Velodyne F1800R Subwoofer - Hum, and occasional LOUD popping

Certainly a good place to start.

I'd also suggest the "tap on the PC board and components with a piece of dowel or other insulated stick, and see if you can make it pop" trick.

I suspect that there may be a broken and thus intermittent solder connection somewhere in the amp. Transistor leads soldered to the PC board traces are probably the first place to check. These leads can carry a lot of mechanical stress... as the amp heats up and cools down, the expansion of the leads can fatigue and eventually break the solder junction.

Re-do the junction with fresh solder (a drop of RMA flux doesn't hurt) and you may well fix the problem.

I had an amp go flaky in this way last year, with symptoms that sound like yours... popping, snaps, and a sort of sizzling hiss in one channel. One of the driver transistors on the main PCB had cracked loose in this way.

Remembering something else the Velodyne guy said on the phone. The power amp in the "can" is supposed to be a "3-dimensional" circuit inside the can. I don't know exactly what this means, but he implied that it was not repairable. Thus, the hope it is just the caps, perhaps.

Look for the obvious, like a separated surround. IIRC this may have been one of the units with the accelerometer in the woofer and a servo circuit. Separated surrounds would cause this kind of symptom on them.

Leonard

The surround look perfect. Pushing in on the cone, I notice it seems to have a very stiff suspension.

Lots of their amps are made with a heat sink wrapped around most of the amp circuit. They are a PITA to service. With that kind of symptom, I'd be looking for a cap or a leaky FET, possibly an op amp going bad.

Leonard