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REL subwoofer hum

I own a REL stadium III, and have owned it for some time now. Just recently I noticed that it will produce an audible (although low level) hum when I turn my system’s amplifier off. I have the Stadium hooked up in the recommended manner: I have it hooked up with the neutrik cable to the Speaker B terminals of my amplifier. Speaker A terminals are occupied by my Sonus Faber concertos. When both sets of speaker terminals are on, the sub is quiet. When I turn off the B speaker terminals, or turn off the amp altogether, a low level Hum is output by the REL. I have not noticed this hum before and believe it to be a new occurrence. However, I guess it could be a ground hum. My main amplifier, and the REL are plugged into two different outlets, both outlets have quality AC filters/surge protectors, and I use the stock power cords for the amp and REL. Should I alter my hookup method? Would better power cables help? I really don’t want to have the REL serviced as, I’m sure you know, it weighs 110 pounds, and I don’t want to have to move it. If it is a so-called "ground hum", how do I alleviate it?

phoenix469
tmsorosk
1,013 posts
 
60hz hum or what some call a ground loop problem is common with subs . Audioquest has a sub interconnect that has a ground lug built in , it solved the problem for me . I've not heard of chassis grounds ever harming a component or causing a warranty problem .
Floyd Toole said everything should be grounded to the preamp , to get the lowest noise floor possible .
steam3642
124 posts
 
I tried again with another wire combination on the
M/F kw 500 , as per the Rel manual : red wire to right channel positive , yellow wire to left channel positive and black wire to negative left channel . I found that if i connect all 3 wires to either the left or right channel the hum stops when the m/f is powered down and runs as per normal when powered up Rel appears to operate fine , would this be due to it having a bridged/dual differential internal design , apparently both left and right channels are
open/hot aand feature a bridged output.
steam3642
124 posts
 
I have removed the hum when the Kw -500 is turned of by connecting the 3 wires of the speakon connector to one channel of the musical fidelity , instead of running the red wire to the left channel i have connected red and yellow to the right channel along with the black ground wire. Not sure if this is an acceptable solution but does not appear to be having a negative affect on the amplifier
So all 3 wires are now connected to the right channel and no hum when powered down and m/f and rel works as normal when powered up.
documentroom
24 posts
 
I have the same problem. I have a new rel g1. Expensive sub for sure. Talked to sumiko and they helped but still have that dam hum. I've tried everything. Using ayre mono mxr. Fully balanced system. Even when I ground to preamplifier. Still get the hum. Im about to build out a critical listening room. In the design stage so I might just have to deal with this. I hope the rel is wired wrong on the inside. Any help.
chrisautosound's avatar
chrisautosound
7 posts
 
We had enough clients with this humm problem and others like; distorted audio, static noise.

Unresolved by REL we recently traced out and examined the schematic and found several simple mistakes.

About the humm. The balanced speaker level input is simply miss designed. As a result it does not reject noise or hum. Solved

If using the high level input, there is distortion at anything above watt. A second design flaw, solved.

At high levels using any input the sub sounds like the amp is clipping or the woofer is bad. It can even sound like a flimsy cabinet. A third design flaw limits undistorted ouput to few watts. Again solved.

The woofer, amp and enclosure are fabulous. Once the electronics are overhauled the sound is too.
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