CD / Radio Speaker testing...

[haslemere_harry]

Is there a way of testing whether or not a speaker has blown by using a multimeter? One of mine has given up the ghost and is such a bu**er to get to, and the wiring so tightly secured & routed, that I would rather find some means of testing it in-situ before going through the process of removal.

Any tips appreciated.

Thanks in advance!

Mark

 

[misterg]

You should get continuity (i.e low resistance) between the two wires to it (almost a short circuit). If you don't there's a problem. If you do, there might still be a problem if there is a short somewhere, but much less likely IMHO.

Andy

 

[cozzykim]

Is there a way of testing whether or not a speaker has blown by using a multimeter? One of mine has given up the ghost and is such a bu**er to get to, and the wiring so tightly secured & routed, that I would rather find some means of testing it in-situ before going through the process of removal.

Any tips appreciated.

Thanks in advance!

Mark

Check with an ohm meter, most speakers will be 4 or 8 ohms, sometimes even if it measures O.K. overheating can cause the coil to distort and jam in the magnet

 

[Ardenfour]

You should get a reading of around 4ohms. You can also brush a 9v PP3 type battery across the speaker wires, you should hear a crackling from the speaker. The voice coil can become jammed or displaced through entry of dirt, grit or steel fragments which are attracted to the magnet, giving a correct reading on meter but no sound. Can you remove a grille to gently press the cone to see if it moves freely?

 

[misterg]

You should get a reading of around 4ohms....

I'm guessing where you got that figure from, but will point out that the DC resistance of speakers bear little relation to their nominal impedance (4 ohm, 8 ohm, or whatever).

Just look for continuity...

Andy

 

[st599]

Check with an ohm meter, most speakers will be 4 or 8 ohms, sometimes even if it measures O.K. overheating can cause the coil to distort and jam in the magnet

4 or 8 ohms impedance NOT resistance. Caused by the inductance of the coil and frequency dependent. Resistance will be minimal.

 

[Ardenfour]

Yes it is impedance, but any speaker I've checked (quite a few) have produced a reading close to the rated impedance ( which incidently will vary according to frequency) using a fluke meter on resistance scale. A dead short reading, ie zero resistance, on a speaker coil would suggest to me shorted turns, and a duff speaker.

 

[cozzykim]

4 or 8 ohms impedance NOT resistance. Caused by the inductance of the coil and frequency dependent. Resistance will be minimal.

Thanks for the "heads up" Yes I do know the difference between R and Z.

I think you'll find it depends on the power handling rating of the speaker amongst other things, with a 200W driver relying on just a few turns of copper wire in the coil having a relatively low resistance and impedance varying with frequency.

I've just checked about half a dozen 1 - 5W speakers and they were ALL within 1ohm of their label impedance.
I would suspect that smallish marine speakers will be similar.

@halcyon, thanks +1

 

[haslemere_harry]

Great, thanks everyone- tremendously helpful as always!

Mark

 

[Ardenfour]

Awrite cozzy kim wasn't tryin' to be a smart a**e, just my experiences

 

[st599]

Thanks for the "heads up" Yes I do know the difference between R and Z.

I think you'll find it depends on the power handling rating of the speaker amongst other things, with a 200W driver relying on just a few turns of copper wire in the coil having a relatively low resistance and impedance varying with frequency.

I've just checked about half a dozen 1 - 5W speakers and they were ALL within 1ohm of their label impedance.
I would suspect that smallish marine speakers will be similar.

@halcyon, thanks +1

Are you then not measuring the resistance of the cross-over, not the speaker.

 

[cozzykim]

Are you then not measuring the resistance of the cross-over, not the speaker.

Yes, if a boat speaker has a crossover system, but you have to start somewhere and a simple resistance test will at least show O/C or S/C as a fault.

Unless you have a better idea, in which case, why not post it?