Volume control for extension speakers

  Pine Man 10:15 01 May 06
Locked

Are there any electrical geniuses (or should that be genii?)out there?

I have fitted a pair of extension speakers from my PC into another room and want to be able to control their volume in that room rather than from the base unit.

Is this simply a matter of wiring in a variable resistance or do I need more 'bits' to go with it?

  hzhzhz 10:40 01 May 06

click here might be of help

  Pine Man 11:09 01 May 06

Thanks for that hzhzhz but I have looked at retailers for electrical accessories but they don't really help much.

I have actually got a volume control from an old stereo system which appears to be the same rating as the extension speakers and I want to use that to reduce the volume if necessary without going back to the base unit.

I have no idea how to wire up the volume control to the speakers and attempts have resulted in the speakers being either on or off rather than reduced in volume and I wondered whether I needed some additional electrical'stuff' to go with the volume control.

  Gongoozler 11:41 01 May 06

Hi Pine Man. A volume control in a passive speaker is not really a very good idea because it is likely to severely degrade the sound quality. If your speakers are of the active type such as is normal in computer systems, then they have amplifiers built in, and you could then run both systems directly from the PC audio card and use the volume controls in the speakers. A jack splitter cable such as these from Maplin might be suitable click here

  Pine Man 11:49 01 May 06

Thanks Gongoozler I may have to go down that road if all else fails.

At the moment I have got two speakers from the same old stereo system as the volume control and I was hoping that it was possible to utilise that volume control on the cables that feed the speakers.

I'll leave this thread for a couple of days and see if anybody else has a suggestion then probably scrap the lot and start from scratch along the lines you suggest.

  Gongoozler 11:59 01 May 06

Hi Pine Man. You can use a volume control directly on the speakers, but not the one that comes from an old stereo system. Speakers generally have an impedance in the range 3 to 10 Ohms, whereas amplifier volume controls are more likely to be about 10kOhms which is why yours is acting like an on-off switch. If you can get a potentiometer of about 100 Ohms, this might do the job, but it would have to have a wattage rating comparable with your speakers. Because speakers are designed to be driven from a low impedance this would also degrade the sound quality.

  Pine Man 12:16 01 May 06

Thanks again Gongoozler.

On the back of the volume control it has the following - 100K?8X2.

The speakers are 8 ohms.

Does that help?

  Pine Man 12:18 01 May 06

On the above thread I had pasted in the ohms symbol between the K and the 8 and obvioulsly it didn't come out!

  Gongoozler 12:28 01 May 06

Hi Pine Man. The volume control you're using is 100K, i.e. 100 thousand Ohms, so anything after the first step of rotation will be a resistance hundreds or even thousands of times that of the speakers, so by Ohms law will be as good as an open circuit in the speaker line. Low value potentiometers are not very easy to find in retail outlets, and as I said earlier you will need one with a few watts rating. Maplin don't stock any, and those I have been able to find are expensive.

  Pine Man 12:33 01 May 06

Thanks very much indeed for your help. I am clearly approaching this project from the wrong direction altogether and will get myself a second set of PC speakers as you suggest.

This must be one of the most useful forums on the internet.No matter what what questions you ask somebody will come up with a solution.

Thanks once again.

  Gongoozler 12:38 01 May 06

Hi Pine Man. You're welcome to the help. Having retired as a circuit designer a few years ago it's good to know that my knowledge is still useful. The only problem I can see with using a second set of PC speakers is the small risk of an earth loop, wherein the widely separated speaker mains earth points could induce mains hum, so it might be worth borrowing a set of speakers just to check.

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