Audio Systems: jbl model b380 subwoofers, rubber edge, dust cap

Question
I have (2) jbl 15" subwoofers purchased approx.25 years ago.they are powered by (2) separate adcom amps bridged at600 rms.(5years ago i had the speakers worked on but i never used them untill recently, my original reason for having them fixed was they would emit a cracking or popping sound at high sound levels. i am not sure about the exact repairs i think the rubber edge, dust cap,something about the spider, they sound good but, when my system reaches about 100-105dbs they still pop and crackle. i replaced the cable to the receiver, and have ruled out both amplifiers and cable as being the problem as both speakers emit the sound problem i have also been told and read that the sub will handle a great amounts of clean power.I would like to know what the problem could be and if it the speaker shoul be reconed and who could you reccomend a reliable shop to test of fix it.

Thanks
Fred S.

Answer
Hi Fred,

Thanks for the detailed question, but in the end, it's almost impossible to diagnose a problem with audio gear if it's not sitting here and can be tested.  The pop & crackle is likely caused by one or both of two things:

1. The power supply is not strong enough (high enough wattage) to properly drive the subs.

2. The magnet and cone mover is bad and need to be replaced, and is just always going to break up when driven to a certain level.

It could be those were never rated to be driven at more than 100dBs level, so you might just be pushing it too much.  My best is the power supply just can't handle that load and would need to be upgraded.

As for a shop that can fix it, I don't know where you live, so unless you were in Portland, Oregon I can't recommend but you can always check the phone book and/or do a Web search for local repair shops.  A new, upgraded power supply will probably take care of everything.  Good luck!  Cheers, Wink