Why does my subwoofer makes popping noise after (only after) playing for 10 to 20 minutes? [closed]

Question

I have a 5.1 audio system set up. Recently I notice the subwoofer will make popping noise after playing for 10 to 20 minutes. It can be solved by turning off the the subwoofer, unplug the audio cable. But the noise will come back.

If I only turn off the subwoofer for 30 seconds and let the capacitor runs out of power and turn it back on, the noise will come back noticeably much sooner, in about 3 to 5 minutes.

I tried to plug the subwoofer directly to a laptop, a phone, and a bluetooth player via an adapter (the subwoofer only accept RCA Audio input and has external power), similar situation also happens but sooner. On a laptop or a bluetooth player, it will start making noise in about 5 to 10 minutes, and on a phone it will start making noise in about 10 minutes.

I suspect it could be either a failure of the RCA input or something wrong with the capacitor. How should I trouble shoot this?

I am happy to provide photos of the board inside of the subwoofer if need be.

P.S., I just remembered something. I recently resoldered the RCA socket since the original one gone bad and I had to replace it. Would it be possible the RCA socket was soldered poorly so it created a current?

P.P.S. Not sure if this is off topic. It seems to have something to do with the sound design.

Answer 1

OK, so it seems that this question is about a consumer-equipment, 5.1 surround sound system with an active-subwoofer.

The sub-woofer has an RCA in, and when connecting to various sources as described will produce a "popping noise" after a period. Period is varying, but can be "reset" by powering off, and powering back on.

The sub-woofer had the RCA connector replaced, or resoldered at some point in the past.

That is how I got the problem statement.

The most important troubleshooting steps you have already done, which is connecting the sub-woofer to various sources and you have found that the problem still exists with multiple sources.

This means that the problem is very likely inside your active sub-woofer.

An active-sub-woofer has a number of components, which all need to be checked to ensure they are not causing the problem. Without specifications, here is a list of typical components you may find in an active-sub-woofer:

• power supply: this is probably a switching power supply.
• (active) low-pass filter prior to amplifier stage
• pre-amplifier / gain control:
• amplifier
• (passive) low-pass filter (in case there is not an active one)
• sub-woofer
• physical cabinet (any loose components/screws)

each one of those components can cause noise, and will have to be checked according to the circuit-diagrams by someone which understand how those circuits work.

Then all of that might be implemented in a single "chip". So it could be that this is just the problem. Either way: you will have to get someone with electronic experience to take the next step of fault detection.

This is as complete as an answer possible, based on the info given.

There are two more things you can try:

• Ensure you test again, but now with known good cables between source and sub-woofer
• "borrow" a know good sub-woofer from a friend, and try this out on your system; this will tell you that it is the sub-woofer. (although it is pretty much proven to be it based on your info already given)

Good Luck.