Audio Problem, need some help

[vtm3]

I completed an audio upgrade with some help from the forum about a year ago. I did the sws8's two pdx 4.1's, one for subs and one for the speakers. I have base audio, I had a small problem with an amp and I also used an loc that was not necessarily needed, but took a lot of noise out of the system.
Everything was fine until aboout two months ago an intermittent problem arose. The sound will just cut off for a second. It seemed to be random, although I just now seem to be able to recreate it. When at a full stop or close to it, foot on the brake, let off brake and hit gas, about 50% of the time it will cut out. I had it diagnosed by audio shop before I discovered how to recreate it, and they could not reproduce the errorr, so of course they have no clue. I took it to BMW and they could not produce the error, but what they told me concerned me about the entire electrical system. They basically said everything from BMW was good, the aftermarket stuff they could not look at (I knew that) and my entire audio system in the car is pretty much "as is". Even if I could determine that it's a defective head unit, that the warranty is now void, because any replacement of anything aftermarket in the entire electrical system could have caused a surge that would disturb the balance in the precarious electrical eco-system. Does anyone have any thoughts on what to look at to cause the problem, and or any ideas on the validity of the warranty being void. I full expected anything after the amp in the system to be void, but the head unit does not seem to make sense.

[Technic]

Originally Posted by vtm3

I completed an audio upgrade with some help from the forum about a year ago. I did the sws8's two pdx 4.1's, one for subs and one for the speakers. I have base audio, I had a small problem with an amp and I also used an loc that was not necessarily needed, but took a lot of noise out of the system.
Everything was fine until aboout two months ago an intermittent problem arose. The sound will just cut off for a second. It seemed to be random, although I just now seem to be able to recreate it. When at a full stop or close to it, foot on the brake, let off brake and hit gas, about 50% of the time it will cut out. I had it diagnosed by audio shop before I discovered how to recreate it, and they could not reproduce the errorr, so of course they have no clue. I took it to BMW and they could not produce the error, but what they told me concerned me about the entire electrical system. They basically said everything from BMW was good, the aftermarket stuff they could not look at (I knew that) and my entire audio system in the car is pretty much "as is". Even if I could determine that it's a defective head unit, that the warranty is now void, because any replacement of anything aftermarket in the entire electrical system could have caused a surge that would disturb the balance in the precarious electrical eco-system. Does anyone have any thoughts on what to look at to cause the problem, and or any ideas on the validity of the warranty being void. I full expected anything after the amp in the system to be void, but the head unit does not seem to make sense.

Did you use the OEM remote turn on signal? If so, are you using a relay with it? If not, install one. Report back.

[vtm3]

Thanks, I did not put the amps in myself. But I know they did use the OEM remote turn on and 99% sure no relay. I will check, install and report back. I appreciate it!!!!!

[vtm3]

I had a relay put in and still the same. Hitting the gas pedal produces a second of signal loss. It does not seem to lose any power. It just seems to be complete loss of signal. It's still random, but the harder you hit the gas, the more often it losses signal. Any other ideas would be appreciated.

[808MGuy]

Originally Posted by vtm3

I had a relay put in and still the same. Hitting the gas pedal produces a second of signal loss. It does not seem to lose any power. It just seems to be complete loss of signal. It's still random, but the harder you hit the gas, the more often it losses signal. Any other ideas would be appreciated.

Loose connection somewhere? Maybe hitting that gas causes enough of a jolt to shake it loose just for a second. When the signal goes out, do you notice anything else like lights or the iDrive screen dimming. This would be an indicator of a voltage drop condition.

[Technic]

Originally Posted by vtm3

I had a relay put in and still the same. Hitting the gas pedal produces a second of signal loss. It does not seem to lose any power. It just seems to be complete loss of signal. It's still random, but the harder you hit the gas, the more often it losses signal. Any other ideas would be appreciated.

Is there any way that you can make sure that the PDX remain on while this signal shut down is in progress? Like, listening to that relay clicking at the same time that the signal is lost?

That will tell us if the problem is at the amps or at the OEM HU. If the amps shut down then you have a problem with the actual OEM remote line, thus with the OEM HU internals. If the amps stay on then you have an issue with either the OEM HU balanced outputs or somehow with the power going into both amps.

Are the gains of those amps at minimum?

[vtm3]

I have the car in neutral and hit the gas to produce the error. So it appears to be electrical not a jolt.
I do not believe I have the gains at minimum, but I will check and respond. All indications to me is something wrong with the OEM HU. The dealership has said because I installed an aftermarket amp that any warranty with the audio is now void(including HU). Has that been your experience?

[Technic]

Originally Posted by vtm3

I have the car in neutral and hit the gas to produce the error. So it appears to be electrical not a jolt.
I do not believe I have the gains at minimum, but I will check and respond. All indications to me is something wrong with the OEM HU. The dealership has said because I installed an aftermarket amp that any warranty with the audio is now void(including HU). Has that been your experience?

Yes, the audio warranty is void once you add aftermarket amps.

Set the gains to minimum; the PDX accepts 4V (not clear if it is peak or RMS), the OEM HU puts out 5V.

Where is the 12V connection for the amps?

[vtm3]

One line from battery to distribution block, that splits to both amps.

[quality_sound]

$10 says your alternator is spiking voltage when you press the accelerator.

[vtm3]

I had a AA pulley installed in November, could this be the cause? Combined with the audio upgrade? I thought it to be irrelevant but now I am guessing maybe not. And if you are correct, I will give $10 when I pick up my 2014-2015? ED M3

[Technic]

Originally Posted by vtm3

I had a AA pulley installed in November, could this be the cause? Combined with the audio upgrade? I thought it to be irrelevant but now I am guessing maybe not. And if you are correct, I will give $10 when I pick up my 2014-2015? ED M3

If the alternator is spiking then you should see other modules being affected, especially the lights. And most probably the dealer should have seen it as an error in ISTA/P.

Do the test at night with the lights on. Something else should at least flicker...

[vtm3]

Thanks man. Heading to work now. I will test it on the ride in!

[vtm3]

Nothing. Sound did still go out, and I could not detect any dimming at all. I read in searching for pulley issues that the alternator cuts off under hard accelleration? Any possible relevance?

[vtm3]

If I have to replace the head unit, I assume there are still zero out there that will work with the steering wheel controls?

[Technic]

Originally Posted by vtm3

If I have to replace the head unit, I assume there are still zero out there that will work with the steering wheel controls?

Before replacing anything try to find out what is the real problem.

Take you car back to the installer and ask them to monitor the OEM HU outputs voltage with a constant 1KHz tone while you are reproducing this issue. This can be done at the amps inputs by splicing a RCA plug to the wires and connecting it to a multimeter. If that checks OK (constant voltage) then test both the OEM HU and the amps 12V voltage while you reproduce this issue as well...

For sure something is dipping way below its required voltage, either the 12V power, the 12V remote, or the 5V balanced outputs.

[artifice]

Maybe a ground has come lose? I'm not sure, but Technic sounds like he knows what he is talking about. Trace the problem from the amp to the head-unit, I wouldn't replace the head-unit and potentially still have the same issue.

[quality_sound]

Originally Posted by Technic

If the alternator is spiking then you should see other modules being affected, especially the lights. And most probably the dealer should have seen it as an error in ISTA/P.

Do the test at night with the lights on. Something else should at least flicker...

You won't see a flicker with HIDs, the ballast smooths the spikes. The AA pulley would actually LOWER the available current/Voltage. I'm still betting it's a bad regulator letting the Voltage spike. I've seen it on other cars with no other symptoms. I don't believe it's a dip because the issue happens when he presses the accelerator, not the other way around.

Easy enough to check, just measure the Voltage at the amps' terminals and have someone press the gas. If it spikes there ya go.

[Technic]

Originally Posted by quality_sound

You won't see a flicker with HIDs, the ballast smooths the spikes. The AA pulley would actually LOWER the available current/Voltage. I'm still betting it's a bad regulator letting the Voltage spike. I've seen it on other cars with no other symptoms. I don't believe it's a dip because the issue happens when he presses the accelerator, not the other way around.

Easy enough to check, just measure the Voltage at the amps' terminals and have someone press the gas. If it spikes there ya go.

I was thinking less of the HID lights, and more towards interior lights as flickering, especially the OEM HU night illumination.

[vtm3]

Thanks Everyone!!!!!
I will do all of the above and post findings!

[vtm3]

I turned the gains down to minimum and it acted exactly the same. Reproduced the signal loss on high rev. I thought I had an interior light flicker, but I cant reproduce it even when I can reproduce the signal loss. I will test everything suggested and repost. I really appreciate the help!!!!!!!

[808MGuy]

Originally Posted by vtm3

I turned the gains down to minimum and it acted exactly the same. Reproduced the signal loss on high rev. I thought I had an interior light flicker, but I cant reproduce it even when I can reproduce the signal loss. I will test everything suggested and repost. I really appreciate the help!!!!!!!

That seems to eliminate any condition related to the amp's current draw (like a voltage dip due to high load). So its either HU related or electrical system related. Technic's suggestion about a spike seems to be looking more likely. Like he suggested, put a meter on the input to the amp or right at the battery and then have someone rev the engine. You might have to hold down the accelerator for a bit because digital meters typically don't react that fast. If you have an analog meter that would be the best for this particular test.