The following is an e-mail question I sent to Bob Hazelwood who is a former product manager of A/D/S and currently works for Cambridge soundworks. He has been active in the past with posting valuable information in this board regarding stereo issues with the new E46. His answers follow my questions. I hope some of you find this useful as I have.
I have a 99 323i with HK and in dash CD player. I plan on installing 2 12" Infinity Betas in sealed enclosure that I took out of my previous car. I think I have the wiring figured out for the sub amp. Pretty straight forward. (plan on using RF 225.2 2channel which is also out from my previous car. (built in low/high pass X-over) Works well in driving these subs)
However I still have some questions..
Q1. I would like to replace the front speakers (3 on each door). You suggest that in your previous post that you should replace BOTH the speaker & the factory amp b/c X-over points are built into the amp. I plan on replacing the amp like you suggest. I would actually like to use a 4 channel to drive both the fronts and the rear fills. What features should I look for in an amp that I plan to use to drive the front speakers? Do they need to have line level inputs? Built in X-overs?
There are two ways to keep the factory speakers. Build a new passive crossover to do the job, or use 6 amplifier channels with electronic crossovers.
Of course the second method is the best, but also the most expensive. The first method involves a lot of trial and error to make something which sounds good, since nobody makes an exact match commercial crossover for the BMW speakers. With the HK version of the BMW system, the amp is a multichannel design with electronic crossovers. Each channel is pretty small at about 14 "real" watts. But the other thing to consider is that overall you'll get the most predictable results by simply replacing the front speakers with a good two-way set up and using a conventional amp. It will end up suprisingly cost competitive with either of the first two options.
You should connect the BMW head unit directly to the new amp using the line-level (RCA plug) inputs of the amp, NOT the speaker level inputs that installers tend to recommend. Everybody assumes that the BMW head is high power and they tell you you need speaker level inputs or converters - it's not, and you don't.
Q2. HK has a "HK" button just in front of the shifter. When turned on, it creates a surround effect which I enjoy. What effect will changing the factory amplifier have with this feature? I wish to preserve this feature.
Well, if you replace the factory amp, you'll lose this feature. On the E36's, (at least the one a friend had) this switch only affected the rears If it's the same way on the E46, then you might want to consider leaving the factory rear speakers connected to the HK amp and just replace the front amp/speaker combo.
Q3. Lastly, since the battery is located in the trunk, can all of the wiring stay contained within the trunk without having to run wires past the rear seats?
Yep. You should not have to run ANY new wires except for main power to the battery and a good ground wire from the new amps. All of the other BMW wiring can be used sucessfully.
Product Manager, Cambridge SoundWorks
'93 525i 5-sp. Sharked, BL/ss'd, H&R + Bilsteins BMW CCA (Boston)
Speaker sizes are different for the E46 from the E36, but the amplifier wiring is the same. a/d/s has all the information on speaker wiring if you call them at 781-729-1140. E46 information will be posted on the website very shortly, but you can have them fax you the information you need.
Their marketing people seem very competent, and willing to answer all your questions over the phone.