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1997 Z-3 2.8 Stereo Upgrade

Why?

Enough has been written about the shortcomings of the stock Z-3 stereo, so I won't add any here. I don't know if the problems have really been fixed in models later than my 1997 2.8, but based on the comments around the Z-3 message board, it seems unlikely.

So, I set out to upgrade my stereo prior to a cross country trip from Boston to Los Angeles (yes, REALLY cross country).

Having had my brain freshly minced from three years of graduate school, I approached this like any other engineering problem. So, first state the goals, then describe the problem.

The Goals

The easiest way to spend too much money is to go and buy stereo equipment without understanding what you ultimately want. I was starting out with the base 1997 stereo, so my goals were:

1. Good sounding jazz and classical music at freeway speeds with the top down. It is important to understand which type of music you prefer. Classical requires quite a bit more dynamic frequency range than say, gansta rap, which requires a great deal more bass response than classical.
2. In Dash CD/Receiver. I wasn't very impressed with the built-in cassette unit, and didn't really think a changer was worth it for me right now.
3. Maintain useable trunk volume. This is my only car, and I like to be able to get a weeks worth of groceries in the trunk, preferably without setting food containers on top of electrical equipment.
4. Flexibility to alter or add components later to improve the sound as money became available. Minimizing initial equipment cost doesn't reduce the initial installation labor by much, but if you decide you need something different later you can easily paint yourself into a corner. For example, buying a 2 channel amplifier would produced the same system that was installed in my car. But if I ever decided to add a subwoofer later, I would have had to buy a new amplifier, increasing the overall cost.
5. Cosmetically acceptable. I didn't mind the fact that the head unit would make it obvious a new system had been installed, but the system had to look good, otherwise the resale (heaven forbid) of the car could suffer.

The Problem

Initially, the biggest problem was my complete ignorance of car audio technology. So I started reading everything I could find on the web, and think I have a handle on the lingo. I will try to explain every non-obvious term I came across.

The Speakers

If you must only upgrade one thing in your system, the speakers would be it. It will give the most bang for the buck, but will still be far from producing satisfying sound at freeway speeds. Which brings us to the real heart of the matter; the amplifier.

The Amplifier

The obvious causes of car audio problems are the factory installed head unit (the thing in the dash) and speakers. These are the parts of a system that most people are familiar with. There seem to be relatively few cars manufactured with a separate amplifier, most simply use amplifiers built into the head unit. This is OK for them, but not for one of the nicest convertibles ever conceived. So, BMW's engineers had their hearts in the right place, but not the dollars (or trunk volume, which we'll come back to) to meet the challenge, because the REAL root of the problem in the Z-3 system is the separate amplifier shown below, removed from the car:

This is an eight channel amplifier. This means that the stereo takes the input signal from the head unit and splits it up into eight separate channels so that it can drive eight separate speakers, although my car used only six. Nominally, this amplifier claims to produce twenty watts per channel. That is highly questionable. Most amplifiers are rated at the AVERAGE (RMS) power, but head units, and I think this amplifier are rated at their MAXIMUM power. This is like telling you my speed in the 100m dash, and letting you think I could run a marathon at that pace (I CAN'T!!!). Remember this about amplifier and head unit ratings, it becomes really important later.

In order to ensure that each driven speaker receives its proper portion of the sound frequency spectrum, the amplifier uses a "cross over". The cross overs in the BMW amp are fixed, which makes using after market speakers sub optimal since all good speakers come with their own crossovers specifically designed for them.

There are two primary types of signal input used on aftermarket amplifiers. The first is line level input, which is a non amplified, low power signal directly from the head unit audio circuitry. The other type of input is called "speaker level" input. These inputs take the same signal as a set of speakers, and can take the high power signals that head unit amplifiers would send directly to a set of speakers. They are not interchangeable. Of course the BMW head unit and amplifier use neither of these industry standards. If you choose to keep either of the stock components in your system you will have to ensure that the output from your head unit can be safely used with the inputs of your amplifier, this will mostly likely require some adapter hardware. I didn't go down that road, so cannot comment on it further.

There is one additional interesting feature of the BMW amplifier:it is small! Specifically, the dimensions are 7.1"W x9"L x 2.1"H. (I have included enough length for the wiring harnesses.) That is 134.16 cubic inches. When you start going through the specifications for aftermarket amplifiers that have similar functional charactersitics (i.e. many channels, built in cross overs) characteristics you find that this is amazingly small. It also means that you can't find an amplifier that will fit in the stock location that comes anywhere close to filling the functions of the stock amplifier. The price of that small size is sound quality.

Now, I really like my hearing, and I don't intend to blast my eardrums on a multi kilo watt stereo. But the point remains, to hear the stereo with reasonable clarity while doing freeway speeds with the top down requires more power than than the stock amp puts out. This is somewhat a function of the speakers, good loudspeakers can make a poor amplifier sound better, but when the amplifier starts distorting at high power output (i.e. trying to punch through all that wind noise) the high quality speakers will faithfully reproduce the amplifier distortion as well, and since distortion is inherently high frequency it can damage the midrange speakers.

The Head Unit

My Z-3 had the original BMW Cassette deck installed. It was fine, and I really liked the weather band that could confirm the weather that was pouring down on me. But, I really wanted a CD Player, and the price/quality of buying and using a BMW CD-Changer put me off. That said, of the entire system the factory head unit is the least bad, and if you are satisfied with its features, then concentrate your money on the amplifer and speakers.

My Solution

I initially set out along the path of least expense, and started trying to find the MB-Quart's that were recommended in an article by Carter Lee on MZ3.net A quick web search to find the closest local supplier for MB Quart's turned up Rich's Car Tunes, which ultimately proved that is far better to be lucky than good.

I had decided the difficulty of adapting the factory head unit to a new amplifier, or a new head unit to the factory amplifier were just a bit beyond my comfort level for home mechanics. (I don't have a problem tearing my car apart, but electrical things and I typically don't get along, and I really didn't want to screw this up). I had also read about the disastrous experience Robert Leidy had had with his installation . So it was with this in mind that I went down to Rich's CarTunes to get the MB Quarts.

An Afternoon At Rich's

Rich's has quite possibly the best customer service I have ever seen for any business. I walked in looking for the MB Quarts, and left three hours later with a much better knowledge of what I was doing, as well as three significantly different options for upgrading the system, ranging from a little more than I wanted to spend to more than I could possibly afford (I should note that what I initially wanted to spend was unrealistically low for what I wanted). Each of the systems was suggested by Richard Infererra, who I later found out is nationally respected in the car audio business (just check rec.car.audio, if you want confirmation of this). But, what I really walked away with was an impression of how an installation shop should be run.

When I asked to take a look in their shop, they leapt at the chance to show off their work. The shop is visible from the reception area through a large plate glass window, but customers are welcome to look through ongoing work close-up with an escort from the staff. It is well lit, and very well organized with room for about 5 large cars. I saw installations in varying levels of assembly, and everywhere I looked was attention to detail. All wire bundles are braided. They pay as much attention to the aesthetics of an install as they do to the sound quality. This extends into areas of the installation that most likely will be seen by no one but the installer. Two other shops I went to would not let me see their shop "for insurance reasons". Yeah, right...

After a few days to cool down and put everything together in my head, I decided that I would go for it, and have Rich's install a mid-level system with very good components and room to grow.

The system I settled on was very similar to the a/d/s/ recommended Z-3 Level II Upgrade.

My system does not yet have a sub woofer. I used the factory rear speakers with the intention of upgrading them later, and I used A5is speakers which are significantly less expensive than the 336is recommended above. I decided on the 6 channel amplifier rather than a four channel so that I could add a subwoofer in the trunk later.

I could have used some of the outputs from the head unit amplifier to drive the rear speakers, but if I ever wanted to upgrade them to speakers requiring a crossover, the headunit power would probably have not been enough (I now have a set of /a/d/s/ A4im's still in a box awaiting time to install them). In addition, using the head unit output for the rear speakers would have made overall fade adjustment very difficult.

I also decided to use an Alpine CDA-7840 in dash CD/Receiver. If I choose to later I can add an Alpine CD-Changer to this with very little hassle.

The Installation

Locations.

I dropped my car off at Rich's for the install with the instructions to maximize useable trunk space, and let the professionals figure out where to locate the amplifier:

The amplifier is stood on edge angled outwards and backwards slightly. This allows me to load groceries into the trunk without setting the milk cartons on top of warm electrical equipment. The brackets fabricated make excellent use of previously existing studs and bolt holes. There is a carefully cut piece of medium density fiberboard covered with trunk liner material that is a press fit around the amplifier, to protect the wiring harnesses, and make the installation very clean looking. The a/d/s/ crossovers for the front speakers are located in the volume previously occupied by the factory amplifier, and the factory wiring was used where possible.

When I first picked up the car I was a little concerned with the location of the amplifier. On the 2.8 you must lift the black plastic cup up to remove a hold down bolt for the spare tire tray. The amplifier installation interferes with that. I really liked the cleanliness of the installation and thought about it for a while. It only takes 30 seconds to remove the amplifier and place it to the side so the black plastic cup can be lifted out. Rich's installers leave ample lengths of wire (service loops) for moving the components around, and this job can be done quite easily without disturbing the input/output section of the amplifier. Besides I figure if I had an M Roadster I wouldn't have a spare tire to worry about anyway. Eventually I will construct a subwoofer box to fill the left rear corner of the trunk and make the installation very symmetric across the trunk.

The Little Things Count.

It was Rich's Cartunes attention to detail that attracted me in the first place. This shows up exceedingly well in the next two pictures.

The first is an 80 Amp circuit breaker that acts as a backup to the amplifiers' internal fusing. This is not necessary, but it is smart. In addition to equipment protection, it makes it simple to secure power to the amplifier when I want to adjust the connectors, or fiddle around in other ways.

The next picture is a closeup of the business end of the amplifier with the beauty plate removed. It is easy to see the great deal of care paid to the wiring. It is not shown in the picture, but the braiding continues until the individual wires had to split to make it to their respective components. While this seems like useless effort, it is important to realize that after component failure from misuse the most likely place for a stereo system to fail is the wiring shorting out. The attention paid to the wiring minimizes chaffing of the insulation, and subsequent grounding and shorting.

The Cost.

Here is the breakdown of what I paid. I feel I got the equipment at a very fair price. Rich's put probably twice the time into this installation that other shops would have put in. But, they did it right! There was never any sense that they were trying to pull a fast one with me, and I knew going in that I was paying for the best service, not the fastest or least expensive. If I was interested in cheap, I would have bought a Prelude and taken it to Circuit City.

My measure of quality is whether they did a better job than I could have. There is no way I could have come close to the quality of installation that these guys did. I am certain now that I could have installed the system, but it would have been a hack. The guys at Rich's are artists in every sense of the word.

The Final Verdict

Was it worth it? The final system was better than I ever imagined. I have never had a really good car stereo, so had nothing really to judge it by. But this car now sounds better than most home stereo equipment I have heard, and I can take it with me! I have not had any heating problems, but then again the car has been in Massachusetts, we'll see how this works when I get to the southwest this summer.

I apologize if this article has seemed like an advertisement for Rich's Cartunes, but when I find a business that I like as much as I like Rich's I like to shout from the hills. There have been instances of people spending multiple tens of thousands of dollars for Rich to design and install a system, for very good reason. If you are in the Boston area, check him out, and if you are not, people have shipped their cars to him cross country...

Last modified: Mon May 24 18:31:42 EDT 1999