View Full Version : Home theater subwoofer hum

09-17-2013, 08:15 PM
Something interesting came up this morning. Woke up and hear what sounded like something sliding across the outside living room wall followed by a bump. After a careful examination outside with my gun, I came back inside and realized it was the home theater subwoofer making a humming and pop every now and then. I shut off the subwoofer and the sounds stopped.

Let me preface this with saying it hasn't always done this, it just started last night when I swapped out the receiver (Yamaha RX-V363) for a new one (Denon AVR1513). From what I can tell, there's a few thongs that can be the culprit.

Ground loop:
That speaks for itself. There could be some massive power battle going on between the reciver and subwoofer as to who is the ground and causing the subwoofer to freak the fuck out. Resolution would be to go to 2 prong plug (with adaptor) or connect the subwoofer to a different power circuit (easier said than done, this place is so fucking fucked with wiring it's not even funny).

Bad subwoofer cable:
Speaks for itself. I'm using the cable that came with the surround sound system (Infinity TSS-800) plus a standard RCA cable for extension.

Bad amp:
The subwoofer and amp just took a shit.

I'm hoping it's the first or second thing, namely I really hope it's the second. The whole living room (including the patio outlet and lights) are all wired on the same goddamn breaker, as is the GFI and at least one other outlet in the kitchen. Anybody else ever have this pop up? I'm going to disconnect the input from the subwoofer and start testing to see what fixes it.

As it sits now, I have 3 input devices to the receiver. DVD, satellite TV receiver and a PS3 (all HDMI). From the receiver for outputs, there are 5 speakers plus the subwoofer and 1 HDMI cable to the TV.

09-17-2013, 09:45 PM
Mainly for myself so I don't forget what I'm doing tonight....

If the subwoofer is plugged into its own outlet, plug the subwoofer's power cord into an outlet shared by the other components. Use an extension cord if necessary.
If the hum persists, and your system includes a cable TV, disconnect the cable line. If the hum stops, install an isolation transformer on the cable.
If the hum persists, disconnect the remaining component cables one at a time until the hum stops. Install a coaxial isolation transformer on that cable.
If the hum persists, install a line-level ground loop isolator on the subwoofer's line-level feed cable. This usually solves most hum problems.
If nothing helps, disconnect all the audio cables from the subwoofer. Leave the subwoofer plugged in and switched on. If the subwoofer hums, it points to a defective unit.

09-17-2013, 11:51 PM
Do you just leave your sub on all the time? I've rigged mine up to shut off when the receiver shuts off.

09-17-2013, 11:53 PM
Ground loop isolator will diminish your sound. I wouldnt use that.

What I would do is buy some RG6 cable from someplace, and some RCA crimp on ends and make your own subwoofer feed cable. The RG6 is shielded and has a better nominal resistance than the standard RCA crap.

09-18-2013, 12:29 AM
Normally its always on. Occasionally I'd turn it off if we leave for extended time. I'll mess with it tonight. I may just run a cors to loop it into the power conditioner for the rest of the av.

Sent from my SCH-I535 using Tapatalk 4 Beta

09-18-2013, 01:49 AM
Well looks like the internal amp took a shit on the subwoofer. No clue why either :(

I had everything powered off when I put the new receiver in (literally, everything was unplugged and I turned the subwoofer on last). I removed the connection to the subwoofer and the cackling/pop was still there.


09-18-2013, 03:48 AM
I'm not fully aware of the technical woohah and thingamabob...but this don't look right.


I can't fix it, I don't have the soldering iron and skills to fix it. Time to find a new one :(

The Captain
09-18-2013, 03:12 PM
Just buy a new plate amp.


Cheap fix.

09-18-2013, 03:13 PM
Nice work, Tim. Your video is private.

Anyhoo, that could happen if you leave it on all the time. I always turn mine off when it's not in use.

09-18-2013, 03:14 PM
Grb a cheap soldering iron, pick up a couple new components, boom done.

09-18-2013, 05:26 PM
Fixed the video..works now.

The Captain
09-18-2013, 07:03 PM
Problem is even if you fix the burned out components, you don't know what caused it in the first place...

Resistors etc are easy and cheap enough to try though.

09-19-2013, 06:42 PM
Sometimes when shit like that goes on a multilayer PCB you fuck up something in one of the middle layers of the PCB and its hard/impossible to fix without a new PCB.

Not saying not to try, just saying if its multilayered, you could be shit up a creek.

09-19-2013, 07:15 PM
I bought a new woofer last night. Small lil' 100w Pioneer.

The Captain
09-19-2013, 07:48 PM
My subwoofer usually hums when it doesn't know the words.

09-19-2013, 07:49 PM
If you'd waited another 4 months, I would have sold you my old Sony.

09-19-2013, 11:05 PM
Now try and fix the old one Tim. You may learn a thing or 7

09-19-2013, 11:16 PM
I may take you up on that still.

I like my bass. This is more ideal for a bedroom bass level (imo).

09-24-2013, 11:06 PM
That daughter board looks to be all through-hole so should be a simple fix if you know the components and values. You are correct though Rob, if it was a multi-layer pcb then the traces would most likely be FUBAR. I would just keep it around for experimentation purposes. Not for putting back into standard duty. Especially since it looks like something went very, very wrong in there. Just remember: Fire bad/ :D :P

Glad you got a pickup to suit your needs at a decent price Tim.

09-26-2013, 06:20 AM
Power conditioner. Without a power conditioner, your audio equipment dies.