Problem with stage monitors...

[Blah067]

Our school has 4 JBL stage monitors.
We need all four of them for the upcoming show.

Problem: in previous shows, I always find two of them that sound just...dumb.
They sound almost like a speaker only receiving half of its biamp single (no, I'm not biamping these). One is lacking highs and sounds muffled, and one is lacking lows and sounds like a tin can.

This is what I KNOW...
It IS the speakers (I've replaced all cables, patches, board channels etc etc).

I haven't had time when I find problems to FIX the problem...or troubleshoot it, because I've always been in time crunches.
WHAT can I do next week when I have the space reserved purely for fixing this among other things? What can I do to "fix" them or find the problem?

One though I had is that perhaps an internal switch got flipped or a driver is blown? (We have no limiting on our aux sends for effects).

[rroten]

It sounds like you have blown drivers. You can either bring them to a certified JBL repair tech, or change the drivers yourself. I think I've heard that JBL parts are hard to come by.

Ryan

[avkid]

Where are you, and what model are the speakers?
(PM if necessary)

[Eboy87]

Is there a processor in-line with the console and monitor amp?

I agree, it either sounds like a blown driver. Other possible causes could be bad soldered connections on the crossover network or input jack. The crossover network could also be bad; components loose or broken off.

A quick way to check to see if your drivers are bad. Open up the cabinets. Get a 9V battery and a 9V battery harness from Radio Shack. Touch the harness leads to the tensile wires on the drivers. They should pop and move. If they don't, the driver's toast (or the battery's dead). You can also check with a multimeter. If the voice coil shows infinite resistance, the VC is open.

Only other thing I can think of would be a processor sending a high passed or low passed signal to the different amp channels. Which brings us back to question #1.

[mixmaster]

Originally Posted by rroten

It sounds like you have blown drivers. You can either bring them to a certified JBL repair tech, or change the drivers yourself. I think I've heard that JBL parts are hard to come by.

Ryan

I've never had problems getting replacement drivers from my JBL rep. If you need a new driver you can get most of those through the same JBL dealer that you got the speakers. They also sell recone kits for most of their speakers, horn diaphragms, speaker cones etc, if you are up to the task of doing your own recone.

More to the point I'd be finding out what caused the drivers to blow before I went and put new drivers in the cabs.

Matt

[museav]

Knowing the models would definitely help, some speakers that can be biamped may have both full range and high/low connections and something could be miswired. Blown drivers or bad crossovers are also a definite possibility but it being the low in one box and the high in the other indicates perhaps two different problems.

[rroten]

Originally Posted by mixmaster

I've never had problems getting replacement drivers from my JBL rep.

Figures, the guy who told me this was a dealer that doesn't deal JBL. Goes to show you to take all dealers' advice with a grain of salt. The drivers could easily be damaged by any prolonged feedback or transients from unplugging/turning off gear with the amps still on. This is especially true for the high frequency drivers.

Ryan

[dafunkmonster]

Are they externally-powered or self-powered? I've watched people spend a half hour trying to troubleshoot self-powered stage monitors, only to figure out that it was an issue of the knobs on the back being set incorrectly...

[airkarol]

Originally Posted by Blah067

Our school has 4 JBL stage monitors.
We need all four of them for the upcoming show.

Problem: in previous shows, I always find two of them that sound just...dumb.
They sound almost like a speaker only receiving half of its biamp single (no, I'm not biamping these). One is lacking highs and sounds muffled, and one is lacking lows and sounds like a tin can.

This is what I KNOW...
It IS the speakers (I've replaced all cables, patches, board channels etc etc).

I haven't had time when I find problems to FIX the problem...or troubleshoot it, because I've always been in time crunches.
WHAT can I do next week when I have the space reserved purely for fixing this among other things? What can I do to "fix" them or find the problem?

One though I had is that perhaps an internal switch got flipped or a driver is blown? (We have no limiting on our aux sends for effects).

My first guess would be the drivers. I'm not sure where you are, but if you're in the NY area, and need someone to handle a repair, I highly recommend DBM Pro Audio, in NYC. Great people, great service.

[Blah067]

I can completely 100% confirm that it is something inside the speakers. All rack gear and cables are OK! I have switched everything (literally...everything), and I know its the speakers.

They are passive speakers (just answering questions).

Yes we have biamp and passive connections, I am using the passive ones correctly, no worries there.

For the record, these speakers have ALWAYS been this way (since I came in about a year ago). I know a marching band show used them as house speakers...with no limiting certainly...I know the damage didn't occur during MY USE.

Our TD also said "well...until we need all 4 of them at once, we won't pay to have them fixed...."