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I have speakers that come with my computer. Two small desktop speakers and a subwoofer with a base volume control on the back. It's worked for years. I was listening to Spotify on my speakers as loud they would possibly go and with the base turned up to max and suddenly the subwoofer stopped working.

I've plugged the speakers into my Android HTC Desire Z handset and again, the desktop speakers play music but the subwoofer doesn't (even after fiddling with the volume control).

So I figured I'd broken it. I went to Amazon and bought a replacement one. I bought this one: http://www.amazon.co.uk/dp/B002N46YD8/ref=pe_217191_31005151_dp_1 but it doesn't work either, on either my desktop nor my Android phone.

I had a play with alsamixer and the LFE and center controls are switched on and the speakers are okay... but still no base.

Am I unlucky enough to bought a new subwoofer which is already broken out of the box or is there something else which is wrong and I could look into please? Are there any other tests which I could perform to see if the problem is me or not?

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1 Answer 1

Unpowered speakers

Unpowered speakers are driven directly by the amlpifiers in the computer's audio circuitry. In this case the computer has separate stereo connectors (1,2,3 in diagram below) for pairs of speakers in a 5.1 system.

six connectors

I've plugged the speakers into my Android HTC Desire Z handset

The headphone socket on a mobile device is designed headphone impedance (e.g. 16Ω) for unlikely to be able to adequately power a low-impedance speaker (e.g. 4Ω), especially a large speaker or low-frequence speaker. It simply isn't designed for that job and can't supply enough current.

I was listening to Spotify on my speakers as loud they would possibly go and with the base turned up to max and suddenly the subwoofer stopped working.

It's possible that the speaker failed and in so doing, it also damaged the output circuits of the sound card.

It's possible that the audio output circuits failed (over-current) and your sub-woofer is actually OK.

Are there any other tests which I could perform

If you have a multimeter you can do some crude measurements of speaker resistance to make sure it isn't short-circuited and then try plugging it into the subwoofer output of another computer.

Powered or "Active" speakers

Powered speakers are usually driven by a line-out connection on the computer (5 in diagram above), This is usually connected to an amplifier and crossover circuit inside one speaker (e.g. subwoofer in a 2.1 system).

In this case if the left and right speakers are connected to the subwoofer and are still working, the problem is very likely inside the subwoofer.

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The subwoofer has its own power supply from a wall socket and I am similarly convinced that at one point or another I did listen to music on my phone and the sub worked (before the old sub broke). Alas, I've also tried a laptop computer and it too plays music out the speakers but not the sub woofer. Now testing three devices with the new subwoofer it's looking more like this is broken and needs to be sent back. –  Philluminati Nov 17 '12 at 21:55
Do you mean the first subwoofer, after failing, fried the output circuit of the sound card and then, when @Philluminati tried the speakers on his cellphone, might have damaged the output circuit of the telephone, too? –  sinni800 Nov 17 '12 at 22:14
See updated answer. Also, you should avoid connecting audio sockets to the "wrong" type of device. line-out should go to line-in, headphone-out should go to headphones (not to line-in unless specifically designed for both) See Answer and Answer –  RedGrittyBrick Nov 17 '12 at 22:22
Firstly, I want to sincerely thank you for a well written and well thought out response. I really appreciate anyone who takes the time to answer my questions, especially ones that are as tricky as this. –  Philluminati Nov 23 '12 at 15:35
I filled out the form for Amazon's return policy and reported the existing (new) subwoofer as faulty. I requested the exact duplicate model be sent. It arrived last night and when I plugged it into the headphone socket on my phone it worked perfectly, with subwoofer playing music and sounding quite awesome. I haven't tried my computer yet but since my phone worked I think the situation is that I'd broken my original sub woofer and the first replacement one I bought from Amazon just happened to have the same flaw out of the box. –  Philluminati Nov 23 '12 at 15:41

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