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PostPosted: 25 Apr 2011, 10:40 
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Joined: 25 Apr 2011, 10:38
Posts: 3
Hey guys,

I was wondering if anyone would be able to help me with this. I have a big 5-year-old Bush DVDAV11K subwoofer (8 Ohm impedance, 230-240V 50Hz) hooked up to my laptop, and two smaller speakers working through the subwoofer. The speakers work fine, but some days the subwoofer works and other days it produces nothing at all.

I've taken it apart and all of the wires seem fine. I've disconnected and reconnected the connections and they seem fine. But it still only works every second day. (It's working now for example for the first time this week).

Does anyone have any advice?

Cheers,
Ryan.


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PostPosted: 26 Apr 2011, 07:48 
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Joined: 04 Oct 2008, 11:29
Posts: 375
Location: Chillicothe, Ohio
Is it possible the voice coil/coils in the sub could be damaged, due to abuse? Is the sub powered by its own amp?

I own a JBL sub that worked off and on for some time, only to discover that it has a horrific amp design. It eventually quit altogether.

http://www.amazon.com/JBL-PB12-250-Watt ... Descending

Here are the reviews from Amazon. 27 of 44 rate it 1 star. Mine was repaired twice under warranty, but lasted just a short time on both occasions.

Cheers,
Greg


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PostPosted: 01 May 2011, 11:03 
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Joined: 25 Apr 2011, 10:38
Posts: 3
Hi Greg, Thanks for the response. Sorry to hear about you buying that crappy sub.

It could be the coils I suppose. I suppose I can take it apart to check that out.

No, the sub isn't powered by its own amp. I just have a cable going from the earphone jack in my laptop that splits into Left (red) and Right (black) cable before going into the subwoofer.

I'm pretty clueless about this stuff. Should a subwoofer definitely be powered by its own amp? If so why?

Thanks again,
Ryan.


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PostPosted: 22 May 2011, 15:50 
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Joined: 25 Apr 2011, 10:38
Posts: 3
Hi again everyone,

I have since replaced the cable leading from the laptop to the subwoofer.

Strangely, the problem has now mutated. Instead of producing bass only every second day, now the main problem is that it is producing a low-level rumbling all the time, even when it's got no input going into it at all.

In the past it used to emit a low-level thudding, and as I've written above, the bass used to cut out completely sometimes.

People have spoken a lot about "the amplifier in the subwoofer", but I honestly don't even know if there is one. How can I find out?

It has also been suggested that the coils/voice coils could be gone.

Can anyone help?

Ryan.


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PostPosted: 22 May 2011, 22:06 
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Joined: 24 Jun 2010, 00:48
Posts: 788
Location: Christchurch, NZ
Hi Ryan,

From what you say, the subwoofer is probably an active type (with an inbuilt amp inside).
The active sub also has 2 extra amp modules powering both your L and R speakers.

It seems to be a problem with the inbuilt amplifier - though this will be tough to pinpoint.
Got any pics of the internal amplifier?

_________________
Kind Regards,
Dinesh

Some of my diy audio projects:


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PostPosted: 31 May 2011, 17:18 
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Joined: 31 May 2011, 17:04
Posts: 3
Hello Ryan,

I believe you have some grounding problems

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http://www.subwoofer-building.com/


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PostPosted: 21 Jun 2011, 12:58 
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Joined: 21 Jun 2011, 07:42
Posts: 13
Location: Atlanta, GA
diycoholic wrote:
I believe you have some grounding problems

I'll second that. I had an old Klipsch KSW10 which would do that same thing... cut in and out.. work one day and then not. It turned out to be the power fuse holder was bad and the amp would never turn on.

Or you connections are bad. I've seen the 3.5mm stereo female plugs wear out over time. My old Monsoon computers speakers did that.

Pics may help if you can.

_________________
Adam M.
AM Audio
amccallaudio.com


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