5 series head unit to amp question. Non DSP - BMW Forum - BimmerWerkz.com

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post #1 of 7 (permalink) Old 10-17-2005, 02:56 AM Thread Starter
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5 series head unit to amp question. Non DSP

: Hi everyone and thanks in advance for any help you can offer me on this subject. I have done countless hours of reading but am not sure I got the answer to this one.

I bought a new head unit that has a built in amp that pushes out 50w X 4. Is it ok to "connect" the head unit to the AMP?(when I say "connect", I mean that the wiring harness from my Head Unit is matched witht he BMW wiring harness that is already there. Which would result in my HU's 50w signal going straight to the amp) P.S. (if I am wrong in this assumption, please tell me)

Would this cause a problem as I am thinking( and I sure might be wrong) that the amp is what amplifies the signal to the speakers. Usually, an amp is fed a standard signal from the factory head unit and the amp does the rest. However, what if the signal coming from the head unit( to the amp) is already amplified at the specs I mentioned earlier. Does this pose some type of problem for me?

So for BMW E39 owners, please give me your advice:

1. Leave the factory amp? Does it sound ok? will it be a problem?(Ok being 10x's better than stock) haha
2. change the amp? (sounds complicating and it is so hard to find an amp in Japan. surprisingly.

Again, any help would be greatly appreciated.

Last edited by greenwave; 10-17-2005 at 07:15 AM.
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post #2 of 7 (permalink) Old 05-27-2006, 08:21 AM
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it will be ok to connect your new headunit to the amp through the harness. the new headunit is not actually 50watts by the way. that's it's peak output. it's probably under 20watts normally. getting an aftermarket amp will probably be a pain as you have to get 2 or more amps if you have a 10 speaker system. i would get new speakers before getting amps for stock speakers.

buy a wiring harness made for your bimmer so that you don't have to cut your car's wires, it will save you a lot of time and headache.
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post #3 of 7 (permalink) Old 05-27-2006, 11:04 AM
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Going with an aftermarket amp and using the stock wires is possible if you do some careful planning. The stock wiring is actually very good, all twisted pair to cancel out noise. I hooked an aftermarket amp into the stock head unit along with a subwoofer. I used wire taps to hook wires from the 4v preamp outputs of the stock headunit to RCA leads into the amp, the same for outputs from the amp to the speakers. The two sets of harnesses coming out of the amp are a mixture of inputs and outputs, ground, power, etc. There is a plethora of info on the wiring diagram for non-dsp setups, do a quick search around this website or google and you can find what you need. I found the stock amp to really not have enough power for my musical tastes. Replacing my amp, adding the subwoofer, and doing all the wiring took me about 6 hrs total. I also replaced the front tweeters and woofers, leaving the midrange speaker disconnected, since I did not have an output on my crossovers for it. It sounds amazingly better now!!

Also, when hooking up a sub, the trunks are pretty well sealed - placement and subwoofer type is key. You have to really crank the bass up good to hear it at a good level inside the cabin. Having the ski passthrough option in the rear seat would help out. I use a 10" MTX sub in a sealed box, and its plenty of bass for my taste. I would like in the future to possibly check out one of those Infinity self-powered subs, they take up tons less room and I hear they are nice and powerful.

and yes...BUY A HARNESS for the aftermarket headunit.

Jason / 1997 528i
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post #4 of 7 (permalink) Old 05-30-2006, 02:11 AM
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Buy the harness. Install your head unit, nuff said.

Honestly, your sound should improve from running the 4x50w amp in your head unit, your amp will step down the wattage on its own, but for signal integrity, the more power the better. The only caveat bieng the stock speakers, and whether you decide to leave them or upgrade them.

If you plan on aftermarket speakers, or a full sound system, however, the stock amp in that car is too low of a wattage to run aftermarket speakers with even a hint of clarity or clean sound in general. Here's the order I'd reccomend for upgrading your complete sound system.

1. 4 Channel amp
2. Rewire (Not difficult at all, takes about an hour to get everything nice and hidden)
3. Mono/2 channel bridged amp
4. Subs, (Don't go too crazy, 2 15" component subs are overkill, you do drive a BMW, you don't need earth shattering bumper loosening basslines)

4 channel amp and some decent two way/three way speakers, for the e34, they're some odd size like 5 1/4 if I remember correctly, not sure about the e39, if they're 6" or above, you can probably ignore the rest of this unless you're an audiophile. You'll want subs eventually, since with such a small speaker size (5 1/4 as oppoosed to 6x9) , you won't really get all that great of a boom from them. You will, however, be happy with the results for about 6 months to a year, so you'll have some time to think about it.

when you install that amp, ignore the stock wiring, its too small of a guage to be useful, and you'll spend DAYS trying to figure out the stock wiring harness and what goes where. Just get some decent speaker wire, and hide it behind some panels, its not hard with all the trim in the doorsills to sneak it under. The location of the battery is also sorta nice for this kinda setup. You won't have to worry too much about running power wires, just punch em through to the trunk through the openings BMW so graciously provides. Worst case, run them up the seat through the ski bag opening, its not hard to punch through and is hidden by your rear folding armrest.

All in all, for just adding a head unit, the BMW sound system isn't that bad. But as with all things car/car audio related, you sorta get stricken with some sort of fever that makes you want more and more and more.

Last edited by d3ity; 05-30-2006 at 02:15 AM.
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post #5 of 7 (permalink) Old 07-20-2006, 11:40 AM
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Just went through this problem myself and it can be fun or a real pain, depending on what you end up doing.

I have replaced the Head Unit and removed the stock Amp, I designed, fabricated and mounted my own 2nd order passive Xover to run the stock speakers.

I took many hours of wire checking and numerous diagrams to finally get a true wiring drawing for my 535i stereo system. BMW has done a great job on the wiring with the exception of a missing set of grounds for the replacement head unit.

I respectfully disagree with d3ity on "ignore the stock wiring, its too small of a guage to be useful,". The stock wiring system if of excellent quality and the twisted pair configuration has great noise cancelling properties.

BMW wired their head unit to utilize a common ground on the left side and one on the right side. My aftermarket head unit (Kenwood) did not like this configuration and therefore I had to run a second pair of grounds to the rear of the car.

BMW designed the speaker placement with care and replacement of speakers IMHO should be well planned. So if anyone knows where to find good replacement speakers PLEASE let me know, thanks

I have to add a sub to my system and that is next on the project, if I had been thinking I would of added the output on my Xover network but alas had a brain fart.

Great thread here and thanks to all for their informative ideas and comments.


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post #6 of 7 (permalink) Old 06-20-2007, 06:57 PM
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hey Jason,
I have same car like yours. I am trying to upgrade the sound system. I bought mbquart qsd213components for front and rear powered by alpine pdx4.150 and alpine 9885 head unit and now shopping for alpine pdx 1.6 amp and sub. also i am not good in electroincs so don't know what kind of sub and where to place then in trunk. Any ideas i will really appericiate. Thanks for the help in advance.
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post #7 of 7 (permalink) Old 06-28-2007, 11:23 PM
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I recently traded out my 10" MTX for a 12" Kicker Solobaric (old round style) and all I can say is WHAT A DIFFERENCE!!. Requires much smaller enclosure (translated = more trunk space), much louder, so I can actually have some control over my bass since I dont have to have it at full level anymore just to hear it.

I have always had Kicker solobaric subs (aside from the MTX) and I will never stray again. My sub is just in a small enclosure that fires sideways, pushed up in to the back of the trunk. If you have any other specific questions, let me know! you can email me at jasonawinters@bellsouth.net as well, as I'm not on this forum that much these days.

Jason / 1997 528i
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