Pondering REL and Dynaudio subwoofers.

@bartsw  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, that had been advised to me by someone.  I've yet to try that.  The Rel uses high-level connection which is where the hum issue comes into play.  By using the low level connection, hum is not an issue, but I think the Rel performs best on high level in my testing.

  But I am torn between keeping the classic 99 or trading it in for the Sub 6.  As @m-db  has detailed so well. There are big advantages with the sub 6 that really appeal to me and my tastes. I would position it between my preamp and amplifier for its full DSP capabilities.  Only downside is that I have to get some more XLR cables to connect them all.  My Starkrimson only has XLR inputs.

Since this is likely my last subwoofer I'll get, i should choose carefully.   

@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.