DIY: Install Aftermarket Head Unit into factory Bose sound system (PIX)
Hi,
Just wanted to share with you my DIY install of an Alpine CDA-9845 stereo head unit. I always regarded the factory Bose sound system to be a very good sounding system from the very beginning. It is well balanced, demonstrates excellent sound imaging, and just plain sounds great from low to high volume. 11 speakers all powered from 1 Bose amp, all made in the USA. I did some disassembly and found the 6 disc CD changer is made in China and the Becker 1462 HU is made in Germany. Unfortunately, the amp does not appears to have any provisions to adjust and raise the gain since my Alpine only put out 2V max.
Anyways, I had an old Alpine HU laying around after I sold my Toyota last year and decided to experiment and see if just changing the HU would impriove sound and add some updated features like MP3/WMA capbility and AUX input for my XM radio. After cruising the boards here, I realized there would be a few trade offs.
First, an ideal HU would be one that features a 4-8V preamp output but my Alpine has only 2V max. My ideal HU would be a Nakamichi CD-500 with 24 bit DACS, audiophile grade preamp (4V), AUX, and MP3 ability. Maybe in the next few months...
Second, a few stock features would be lost in my case: loss of speed depend voulme control and CD changer function. Another thing I also lost was the cool 1hr. Becker on feature w/o ignition key on.
OK, so here's what hardware you'll need:
1.) Harness adapter: Metra 70-1786 for any Mercedes 91-97, $29.99 from Fry's. This makes cutting and splicing unnecessary. The also facilitates a very quick swap back to stock.
2.) Antenna adapter: Metra 40-VW12 for European car 1988-up, $9.99 from Fry's. Self explanatory.
3.) Ground loop isolators (2X): Scosche ES-034, RCA style, $14.99 from Fry's again...I tried w/o isolators and there is a mad thump whenever you power up/down, switch music sources, change stations, change tracks, hit any HU button. Serious ground loop between HU and Bose amp. I spent a couple hours tracking it down but pulling panels and this well built machine made me nervous about breaking things...this ALSO cleaned up the signal path in a big way. At first, the Alpine sounded rather crappy but the isolators eliminated that issue.
So, ~$70 bux in all to convert.
First pix shows stock double harness for amp, power, ground, etc. Smaller harness is for CD changer but not used any more. Thicker single cable is antenna.
Second pix shows all wiring connected: HU to isolators then to harness which inputs to the amp. Othe harness wires are red butt connected, just match color wires to each other. Double check wiring diagram in harness instructions.
Third pix shows Scosche ground loop isolators which barely fit back in there.
Fourth pix shows the harness.
Fifth pix shows HU cage adjusted to fit in opening, 1 standard DIN size.
Sixth shows HU and trim installed.
Seventh pix shows Alpine faceplate and XM radio.
Eigth and inth show all plus AUX input to XM radio or any 3.5mm stereo plug such as my Samsung Blackjack II. AUX wire goes thru carpet between left glove box and right side center HVAC controls.
I'll spend the next few weeks evaluating the sound and may go with my first choice NAK CD-500. Used to have a Nak RD-350 HU in the Stang back in the day with Audio Control processors, Carver and PPI amps...(old school stuff).
Thank you so much for taking the time to document this so clearly. I have seen bits and pieces here on the forums, but you have really put it all together. As for the HU, I doubt you will get much better sound out of the Nak, since at that point, it will be limited by the capabilities of the Bose Amp and speakers. I would think the Alpine would give you great sound.
Thanks for the post, since I will be changing out head units on my '95 S500, a little bored and to add system Bluetooth.
I ordered the Eclipse CD7200, which has 8V pre-out, and built-in full Bluetooth (rather than wiring a system add-on module), a slick USB interface (you do have to add a iPod module for full iPod usability, then wierd ass equalization )Alpine's new mic system much better) etc..
So trade off's, but still the deck with full Bluetooth system functionality is under $400.
You can shop the harness and accessories on-line, ABT offers Metra accessories at sharp prices including prepaid US Mail.. the harness was $12, antenna converter like $8, and a good ground loop isolator I picked up from another website for $12 (and its a gold plated $30 upgrade model)..so like $32-$35 bucks for the all the adapters..
Just going to 4V preamp or higher would almost be a requirement. I can turn my Alpine volume to max with clean music and it gets very loud but doesn't clip or distort. I think it has more room to go higher. It is sounding very good to my ears this morning. XM is also improved since I am going from a tape adapter to AUX in. I noticed better channel separation and overall fidelity with music.
A couple of notes: the aftermarket HU will require you hooking up the amp turn on wire instead of the antenna power wire since the stock system requires both. The stock wire allows the antenna to go up AND power up the amp. If you hook the ant. wire only, then the Bose amp will power only during radio operation, not CD or other music sources.
I may shop around for those pieces on line and save since Fry's has a liberal return policy...
I read that about the way the Bose system is designed. For the most part I agree with the amount of time they spend integrating the Bose technology into our cars and how it would be difficult to improve upon that sound. However, the stock tuner is a total piece of crap, IMHO. The CD player sounds fairly good for most of the music I play. This upgrade to the HU, would probably fill out the rest of the system and provide some cool features (BT, USB, iPod). I will see if I can find the specs for the tuner, but I remember them being quite poor, very low S/N ratio and weak freq response.
Linear Mode
