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Speaker/Stereo Amplifier Question

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thakidd:
I need a new set of speakers for my computer as the previous ones bit the dust after cat took claws to them. I have an old stereo amplifier that works. It is suppose output to a pair of 8 Ohm speakers which bit the dust along time ago. This stereo is 15 years old so there is not a switching option to step the stereo amplifier down to any other ohm setting.

A friend of mine gave me a set of 5 surround sound 3 Ohm (each) speakers. I hooked a speaker up to each channel (left/right) and noticed a distinct buzz at low volume. I am wondering if I could hook two of the 3 Ohm speakers up to each channel of the stereo amplifier to minimize the buzzing sound. I am also wondering what I need additionally to cancel out the extra 2 Ohm (Speaker 1: 3 Ohm + Speaker2: 3 Ohm = 8 Ohm - 6 Ohm = 2 Ohm left).

Total n00b on speakers etc so any input is greatly appreciated.

If the above is not the problem, I would love to know what other steps I could take to stop the buzz and use at least two speakers which the stereo amplifier.

Lance:
Is it a sort of mid frequency static like buzz or a low hum?

DJPhil:

--- Quote from: thakidd on December 01, 2010, 05:14:29 pm ---I am wondering if I could hook two of the 3 Ohm speakers up to each channel of the stereo amplifier to minimize the buzzing sound. I am also wondering what I need additionally to cancel out the extra 2 Ohm (Speaker 1: 3 Ohm + Speaker2: 3 Ohm = 8 Ohm - 6 Ohm = 2 Ohm left).
--- End quote ---
Speakers are often listed at their minimum resistance, which is a bit higher than the DC resistance, but their impedance varies drastically over the audio range. Here's a Wikipedia article to get you started.
You can certainly use two speakers per channel, and it's not worth worrying too much about the extra two ohms. It's safe to tinker with, at any rate, as the risk of damage increases as the impedance drops. A solid state amp (just about everything nowadays) will be damaged by a short and indifferent to an open circuit, and tube amplifiers are largely the opposite. Small amplifiers will have trouble delivering power to a low impedance load, and I believe operating at lower volumes begins to bring out the distortion at the frequencies the speaker presents the lowest impedance (low end and mid minus the resonant peak).
If it doesn't sound right no matter what you might want to try hitting a thrift store and looking for different speakers.

Hope that helps. :)

thakidd:
Its a low hum with a small bit of static. It got better after I hooked two speakers in series but its still quite noticeable especially when no sound is currently playing.

So the current hook up is as follows:

Amplifer (+) --- Speaker1 (+)     Speaker1 (-) --- Speaker2 (+)     Speaker2 (-) --- Amplifer (-)

DJPhil:

--- Quote from: thakidd on December 01, 2010, 09:36:05 pm ---Its a low hum with a small bit of static. It got better after I hooked two speakers in series but its still quite noticeable especially when no sound is currently playing.
--- End quote ---
That's not likely to be related to the speakers. Sounds like 60Hz pickup from the front end of the amp. Disconnect the amp from the computer and see if you still get a hum. If you pull the cord from the computer and touch the end you should hear a loud hum/buzz from at least one channel. Make sure the volume isn't turned way up, it'll be loud! If this sounds roughly similar to your hum, you've found your trouble.
To fix this, try increasing the level coming out of the computer until it's as high as you can get it without distortion. This should help by swamping the interference with a stronger signal. If nothing you do rids you of the interference then it might be a bad ground connection (or a dirty circuit board, or a dozen other things) within the amp.


--- Quote from: thakidd on December 01, 2010, 09:36:05 pm ---So the current hook up is as follows:

Amplifer (+) --- Speaker1 (+)     Speaker1 (-) --- Speaker2 (+)     Speaker2 (-) --- Amplifer (-)

--- End quote ---
That's just fine. Standard loudspeakers have no polarity, but the terminals are marked so that both channels are in the same phase. If they weren't in agreement it could cause some odd distortion and canceling effects on any part of the signal that's sent to both channels. This usually makes vocals sound quiet or really weird. It doesn't hurt anything, just sounds awful.

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