Switching off a sub woofer
Shashi Kumar -- Sun, 06/17/2007 - 10:59
Whenever I switch off the power supply to my powered sub woofer there is a loud pop sound. Is this normal? More important is it harmful to the sub woofer? Yes there is an auto on off system in it which will do the switching automatically. But I have seen that after switching off the rest of the system at night, the sub is still on in the morning.
The pop should not hurt your sub unless it is really, really loud. I would recommend just leaving the sub powered on all the time, though. The current draw at idle should be inconsequential, and in my opinion it is usually easier on the amp to avoid all the heat up / cool down cycles that go with turning it off and on repeatedly.
What you describe could be caused by some DC offset from your input source.
Try this - disconnect your input cable one evening when you turn off the rest of your system.
If the Sub has "gone to sleep" in auto mode when you check it the next morning then the problem could be coming from your receiver or pre-pro.
Also does the sub make the same sound when you turn it off when there is no input connected to it?
Steven Stone
Contributor to The Absolute Sound, EnjoytheMusic.com, Vintage Guitar Magazine, and other fine publications
Thank you guys for the response. Apologies for the delay from my side, but if you look at the dates of the posting you will know why.
I am a little unclear as to what Doughy intends by really really loud. But the pop is loud, and can surprise somebody sitting in the room.
Replies to Steven' queries:
The sub makes the same noise even when there are no inputs connected to it.
I have disconnected the inputs to the sub tonight, and I will be able to post the result tomorrow. The only issue is that this is going to be a bit uncomfortable, as I drive my main speakers through the sub's speaker level connections.
One last thing, Definitive Technology (the subs manufacturer) seems to have overcome this in their next model down the line, as the new model switches on & off silently.
SK
If having no inputs attached gets the same result, then its not a DC offset issue.
Have you tried floating the ground if the sub uses a three-way plug?
If this also fails or it has a two-way plug, then it's time to contact the manufacturer.
A well-designed and properly-made subwoofer should not pop when turned off.
Steven Stone
Contributor to The Absolute Sound, EnjoytheMusic.com, Vintage Guitar Magazine, and other fine publications
My sub (which is always on) makes a minor POP noise when I turn off the incandescent ceiling light/fan in the room where the sub is located. Oddly, the ceiling fixture is not on the same electrical circuit as the sub. The switch for the ceiling fixture is a standard on/off mercury switch (no dimmers or rheostats of any kind). Anybody know what could be causing this situation and whether this indicates any problems I should be concerned about?
The subwoofer's amplifier could have some DC offset; this would cause the popping noise when turning off or on (with or without an input connected).
I had made a posting prior to this, but something seems to have gone wrong.
As per Steven's suggestion I had disconnected the inputs to the sub, and by the next day it had switched off by itself. However, even previously, when the auto-off had failed, I have switched off manually, and, when the next time I use the sub, the auto functions normally. I mention this here, because, to disconnect the inputs, I had to switch off the sub manually first, and then switch on again in order to run the test.
Posted below, is the reply from the subs manufacturer. The text in red are my comments.
The "thumping" sound heard when th sub first receives electricity (and when it's unplugged) is normal. It's not "dangerous" and won't cause any harm to your speaker. (I'm sure it's annoying though.)
I'd recommend plugging the sub into an "unswitched" outlet that receives AC power all the time. This way you won't hear any popping or thumping when you turn your system on or off.(I think he misunderstood my query, and thought that I switched off the power to the sub also when I switch off the power to the system)
The amplifier used in the sub has a unique power supply that draws its power from the AC outlet as needed. It doesn't have a traditional transformer and it doesn't' store its power on board. A draw back of this unique design is that it produces a transient when it first receives electricity and when it stops receiving electricity.
SK
my carver sunfire subwoofer is making short thumping noises about every 20 to 30 minutes when I am not using the system.
It started about 4 months ago on a 10 year old system that never had this as an issue
Any ideas
Bruce Seideman
I suspect your auto-on relays or the auto-on circuit. Try putting it in manual on and see if the thumping goes away.
Steven Stone
Contributor to The Absolute Sound, EnjoytheMusic.com, Vintage Guitar Magazine, and other fine publications
Hi there,
I've jsut got my Jenson VX900 Banpass sub back from repair as it stopped working (pots failed)..
Now evertime I turn my receivrer/dvd player, or sw itch from AUX/DVD/TV/RADIO etc...or even when i pause or change scense in a movie, my sub makes a "thump" noise...
I've tried putting the some on manual, and also plugged it in to its own power..
Any suggestions or help would be great
Cheers
- Ash
Many subwoofers, including some VERY pricy ones, make a thump when they turn on. But since yours is making a thump when you change sources it may be some DC offset on your input line to the sub. But you also note a thump when you change scenes in a movie - that could once more be turn on thump. If possible, put your sub on "manual" instead of "auto" turn on. That way it will be on all the time instead of waking up every time it senses a low frequency signal and going to sleep if there is no signal.
Steven Stone
Contributor to The Absolute Sound, EnjoytheMusic.com, Vintage Guitar Magazine, and other fine publications
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