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!