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New Rel Carbon Special Sub “Roars” when there is no signal!

I’ve been breaking in my new Rel Carbon special subs (I have a pair) and one of them started having an issue after about 12 hours of playing them (quite loud).

Just recently the left sub makes an absolute roaring sound when the music signal stops, or when I turn the volume all the way down.  It starts as a quiet rumble but VERY quickly builds to an absolute massive roar.  Was worried about damage but it seems fine provided a music signal is playing.  The issue did not happen until just recently. Now, when I simply turn on the sub, even with the Amp in standby mode, the roar starts building and I have to shut off the sub really, really quickly.

I have my Rel’s connected to my Gryphon Diablo 300, using Rel Bassline Blue high level cables, using Rel’s directions for connecting a balanced differential amp which I’m told the Diablo 300 is.  I have each sub’s high level cable connected to the amp with each cable’s yellow and red lead connected to the red speaker output, and both black ground leads connected to my Diablo 300’s ground terminal.

There is one thing different about each sub right now - the sub without any issue is connected to the wall to a dedicated 20A circuit.  The sub that just recently developed the issue is connected to a shared 15A household outlet - temporary until I acquire longer power cords. I have half a mind to plug the “working” sub to the shared household AC circuit to see if the problem is limited to that line but I’m a bit scared of damaging something.

My Diablo 300 amp is connected to a Torus RM 20 that is plugged into another dedicated 20A outlet….

Any guidance would be appreciated!

 

 

 

nyev
nyev OP
1,027 posts
 

@jetter , thanks and if that’s true I have TWO defective subwoofers (Ahem, sub-bass systems…), as the problem is always on the left even when I switch the subs.

I do have a terrible amount of coiled power cords (high end Audioquest) behind my system that I think is also a possible culprit. In fact, if my AQ Dragon feeding my amp is too clustered with my streamer’s AQ Hurricane cord, there are slight but very noticeable and annoying issues with my sound’s balance.

Keep in mind when I have my crossovers set to where I like them set, there is no issue.  The issue only happened when I set the crossover to the 12 o’clock position for burn-in.

holmz's avatar
holmz
2,328 posts
 

I do have a terrible amount of coiled power cords (high end Audioquest) behind my system that I think is also a possible culprit.

Well the speaker wire carry a lot of current, and so does the sub.
Any magnetic field that is coupled into the speaker wire or IC would generate a 60Hz signal.
I suppose a coil of wire is a great way to make an electrical coil. 

I’ll quote myself…

I would swaping the left and right SpeakOn cable, and also the power cables.

nyev OP
1,027 posts
 

@holmz, sorry I didn't update you, but swapping the power cables made no change (I had also swapped the SpeakOn cables before your suggestion and there was no change).

 

nyev OP
1,027 posts
 

Small update - as I mentioned I was suspecting the sub might be driving the drivers of my left main speaker and that is where the ever increasing feedback is coming from, since the speaker cables are tied to the SpeakOn cables at the amp. Of note, the issue happens even if my amplifier is completely unplugged from power.

Seems I was right - there IS an interaction with the left speaker. I tried disconnecting the left MAIN speaker cable and trying again. This time, I heard a flat 60Hz tone that did NOT build into a roar. It was flat, and not too loud. Reconnected the speaker, and the feedback loop with a building rumble was back....

My latest guess is that the sub or SpeakOn cable is picking up AC noise at 60 Hz (only when no music signal is input for some reason), and the sub is feeding that back into my left speaker, adding the amplified noise back into the speaker cables and thus the SpeakOn cable as well, which feeds the amplified noise back into the sub, creating an infinitely building feedback loop.

wlutke
723 posts
 

Forgive me if I missed something but,

As @sryeager noted you may have a ground loop between the two RELs.  Plugging them both to the 20A line with an extension cord would be an easy check.  An acoustic  feedback loop with the amp unplugged is a non starter. Two REL inputs tied to the speaker terminals will not drive a speaker either.  A ground loop can, and the pure 60Hz tone suggests that.  A weak or missing ground can do strange things.  My 2 cents.

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