I finally added a second REL Sub


It's taken me years to get to this point.  Subwoofers were 2-channel system blasphemy when I was coming up in the hobby.  As of today, I now have 2, REL T9is.  They are providing sub-bass and filling out the picture for Klipsch Cornwall IVs.  Even with a loudspeaker as massive and efficient as the Cornwall IV, they fill things out nicely.  

How pleasing it was to hear the two in unison.  I run them so low on crossover and volume that the only thing you hear is sweeter more extended highs against a fuller picture down low.  They are simply not audible in their own right.  Yes, it's true--good sub bass management helps treble and midrange.  

As a hack musician of 20 years or so, I can tune them by ear when I hear a well recorded kick drum, bass guitar and horns.  I tried tuning with mics and software but the good ol' ear does very well here.  

If you're on the fence about one or maybe a second you owe it to yourself to try it.  Is SWARM next? Doubtful.  This is, however, very pleasing indeed. 
128x128jbhiller
Thanks for posting this, it adds more confirmation of the same. I recently returned to a dual stereo sub configuration myself.  Was not for added bass.  The sole purpose and hope was to recapture a more balanced sound stage and presentation.  I was not expecting an overall improvement in imaging and sound stage depth, and this returned as well.  I'll never go back to a single sub configuration, or will have no sub at all.  
Just went this direction, and am waiting for delivery of two Rythmik subs. I have a REL now and may sell it or see if I can either add it as a third or use in another room. 
Yes two subs is great for every system. Best upgrade I ever made. 
Something you should try is high passing them. I 100% sure you will get better sound, as in much better. Crossing them over higher (40hz-70hz, I use 60hz,). This is not a low pass but a crossover to the mains and it will take your system up another level. 
The subs simply outperform your speakers under 80hz. At 60hz the drivers in your main speakers start to fall off and struggle. This also will take a lot of vibration out of the main boxes abs let the mids do their thing. 
There are a few options from JL and bryston for active crossovers. Something like a mini dsp might be a cheap way to try it if your preamps does not support it and the JL-CR1 is too pricy.  
https://www.soundstageultra.com/index.php/equipment-menu/537-jl-audio-cr-1-active-subwoofer-crossove...
The Distributed Bass Array concept at the heart of the Swarm subwoofer system was developed well over 20 years ago. More than likely it was around while you were coming up. Or at any rate it has been known a very long time. The sad, puzzling, perplexing part is why something so powerful and beneficial is still flying under the radar. Even now, you have two, when it would be so much better to have four. No not four as big and powerful, but whatever four you can buy for the same money. So the secret is still not understood.  

Sad. Puzzling. Perplexing.

Oh well. Two at least is better than one.
Yes, Millercarbon, I started the hobby in earnest in the 1990s.  

It is sad and puzzling the these devices got such a bad rep that they have been held back, at least a bit.  For every a-phile who uses one, it seems there's more who cannot stand them. 

I think they are wonderful when executed right.