Maintaining & repairing PA speakers?


After a busy few weeks, my PA speakers are not sounding quite right. My main speakers and monitors are all rather old, so I guess it's about time they were checked over & repaired as needed. We may have damaged them, or more likely they have degraded over time and I have only just noticed.

In particular one of my mains (JBL MPro 412) sounds a little muffled in the high end, and I suspect we may have damaged the HF driver. Also, my monitors (Passive FBT Maxx 4) sound different to each other.

But where to start? Is there a simple way to check drivers are healthy (checking resistance with AVO?).

Do the caps on the crossovers degrade like they do in old valve amps?

Any guidance would be really welcome. Especially as I don't speak the local language here to well, so dealing with repair guys is hard work, and expensive!

Rex Anderson

Good to have some basic test equipment plus use your ears. You should be able hear if a driver is blown by playing a CD through the system. Do one side at a time, not both at the same time.

An oscillator will let you run tones through and really hear if something is not working as you sweep from 20 nHz to 20 kHz.

Could be driver or crossover.
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