DIY sub help

[Cdub]

I have Stryke AV12 in an enclosure with 2 15" PRs powered by a 350 watt plate amplifier. I have two identically built subs in this configuration. One of them is having a few issues.

1) When played at low levels I hear a clanking or rattling noise like the driver is bottoming out, but the driver is barely moving so I'm not sure what it could be. Any ideas?

2) When the sub is plugged into the wall with or without sound input there is a hum. I'm fairly sure this is not ground loop hum because my other subwoofer does not exhibit this problem. Could it be a "bad" amplfier?

Thanks for any input,
Chris

[joecarrow]

1) Passive radiators often have threaded rods with a nut that allows you to add mass to tune them. If you have a washer on the rod and the nut isn't tightened down, this could cause your rattling noise- and it would happen at low levels. You could take the PRs out, play the sub quietly without the PRs and see if the noise is still there- if it's not, check for anything on the PR that could be tightened down that isn't. If the noise is still there with the PR gone, you know it's the driver.

Be careful, though! With the PRs removed, it will take a lot less power to damage the AV15. Start with really low volume, and if possible use a well controlled test signal.

2) By process of elimination, the only difference is the amplifer? Could it also be a bad cable? The AV12 certainly wouldn't introduce a hum. If you just bought these amps and you can narrow it down to just the amp, I hope you can get it replaced under warranty. If not, it could be a broken solder joint inside the amp. If you're really comfortable with electronics and can work with them safely, you could open it up and visually look around for any cold solder joints- probably on the input jacks- and hit them with a little fresh solder.

If you don't have experience working with electronics that include line voltage, and the appropriate safety precautions, I'd recommend getting the amp serviced. It sounds like you're fairly close to narrowing it down.

I hope that helps.

[Cdub]

Thanks Joe. I'll check out your ideas and keep you updated.

If anyone has any other ideas, it would be appreciated.