Low Voice Coil Resistance Reading (possible causes?)

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I'd be very grateful if someone can help me understand what's happing here. First of all, this inquiry ISN'T a question about why the resistance in ohms when testing a voice coil through a multimeter is always slightly lower than that driver's impedance specs. This is a different question...

I have a compression driver diaphragm that has a MUCH lower than expected resistance reading when tested with a multimeter. By low, I mean 2 ohms resistance for an 8 ohm driver. What would cause a voice coil to read that low when it otherwise looks in good shape and has continuity, the right number of turns, a good connection with the terminals, etc.? It also seems to have much lower than expected SPL (around 104 db when the specs say 110. I'd love to understand what would cause this and how to approach a repair (the diaphragms are sadly long out of production).

Thanks!
 
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If the compression driver uses a ribbon wire,single layer voice coil;the return wire which is placed flat at right angles to the coil can be the cause of the low resistance reading.This is still the shorted turn problem as indicated by KatieandDad and I specify this particular case as it can be corrected by peeling back the return wire and then resetting it with a suitable adhesive.
 
Thanks for the replies. Shorted turns makes sense to me. I could also see how the return wire could possible cause lowered impedance if it is shorting into the turns. The voice coil happens to be ribbon single-layer wire, likely to be aluminum, less likely silver. Does anyone have any suggestions about where I could find someone to re-coil to original specs of the compression driver?
 
A shorted turn will have little effect on the resistance. It will have a dramatic change on the impedance. An old used driver will have lost magnetic field and have lower output.

I would question how you are measuring the spl level as the normal method requires a plane wave tube.
 
Does anyone have any suggestions about where I could find someone to re-coil to original specs of the compression driver?
Make and model number of the driver would help with suggestions.
If you want to match another driver, original specs are less important than the other driver's present specs, "original" specs were often different in different times.

In addition to the previous shorting possibilities mentioned, a magnet chip or other metal (or carbon) debris in the gap could be the problem, removing the coil and cleaning the gap would solve that.

Then the next problem is properly aligning the diaphragm.

If debris is causing the partial short, you may read a resistance from + and - to the magnet structure, try meg ohm scale as well as ohms.

If you already have removed the diaphragm and it reads low outside the gap, debris is obviously not the problem ;) .
 
The driver is a Goto Unit SG-370. I don't expect many on this board have a lot of experience with them and diaphragms are nearly impossible to find. I removed the diaphragm to inspect and the resistance measurement didn't change (still 2 ohms). I have experience aligning large and small JBL diaphragms by running test tones. I'll try the return wire first because that's the simplest. If that doesn't work, I'll look for someone to coat and re-wind the coils if that's feasible.
 
If the speaker is driven too hard then the enamelled copper wire can melt together and short out. In my experience it is usually a partial short.

I had an amplifier fault that blew my speaker. I fixed the amplifier and when I started to use it then it just blew again. Of course the faulty speaker caused by the amp fault had caused the problem again.

You can either rewind the speaker or just replace it.
 
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