Pondering REL and Dynaudio subwoofers.

@grantgg 

Yes I have one more fix to attempt, I’ve tried several others, which is putting a three-prong to two-prong a/c adapter on the subwoofer and or amplifier

Somewhere I heard this is not safe.

The Rel uses high-level connection which is where the hum issue comes into play.

OK. I also have this problem with high level, not low. You might be able to resolve this without a ground loop / hum eliminator. I use an SVS speaker level subwoofer adapter since my sub does not have high level. Try this:

1. connect the positive line from the class D amp or speaker to the positive on the adapter (you directly to the sub)

2. leave both left and right negative terminal disconnected on the adapter (for you being the sub) from the class D amp or speaker

3. connect a line from the ground screw / or chassis screw on the class D amp to one negative terminal on the adapter (you directly to the sub)

I would check with REL to see if this is OK. They might have a video on this. They will ask if the amp is differential, which it likely will not.

REL tutorial video mentioned above but the instruction is slightly different:

https://www.youtube.com/watch?v=NFbcAgpBID0

Replace the amps. 

@bartsw  yeah, thank you for your input. If I understand you above correctly, I have tried those methods,.  My last exchange with Rel support had to do with ways to power off the subwoofer, instead of fixing the issue. Not an ideal solution.

I will vote for the Dyn sub. I have an 18S, not the sub 6, paired to C4’s. They are mechanically identical - the firmware is different and they do not have grills. I went with the 18S because I got it new on a holiday offer of £1k and the sub 6 was £2k, and I had not tried it out yet. I will replace it with a pair of sub 6’s sometime during the summer for aesthetics and symmetry. 

The sub 6 is easier to match. It took me five minutes to match the 18S. It has a built in 40hz pre-set which suits me fine. After that  it is just a matter of volume matching and placement. 

The Dyn subs have a 3 millisecond delay (about 6 feet) so easier to place than most subs. I am not sure about the Rel. I have had Velodyne, JL Audio, and SVS subs. imo the Dyn is the best of all of these. 

As with anything else, this is subjective and what matters most is what you like in your room. I would recommend trying them both out and that way you make the best decision. This also allows you to kill the ’What ifs’.

Cheers.