Forum Thread

Check speakers for short circuit?

Devedander 8,844 826 August 17, 2010 at 03:35 PM
My buddy has a receiver that went into protected mode and the manufacturer says it's because there is a short somewhere in the speaker system..

We are going to replace and test his speaker wire, however he wondered how you know if there is a short in your actual speaker... I have no idea how to test this... anyone got any ideas?

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Joined Feb 2009
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#2
I guess the reason is the speaker ( or cable) draw too much current from your receiver. The Speaker Impedance might be the key..
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#3
Use a temporary speaker wire and test each speaker 1 at a time or just unhook each wire from receiver until it goes away. If your handy with a volt/ohm reader use that with a 9volt battery on the other end of the wire.
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#4
Best way: coil ringer

Next best way: ohms function of a multimeter.

Speaker wires can be tested with just an ohm meter. Disconnect them at both the amplifier and speaker ends, and measure the resistance between the wires. It should be infinite. Measure both ends of one wire at a time. Each wire should be zero ohms, but a few tenths of an ohm is OK (usually means the meter's own wires and contacts have some resistance).

What's the impedance of each speaker? In practice, the minimum impedance is the same as the DC ohms reading, except for piezo tweeters, and will usually be 4-8 ohms. However some amplifiers don't like 4 ohm speakers, and if you have more than one set of speakers per channel, it's highly likely the impedance will be 4 ohms or less. BTW, do NOT increase the amp ratings of the fuses because they're already as high as they should be.

Another thing to check for is the presense of DC voltage at the amplifier. It shouldn't be more than about 1/10 VDC. If you read several volts, one of the output transistors has shorted.
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#5
Thanks all, he is going to replace the speaker wire anyway (his old wires had splices here and there and looked bad anyway).

The speakers themselves are what he is worried about.

isolatedbody the problem is the receiver seemed to take weeks to go into protected mode... as if it's somehow slowly building up some kind of problem until it goes into standbye.

larrymoencurly speaker impedance we will be looking at because I think it's possible he has mixed and matched some odd combinations. Also testing DC voltage at the reciever, is that between speaker connecter and the case or what?

So it seems like from the responses, there is no real way to check for a short in the speaker itself (as inside the speaker box itself)?
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#6
Splices are probably the points of failure
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#7
Second vote for splices here.
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#8
Quote from Devedander View Post :
larrymoencurly speaker impedance we will be looking at because I think it's possible he has mixed and matched some odd combinations. Also testing DC voltage at the reciever, is that between speaker connecter and the case or what?
Between the two terminals for each speaker. This can be done at the receiver or the connected speaker terminals; it doesn't matter.
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