KLH Audio Players & Recorders - Page 4 - Recent Questions, Troubleshooting & Support

see if your manual is at this link. Klh model 990A manual Google Search

I suggest you go over your receiver set-up instructions. See if you need to set the receiver to acknolwedge the addition of the subwoofer. It should be in your receiver set-up steps. Just as a check, hook up one of your other speakers to the subwoofer lead to see if gets audio signal. I'm guessing the issue is your receiver settings.

There are a lot of folks who've had power supply issues with this sub. Typically, the large resistors fail, which takes out the capacitors.

If you know how to read schematics and replace parts, then these might be helpful to you:

Here are the two pages of schematics from KLH. I wrote to their tech department and explicitly asked for permission to share them here.

Here's the lower board, which has the power supply:
KLH ASW 10-120 subwoofer schematic - lower board


Here's the upper board:

KLH ASW 10-120 subwoofer schematic - upper board

Klh asw10 120b owners manual

If you wish to get some details; check the site linked here. Pull up older posts. http://electronicshelponline.blogspot.com/ Circuit diagrams of many popular brand TVs and other devices are given.

Without knowing what they're hooked up too.. SOUNDS like your uder powering them, OR over powering them. Look at the back of the speakers the wattage is what your looking for, look at your amp, example: 1000w speaker running on 50w amp = not good.

You might have blown the speaker. This happens when you play things too loudly and you ruin the speaker inside. You can test this by playing something with a decent amount of bass and turned up a bit. If you hear like a "rattle" in the sound or like something isn't right in the heavy bass notes, then you definitely blew the speaker out. This isn't a tragedy. They're fixable if you bring them to a place that repairs speakers. But I would definitely test it first by hooking it up and playing a loud song with a lot of bass. Hope that helps a little! Please rate my solution!
- Frankie

If the sound is more of a low hum than a buzz, you probably have bad capacitors in the power supply...Time to take it to a shop.