More factory amp help needed!

[onewhippedpuppy]

Ok, so I took apart my factory amp, intending to bypass the amp portion and wire directly to the crossover. Unfortunately, when I got it apart it looks different than I expected. Here's what I expected:
http://www.bimmer.info/forum/showthread.php?t=19977&page=3&highlight=factory+amp

What I have appears to be an amplifier only, it was mounted inwards in the driver's side rear quarter panel. I took it apart and it has none of the windings like a crossover does, and different connections. Did they make a change to the factory amps? Mine is a 3/95 build date. If so, where is the crossover/crossovers? Any help would be appreciated, it's in pieces now.

[Anthony (M5 in Calgary)]

Pictures please. I've never worked on an E34 stereo newer than a '93...

[onewhippedpuppy]

http://img103.imageshack.us/img103/3136/amp0013zs.jpg
http://img133.imageshack.us/img133/407/amp0024qr.jpg
http://img103.imageshack.us/img103/8472/amp0032vu.jpg

[onewhippedpuppy]

http://img103.imageshack.us/img103/4378/amp0040ld.jpg
http://img133.imageshack.us/img133/7110/amp0056nb.jpg

[onewhippedpuppy]

Sorry for the size and crappy quality, I'm at my in-laws and they don't have an image re-sizer, and a crappy digital camera.

[onewhippedpuppy]

Anybody have any ideas? I can't find any wiring diagrams, I really don't want to just put the damn thing back together again.

[genphreak]

Anybody have any ideas? I can't find any wiring diagrams, I really don't want to just put the damn thing back together again.You have a more up to date system. Your amp looks like a normal power amp instead of the bodgey booster we are all so happy about replacing, but I am no expert...

I would guess that they went to a line-level feed to the boot-mounted amp, and may have put passive cross-over components in line with the speakers themselves (ie mounted on the driver assemblies) as this is the way it should have been done in the first place...

Check out the feed from the head unit- measure the output to see. Perhaps connect it to a speaker to see if you get more than a peep out of it. If it barely makes any noise with the volume on half-way, I am right.

If so, you can simply replace the amp with an aftermarket one to get more power and/or add a sub. Either way, you won't get the results we've been getting in the eralier cars as your factory setup is probably better, but adding a sub should you do this will certainly help as you can probably imagine.

Has your car got a total of 6 speakers up front and 4 down the back btw or is it a different configuration?

Gee those pics sucked big time... :) Nick

[onewhippedpuppy]

This is what I get for taking a project with me. It's the same speaker configuration, I found what looks like the same pin-out for a '95 E36 amp, I may try checking voltages like you suggested, or just hooking up a speaker direct.

[SRR2]

You won't find inductive components in an electronic crossover. Why? Because they're big, expensive, and hard to mount, plus their functionality in a passive crossover can be easily synthesized by capacitors and active components. I don't have any information on that circuit, but I can state with confidence that the crossovers are there, and you'd find them somewhere just before the output amps.

With more information about the circuit, I'm positive that you can accomplish what you're trying to do.

[onewhippedpuppy]

Further weirdness, my Sony HU doesn't have any sort of OEM interface adapter. The speaker outputs are wired to an adapter that connects to the BMW wiring harness, that's it. So my factory amp is getting an amplified source from the HU. Probably a big part of the reason it sounds like crap. I may try purchasing one of these before I go any further with modifying the amp.

A small note about the amp, I think it still has a built in crossover. The pin-out that I have found has seperate outputs for each mid-bass, midrange, and tweeter, so they must not be built in.

[SRR2]

I would guess that they went to a line-level feed to the boot-mounted amp, and may have put passive cross-over components in line with the speakers themselves (ie mounted on the driver assemblies) as this is the way it should have been done in the first place...

No no no! To the extent possible you want to have the crossovers BEFORE any amplification. The reason is simple: when you have waveforms with significant bass content, the high frequencies are riding on top of that and are the first thing to go to hell when the peak of the waveform hits the rails. IOW, it would sound MUCH less powerful than the specs claim. You can think of it in much the same way you think of separating frequency bands prior to the speakers -- the amps can be optimized for the range they're carrying similar to the way speakers are. But more importantly, the waveforms on the output no longer have full-range content, which tends to keep the highs a lot cleaner.

[Tiger]

I installed my HD radio without the OEM Interface adapter... that $30 line adjuster... but my head unit is a floating ground head unit like the factory. Maybe that is why you got crappy sound while I got great sound.

Maybe Sony headunit used common ground setup instead of floating ground. Send me the model number of that Sony headunit and let me see if I can find out from the owner's manual. On the headunit itself... is there any sticker or label warning you that speaker grounds must not be tied together, etc?

You do have the wiring harness that hooks up to factory wiring harness... normal.

Wanna buy my OEM adapter? I got it from Crutchfield. Never hooked up.

There is one thing I want you to try... adjust your fader... heavier to front... If you got up to +5... try +2 or +3 Front. Does it sound clearer? or same?

Try adjusting your tone... if bass too heavy, dial it back... treble too high, dial it back and vice versa. Any change in sound quality?

Are the wiring direct to corresponding colors? No bundle up of 2 or more wires together?

[Anthony (M5 in Calgary)]

Sorry for the size and crappy quality, I'm at my in-laws and they don't have an image re-sizer, and a crappy digital camera.


Pix are fine. Never seen this type. What are the 5 chips with heatsink tabs? TDA2005S?

Looks like this is still a booster amp setup (speaker level input to amp) but instead of 4 mono power chips driving a passive crossover network there are now 5 chips running in stereo for 10 discrete active crossover outputs.

One way to drive this system will be to add a separate passive crossover setup and another amplifier. I don't know if an older booster amp is correctly pinned to plug in or you could use it for its crossover and drive it from the head unit's speaker outputs.

SRR2 is absolutely correct about the improvement active crossover gives you. If you had a head unit with a built-in subwoofer output it could be set up to filter the lower frequencies from the speaker outs (effectively converting the OE booster amp to a high-pass amp) which would drive the factory speakers to higher SPL without distortion. Adding a separate amp and sub would round out the package.

I don't see an easy out here.

Be careful testing speakers by connecting full range signals - you may be wiring directly to a tweeter or midrange and the low frequency signals will kill them.

[onewhippedpuppy]

I didn't have a concise wiring diagram, or at least one I trusted, so I just put it all back together. Thanks for all your help guys, I may just leave well enough alone. I may look at adding a seperate amp and crossovers in the future.

Tiger, oddly enough all the adjustments have the effect that I would expect. It puts out pretty well before it starts to seriously distort. There's no mention of floating grounds in the manual.

[Russell]

How do you guys Know this stuff? Are some of you electrical engineers, sound systems developers, installers or what? I am impressed when I see all this dialogue on sound systems. Way above me. Also,I think my 95 stock systems sound fine. Execpt, I set the bass lower as I thought it "boomed" too much. Hey, what do I know!

Just wondering.

[Derek A.]

You might want to try and see if you can plug an older style amp into your speaker out plug. I would assume that that wiring wouldn't have changed. If you can get an older one to work - you are still in business. The only think you are going to need from the existing wiring in is turn on power.

The piece you have is made by alpine - us older folks have Blaupunkt stuff installed from the factory.

[Tiger]

Boom is easily controlled in stock system... just dial back your bass 2 notches... and you will like it alot more.

[Tiger]

The reason I asked about the fader is that by moving the fader... you not only bring more to front... but at the same time you are lowering the overall signal output to the amp... therefore it might sound better... you just have to crank up the volume more to reach the same sound as before... But overall... it should be less distortion.

As for the wiring harness... what I meant is one wire to the other wire... there are no two, three or 4 tied together or something like that.

[Russell]

That's what I did. Think I saw it in the archives or was it the roadfly archives?? :)

[SRR2]

The factory amp expects speaker-level inputs. Take out the "interface" you don't need it. It can only make things worse and degrade the signal. Drive the factory amp with the (+) outputs from the HU. Leave the (-) outputs open and insulated.

[genphreak]

No no no! To the extent possible you want to have the crossovers BEFORE any amplification. The reason is simple: when you have waveforms with significant bass content, the high frequencies are riding on top of that and are the first thing to go to hell when the peak of the waveform hits the rails. IOW, it would sound MUCH less powerful than the specs claim. You can think of it in much the same way you think of separating frequency bands prior to the speakers -- the amps can be optimized for the range they're carrying similar to the way speakers are. But more importantly, the waveforms on the output no longer have full-range content, which tends to keep the highs a lot cleaner.Agreed, but practicality is important. In these cars the crossovers are after the amplification for this reason- even the booster amplification as (most of us) are all to gut out the old booster amp and provide a new full-frequency high-level signal from our aftermarket one/s.

I can't imagine tri-amping in a production car is really an option as it triples up on number of power amps required, though when one goes to the trouble of building these tailored-type boxes I agree it isn't really much more effort... I just think these booster arrangements are antiquated and were a really bad way to go sonically- whish I find surprising as they went to so much trouble to have eq modules for different interiors and integrated splits all over the place at a time when competitors were just about gettting their heads around installing coaxial drivers and 15W/ch head units. :) Nick

[genphreak]

Pix are fine. Never seen this type. What are the 5 chips with heatsink tabs? TDA2005S?

Looks like this is still a booster amp setup (speaker level input to amp) but instead of 4 mono power chips driving a passive crossover network there are now 5 chips running in stereo for 10 discrete active crossover outputs.

One way to drive this system will be to add a separate passive crossover setup and another amplifier. I don't know if an older booster amp is correctly pinned to plug in or you could use it for its crossover and drive it from the head unit's speaker outputs.

SRR2 is absolutely correct about the improvement active crossover gives you. If you had a head unit with a built-in subwoofer output it could be set up to filter the lower frequencies from the speaker outs (effectively converting the OE booster amp to a high-pass amp) which would drive the factory speakers to higher SPL without distortion. Adding a separate amp and sub would round out the package.

I don't see an easy out here.

Be careful testing speakers by connecting full range signals - you may be wiring directly to a tweeter or midrange and the low frequency signals will kill them.Agreed- i really didn't take a close enough look. This is a booster amp. But here the PCB for the crossover and the booster are integrated (in the earlier e34 it was separate), so gutting it is not possible without a circuit diagram so you can use the requisite electronic wisdom, intelligence and the right info to tap the right lines.

However as Anthony and SRR2 have suggested the crossover may be a line-level one in your unit (working on the pre-boosted signal). If the amp setup is different (I assumed the chips were the same as they look similar to the earlier ones I am familiar with) they may have done this for reasons suggested earlier and to reduce size and cost of the crossover components. That would make it simply impossible to gut this setup: In this case you can only replace it with a complex arrangement of amplifiers and line-level cross-overs to drive each speaker in your system with the right frequencies, and would be an excersice in adjustment trying to get the cross-over frequencies adjusted right, somehting BMW have spent considerable time doing. I think you'd be better off finding an older e34 amp (from a 535, say) and gutting that instead; (so long as your speakers are the same and you have the speaker connection pin-outs from your wiring loom (and the 535 amp) you can do this without too much trouble). I can't say how great it sounds once there is a real amp running everything and a sub to give it the bass it always lacked.

:) Nick

[SRR2]

Well, I don't know anything about what's in your car, but my '89 535 had individual channels for each speaker. As far as the number of amps is concerned, that's no big deal. The amplifiers are very cheap. They're single-chip devices with amplification and power stages together in one simple package. In quantity, they're probably under $1USD each.

The audio in that '89 was satisfactory for my purposes, however I never expected it to achieve concert-hall levels, nor did I expect it to produce window-rattling bass. But it worked well enough for the 16 years I had the car.