REL Q150E - bizarre humming fault


Well-known Member
My REL has recently developed a humming noise.

If you remove the LFE connection and leave in the Neutrik connection, it persists.
If you remove the Neutrik connection and leave in the LFE connection, it persists.
If you remove both connections, it persists.
If you remove the power cable it disappears.

From what I've read on these very forums, I have a ground loop problem. However, several things bother me;

1. The hum persists no matter what electrical socket I use in the house.
2. The hum persists if I cut the earth wire within the power cable.
3. The hum persists no matter what power cable I use.
4. The hum persists no matter what LFE cable I use.
5. The hum is AMPLIFIED if I touch the Rollover dial. If I remove the plastic dial and touch the exposed metal post, I can make it hum very loudly :eek: .
6. If I touch the exposed post and one of the LFE sockets at the same time, the hum is eliminated completely. Is my body acting as earth in this instance?

I discovered that by connecting a wire between the earth terminal of my amp and the Rollover dial post, 95% of the hum is eliminated. It only disappears completely when I touch one of the LFE sockets.

My guess is the REL has developed an internal PCB fault, through my own stupidity. I recall hearing a humming noise a few days ago when I unhooked the sub from the amp without first powering it down. It was only reconnected for the 1st time yesterday.

Any thoughts/comments before I look to having it repaired?


Distinguished Member
It does sound like an internal earthing problem.
If you feel proficient enough, it might be worth opening it up if it's out of warranty.


Distinguished Member
Hi Gareth, does indeed sound like an earth problem of some sort :)

sorry i cant offer any other advise :(

hope you're getting on ok with the 7600 :thumbsup:


Got the exact same problem. Used to leave sub powered up all the time, but now have to turn it off when not in use. Have disconnected it from hifi as it is too annoying. Just connected to AV amp now and even then on quieter scenes it bugs the **** out of me :mad: :mad:

Have you had an success in repairing the fault?

bad ass

Novice Member
hi, ok my Q150 had the same problem. Where I work we area dealer for rel, so I gave the rep a call and suggested to give their tech support a call. gave them a buzz and they were happy to take a look. after taking a look and checking their own stock they discovered it is a commom q150 problem and also in the quakes, especially so when the neutrik connection is present. the way I solved the problem is ust to not bother turning off my amp. I've even had it on the strata 5. the only rels I havn'e had the problem with is the new r series ( R205, r305, and r505) however saying that the new r series aren't that great.
the controls are ina stupid place and hard to get too, even though the subs themselves are the same finish the grills are vaious shades of grey/black. I also don't think they're as punchy and as musical as they used to be.

hope this helps


Well-known Member
Thanks for the replies guys.

As the sub's out of warranty I whipped off the back to take a look inside. Surprisingly little in there, but TBH I have no idea of what to look for.

Earthing the rollover dial to the amp has helped reduce the humming significantly. It's still there if you hold your ear up to it, but it's undetectable from my viewing position 12ft away.

I've decided to leave it as it is for the moment. From reading other similar posts on this forum, it would appear some REL subs suffer from a background hum as a 'normal' feature.

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