Blew a 2nd speaker?

[The DirtMerchant]

OK, several months ago (6-8) I had some visitors and somebody cranked the audio WAY high for a second.
I noticed my front left mid/woofer was sounding like it had laryngitis. I took it out of rotation
and replaced with one of my rears (that was collecting dust in the garage) and didn't think much of it. In the last few months I noticed that the left and general volume was lower than what I was used to and I had to turn up the volume more than usual. And I went up close and the mid/woofer on the left is out completely. On the right voice are heard clearly, on the left high pitch echo and that's it. I have no idea how the speaker was messed up the 2nd time.

To confirm it is the speaker and not the signal, I switched L/R cable. R cable connected to L speaker, not hearing much. L cable connected to R speaker, everything is hunky dory.

Are there any other basic tests I should run to confirm a speaker issue? Or do I just bring it somewhere for repair? (there's a licensed Mackie repair shop a few towns away).

Should I have any worry of a line issue causing damage to my L speaker?

 

[MakeMineVinyl]

If you swapped the channels and the same speaker was still bad, it is probably the speaker and would need to be taken for repair.

 

[Dentman]

Seems odd to me that twice the same channel blew a speaker. If your receiver/amp is savearly underpowered well then it would be easy to do. That aside it seems odd.

 

[MakeMineVinyl]

Seems odd to me that twice the same channel blew a speaker. If your receiver/amp is savearly underpowered well then it would be easy to do. That aside it seems odd.

I didn't realize it was the same channel that blew the speaker. If that is indeed the case, I would get a volt meter and measure the DC voltage across the speaker terminals with no signal. It of course should be zero volts! If it has anything more than maybe 20 millivolts or so, then that amplifier channel has excessive DC offset which absolutely can cause heat damage to a speaker. Specifically, DC can heat up and eventually deform the voice coil former which will cause the voice coil wires to rub against the magnet plate, eventually causing a short or open circuit. Also, although it is less likely, the amplifier could be in ultrasonic oscillation which will cause the same damage to the tweeter. Unfortunately the only way to test for ultrasonic oscillation is by looking at the no signal condition on an oscilloscope. A usual handheld meter will typically not have response high enough in frequency to detect this type of oscillation.

 

[The DirtMerchant]

I didn't realize it was the same channel that blew the speaker. If that is indeed the case, I would get a volt meter and measure the DC voltage across the speaker terminals with no signal. It of course should be zero volts! If it has anything more than maybe 20 millivolts or so, then that amplifier channel has excessive DC offset which absolutely can cause heat damage to a speaker. Specifically, DC can heat up and eventually deform the voice coil former which will cause the voice coil wires to rub against the magnet plate, eventually causing a short or open circuit. Also, although it is less likely, the amplifier could be in ultrasonic oscillation which will cause the same damage to the tweeter. Unfortunately the only way to test for ultrasonic oscillation is by looking at the no signal condition on an oscilloscope. A usual handheld meter will typically not have response high enough in frequency to detect this type of oscillation.

I have a volt meter...how do I do this on a Mackie HR824? I may have forgotten to mention that these are the speakers that I have. Not sure if everything still applies the same to actives...

Take it I have to open up the back and do that, right?
Only available connections I have on the outside are the XLR and RCA plugs...

 

[MakeMineVinyl]

I have a volt meter...how do I do this on a Mackie HR824? I may have forgotten to mention that these are the speakers that I have. Not sure if everything still applies the same to actives...

Take it I have to open up the back and do that, right?
Only available connections I have on the outside are the XLR and RCA plugs...

Yes, with a powered speaker you will have to gain access to the woofer terminals by removing the amplifier backplate or the driver itself. Just be careful for high voltages from the AC line.