I've been having problems with a noticeable "hum" emanating from our JBL Venue Sub 12. I even have the same "hum" coming from our center channel speaker, but it's not nearly as loud. So, I've done some "searching" here on AVSForum and figured there is a ground loop occuring within our system. Upon trying to locate the culprit, I was changing settings around and unplugging components when I seemed to have found the answer. The "hum" completely went away when I changed the one of the switches on the back of the subwoofer from LFE to Normal. I'm not sure this is the origin of the problem...but at least it stops the increasingly annoying sound.

Can someone tell me the difference between the LFE setting and the Normal one? Will having the sub set to Normal affect dvd playback? I have all my speakers set to "small" and the crossover at 80.


Thanks for the help.

I could be wrong but I think "LFE" means that the crossover is managed by the reciever. "Normal" setting uses the crossover adjustment setting on the amp of the sub.

SimpleSetup,

I think you are right. After you posted, I played around a little more with the settings on the back and moved the crossover dial around and it definately changed the output coming from the sub. Now I really don't know what to do. Do you think I should just set the sub's crossover to as close to 80 as I can get by eyeballing it? I suppose I could always delve a little further into the source of the problem....but I was hoping for an easy fix.

Thanks.

The "hum" completely went away when I changed the one of the switches on the back of the subwoofer from LFE to Normal. I'm not sure this is the origin of the problem...but at least it stops the increasingly annoying sound.

Assuming you have your sub connected to the Subwoofer/LFE output of your receiver, (and not at the speaker terminals), the hum went away when you switched to Normal because you completely blocked *any* signal from going to the sub, including the subwoofer signal. The sub doesn't recognize any signal on the LFE input when set to Normal. You won't have any hum, but you won't have any sub output either.
SimpleSetup,

I think you are right. After you posted, I played around a little more with the settings on the back and moved the crossover dial around and it definately changed the output coming from the sub. Now I really don't know what to do. Do you think I should just set the sub's crossover to as close to 80 as I can get by eyeballing it? I suppose I could always delve a little further into the source of the problem....but I was hoping for an easy fix.

Thanks.
First, fix the hum. Check the Hum FAQ (http://www.avsforum.com/avs-vb/showthread.php?t=322698) for help. It's probably a CATV ground problem which is most common. Try unplugging your CATV and see if it goes away. If it does, you need to have your cable company come out and re-ground your cable line to the electrical ground of your house. Alternatively, you can try a Surge Suppressor with CATV suppression. Plug your audio components, including the sub into the SS as well as the CATV line. This will give them all the same ground potential and will usually eliminate the hum. Once you've done this:

Second, turn the sub back to LFE.

Third, turn the sub's crossover to it's highest point or disable it.

Fourth, use the bass management in your receiver to select crossovers and speaker sizes, (as you've done with the "Small" speakers and 80 Hz crossover.)

Craig