NOTE: The following questions/answers pertain specifically to the way I installed the 6x9's into my '95 M3 using them as subwoofers to go along with the factory 10-speaker non-HK stereo system, so your experience may vary with a different E36 version. The details in this FAQ are just a guide, so proceed with caution and at your own risk when attempting this on your own car! If you have any other questions about this installation, feel free to e-mail me.
Do you sell these 6x9 adapter plates?
No, I only made these plates for my car and I don't have any desire to mass produce them. These plates can easily be fabricated from 3/4" MDF with some basic tools, a little time, and a little skill. However, if you are lacking the skills, tools, time or desire to make them yourself, then a pair of 6x9 adapter plates very similar to the ones I've made can be purchased from Kurt Lewis at: Scorpion Sound Products <--no longer in business
UPDATE: Templates have been created by Brian Austin for you to download and build the plates yourself (Thanks Brian!!!). Keep in mind that the rear deck plate template pictured is for the driver's side of the car, so the passenger side would be a mirror image of this template.
Rear Deck Plate Template Speaker Plate Template
I've also included a PDF file of my top plate templates that you can print and use as your own correct size template.
Which 6x9's should I buy?
You definitely want to get an efficient pair of 6x9 speakers. The efficiency of the speaker (also known as sensitivity) is actually more important than it's power handling capablabilities when using it with the low power factory amplifier. The sensitivity should be around 91db or higher (the sensitivity level for speakers are usually documented in their specifications). For example, most Pioneer 6x9's have a 93db sensitivity (very good) whereas some Alpine 6x9's only have an 88db sensitivity (not as good). The higher the sensitivity, the easier it will be for the factory amplifier to drive them, and the more output they will produce. I actually bought some cheap dual cone Radio Shack 6x9's ($16 each) to experiment with originally and they actually sounded pretty good (I think their sensitivity was 90db or 91db), but I later acquired those used Pioneers for only $10/pair from a friend (I returned the Radio Shack speakers for a refund). I personally recommend Pioneer because they have a high sensitivity level, usually have a polypropylene cone with a rubber surround (long lasting), and can be bought for around $80/pair brand new.
Is it necessary to remove the midrange/tweeter pedestals?
I removed the midrange/tweeter pedestals because the midranges were damaged, and I only intended to use the 6x9s as subwoofers anyway. Depending on the type of 6x9 you get and how your adapter plates are constructed, you may have to remove the pedestals as there may be some interference (some pedestals stick up out of the 6x9 a little bit and may contact the edges of the adapter plate's smaller opening).
Will it sound good/better if I use some 3-way or 4-way 6x9's?
When wired up directly to the factory amplifier (using the wires that were originally for the 4" woofer in the factory enclosures), the 6x9s won't reproduce the higher frequencies accurately because the factory amplifier has built in crossovers. The amplifier's low pass crossover point for the rear speakers is high enough so that the 6x9 will put out a lot of midrange (too much), but won't produce enough higher frequencies to balance out the sound. This is another reason why I wouldn't waste too much money on expensive 3-way or 4-way 6x9's, because you won't get the full range of sound from them due to the amplifier's built in crossover network.
Are the low pass coils really necessary?
I personally didn't like the sound of the 6x9's without the low pass coils, which is why I added them. Without the coils the 6x9's overpowered all the other speakers in the car with way too much midrange.
Are the high pass capacitors for the front kick panel speakers really necessary?
I highly recommend using the high pass capacitors (aka - "bass blockers") on the factory front kick panel speakers. My front kick panel speakers were popping with distortion at higher volumes, even though the 6x9's sounded great, because the kick panel speakers are trying to reproduce the same low frequencies that the 6x9's are now providing, but are not as capable for this task as the larger 6x9's. The high pass capacitors eliminated the popping from the fronts by blocking those lower frequencies from going to the kick panel speakers. You can read more about low pass and high pass crossovers at PAC Audio
Where can I purchase the low pass coils and high pass capacitors?
The low pass coils and high pass capacitors can be purchased from any high-end car audio shop. They'll either have them in stock, or they should be able to order them. Just ask for two 5.1mHy (mHy stands for "mili-henry") 125Hz low pass coils and two 265mfd (mfd stands for "micro-farad") 150Hz high pass capacitors. The pair of coils should run about $30, and the capacitors (aka "bass blockers") should be around $10 to $15 for the pair. You might also be able to source these parts online from such places as Crutchfield.com or PartsExpress.com
How are the 6x9's wired up to the factory amplifier?
The factory rear speaker wire plugs (for my '95 M3 10-speaker non-HK system) have 4 wires in each plug. The two outside wires are for the tweeters and the two inside wires are for the woofers (which you'll use for the 6x9's). I just snipped the two inside wires off about 3 inches away from the plug (leaving enough room to reconnect them if I ever decide to return it to the stock setup), and used some crimp-on blade terminals that most speakers use. You can get these connectors, or any others that you might need, at most auto parts stores, any Radio Shack store, or car audio shop.
What are the color codes for the factory amplifier wiring?
Here is the rear speaker color codes for the 10-speaker non-HK system in my '95 M3...
(Note: this speaker wiring may be different for older or newer E36's)
yellow = left tweeter positive (do not use)
yellow/black = left woofer negative <---this one goes to the (-) of your left 6x9
yellow/grey = left woofer positive <---this one goes to the (+) of your left 6x9
brown = left tweeter negative (do not use)
blue = right tweeter positive (do not use)
blue/grey = right woofer negative <---this one goes to the (-) of your right 6x9
blue/violet = right woofer positive <---this one goes to the (+) of your right 6x9
brown = right tweeter negative (do not use)
And here is the front kick panel speaker wire color codes...
blue/white = left front woofer positive
blue/brown = left front woofer negative
blue/red = right front woofer positive
blue/brown = right front woofer negative
A detailed wiring diagram of a factory 1995 E36 non-HK stereo system can be found in the E36 stereo section of UnofficialBMW.com.
How do the low pass coils wire up with the 6x9's?
The coil is wired up in series with the 6x9 on the positive wire. So... for example, on one side of the car, you'll take the positive speaker wire coming from the amplifier (that was originally for the 4" woofer) and connect it to one end of the coil. The other end of the coil will connect to the positive terminal of the speaker (either directly or with a short length of speaker wire). The negative speaker wire coming from the amplifier will just go directly to the negative terminal of the speaker.
How do the high pass capacitors wire up with the front kick panel speakers?
The high pass capacitors wire up on the front kick panel speakers the same way the low pass coils wire up with the 6x9's.