My experience adding subwoofers to 2 channel

It is not only phase but arrival times that are important. Two woofers can be in phase at a specific frequency but if one is say 15 feet from the listening position and another 10 feet from the listening position the arrival times will vary and the woofers will be out of phase at all other frequencies. This will muddy the bass and soften the impact of bass drums and such. You can fix this by using digital delays on the speakers that arrive first so that they all arrive at the same time but this works only at one place which is really all I care about. Everyplace else in the room is "background music." There is more to consider than just acoustics. The best approach is to make the woofers function acoustically as one driver which they will do as long as they are within 1/2 wavelength of the highest frequency you care to reproduce. So if you are crossing at 100 Hz the woofers should be no farther than 5 feet apart giving an array 15 feet wide. Below 100 Hz this array will function as one driver giving you one arrival time pretty much anywhere in the room. Now you just have to adjust the arrival time to match your satellites which you can easily do with a tape measure. Try it.

@mijostyn +1
a swarm is even bass, not accurate.

vinnydabully

We have had many years relationship with our REL rep (was with Magico at one point),

and he shared the REL G1 Mark II’s idea with us , since REL’s specialty if u will, is Sub-bass with 2 channel systems. But perhaps the S Series would be your choice. The G1’s are 5500 each, and we have 2 stacks of 3 shown in the photo gallery. Amazing. The Wilson Alexx speakers are the left n rights. Even the T7i’s I have played with our M7900 that we took as trade-in, and it sounds amazing with the $1000 each x 2 sub base.

But the G1 MarkII’s sound Absolutely incredible sound when you use the 3 in what they call an array stack of 3.

But that may be more extreme than you desire. But they many levels of Sub Bass for 2 channel. And their speak-on connector system with connecting the red & yellow wires to the + side of one speaker and the black to the ground terminal on said speaker. And then do the same for other side.

It was fun setting the different frequency for reach, and then going in to experiment with phase.  Very easy to work with.

Here is our high end listening room (the photo of the G1’s is in the slideshow at bottom of page, sorry, I took the photos w iphone, but the REL stacks of 3 you can see behind the Wilson Alexx speakers. In the top of page photo u will see JL Audio f212’s but those are now in the back of the room used for 5.1 only. The G1’s are for 2 channel and have high level connection, and then for 5.1 listening, we then use LFE:
http://audibleimagesav.com/the-transporter/

https://relsupport.zendesk.com/hc/en-us/articles/115004648928-Differential-Amp-Connection-Method

I use the T5i with my little NAD 3020 office system with a couple of MartinLogan Motion 2’s and it sounds great. :)

Art H.

A single sub, with bass traps and DSP, when optimally placed, is an amazing thing. People keep adding more subs, and more complexity because they never heard the single sub well integrated to begin with.

Unpacked the second set of subs this morning and fired em up.I haven't fussed with finding perfect placement yet but it's sounding really good already.The room is energized in a way that I can actually feel it on my skin.Not boomy or overblown whatsoever.Acoustic and electric bass sounds more natural and three dimensional.It's one of those moments where I just relax and know that this is the way it's supposed to feel.Like when you find the perfect compliment of tubes for your amp or get your speakers positioned perfectly.Sigh...there it is.
I was happy with the two subs but this is definitely a step up.