mr_mbuna

I'm having a problem with the audio setup in my car. Hopefully someone here can help. Just for background info, my audio components are:

-Blaunpunkt San Francisco CD70 Headunit
-US Acoustics USX-4085 4-channel Amplifier (85w RMS x 4)
-MB Quart Premium Series PSD 216 6.5" Front Component Speakers (85w RMS)
-Infinity Reference 6952i 6" x 9" Rear Coaxial Speakers (100w RMS)
-New Power, RCA, and Speaker Wiring

The problem I am having is an intermittent "crackling" or "staticy" sound on my rear speakers (*UPDATE*: Problem occurs on front speakers as well.). Not so strange in and of itself - just replace the rear speakers, right? - but look at what I have learned from my troubleshooting:

-Problem still occurs after replacement speakers have been installed
-Problem does not occur when engine is off
-Problem greatly lessens when A/C or Heat is On
-Problem usually occurs at high volume, but will also occur at low volume
-When fade is +9 (max front fade) and front speakers are disconnected, the problem does not occur.
-When fade is +9 (max front fade) and front speakers are connected, the problem does occur.
-Problem still occurs when Output Channel 3 and Output Channel 4 are reversed.
-Problem still occurs when Input pairs (1&2 aka front preamp from HU) and (3&4 rear preamp from HU) are reversed.
-Problem occurs regardless of whether seat back is up or down
-Problem occurs on a variety of music sources and genres.
-Problem does not occur when system is muted at headunit.
-Problem occurs on both rear speakers.
-Problem does not always occur at the same spot on the same music.

Everything was installed at a business. However, their line recently has been to keep swapping stuff out. So I called other larger and more reputable businesses, and they gave me some troubleshooting tips to try. From these tips, I obtained the above information. Please help.



A gallery of photographs related to these issues can be seen at: http://www.imagestation.com/album/?id=4291316453

The other thing that gives me pause is the closeness of my trunk torsion bars to my speakers. Take a look, and tell me if you think this is a potential problem:

Three pictures of the torsion bar proximity are located in the above gallery. Here is one as a sample:



Finally, those in the know, please take a look at the side of my amplifier that has all the settings and controls on it. Please confirm that these are set correctly for my application.



Thanks everyone!
Ben


[Modified by mr_mbuna, 3:27 AM 9/27/2002]


[Modified by mr_mbuna, 3:38 AM 9/28/2002]

gleinz

The only thing I can think of that you're experiencing some "engine whine" that is being picked up by your stereo system. I'd just check to make sure all the wiring is good...

kwhitelaw

Good job on the troubleshooting. Now, where is the amp grounded? You may try moving that. It may help to ground your radio outside of the factory harness and running new constant/ignition wiring. Since you say the noise lessens with the A/C or heat on you may be getting some bleeding through the wires where they connect at the fuse block. The fuse box is one of the noisiest parts of a car. Does your radio have an internal amp? Maybe try running the rears off of deck power and see what you get. If the sound goes away, then look at your amp or RCAs. If the sound stays, run a new pair of wires off the back of the deck straight to the speakers. Since you swapped the speakers that rules them out, probably. Lastly, if after bypassing the amp the problem is still there, look at the deck. Stick another deck in temporarily and see what you get.

Also, there is not much you can do about the torsion bars in your car. Those Infinity's have a rather large magnet. You may be able to space them up but then you run into a problem with trying to get the speaker grilles back on. As long as the bars don't get caught up on the magnet, you'll be fine. If it is rubbing slightly, take some velcro and wrap it around the bar to lessen the noise made from the rubbing.


[Modified by kwhitelaw, 8:43 PM 9/26/2002]

nsxxtreme

Check your grounds again and again. Ground the case of the deck to the car. Make sure the amp has a good clean ground.

I think kwhitelaw explained it well.

mr_mbuna

The amp is grounded to a body part, as shown in this picture of where the ground wire from the amp connects to the body:



And I don't think I'm up to all that swapping of the decks... ugh. When the shop installed my system, they ran new power wiring from the battery to the amp. Is this what you meant by "new constant/ignition wiring"? My radio does have an internal amp, but I don't want to a) run wires up to it, or b) waste 100w RMS speakers on a 45w x 4 MAX Blaupunkt internal amp.

Thanks,
Ben

kwhitelaw

Wiring the speakers to your deck is temporary. Just to rule out the amp. Slide the deck out and hook right to the harness. Disconnect your new wires under the rear deck and use the factory wires. When everything is done and fixed, hook it back up the old way.
It's hard to see the ground from your picture. Just make sure the paint under the bolt is clean of paint. What I meant by new constant/ignition wiring is the wiring that powers your deck. Typically, your constant and ignition wires tie into other wiring that uses constant and ignition power near the fuseblock. Such as the domelight, clock, AC/heater, etc. With all those relays at the fuse box clicking on and off all the time and all the wiring running in your car, it is possible that noise is being induced into your system. Running a ground off your deck straight to the chassis is a good idea also, as nsxxtreme stated.
Lastly, where are your speaker wires and RCA's run in respect to the power wire. Most people will tell you to run them on opposite sides. This is fine but not totally needed. You may want to check and see if the RCA's and/or speaker wiring run near your ECU in the passenger kick or the cruise control brain on the driver kick. You may be picking up noise from there also. Also check your factory grounds throughout the engine bay.

mr_mbuna

I paid a shop $341, incl. parts and labor, to install my amplifier, wiring, front speakers, and rear speakers. Should all this troubleshooting and re-work be done by them for free? I'm not sure how it usually works... does installation mean installation once or does it mean installation till its perfect?

Thx,
Ben

nsxxtreme

Yes they should be doing it for free. If it doesn't work correctly then it's not installed corecctly. for that long ground and the location they chose. What part of the car is that? It almost looks like the inside of a door.


[Modified by nsxxtreme, 6:10 AM 9/27/2002]

mr_mbuna

The plot thickens...

Okay, today I listened real close and it seems that the front speakers, at least the tweeters, also make this crackling sound. I heard them making the sound when the fade was -9 (all the way to the back). I also muted the music as the speakers were crackling (it is like an interference to the signal. the crackling does not overpower the music, which is why it makes it so hard to hear), and the problem stopped immediately. So, let me add two more qualifications to the problem list:

Problem occurs on front tweeters as well for sure. May also occur on front 6.5" speakers; hard to tell.
If system is muted while problem is occuring, the problem immediately stops.

nsxxtreme: I have a sedan. It has a fold-down trunk, and the amp is mounted on back of the seat. The ground is mounted to prolly the closest available body metal. Take a look (geez, its like I'm posting my entire ImageStation gallery!):



Thx,
Ben

mr_mbuna

I was talking to somebody at work today, and they felt sure that the cause of the problem was that the power lines and RCAs were run together, and I was picking up interference from the power lines. I am unsure whether they are run together or not, but he said he would be they were due to the symptoms I described.

Is this a plausible explaination? I really need some more opinions - but only if you are sure of what you are saying (don't want to shop to throw invalid facts back in my face) - before I go back to the installers to get them to fix it.

Ben

jdmotorsports

could be. but take tekens advice. make your ground as short as possible, use star washers and ground it to the floor. also make sure your power and rca are not on the same side.

mr_mbuna

Just came back inside from messing with the car, and I have new info. The RCA and Power cables are separated. Also, I am now positive that the problem only occurs while the car is on. When the car is off, the sound is perfect at all levels. So that should rule out component problems, right? And the problem is not altered / does not respond to changes in engine RPM.

Thanks,
Ben

fixhondas

Disconnect your RCA cables from the head unit- does the sound go away? If so, the noise is probably originating from your head unit. If it is still there, disconnect RCA cables from the amp and see if the noise is still present. IF it goes away I would say your RCA cables are not in great shape. RCA cables should pass over power cables at right angles and not run parallel.

Does this occur only with AM/FM? if so, your antenna cable may be compromised.

What brand ignition parts did you use- the distributor cap should be made by TEC and your wires should be made by Sumitomo if they are Honda parts. If they are not you should use Honda parts- aftermarket igniton parts are GARBAGE. Your plugs should be NGK or DENSO.

Check all engine grounds and be sure they are in good shape. Be sure to clean the metal on all audio grounds.

Turn the gain down on your amp as much as you can. Be sure your valve cover ground strap is decent.

mr_mbuna

fixhondas,

I haven't tried doing that but I'm pretty sure it won't work. The crackling only occurs when there is music playing. When I mute it, it stops. So if disconnect the music source I'm quite sure it wouldn't happen.

I did some voltage checking... and when engine is off, car is at 12.5v and system is great. When car is recently started, voltage is at 14.5v and system crackles. After driving a while and reaching my destination, I couldn't get it to crackle so I check the voltage and it was 13.95v.

So it seems that when my meter reads under 14 v at the battery terminals, the system is OK. What does this tell us?

Thanks,
Ben

fixhondas

What about these ideas- did you look into them???? AM/FM? try putting down your antenna. What yr/model is your car?

Something else you might try while the engine is running- smack the alternator with a large prybar, maybe your brushes are worn and not fully seated against the alternator's armature.

EndlEEsss

A lot of wrong things could be happening.
Your amp could be on its way to being RIP.
Crackling noises usually occurs when the + and - speaker wires are brushing against each other.
Whining noise usually bad ground.

This is what i would do:
Under normal condition, where the speakers crackles
Disconnect all the speaker wires from your amp except for one.
So start with the front left speaker and listen to it with the car on. and see if you have any cracking noises.
Then take that off and do the same thing for the other speakers.
that way you can isolate which one is crackling.
after you find one that is crackling run a NEW wire from the amp to the speaker for a test, and see if that crackles.
good luck, ill be back to see your progress

mr_mbuna

All the speakers are crackling. I had the installers redo the ground and they rerouted the power wire and tuned the amp (adjusted gain, etc.). Problem not fixed. So I get in there with them and they show me some stuff and listen to the problem for the first time firsthand (only happens when its cold; had to be nighttime) and they determine it is a bad amp. I have a US Acoustics USX-4085. Damnit. How can I double-check their analysis?

Ben

EndlEEsss

Why dont you get another amp from a big name retail store that you can return for trouble shooting?

freestylecustom

Im guessing you guys having this problem have two amplifiers?

VegaS10

This thread is 10 years old, and you really had to drag it back up?

Seriously?