Adding a Sub do i go with 1 or 2 ?

I have had some time and spare money to spend on my system, I run Soundlab Dynastats the bass is good and adjustable but feel i would like some more deep bass,

I am looking at Rel Sub woofers as i like their idea of amplifier terminal connection to high level input on Sub,

Is it best to go with 1 good Sub or 2 good Subs ?

Is there benefits to adding 1 Sub in each channel ?

All advise is very welcome thank you.
I use a REL just for the way they connect to the amp; only use one and find it suitable; guess it depends on your room size and characteristics as to whether one or two is more desirable; I'd get one and you can always get another one if you want to.
2 subs- one for each channel, just like you have 2 speakers. Each channel have differing signals, both in higher and lower frequencies.
What I like about the REL is that it connects to each of the two L & R positive speaker outputs and to either one of the negative outputs; so it gets the same signal the main speakers are getting. As for having one or two subs, one is ok for me.....low frequency sound is non thunder or a jet engine; you can't tell exactly where it's coming from
I am old school and like to drive and active sub by way of speaker level outputs and though REL and others can rationalize 2 subs for 2 channels I have never found it necessary cost effective or practical in my installations... Start with one. Enjoy the music!
I've had one and it was good. I've had two and it was better. I currently run two subs; it can help take care of room nodes. There is some research out there that says more and more subs is better and better but I stopped at two and you probably should too. Integration with your mains is essential. RELs make that easy but it can be done with other subs too--albeit in a different way.
astewart8944 is right about more taking care of modes, but while the research shows greater benefit from more, it also shows greatly decreasing incremental benefit from more than four. So what you want is four. Also they need to be placed asymmetrically, and somewhat out of phase. Do this and you'll get amazing bass. Read the Swarm threads.
I use a single REL S/5 SHO and sounds great...a friend has an almost identical system, but very different room, and he uses a pair of REL S/3 SHO and sounds depends a lot on system and room...
Are the new S/5 SHO and S/3 SHO as good as the REL Stentors ?
Hard to believe how far off you guys are. Its not a question of which sub. Only when you get to four subs, properly located, only then does it matter which drivers you are using. As long as you stick with the old paradigm of one or two, you are so far off base it really does not matter what you use.

Insert gif of head banging into keyboard until turned to mush. That is what you’re doing.

Frankly I was more than a little shocked to learn the answer has been there now for well over a decade. Seriously. Go do a search.

Guess its like autophagy, induction cooking, or any of a number of paradigm-changers. Hardly anyone adventurous enough to adopt the new. Almost everyone exposed to newer and better lamely sticks their head right back in the same old feed bag.

Seriously. Go read the threads.
I use 2 RELs on the same (mono) power amp derived signal as that seems to allow for the standing wave/null issues to be addressed to some degree, although one sub can work fine when properly set up in spite of claims otherwise. A stereo sub arrangement won't put equal bass levels in each sub so they then can't help each other as much, and my subs are adjusted carefully and the stereo image from the mains is excellent. Much has been made of the 4 sub solution ideal and I like the "swarm" system's design goals, but if you don't have room for 4 subs you can still enjoy music although I recommend you not invite Millercarbon over anytime soon.
The AK swarm of four is typically run in mono 

"The AK swarm of four is typically run in mono."

This is because virtually all recordings have mono bass. Ford Motor Company wanted to find out how common stereo low bass was in deciding whether they needed stereo subs for their high-end sound systems. They tested hundreds of CD’s and did not find a single one with stereo below 100 Hz. Now they probable overlooked the few audiophile recordings that have stereo bass (which I’ve heard rumors of), but the point is, it is very rare.

That being said, there is some benefit to adding a second amplifier and running the Swarm in stereo or dual mono. The benefit comes from using the phase controls on the amps to put the two subs on the left side of the room 90 degrees apart from the two on the right side of the room. This is called "phase quadrature". The low-frequency phase difference at the left and right ears synthesizes hall ambience, and makes it sound more like you are immersed in a large acoustic space. Credit to David Griesinger for this technique. It also helps with the modal smoothing, so that you don’t need to reverse the polarity on any of the subs.

But you are correct, the normal configuration is mono, and when using a single amplifier in most cases the polarity of one of the four mono subs is reversed, which improves modal smoothing a bit.  The main point of the Swarm is smoothing of the in-room bass, because "smooth" bass is "fast" bass.  It is the (typically room-induced) peaks which decay slowly and make the bass sound slow. 

Regarding the number of subs, as a general principle two subs are twice as smooth in-room as one, and four subs are twice as smooth as two, assuming the subs are intelligently distributed. Eight subs are grounds for a divorce, so I stopped at four.

Regarding the Dynastats, I’d be tempted to shove a pound or so of fluffed Polyfill into the cabinet, and then plug the port with an expandable plumber’s test plug, turning it into a sealed box. It will probably still go down to the upper 60’s or so, but my guess is that it will blend better with the sub(s) in sealed-box mode.


Swarm guy/former SoundLab dealer

HI The RELS I have picked up are Stentor and Stadium, they are both ported and so far using a flat crossover setting with just gain control the bass is awesome,

I have both Subs set up in mono using the xlr high level input,

I am on the look out for another Stentor for £350 it is an absolute bargain.

Thanks everyone for advise 2 is working better than 1 in my room/system.

The Stadium on its own was not good enough but along side the Stentor its awesome.

I have the Stentor between my Soundlabs and the Stadium in line with the Stentor behind my rack.