Subwoofer humming on and off

Pamz

Novice Member
Hi everyone,

I am at my wits end. It could just be time for a new subwoofer but I don't want to sink hundreds of dollars on that right now.

My subwoofer (Definitive 375w) hums off and on for no particular reason it seems, maybe 25% of the time. For example, it will hum very loudly (despite what volume I have the sub or receiver at) for about 15 minutes (very annoying when youre trying to do schoolwork) and then not hum for an hour.

It does this whether it is plugged into the receiver or not. I tried using a "cheater plug" to no avail. I have also tried plugging it into a different outlet away from other equipment using an extension cord. I have also tried plugging it in alongside all the euipment that is in use at the same time (receiver, tv, wii, dvd player, etc.).

Is there any fix for this without getting into electrical stuff? Should I invest in one of those products that is supposed to eliminate subwoofer hums such as the ground loop eliminator or subwoofer isolation transformer? It seems like it just started doing this a few months ago when I stirred up some wires back there. I read on another thread that maybe the wifi router is too close? IDK!!!! It's driving me nuts! The subwoofer is 10 years old.

Any advice appreciated, thanks.
Pam
 
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fatboy frank

Distinguished Member
The only thing i'd suggest right now would be to look into your cabling as you mentioned it only started once you "stirred up some wires back there" subwoofer cables as with all cables can be susceptible to picking up interference/crosstalk or electrical interference especially if they aren't shielded cables and are running near power cables.

Try moving/re routing the subwoofer cable and see if that helps, it might be worth turning off and disconnecting some of the other equipment while you isolate which bit of kit/cable or cables is causing the issue.

Subwoofer hum/ground loops can be a real pain to fix, so good luck. It could also be internal electrical components in the sub that have failed or failing due to age, 10 years is quite old.
 
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Cliff

Distinguished Member
If it hums whether it’s connected to the receiver or not, it points to a fault in the sub electronics. I would check the smoothing capacitors. Subs are usually left on for long periods and as it’s 10 years old then they might be failing. Find a local repair shop that can replacement them. (Easy job)
 

davidf

Well-known Member
I’d plug it into the cooker’s electrical socket in the kitchen. There’s nothing else on that spur, so if it still does it, it’s an internal thing. Plugged in around the house, Class AB based sub amps could be affected by DC noise introduced by other products in the house.
 

fatboy frank

Distinguished Member
I’d plug it into the cooker’s electrical socket in the kitchen. There’s nothing else on that spur, so if it still does it, it’s an internal thing. Plugged in around the house, Class AB based sub amps could be affected by DC noise introduced by other products in the house.
I believe the OP is from across the Pond in the US, so that might well not be the case over there!
 

Cliff

Distinguished Member
I’d plug it into the cooker’s electrical socket in the kitchen. There’s nothing else on that spur, so if it still does it, it’s an internal thing. Plugged in around the house, Class AB based sub amps could be affected by DC noise introduced by other products in the house.
What? Please.... Did you read that on another forum.
‘scuse my bluntness but you shouldn’t really post if you don’t know what you are talking about.
 

SyStemDeMoN

Well-known Member
Sounds like the amp in the sub needs attention.
A repair should cost around $50 in the US ?
Just had mine done in the UK by the manufacturer and it cost around that posted and delivered.
 

davidf

Well-known Member
What? Please.... Did you read that on another forum.
‘scuse my bluntness but you shouldn’t really post if you don’t know what you are talking about.
Please do shower us with your alternative wisdom...
 
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Cliff

Distinguished Member
Please do shower us with your alternative wisdom...
See my post #3. probably smoothing capacitors in the psu.

As a general point, and not directed at you particularly but includes you, I see forum postings on technical matters that are complete mumbo jumbo. They have been posted and reposted on forums so they almost become fact. Anyone who has no grasp of electronic theory, might actually believe what is written because he has seen it multiple times.
I think forum members should not repost stuff that they don’t understand- because the nonsense becomes self generating.
 

davidf

Well-known Member
@Cliff
what I posted had nothing to do with “reading it somewhere else”. It was based on experience of Class AB amplification humming due to other products in the house. I recently witnessed an amp loudly humming when a particular electronic item is used elsewhere in the house. Others on forums have had similar issues which are user dependent, mostly to do with DC noise. Most amplifiers filter this out (at the expense of some sound quality), but some don’t.
 

Cliff

Distinguished Member
@Cliff
what I posted had nothing to do with “reading it somewhere else”. It was based on experience of Class AB amplification humming due to other products in the house. I recently witnessed an amp loudly humming when a particular electronic item is used elsewhere in the house. Others on forums have had similar issues which are user dependent, mostly to do with DC noise. Most amplifiers filter this out (at the expense of some sound quality), but some don’t.
Was this mechanical noise from the transformer? If there is distortion on the AC mains, perhaps one half of the cycle heavily loaded, then the hum from the transformer could sound different. But transformers are generally quiet anyway, and you would have to have your ear close to the amplifier. This will not be passed on to the amplification because of the rectification to DC and smoothing capacitors to remove all ripple. If you hear hum on the audio then there is something wrong with amplifier and not the mains.
 

BFG

Member
I’d plug it into the cooker’s electrical socket in the kitchen. There’s nothing else on that spur,

This is true and useful. In the UK, the socket built into a cooker switch is on its own circuit (by law*).
It's also fed by thicker copper than any other 13A socket in your house and has fewer joins / connections, so it's the circuit least likely to have noise introduced along the cable inside the wall. Not all houses have a socket / switch combo. Some just have a switch, but if it's this sort:

Then it's useful for a number of electrical tests.



* (well, Part P / building regs anyway)
 
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