the panel’s in place.

I placed a work light in the driver’s footwell, but made sure to have it sit atop a sheet of metal to prevent the work light housing from burning the carpeting. The kickpanel is molded to the footrest. Start by removing the hood latch handle. This will expose the plastic locking cam underneath. Turn that 90°. To simplify the kickpanel removalloosenen the panel covering the pedal sets.

…this is because there’s a catching clip at the top of the footrest. The pedal set panel doesn’t have to be removed, jloosenedened enough to get uncaught from the kickpanel’s footrest. Also notice the right side of that footrest has two plastic blades that sit inside gashes in the carpeting.

Again, pay very close attention to how this panel comes out. In addition to watching the clip and blades, you’ll need to clear the spot where the hood latch handle was. Once the panel’s off, remove the stock speaker and replace the connectors with attention paid to crimping the larger 6mm connector to the positive yellow/red wire. A 5/16th socket was used to reach the bolthead.

With the new connectors on the MB Quart speaker, put everything back together. Replacing that kickpanel proved trickiest of all. Patience will ultimately be the key. Be sure the footrest is pushed far enough to the left where those plastic blades will seat back into their respective carpet gashes. Use your fingers to feel your progress.

With the kickpanel in place, turn the locking cam, replace the hood latch handle, and lock down the pedal set panel. The project is complete!

So now comes the $148 question…how does it sound? Knowing that cranking the stereo up with the car parked won’t tell the tale, I struck out for the nearest highway. Instinctively, I turned the stereo up to the normal threshold level…a 270° clockwise twist from dead silence. Whoa! What’s this? I think I hear lyrics. I further turned the stereo up and headed into a wolfpack of cars deliberately seeking the sound of tirewash. YES! Music! I could feel the footrest vibrating from the MB Quart’s bass…if I ever turned up the old speakers to this level, all I would get was distorted mush…no thanks to the old crappy coated fabric cones. Will this new setup ever bdistortingoring? Yes. But unlike the old system, there is an appreciable span of volume travel with the top down, with the windows down, at highway speeds and amongst the din of tirewash where you can hear the music and lyrics with far greater detail than the old system ever hoped to give at 35mph with the windows up. This volume limit is where it will hamper the attempt at conversing with your passenger.

On my second run, I hooked up a portable CD Player to the head unit via cassette adapter to give me an idea what a future CD Changer upgrade will be like. WOW! These speakers go even further to show how night & day the move away from the FM tuner is. I had to readjust my bass/treble levels to tone down the shininess I never heard before. Listening to the clarity of the Cranberries’ “Dreams” with the top down was the reward for a job well done. This cassette adapter may have added more volume as I heard more volume even though I didn’t touch the knob. When I ejected the adapter, the volume from the FM tuner was lower. I’m not sure if this characteristic will occur when I get the BMW CD Changer. Finally, the last step I am looking forward to investigating is how adding the factory rear speaker and amp upgrade will improve things. The new amp supposedly delivers a hair more power in addition to the rear channels, but I don’t know by how much. And no one’s mentioned if those 3½” rear speakers are a coaxial type. Based on my new experience with MB Quart, I might look for an equivalent 3½” replacement when it comes time to add the factory rears. Having a rear set of speakers ought to provide a satisfyingly immersive experience. This modest approach to upgrading will position me where I’ll be able to hear at least 85% of the music at top-down cruising speeds and know that I haven’t lost any storage space or given passing thieves a hint there’s actually something worth stealing underneath those panels. I’m certain the audiophiles can show me how their $4000 setup differs from mine; how their fidelity can reveal Pete Townsend’s breathing during the faint guitar riff in “Who Are You”, or how the wife can feel them returning home by the ground tremors. Despite that, I’m sure I’ll remain happy with this simple, inexpensive, not-too-invasive upgrade. Guess I’m just an underachiever.

Items you’ll need to gather for this modification:

Two (2) MB Quart QM 130 TX3 midrange speakers

Flathead screwdriver

Phillips head screwdriver

Crimping pliers

5/16″ socket

Two (2) 5mm crimp connectors

Two (2) 6mm crimp connectors

Four (4) one inch segments of heat shrink tubing or electrical tape

Compact work light

Long Term Update:

The speakers featured in the article may no longer be available

Notice: The author assumes no liability nor offers any guarantees your upgrade experience will go as smoothly or result in the same improvements. All known issues have been laid down in the clearest manner possible. Despite this, the amount of redundant e-mail sent to the author is expected to be substantial. Not all questions will be answered…some might even get laughed at. Journalistic integrity ofarticlecticle has been backed up by theBaba. Send all complaints to him.

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