Sub to complement KEF LS50s: SVS vs. Rythmik

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 http://www.soundoctor.com/ 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

classdstreamer:
"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"

Hello classdstreamer,

     Welcome to Audiogon. I’ll answer all your questions but I first wanted to clarify something on your current hookup of a single sub with your pair of KEF LS50 mainspeakers. You didn’t mention which exact sub you are using but it seems like it has the capacity to be connected using either line level or speaker level connections. You stated: "I connected mine via the speaker level input--speaker cable from the integrated to the sub, then from the sub to the mains." This is fine as long as your sub is just reproducing the bass frequencies at or below whatever you have the crossover frequency on the sub set at and the sub has an internal filter that passes all frequencies above whatever you have the crossover frequency on the sub set at to your KEFs. Or, are you running the LS50s full-range?  
     In either case, can you post and name the exact brand and model number of your sub so I can verify a few things?  Here are the answers to your questions:

1. "Paul at PS Audio says the speaker level/high level input is the best because it preserves the sound characteristics of the power amp, which also allows the sub to blend better with the mains."  Is this true?

     Numerous individuals and some subwoofer companies claim this to be true. However, I’m unaware of any objective experiments, testing or even any objective explanations or information that verifies this as valid. The only supporting information supporting this theory are subjective claims from individuals and the marketing departments of subwoofer companies that, apparently, are unable to be verified objectively. 
     Based on my personal 40 plus years of experience setting up and using various subs in my systems, I have perceived no subjective audible benefit of connecting my subs via the speaker level inputs when compared to the line level inputs, and vice versa.
There is, however, a more logical and objectively verifiable benefit to using subwoofers that can result from the main speakers and the main amp(s) being relieved from reproducing the deeper bass frequencies and instead having the sub and its dedicated amp responsible for reproducing all bass frequencies at or below a specific frequency. In theory, the limiting of the main amp and speakers to reproducing only the midrange and treble frequencies(through the sub’s high pass filter if it has one), combined with the sub and its amp reproducing only the deeper bass frequencies, will result in improved performance in the entire audible frequency range of 20-20K Hz provided good blending or integration between the two frequency ranges can be achieved.
     I have personally and subjectively perceived these benefits with specific main amp, main speakers and sub system combinations. But I believe the significance of the perception of this benefit is dependent on the specific amp, main speakers and sub system components utilized.
     For example, my current system components are 1,200 watt class D monobloc amps, Magnepan main speakers and a 4-sub distributed bass array system driven by a 1K watt class AB amp. I perceived no overall sound quality benefits by limiting my main amps and speakers to reproducing only the midrange and treble frequencies. I actually prefer the overall sound of my amps and speakers running full-range and my four subs reproducing all deep bass frequencies in mono from 40 Hz and lower. This does cause an overlap and slight overemphasis on frequencies from 34-40 Hz but I think I must enjoy this. 
     My theory is that this was due to my amps being sufficiently powerful enough that the relief in not reproducing the deeper bass frequencies in my amps for my main speakers, that only have bass extension down to 34 Hz anyways, was not as beneficial as it would normally be on a combination of less powerful amps and speakers with deeper bass extension.
     I suggest you just compare the overall system sound with the speaker/high level connection to your sub with the line level connection and use the method that sounds best to you. I’ve learned the best way to blend or integrate the sound of one or more subs with the main speakers is precise adjustments of the sub’s volume, crossover frequency and phase controls. 
     The goal is to set the volume and crossover frequency as low as possible while still sounding good to you overall. Remember, best results for most individuals’ preference are achieved when they’re not constantly aware of the subs being engaged, it’s normally preferred that they only engage when the music or HT content calls for it.

2. "My thinking is that 2-4 subs may require connecting via the line level input, no?"

     Not necessarily, some subs are able to be daisy-chained together as more subs of I believe the same brand, and possibly the same model, are added. Daisy-chained just means sub#1 is connected normally and sub #2 is connected to sub#1 via a specified method, sub#3 is connected to sub#2 and sub#4 is connected to sub#3 via the same specified method. Usually daisy-chaining on most subs is possible whether the speaker level or line level connections are used for sub#1. But again, you need to state the exact brand and model number of your sub so I can verify your sub is capable of doing this.


3. "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?"

     As stated previously, I cannot discern any significant difference between connecting a sub via the speaker/high level input and via the line level input but it’s possible that you can. However, I believe virtually everyone can clearly discern the bass response performance improvements in their systems/rooms resulting from increasing the number of subs utilized, beginning with adding a 2nd sub and continuing with each additional sub up to four. Any improvements gained beyond four subs will be much less significant and likely beyond the law of diminishing returns. 
     The improvements clearly noticed with each additional sub will include the expected progressive increases in the maximum bass output level and increased dynamics but also the less expected progressive increases in the perceived bass detail, smoothness and the level of blending or integration of the deeper bass from the subs with the mid-bass to treble from the main speakers.
     Overall system sound to expect will progress from two subs sounding twice as good as one sub, three subs being a significant improvement approaching state of the art bass response and four subs sounding twice as good as two subs and likely considered by a listener as state of the art bass performance for both music and HT content.

4. "Also, should my second sub be the same brand/model as the first? Or does quantity of subs outweigh brand consistency too?"

     It’s not required that additional subs are the same brand/model as the 1st sub but may be very useful and important if you plan on daisy-chaining the 2nd sub and plan on adding even more subs in the future.
Sub quantity does generally outweigh brand consistency but probably not if daisy-chaining of subs is desired in the future. It still may be possible to daisy-chain subs of different brands but it depends on the exact brand and model of your current sub and future subs.

     Please post the exact brand and model of the sub you’re currently using.

Tim