Gain level on a REL sub

We are really talking about two different speakers here.  I had the same Hsu sub and yes, it was a beast, providing very deep bass with slam factor.  But, after messing around with it for a year I ended up realizing that I just did not like it.  The only way to get rid of the port chuffing was to bung up both ports.  Even then it was just too slow for my Snell D's and certainly for my LRS.  I never tried it in a home theater setup and I imagine it would be great for that. 

Enter the REL T9x and it was a whole different ballgame.  For me, the REL is much more nuanced and punchy, quick and 'musical'.  I will be putting another one in my system at some point in the future.  Or maybe try a different sub for flavor - Rhythmik perhaps?  But, not a Hsu.   

Anyway, I can totally see where you are coming form OP.  The REL will not do what the Hsu did.  Not in a million years.  But, I will say that I never turn the gain up on my T9x more than 5-6 clicks.  Even in my long 40 x 15 basement the T9x gives me more than enough.

Seems like the OP is telling us that he thinks it is operating correctly but is just a different kind of speaker than his prior sub.  I would say, however, that if the gain is at 100% there must be some issue.  That just isn't normal. 

I know this is basic, and I know we all know this, but MAKE SURE your  main speakers are in phase.  I bought a new integrated to take to my vaca home, and pulled out two cheap pairs of small speakers, to try it and compare.   I accidentally wired the second set backwards, with one speaker's wires reversed.  My o my did they sound bad.  I finally figured out what I did (embarrassingly), switched the wires, and the bass, image and everything improved.

@jji666 Yes, i am aware of them being different  sounding subs. They both are great subs but in different perspective means. As far as the far as the gain setting, it is not maxed out.  It happens to be at a little before 3/4. 

@fastfreight I have color-coded speaker cables. I would have to be color blind if that was the case.

I am in a similar position with the gain control near to max on my REL S812. The issue for me is that I am using high level and my speakers are very efficient (Avantgarde Duo 107dB/W). So there is very little voltage going to the REL.

In my situation it is ok because I have the REL situated just behind my listening position. If the sub were further away from the listening position then I would like more gain. I am aware of another Avantgarde/REL subs owner with a similar issue.

I had an SVS SB3000 sub prior to this and faced a similar issue.

I haven't tried the low level output from the pre amp. I'm not sure if this would make much difference as I only need a small amount on the volume control to drive the speakers loud.