Sub to complement KEF LS50s: SVS vs. Rythmik

Hi all. I'm considering adding a subwoofer to my current set up: Bluesound NODE2i (Tidal MQA) to Cronus Magnum II to KEF LS50s. I'd like to supplement the KEF's on the lower ranges.

I'm considering 2 subs and have located a few deals:

  1. Salk Sound Rythmik F12 in white for ~$1100 
  2. SVS SB4000 for ~$1200

I particularly like the room control on the SB4000, but am not wed to it. Any thoughts between the two? Anything else you'd recommend in this price range?

A few other notes: room is 12 x 30 feet, with a wall of windows (NYC condo). Acoustic paneling is next! Likely don't need all the size/wattage that either of these subs provide. Perhaps getting a MartinLogan "X" with the room correction could suffice, but would rather buy top notch and be done with it.

I'll utilize this for 75% music / 25% movies. Music tends to be bluesrock/jam bands/jazz

I own two 12" sealed Rythmik and super happy with them in an all audio setup. Looking at the frequency  response of LS50 it seems these start to drop right after 100Hz. Maybe a better option are Rythmik double 8" (F8??) subs that can play nicely up to 250Hz, even if you don't need to xo that high, it seems regular subs wouldn't work best with your monitors as they tend not to be optimal above 80 or 90Hz.
I own the LS50s and paired them with two REL T5 and it works well.  The LS50s do have a bit of a bass boost that is unfortunate.  Perhaps installing the plugs would help?  TBH I should have/didn't try but that might have flattened out the bottom.  Anyway I do like the REL particularly with the monoblocks because they get the same signal as the main speakers. 
Great thread! I’m new to this hobby, and this is my first audiogon post. I just connected a sub to my KEF Q150s this week. It was a game changer. But I find myself saying "game changer" every time I add a new component. I keep thinking I’ll hit the point of diminishing returns for my money, but that hasn’t happened yet.

My question to any/all of you is, how do you connect more than one sub to your system? I connected mine via the speaker level input--speaker cable from the integrated to the sub, then from the sub to the mains. Paul at PS Audio says the speaker level/high level input best because it preserves the sound characteristics of the power amp, which also allows the sub to blend better with the mains. My thinking is that 2-4 subs may require connecting via the line level input, no? If this is the case, would you say that the trade-off for using the line level is more than made up for by the quantity of subs? Also, should my second sub be the same brand/model as the first? Or does quantity of subs outweigh brand consistency too? Thanks
Hey Jdtalv,

I would say that it is a horse apiece.

I also was debating between a Rythmik F15HP and an SVS SB4000. My feeling was/is the Rythmik servo technology is a better design, I ultimately ended up buying two SVS SB4000 due to my interaction with both companies. Though my interaction was not bad with Rythmik, it was not as professional as my interaction with SVS and since Rythmik is direct sales only I was a little concerned about how I would be treated if I ever happened to run into a problem. They both have at minimum 30 day trial periods so you could try them out in your system.

I also agree that any high quality sub will more than likely work in your system as long as they have a low pass filter (usually incorrectly referred to as a crossover) and phase alignment capabilities. (not just a polarity switch)

Since you say this system is primarily for music you will want a SEALED sub, not a ported or a sub with a passive radiator, and you will want to plug the port of your KEFs. If the KEFs start to roll off at 100Hz you will probably experience directionality from the sub so I also would recommend a minimum of two subs.

Lastly you should also check out for some excellent integration techniques.
i had the ls50s successfully integrated with a single JL Audio D110 subwoofer and the sound was excellent.  
JL makes high quality sounding subwoofers and the tone of the bass is what they really do well, the tone of the notes is addictive.  slam and impact are there too.  
the LS50s with no port plugs had a natural steep rolloff at 70 Hz in my room.  point being that no filtering is required and there will be no directionality to a single sub.  
the JL D110 will be an excellent sounding solution that pairs very well with your amp too, just connect with the high level speaker connections.  the JL is superb at blending as well