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

 The 15A circuit ground still passes through the REL to the bonding.  Fingers crossed.

Seems like there are two votes to try powering the subs with one outlet.  I’ll give that at shot tomorrow.  Note however that the two subs’ grounds should  already be bonded, as  the black leads of the two Speakon cables are both connected to my amp’s ground stud as Rel recommended I do.  

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.

^Nice^ - I think you could be onto something, but the ever increasing loudness is still puzzling.

I believe that the speaker cables are also in the loop, with the SpeakOn hooked up to them.
So the OP might need both of the subs “and the amp” on the same power strip.

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.

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.

@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).

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.

@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.

@nyev 

I am sorry to say this to you.  But you purchased a premium subwoofer and are having a problem I have never heard of before.  Time to buy new connector wires (know you switched left to right) and see if problem goes away.  

If it doesn't, and I had the same problem I would consider that I had a subwoofer that was not functioning properly.   Just my humble opinion.

I totally agree. If it is acoustic feedback and I believe that it is, it is the most bizarre case I have ever come across.

My guess is that the high level speaker cable is the culprit. I’m guessing that since it is a speaker level connection, REL is using speaker cable for the connector. Speaker cable by design is unshielded. I believe you also mentioned that there is a router in close proximity to the offending sub.  My guess is that the router or something near it is emitting a low level signal that the high level connector cable is picking up, sending it to the subs input and so on. The solution could be as simple as raising the high level connector cable off the floor or by using the low level inputs.

@audiorusty that sounds likely. I do wonder however where the offending signal is coming from. As I mentioned I feel like the sound is a 60Hz “megatone”, so likely AC from somewhere. And yes lowering the filter would stop a 60Hz tone from being produced. And it starts with a quiet rumble and builds, it’s almost surely a feedback loop. But, I do wonder how the sub “feeds back” the tone back into the offending input signal, since the output is acoustic as you say. This totally makes sense when considering turntables picking up vibration from speakers and infinitely magnifying it, but I can’t figure out how a sub would do that to itself….

I do wonder if there might be an interaction between the sub and my main speaker driver, somehow generating a micro signal on the speaker cable, which is of course connected to the high level speakon cable at the amp terminal…. That micro signal could then be fed back into the sub in perpetuity, which would infinitely increase the signal level. Probably a far fetched theory, but interesting stuff.  I suppose I could test it out by disconnecting the speaker cable from the main speaker and seeing if the problem still happens.

Sounds like you were experiencing acoustical feedback. Having the issue diminish or disappear all together when you moved the sub is an indicator that you were able to disrupt the phase relationship between the subs output and input and since you lowered low pass filter setting the offending signal is more than likely above that setting and no longer being reproduced by the sub.

Also, the one single thing I’ve not been happy with about my B&W 802 speakers is fixed - the image not follows you as you move left and right from the sweet spot.  Before the Rel’s, things fell apart even moving 2” off of the sweet spot.  What a relief. It was worth it just for that!

I should also mention that after fiddling with position and the crossover and volume settings, my system sounds fantastic.  It took quite a bit of work to get to this point and I wasn’t sure I was going to get to a point where I get all the benefits people speak about when adding pairs of subs for music.  I had a small coffee table to the left of the left sub which was causing things not to gel.  When moving that coffee table away, everything clicked. What is amazing is that the benefits I notice the most don’t have anything to do with bass. The #1 biggest improvement is how solidly formed and coherent vocals become in the middle of the soundstage. 

As everyone says I found that using a pair is far better than one, as the benefits to soundstage and vocals are nowhere near as pronounced when using only one.  

So I discovered that the problem only happens if the crossover setting is set at the 12 o’clock position or higher!  It was in this position only for the burn-in process.  My normal crossover point is much lower than this position.

I still want to fix the issue but this is good news as now I don’t need to worry that the apocalypse won’t be triggered at any time during normal use!

@holmz , thanks and yes I did try swapping the speakon cables, with no change.  Haven’t swapped the power cables though, will try that next.  Not expecting any change, but I’ll let you know if there is.

When sliding the sub forward or backwards the problem goes away. When I leave the sub in place and move the power and signal cables away from other wiring, then the problem remains. It’s definitely something that happens when the sub is in that exact spot, AND the speakon signal cable is connected, AND there is no signal /music playing. Weirdly, it even happens when the amp is turned off and unplugged. But disconnect the speakon signal cable and no issue when powering on! Very weird problem. But nothing wrong with the subs. I’m going to buy a roll of EMI shielding material to experiment with. It’s not too expensive, and maybe I can try multiple layers if needed. The cover with a small bit of carpet or rug for aesthetics, once the issue is resolved.

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

I forgot to mention - just as an indication of just how loud that sound was, when the issue happened the first time and we weren’t prepared to stop it, the sound persisted for about 6-7 seconds, and the problem sub actually UNPLUGGED my other sub connected to a different outlet about 12ft away! Just incredible. I think it’s the loudest sound I’ve heard, ever.

Anyone know of the most effective brand and type of EMI shielding out there?  Seems more practical than the paint option.

@jetter , @lalitk I tried exactly that - swapping the left and right subs and leaving the connections in place. The problem stayed on the left, so there is definitely nothing wrong with the subs.

When sliding the sub forward or backwards the problem goes away. When I leave the sub in place and move the power and signal cables away from other wiring, then the problem remains. It’s definitely something that happens when the sub is in that exact spot, AND the speakon signal cable is connected, AND there is no signal /music playing. Weirdly, it even happens when the amp is turned off and unplugged. But disconnect the speakon signal cable and no issue when powering on! Very weird problem. But nothing wrong with the subs. I’m going to buy a roll of EMI shielding material to experiment with. It’s not too expensive, and maybe I can try multiple layers if needed. The cover with a small bit of carpet or rug for aesthetics, once the issue is resolved.

@sryeager yes it very much sounded like the end of the world! I couldn’t imagine if this happened when on the other side of the house or downstairs, with this sound blaring! I’d be already of not only the sub damaging but also random stuff in the house breaking!

Even if I fix the issue with shielding, I’m going to be forever paranoid that it will randomly return. As I mentioned, for the first bit, there was no issue.

Update:  I wonder if I can get that sound to play when my houses alarm system is tripped.  No need for monitoring with that sound playing - it would literally be impossible to be physically in the house with that roar!

Graphite paint is EMF blocker.

Better shield coils of driver, enclosure, floor options are many.

I have a pair of REL and had a similar issue using the speakon hi-level connectors.

Floating the ground did not solve the problem. 

Trimming the cables helped a lot, but ultimately I connected both red and yellow wires to the red section of the speakon connector. Silence.

Ultimately I bought 3m RCA connectors and ran those from sub-out on my amp to the Low Level input (not .1 LFE) and that sounded better than the stock speakon cable.

If you want to stay with the speakon cable connection, get one made with exactly the wires you need (and nothing else) by Frank at Signal Cables - they will be much cheaper than the $600 REL cable. 

Check out signalcable .com /relspeakon.html

+1, @jetter ….try to isolate the problem. After swapping, if the problem persists then you know there is nothing wrong with subs. Be patient and work with REL customer service and your dealer to eliminate the problem.

-1 on the advise to abandon high level connectivity on REL’s. You might as well save money and get Joe Blow subs if you can’t use high level inputs on REL’s.

I ran two REL T5s for quite a while, and twice I had a feedback loop when I wasn’t playing the stereo but the amp was on.  The first time, from downstairs under one of the subs, I thought the end of the world was imminent.  I put them on the same outlet and it never happened again.  I also grounded the subs to the amp chassis.  But, my house is old with mostly ungrounded plugs, and the subs were both on different ungrounded outlets.

You might try disconnecting both speaker level connections and using the right and left Subwoofer RCA outputs with shielded interconnects from your integrated amplifier to the suspect Sub Bass speaker. They don't have to be fancy cable.

https://www.bluejeanscable.com/store/single/subwoofer.htm

I preferred the low level preamplifier outputs to the REL I used. Far more noticeable was comparing the Studio III to the, at half the price Velodyne Digital Drive conventional subwoofer side by side. Good luck with it.

I would switch the right sub to the left including all of the connecting wires and see if the same thing happens.  How is EMI impacting the sub, is it through the subs remote control function, or somehow through one of the wires connecting the speaker?

@bimmerman2 Talked to Rel today, yes you can have the black wire floating (you should tape it with electrical tape to avoid it accidentally coming in contact with the chassis and causing a short.

if you have a ground stud on your balanced differential amp (NOT the negative speaker terminal as that would be disastrous, you can also connect it to that. Rel recommended doing so to me on the phone today, but it’s not necessary if you don’t have any problems with ground hum.

Back to my issue, after much diagnostic troubleshooting this evening I found the problem. Turns out the position of my left sub is in close proximity to a wireless device ( I think it is a router) in the suite below, despite the thick soundproof flooring. When I move the sub either forward or backwards the noise changes to a low and constant hum. Move it far enough and it goes away entirely.

My next step is to see if Rel thinks it is worth it to source some inexpensive EMI shielding material. My thought is I can lay 1m x 1m of it (or more) it on the floor l, and then put a small rug over it so it doesn’t look bad, and the Rel can then sit on top of the rug. Not sure how effective that mesh EMI shielding is but I think it’s worth a shot.

I’ll talk to Rel tomorrow again to see if they think this is worth trying.  I’m just really glad I didn’t have to send back a defective unit and have a replacement shipped.  My wife was afraid that sound was going to break the houses windows and now the kids are absolutely terrified of my subs.  Rel, you are not helping with my popularity in my house! :)

REL hookup to a balanced differential amp use the yellow and red together only, the black is unused. That's how they are attached to my differential monoblocks. 

+1. Shouldn’t need a dedicated outlet to function properly although you could try it pretty easily. 

Send that one back or contact the MFR