Subwoofer no longer produce base sound

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.

I would check the caps on the power supply. They are rather large electrolytic capacitors that will look like they burst and/or leaking. When these die, the caps ground and the sub will make a loud buzzing sound. If you are handy with a soldering iron you can replace them yourself. Replace them with the same voltage or a little bigger and same with the size.

If the cap. says 16v 4700pF on it, for example, a 20v 5300pF or a 16v 6200mF cap. will work for this application.

The transistors at the output stage of the sub amplifier circuit might be shorted so each time you power on, the circuit draws a very high amount of current which causes the fuse to blow. It's definitely a problem with the circuit so using a higher current rated fuse would probably just result in damaging the amp even more. You should ask a qualified electronics technician to take a look at it. I hope you can fix it.

How do we knwo it has a good input? The problem could be higher up the food chain. Plug a known good audio source into it. Any Line Level source will do.

I saw this post. I have the same problem with my 10-100.
http://www.fixya.com/support/t2753393-klh_subwoofer_about_6_yrs_old_keeps

Sounds like the hum might be mains hum caused by the failure of the power supply capacitor(s) in the sub. It/they will be the largest on the pc board. You will find all the details (needed to replace it) on them. If you find more than one replace both.

Try making sure that your drivers are all up-to-date, make sure your connection is plugged into the correct jack (usually green one for sound)
BTW is this for TV or PC?? also what windows system if its a pc?

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 techdepartment 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

make sure you have the speaker connection right if you do then it is a ground problem try plugging it in a different outlet

The 'Subwoofer' output on your receiver is used to connect to a powered subwoofer with a built in amplifier. Your KLH speakers use what is called a 'passive' subwoofer, it gets its power from the receiver and then passes the higher frequencies to the left and right front speakers after taking out the low frequencies for the subwoofer. A speaker system with a passive subwoofer is good for casual listening, but a powered subwoofer is required for really hearing low frequencies and rumble in movies. The KLH speakers you have were highly rated in their time for their price. The four satellite speakers and center channel speaker have very good sound compared to the little 'midget' surround sound speakers most people buy today.

Here's how you hook them up:

- The left and right front channels from your receiver terminals should go to the terminals on the subwoofer marked 'From Amplifier'
- Your left and right front speakers are then connected to the subwoofer terminals marked 'To Speakers', they do not connect directly to your receiver.
- Your center speaker is connected to your receiver terminals marked 'Center'
- Your rear speakers are connected to your receiver terminals marked 'Surround'

That should get you up and running. If the bass isn't good enough with the passive subwoofer, you can get a decent powered subwoofer like the Velodyne VX-10 for about $150 and 'kick it up a notch'. Good luck and enjoy....