I've had the JBL PB12 for about 18 months, and have had to get the amp replaced (under warranty, no problem) at 12 months because of the horrible "rumbling sound" problem. About 4 months after the repair, the sub seems to go in and out of standby VERY frequenly when the receiver is at low volumes. I've tried everything...changing power outlets, adjusting settings on the sub, everything I could think of. I know I'll probably have to take it in for repairs again and HOPE that either JBL or the repair place will fix it under some kind of warranty, but I was hoping against hope that someone on this board has run into the same problem and has an idea. The way the sub is suppose to work is that when it doesn't get an LFE signal for a while, it goes into standby. My trouble is, that at low volume levels (or in a sountrack with limited LFE use), the sub instantly goes into standby (the lights on the front turn red) and then goes back into "On" mode repeatedly. And when it does this, it makes kind of a popping noise, just loud enough to be annoying. I wish there was a way to disable the auto standby...or at least change the sensitivity. If anyone knows anything about my problem, I'll be happy to hear about it. The good news is, back when my sub first took a dump in January, (right before the Super Bowl), I went and got an 8" Yamaha sub for the meantime while mine was getting fixed. Now, I'm currently using both, but I turn the JBL off when the problem gets really bad. Oh, well...next time I won't skimp on my sub...time for an SVS!