• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Here we go again. Subwoofer hum problem. Please help.

You have to find out if the connection of your rca cable to the sub creates or affects this hum. My sub was humming horribly and I found out that it was because my sub cable was not shielded. I bought a new shielded sub cable and I now have zero hum.
Would you share the brand and model of your shielded sub cable? How much did you pay for it?
 
This thread seems to be going in different directions.
a] If the sub hums with only the AC cord connected, that's one type of problem.
b] If the sub hums when connected to other components via interconnect cables, that's a very different type of problem.
* * * * * * * * * * *
Hum with only the AC cord connected means that the sub is broken. (but try it at another persons home to double check)
 
This thread seems to be going in different directions.
a] If the sub hums with only the AC cord connected, that's one type of problem.
b] If the sub hums when connected to other components via interconnect cables, that's a very different type of problem.
* * * * * * * * * * *
Hum with only the AC cord connected means that the sub is broken. (but try it at another persons home to double check)
It is only one sub hum this thread is referring but it happens in two situations:
a) When the sub is connected to a receiver and plugged into a power outlet via a power bar.
b) When the sub alone is plugged into a power outlet (not connected to anything at all).

Hum happens in both situations.
 
No, I didn't. It was plugged into the power outlet only.
No other electrical connections at all?

Do any of the cables of the rest of the sytem go anywhere near the sub, or near to the mains cable to the sub. I can easily induce hum in my system by placing an RCA cable close to the AVR power transformer.
 
No other electrical connections at all?

Do any of the cables of the rest of the sytem go anywhere near the sub, or near to the mains cable to the sub. I can easily induce hum in my system by placing an RCA cable close to the AVR power transformer.
No, I took the sub to different rooms far away from the system and tried the power outlets there, same hum.
 
I am happy to let you know that the culprit has been identified and the problem has been solved. The solution is to utilize an isolation transformer.

I took the sub back to its owner's place and had it connected to his system and played some music, the same way it was set up before. As expected, no hum came out from the sub. Upon inspection, I found out that the power outlet used to connect to the sub was connected to an isolation transformer. It provided clean power. For verification, I asked to have the sub connected to another power outlet without an isolation transformer attached to it. Sure enough, the same hum occurred. Problem solved.

However, not all sub hum can be resolved with an isolation transformer. Just this one case is applicable.

Thank all for your inputs. Really appreciate them.
 
I am happy to let you know that the culprit has been identified and the problem has been solved. The solution is to utilize an isolation transformer.

I took the sub back to its owner's place and had it connected to his system and played some music, the same way it was set up before. As expected, no hum came out from the sub. Upon inspection, I found out that the power outlet used to connect to the sub was connected to an isolation transformer. It provided clean power. For verification, I asked to have the sub connected to another power outlet without an isolation transformer attached to it. Sure enough, the same hum occurred. Problem solved.

However, not all sub hum can be resolved with an isolation transformer. Just this one case is applicable.
Wow, strange. I'd look into a different sub.
 
Is it a 3 prong plug? If it is, get a 2 prong cheater. If it is RCA try a different cable. Did you use the same RCA cable at the other place it was quiet?

It could be a shielding problem on the RCA, or the power cable. Are they the same cables you used at the other place?

Get a GL eliminator and try it?

I'm not saying it's any of these, BUT an RCA or a PC can both cause problems with noise. Not all cables are the same when it comes to noise/shielding.
Aluminum/copper-clad RCAs can drive you nuts. A cheap PC with poor shielding can too.

Just a thought. I had a problem with cable boxes making noise and the cable guy gave up, I added a GL eliminator and got rid of 95%. I have to turn the
volume all the way up when the source is cable to hear any noise at all.

I had a security camera router POE cause noise on L1, I could move the noise by moving the PS to L2. It stopped the noise to the stereo. I could plug the
stereo into L2 and the noise came right back. I finally eliminated the noise by going to an NVR and dumping both POE routers.

Happy hunting.
 
Is it a 3 prong plug? If it is, get a 2 prong cheater. If it is RCA try a different cable. Did you use the same RCA cable at the other place it was quiet?

It could be a shielding problem on the RCA, or the power cable. Are they the same cables you used at the other place?

Get a GL eliminator and try it?

I'm not saying it's any of these, BUT an RCA or a PC can both cause problems with noise. Not all cables are the same when it comes to noise/shielding.
Aluminum/copper-clad RCAs can drive you nuts. A cheap PC with poor shielding can too.

Just a thought. I had a problem with cable boxes making noise and the cable guy gave up, I added a GL eliminator and got rid of 95%. I have to turn the
volume all the way up when the source is cable to hear any noise at all.

I had a security camera router POE cause noise on L1, I could move the noise by moving the PS to L2. It stopped the noise to the stereo. I could plug the
stereo into L2 and the noise came right back. I finally eliminated the noise by going to an NVR and dumping both POE routers.

Happy hunting.
The sub should have come with a three-prong plug. It would prevent some problems, IMO.
 
The sub should have come with a three-prong plug. It would prevent some problems, IMO.
It should but it can also be a source of noise if there is something dumping through the same ground your amp is using. Like a 220/240 single phase motor on a heat
pump, dryer or stove. Just try it. I've had to do it on valve amps behind noise. They went from having a lot of floor noise to ZERO. IF not having a ground was such a
bad thing why did they do it (and still do). It's a safety ground, but not to complete a circuit. It's usually to prevent over voltage from a chassis if there is a problem.

I still suspect there is a cable issue and shielding or like I said a 220/240 causing noise through that ground wire. What could have happened at the other home is
THEY weren't using the ground prong or they didn't have a problem with any of the 220/240 VAC components being used in that home or they had good shielded
cables to begin with.

Again the RCAs and PC can be a source of noise. BUT the cheater got rid of the noise. Going backwards, you can still hunt down the noise.
The crap I've gone through with RCAs in 12/24VDC in heavy equipment would blow your mind. It was always a 5.00 USD RCA aluminum/copper clad cable
in a 300-500K piece of machinery and a 15.00 usd COPPER cable from PE fixed it every single time. The sub-power amps wouldn't activate unless you turned the
volume UP. Trust me, operators like their music once they get it in the cab. :) Aluminum and stereos just don't work well together in some cases. I hate
the $hit.

I've seen cable routing cause all kinds of noise problems, too. I usually just pick up the run of cables one at a time or the complete bundle and see if
the noise yoyos. You know goes up and down. It's a VERY good chance, careful routing will get rid of the problem. I'm one of those guys that HEAVY
shielding is not my preference. It can really affect the quality of the sound, it's like throwing a blanket over a speaker in some cases.

I've seen power conditioners do exactly that, to a power amp. Plug them directly into a good dedicated circuit and it's quite the difference.

I just went through a houseboat with a buddy recently that was plagued with floor noise, it was the neighbor's 1000 year old freezer that ran on
220/240, they were on the same 220/240 dock plug. I suppose someone could chime in about why it happens, I'm just a mechanic, I'm pretty good
at troubleshooting any kind of noise, even a moaning neighbor at 03:00 in the morning. I told the GUY to use a sock, while I put my muffs on. :)

These are just suggestions, and things I've personally experienced. I throw them out and if something sticks, GOOD if not, it sure didn't cost anything.

In any case, I need to feed the chickens, speaking of making noise.

Again happy hunting.

By all means, let us know.
 
Last edited:
Actually, the hum has been eliminated completely by using an isolation transformer.

For some reason, hum occurs when the sub is plugged into a typical power outlet without an isolation transformer.

Problem solved.
 
Actually, the hum has been eliminated completely by using an isolation transformer.

For some reason, hum occurs when the sub is plugged into a typical power outlet without an isolation transformer.

Problem solved.
To me that sounds like there is a fault with the sub causing it to do nasty stuff to the mains supply which the isolation transformer blocks. Other stuff shouldn't hum that badly just by the sub being plugged in somewhere in the building.
 
I've managed to attach an audio recording of the hum in the form of a YouTube video. Please take a listen and see if you could identify the type of hum and the cause.

 
I've managed to attach an audio recording of the hum in the form of a YouTube video. Please take a listen and see if you could identify the type of hum and the cause.

Here is a FFT of your recording. Center frequency is 359 HZ. Like I said, SVS is having a sale for Black Friday.
IMG_0427.jpeg
 
Back
Top Bottom