E30 Audio Overhaul - My Project Details

[jscribble]

Any chance you could post a pic of the hood latch after spacers? Mine is pretty well pressed against my speaker. Never looked at spacing it, but that just might be a project for this weekend.

[bmwman91]

Any chance you could post a pic of the hood latch after spacers? Mine is pretty well pressed against my speaker. Never looked at spacing it, but that just might be a project for this weekend.

I am not sure if I can get a camera up in there. Basically, chop off the part of the cover that goes under the latch (follow the hard molded edges). You could probably stack 10mm worth of washers under the release latch if you taped them together first.

[jscribble]

I am not sure if I can get a camera up in there. Basically, chop off the part of the cover that goes under the latch (follow the hard molded edges). You could probably stack 10mm worth of washers under the release latch if you taped them together first.

Thanks for the tip. I poked my head under there yesterday, discovered that my seat slide rod disconnected, and decided it was too hot to continue. Front brakes were enough yesterday.

For those without the tweeter pods, my car has pods mounted to my oem blank panels. It looks almost oem, but if you really wanted to get that look it wouldn't be to bad to mold them in with some body filler.

BMW should hire you to design audio systems. GREAT work, bmwman91.

[bmwman91]

Update time:

I think I am done with the amp mods for now. There is one nagging issue left, but that will probably take more time than it is worth. I'll explain at the end of the post.

To start, I wanted to bypass the CH5 crossover so that the nice Audio Control unit I bought could handle that. Crossing over at 220Hz is maybe a little uncommon, but I want to give it a shot since simulations look promising with this crossover frequency. I also like to try to distribute the acoustic energy in decades to reduce distortion in the drivers from nonlinear excursion.

I traced out the input stage with a DMM. Painstaking work...4 layer boards are a pain.


After some jumping & rearranging a resistor...


While I was in there, I replaced the opamps with some true audio-grade ones. The stock ones are MC4558's. Their replacements are OPA2134's which are well regarded for their performance characteristics while still being of a reasonable price.


I replaced 7 total. All you need is some desoldering braid, tweezers & a soldering iron with a needle tip.



The other big project was getting the gains matched & locked in for all of the channels. I don't trust cheap potentiometers because a)vibration makes them shift value, and b)double pots are notorious for having poorly matched resistances (gains varied 8% between CH3 & CH4 with the stock pot). So, I got out my trusty scope & signal generator & did this for all channels. After giving myself a little margin to avoid clipping (outputs generally don't get ALL the way to the rails) I removed the pots & installed some resistors. Yeah, it is sort of ugly, but it is how you get exact odd-ball values.

The gains were set to provide maximum unclipped output with the maximum input signal (13.5V peak) received from the 6XS.



Crazy resistor mishmash goodness!


I was glad to be done with all 5 channels. What a pain!


Just one more close-up of some mods. I did not replace ALL of the opamps since the ones related to the crossovers aren't getting used at all. Maybe if I go & sell this someday I will replace them all if the buyer doesn't want to use an external XO. Spot the "better" ones!


So I had mentioned one annoyance at the start of the post. Well, channels 1, 3 & 4 are perfectly matched. For a given input, they are within 10mV of each other. For some reason though, CH2 behaves differently. The gain in the power stage must be a bit higher than the others, and maybe its biasing is tweaked (probably due to tolerances stacking in cheap components). Its output can be up to 2-3V higher than the other channels at high outputs for the same input, and it clips 3-4V higher (it goes ALL the way to the rails while the others don't). I spent some time with a DMM trying to map out the stage, but it is too much work since I cannot remove that board from the case to see the bottom traces (I could, but I would mess up the transistors' heat sinking). It is probably just a bias resistor that it out of whack. Still, the difference is really only prevalent with really high outputs and I don't plan to operate there much anyway. It might be time to leave well-enough alone!

[bmwman91]

Thanks for the tip. I poked my head under there yesterday, discovered that my seat slide rod disconnected, and decided it was too hot to continue. Front brakes were enough yesterday.

For those without the tweeter pods, my car has pods mounted to my oem blank panels. It looks almost oem, but if you really wanted to get that look it wouldn't be to bad to mold them in with some body filler.

BMW should hire you to design audio systems. GREAT work, bmwman91.

Haha thanks. There are probably reasons why they don't build audio systems the way audio enthusiasts think they should. The main reason would be cost. They know that a)most people see a Bose or Harman-Kardon label & assume it must be good, and b)nobody would be willing to drop $3000-5000 for an audio package on their car (that is what it would cost with mark-up & installation).

It's OK though. This is probably mostly an exercise in anal-retentive masturbation. It's a freaking car full of engine & road noise. I shouldn't be spending this much time & money on it...but if I am going to do something it has to be done right lol.

[bmwman91]

Well, it looks like I am good to go now. After installing the LC6i the ugly alternator whine disappeared. I want to say that I knew it would work, but I was only 90% sure that it would (and that 10% uncertainty had me sweating!). Yay for differential signals & inputs.

I have been spending some time trying to get the bass/mid/treble gains set well on the 6XS. Due to the crappy placement of the mids in the stock locations, I have the gain for them cranked up considerably higher than the other bits. I need to get out there with an oscilloscope again & re-adjust the gains now that the LC6i is in place, so I will tune around having the mids maxed out with the HU on the verge of clipping. Then from there I can tune the bass & treble by ear since their gains just need to be less than the mids' to avoid clipping.

Oh and my CD43 still skips when I hit medium/large bumps. That's annoying. I need to pull it & check the CD carrier. This seems to be the project that will never end.

I also have a cargo net that I need to install in my trunk to keep things from sliding into the sub/LC6i/6XS.

[longtallsally]

Pics of the sub setup?

Good stuff as always.  I actually got a ski pass through seat recently based on your findings...

[bmwman91]

I'll try to get some shots up at some point. The one thing you need to be mindful of with a sub mounted in the ski pass hole is stuff sliding around n the trunk. Right now I have everything tied down with bungee cargo nets, but there aren't too many good places to attach them, so 70% of my trunk is unusable for now. I'll probably do a little welding to make mounts for a real cargo net that sections off the front 8" of the trunk so stuff won't slide into the sub/electronics.

[nickmpower]

how filling is the sound? i have a sub and front speakers and i am thinking of putting rear speakers back in because the sound is not very filling. But I also have the tweeters down in the kick panel

[longtallsally]

I'll try to get some shots up at some point. The one thing you need to be mindful of with a sub mounted in the ski pass hole is stuff sliding around n the trunk. Right now I have everything tied down with bungee cargo nets, but there aren't too many good places to attach them, so 70% of my trunk is unusable for now. I'll probably do a little welding to make mounts for a real cargo net that sections off the front 8" of the trunk so stuff won't slide into the sub/electronics.

Thanks.  I'm pretty sure I know what you did, but just wanted to get some ideas.

I also agree on the bunjee nets.  I've wanted to do those for years in my E30s, however, do you think welding the mounts in is the best idea? I just spent yesterday welding on the frame of a buddy's Jeep and I'd be real concerned with burn-through on the E30 chassis.  It seems that it might be more prudent to drill some holes and mount via bolts.  What I've never been able to decide is if I want to put the mounts on the floor, bulkhead (kinda moot if the sub is there), strut towers, or the rear.  If you do any of those, I'd be very interested for more ideas.

[bmwman91]

Thanks.  I'm pretty sure I know what you did, but just wanted to get some ideas.

I also agree on the bunjee nets.  I've wanted to do those for years in my E30s, however, do you think welding the mounts in is the best idea? I just spent yesterday welding on the frame of a buddy's Jeep and I'd be real concerned with burn-through on the E30 chassis.  It seems that it might be more prudent to drill some holes and mount via bolts.  What I've never been able to decide is if I want to put the mounts on the floor, bulkhead (kinda moot if the sub is there), strut towers, or the rear.  If you do any of those, I'd be very interested for more ideas.

When I come up with something I will let you know.

I agree that welding will be tricky. The body metal is thin, and I am sort of afraid that my MIG will burn though. I just dislike drilling holes & bolting since that can increase the risk of rust & water leakage. I guess that I could try to find some rubber washers & coat everything with PVC paint though. That might be better.

If I did put mounting points in, I think I would place 2 under the rear deck as close to the sides as possible (no risk of rust there), and then 2 directly under them on the bottom, OR on the bottom of the shock towers.

[bmwman91]

Bumpity bump...

I updated the (completely unnecessary) installation diagrams in the original post. Since I first made them, I have had a lot more time to get comfy with Inkscape, so I made them pretty.

Anyway, I will try to get out tomorrow afternoon to take some pictures of the finished product. I still need a new passenger side kick panel. The one that is in there is fugly thanks to some "creative" ideas I had with it a while back. Eew.

Also, does anyone happen to be parting out an E36 that has the diversity antenna & related electronic bits? The CD43 gets terrible reception with the E30's stock, unamplified single antenna. At the very least I would be interested in trying a stock E36 antenna signal amplifier box to see if it helps things at all.

And once again...I love this system. Time to find a used RTA to see just how technically good it really is!

[DesktopDave]

e34's and e38's have very similar diversity boxes, all mounted in the 'c' pillar.  They'll likely be cheaper than e36 parts.  I'm not sure why.  The e34 and e38 seem less loved than our 3-series.

[bmwman91]

Good to know, thanks! I'll have to snoop around on realoem & see what came with what!

[bmwman91]

Oh, and if anyone wants vector-art copies of the diagrams let me know (.svg format). The CD43/electronics art blocks can be used by anyone else with an interest in making these diagrams. Use them for whatever you want (personal/profit/whatever).

OK, as promised here are some pics of the final installation.

The CD43, installed. I have messed with it a little (took it apart, cleaned the optics & checked the springs/dampers) & that helped reduce the skipping. Radio reception is still awful though. If only there was another factory BMW CD player option...


Tweeters...installed.


Driver's side mid. I need a new kick panel cover.


Passenger's side mid. I REALLY need a new kick panel cover! That, and a clean way to attach the back portion to the body so it isn't sticking out so much. Since this cover is ruined already, I will experiment with a heat gun to see if I can re-shape it to sit in there better.


The electronics. The wiring isn't perfect, and I do need to tidy up the stuff on the right.


Yeah I know, you shouldn't have rat's nests for signal lines. It's a car...road noise dominates over anything that might come from ugly RCA cables. I don't hear any odd stuff anyway.


The outputs. Again, it isn't exactly aircraft-grade. It works.


Here is the sub peeking from behind the arm-rest. I do not hear any difference with the arm rest up & closed, or down & open. So, I leave it up. Any attention is bad attention in my opinion, so I like to keep this sucker as stock & boring looking as possible.


I avoid loose articles in the trunk, for obvious reasons. I can still jam all of my climbing & camping gear in there without any worries (it might slide a little, but I can arrange it so that nothing hits the sub or the dials on the electronics.
Yes, a hatchet, 8" knife, fire extinguisher, MAG light, various fluids, a cheap set of tools & sockets & a box of electrical supplies are necessary. For one, I drive a 20 year old German car...duh. Also, I don't like getting stuck by trees that have fallen onto the road & that sort of nonsense.


So there it all is. The sound is very nice. I still need to swap out the 9-conductor cable for some CAT6 cable...there is a very faint bit of alternator whine present when I am revving the motor hard & whatever is on the CD/radio is quiet at that time.. It is completely unnoticeable except under very specific circumstances, and I am the only one who notices...but I still want to get rid of it. I hope you all enjoyed the pictures & story!

Oh, and here is what I did to clean up the rear deck since I am not using the rear speakers at all.
http://www.m42club.com/forums/showthread.php?t=12511