A/V Bose Sub Popping Sound?

This might be a bit of a specific problem, but hopefully someone with more audio / electronics knowledge than me can provide some insight.

I am having an issue with a Bose sub in my car making a popping sound, especially when I turn the volume up.

I took apart the amp and tried the fix mentioned in this guide.

I connected it all back up and it worked great for about 5 minutes, but then the popping came back.

Turning the volume down meant the popping went away for a bit, but then it came back, so I lowered it some more, it went away for a bit and then came back etc etc.

Now it's at a level where there is no popping, but I have to have the volume at ~14, which is adequate, but not ideal.

If I turn the volume back up to where it was after I first fixed it, it pretty much just pops constantly.

I tested with the same song, just to make sure it wasn't a fluke or due to the song choice.

Now, considering it did sound perfect (well, as perfect as the Bose system can be) for a while, I'm assuming the fix did work, but now the relay has gone again?

EDIT:
I left it for a bit then went to go test it again and it had significantly improved and wasn't popping (like just after I fixed it), but then it started to degrade again. Could it be that something is overheating?


Any suggestions on how to fix it?

-Is it just a case of replacing the relay again and being more careful about how loud I turn it up?
-Is there anything else to check?
-Is there a better fix? (A higher spec relay or something?)


Cheers

 

Check the ground of the amp to the cars chassis is good (Tight connection to solid clean bare metal)

 

The next thing to try is eliminating the amp. Popping can sometimes occur when the coil is misaligned (from being driven too hard) or the coil failing. That would be the speaker causing the pop. The suspension on the sub could also be knackered which would also cause popping. This could be why when you lower the volume it stops.

I'm not sure how you are set up electronically but I would take the sub out and check what ohm load it has. If it's something less than 4 ohms (which Bose are known for) then you need to be careful when connecting it to another source. I've blown channels on domestic amps by connecting a 1ohm Bose driver to them.

But yeah, if you could connect it to another source that would eliminate the sub itself and only leave the amp circuit. You can download sine waves to test subs with (it basically makes them rock backward and forward to check for any pops or "cone tick")

 

Thanks for the responses.

I would if I knew where it was connected to ground

Even if I do find out where, it may not be very accessible

Is there any way to diagnose those faults visually?

I believe the amp and sub are rated at 2Ω, but I don't think I have anything else to connect the sub to. I'll have a look and see what I can find. Unless I can just connect it to my PC?

The only thing is, it seems to fix itself if I leave it for a while, but as I say, it slowly gets worse again. I may be wrong, but wouldn't any of the potential faults mentioned be apparent at all times. If say the coil or suspension is gone, or it isn't grounded properly, then surely I should be able to replicate the issue straight away by setting it to X volume on Y song. It shouldn't work fine initially, get worse over time, then fix itself if I give it a rest?

Cheers

 

Bad ground can cause intermittent faults.

Try cleaning the connector to the amp, and the pins on the amps socket with electrical contact cleaner and a old toothbrush. (Disconnect your battery first, but be sure you have the radio code if you need one, as some cars will require one after reconnecting the battery)

If you have a multimeter you could check the resistance of the ground pin to the chassis, it should read almost zero ohms.

 

There is virtually no way to diagnose coil problems or bad alignment just by eye as they are buried.

Try downloading a sine wave and playing it in the car. It will basically make the sub pump in and out so you will catch any scrapes or ticking that way.

 

Probably won't get a chance to do much 'til the weekend.

Would this do the trick?

"Tone Generator. The basic app includes a sine wave generator that generates signals from 20 Hz to 20 kHz, with a 44.1 kHz sample rate, 16-bit samples, and 96 dB of dynamic range. Frequency control via logarithmic knob or keyboard input."

 

Yes probably. Lower it right down and listen..

I forgot to say the other day. If you can access the sub try pressing it gently and evenly inward and listen for any coil scraping. Make sure you apply even pressure though.

BTW be careful with that app. When you get down to a certain frequency you won't hear it. Your sub will be flapping haha. See if you can watch the sub itself when you are running the app.

 

There was no real give in the sub when I tried pushing it - didn't wanna push too hard and break anything though.

Tried running the app at various frequencies and didn't hear anything strange. However the sub didn't seem to be moving as much as when I listen to music. Maybe I was being too cautious with the volume? It seemed rather loud, but maybe that was due to it being an annoying tone rather than music.

 

Did some more testing...

As before, it was fine to start with, so I played some music LOUD for a few mins, then it started to get worse.

Recorded 2 vids, had to use my old K800i, so sorry about the quality :x

Example of the "popping" during a song.


Example of popping using the signal generator at ~80Hz.

Increasing the volume creates a buzz / whine (presumably just from the vibrations? But turning the volume from 17 to 18 makes it start to "pop".

Any help?