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Random thumping from subwoofer

post #1 of 22
12/27/12 at 3:48am
Thread Starter 
Hi,
Ive recently noticed that my paradigm subwoofer is thumping randomly. I have done some testing and found the following:

Different power outlets make no difference
Different surge protected extensions make no difference
The issue still occurs when sub is just connected to power and amp is off
Different cable tried with no change
I have noticed that issue possibly occurs when central heating kicks in, not 100% certain yet though

Any thoughts or suggestions on possible fixes for this?

Cheers

Mick
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post #2 of 22
12/27/12 at 6:45am
Quote:
Originally Posted by raffaz View Post

The issue still occurs when sub is just connected to power and amp is off
If the amp is off there's no signal that could create a thump. If there's a sound the amp must be switching on.
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post #3 of 22
12/28/12 at 8:13am
Thread Starter 
The sub has its own amp, so it doesnt matter if the amplifier is off. As mentioned, it appears to be caused by some sort of electrical interference from central heating.
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post #4 of 22
12/28/12 at 8:54am
Quote:
Originally Posted by raffaz View Post

The sub has its own amp, so it doesnt matter if the amplifier is off. As mentioned, it appears to be caused by some sort of electrical interference from central heating.
If the amp is off there is no signal to the driver to cause a thump. Whatever you're hearing can't be coming from the sub.
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post #5 of 22
12/28/12 at 11:18am
Thread Starter 
Hmm, i guess i must be making it up then eh? I guarantee that the noise is from the sub, i know this because i have been next to it when it does it. I have read that household electrical circuits can cause the issue at the 60hz range and i am after info on how to resolve this. Not to sound harsh, but if you havent anything constructive to add apart from pretty much stating that the noise im hearing from the sub, isnt the sub, then dont bother replying.
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post #6 of 22
12/28/12 at 11:22am
You might wanna listen to the guy who designs speakers for a living, onaccounta he might know something.

The ear is easily fooled, and for a sub (or any speaker) to make a noise requires an input voltage. If the amplifier connected to the speaker is turned off, it cannot output a voltage to the speaker, and the speaker can't make noise. AFAIK, there is no way around that.

If the sub's amp is on (not perfecdtly clear to me) then you need something to induce a signal into the sub's amp.
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post #7 of 22
12/28/12 at 11:23am
Thread Starter 
Heres a snippet from an article regarding ground loops

When two or more devices are connected to a common ground through different paths, a ground loop occurs. Currents flow through these multiple paths and develop voltages which can cause damage, noise or 50Hz/60Hz hum in audio or video equipment. To prevent ground loops, all signal grounds need to go to one common point and when two grounding points cannot be avoided, one side must isolate the signal and grounds from the other.

Is it therefore not possible for the 50/60hz hum to manifest itself as short bursts from my sub when central heating kicks in.
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post #8 of 22
12/28/12 at 11:25am
Thread Starter 
The subwoofer is active though, so it has its own amp which is not turned off, its only the main amp thats off. Im not trying to be funny here, but i have placed my ear next to the sub when it happens and i know 100% that this is where the noise is coming from
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post #9 of 22
12/28/12 at 11:34am
Quote:
Originally Posted by raffaz View Post

The subwoofer is active though, so it has its own amp which is not turned off, its only the main amp thats off. Im not trying to be funny here, but i have placed my ear next to the sub when it happens and i know 100% that this is where the noise is coming from

so part of the problem with BFM may be miscommunication.. I assume by "amp" you mean "receiver." The receiver is not an amplifier with respect to the sub. It contains amplifiers that can be used to drive other speakers, but no receiver amp ever connects to the sub (unless you want to see the sub smoke (or at least have output that is hugely distorted). The sub's amp is the only amp relevant to the sub. From the pserspective of a powered sub, the receiver is a preamp. When you say the "amp" is off to a person who understands, consistent with convention, that "amp" means the piower amplification attached to the device in question, but mean something different, micsommunciation can occur (not that I don't semiroutinely confuse the dickens outta folks by explaining my situation incorrectly . . . )
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post #10 of 22
12/28/12 at 11:34am
Quote:
Originally Posted by raffaz View Post

The subwoofer is active though, so it has its own amp which is not turned off, its only the main amp thats off. Im not trying to be funny here, but i have placed my ear next to the sub when it happens and i know 100% that this is where the noise is coming from

so part of the problem with BFM may be miscommunication.. I assume by "amp" you mean "receiver." The receiver is not an amplifier with respect to the sub. It contains amplifiers that can be used to drive other speakers, but no receiver amp ever connects to the sub (unless you want to see the sub smoke (or at least have output that is hugely distorted). The sub's amp is the only amp relevant to the sub. From the pserspective of a powered sub, the receiver is a preamp. When you say the "amp" is off to a person who understands, consistent with convention, that "amp" means the piower amplification attached to the device in question, but mean something different, micsommunciation can occur (not that I don't semiroutinely confuse the dickens outta folks by explaining my situation incorrectly . . . )
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post #11 of 22
12/28/12 at 11:39am
Quote:
Originally Posted by raffaz View Post

Is it therefore not possible for the 50/60hz hum to manifest itself as short bursts from my sub when central heating kicks in.
No. A ground loop is a constant hum, not an occasional pulse
Quote:
Originally Posted by raffaz View Post

The subwoofer is active though, so it has its own amp which is not turned off, its only the main amp thats off. Im not trying to be funny here, but i have placed my ear next to the sub when it happens and i know 100% that this is where the noise is coming from
I suggest turning it off when not in use. You didn't mention if it does this when the receiver is in use. Whether or not it does would help explain what's going on.
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post #12 of 22
12/28/12 at 11:41am
Thread Starter 
Yep, it sounds like miscommunication, so i apologise for that. My understanding of the term receiver is an av amp with built in tuner. To clarify then, my sub is powered on, my receiver is not. the sub has an auto on feature aswell and this sometimes comes on randomly as well.
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post #13 of 22
12/28/12 at 11:51am
Quote:
Originally Posted by raffaz View Post

Yep, it sounds like miscommunication, so i apologise for that. My understanding of the term receiver is an av amp with built in tuner. To clarify then, my sub is powered on, my receiver is not. the sub has an auto on feature aswell and this sometimes comes on randomly as well.
When the AV receiver is on the output impedance of the LFE line driver is very low. When the receiver is turned off that impedance can become quite high, and functionally speaking that can turn the signal cable going to the sub into an antenna, capable of transmitting RFI and/or EMI into the sub amp; that could make the auto function turn on as well. That's one possible explanation for what's going on. It might be an annoyance but it shouldn't bother anything.
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post #14 of 22
12/28/12 at 12:48pm
Thread Starter 
Cheers for that, i havent noticed if the sub turns on when the cable is connected, but i know it does make the noise when connected or disconnected. Also, previous question was asked wether the sub makes the thumping noise when the receiver is on, i can confirm that it does, for example, i could be watching a film and it will themp during the film soundtrack.
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post #15 of 22
12/28/12 at 2:50pm
Quote:
Originally Posted by raffaz View Post

Cheers for that, i havent noticed if the sub turns on when the cable is connected, but i know it does make the noise when connected or disconnected. Also, previous question was asked wether the sub makes the thumping noise when the receiver is on, i can confirm that it does, for example, i could be watching a film and it will themp during the film soundtrack.
If it's the same thump then something else is going on. It's easy enough to find out if the furnace is the problem, just turn it on and off and listen for the thump. Is it an oil furnace? Normally they don't cause problems, so if it is causing this you should have the furnace electronics checked out.
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post #16 of 22
12/29/12 at 2:01am
Thread Starter 
Its a central heating boiler, im guessing your from the states if your unsure about what im referring to smile.gif its an electric boiler, it has a motorised pump in there and a heater, this circulates the hot water. Im pretty confident that this is the cause, just not sure how i can isolate this from the rest of the electrics. Its only 2 years old and it has just been serviced, so im pretty confident that there is nothing faulty on it, just not sure what i can try next.
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post #17 of 22
12/29/12 at 6:06am
If the boiler is resistance heated it shouldn't cause any issues. You mention that this started recently. That would indicate that something has changed. That change would probably be the cause.
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post #18 of 22
12/29/12 at 6:10am
What receiver do you have? This is a known issue with the Sherwood r972.
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post #19 of 22
12/29/12 at 9:16am
Thread Starter 
Quote:
Originally Posted by Bill Fitzmaurice View Post

If the boiler is resistance heated it shouldn't cause any issues. You mention that this started recently. That would indicate that something has changed. That change would probably be the cause.
I have only noticed recently as i have just setup my new system, havent used my sub for some time now, probably over a year since the sub has been used.
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post #20 of 22
12/29/12 at 9:16am
Thread Starter 
Quote:
Originally Posted by primetimeguy View Post

What receiver do you have? This is a known issue with the Sherwood r972.
I have a yamaha
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post #21 of 22
1/6/13 at 11:09pm
Were you able to resolve this or determine what it was? My sub is doing the same thing - randomly firing. Haven't had any changes to my set up for 2 years, including no additions to the home theater system, changes in set top boxes...nothing.... and it just started a few weeks ago. Have tried different outlets, LFE cables, etc. But can't solve it. Doesn't happen that often (once our twice a night) but when it does its annoying and startling - feels like someone pounding on the wall outside our house.

Curious if you learned anything?
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post #22 of 22
1/24/13 at 12:08am
Thread Starter 
Never solved the issue, i have had to turn the sub off
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