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Recommended subwoofer pairing with KEF LS50w?

Which brand should I go with?


  • Total voters
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owl_of_minerva

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Hello, I've been loving my KEF LS50w's for about half a year now and am ready for the first upgrade: subs.

I have a connection that can get me pretty much any dealer-brand subs for about 45% off MSRP (got the KEFs for $1400 new in June). My connection highly recommends REL subs, but I see them criticized for performance and cost here. I'm intrigued by Rhythmic subs which I often hear as a better, cheaper option, but as they're direct-to-consumer I couldn't get a deal on those. It appears Hsu Research is direct-to-consumer too.

My budget is $1000-1500, but I could be persuaded up to $2000. I'm interested in getting 2 subs. I've heard about DSP and Dirac recommended as purchases along with a sub, but it sounds like another science I'd have to learn (although I'm an electrical engineer, I'm smart but lazy). I'll probably upgrade to a receiver and DSP someday though.

My current setup has the LS50's on a shelf next to a flatscreen they're plugged in to, but when I get a sub I'm going to throw in the KEF S2 stands for them. My current room is about 270 sqft, but I plan to move soon, and I could end up in an apartment or a house (big variable I know). I use the LS50w's for about 60% music, 40% movies. My favorite contemporary film is Bladerunner 2049 and would love something that can handle that.

I was looking at getting two REL T7/i's, but would like to know what's better. I hear good thing about SVS. KEF, B&W, Klipsch, Q Acoustics, and Martin Logan are other options, but again any brand that works with dealers I could get a deal on. I just heard about Norweigian brand Arendal, but it's not clear if my connection can access them.
 

phoenixdogfan

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I'm using the SVS SB 2000 with my OG Ls 50s and I'm very happy with it. If I were you I would look at a pair of SB 3000s which are flat from 20-150 hz and come with a 600+ watt amp, plus a whole lot of integration software. SVS is alway free freight if you need them serviced, and they have something like a 90 day return with full refund no quesions asked. Located in the states, in Youngstown, Oh. , so if you're also in the US no freight/customs hassles which are major these days as I can attest--particularly if you're returning something of value for repair and have to pay outbound freight and inbound duty.
 

Katji

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JL Audio D110
Better than the rest. Better drivers, better amps.
 

dwkdnvr

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My favorite contemporary film is Bladerunner 2049 and would love something that can handle that.

We watched this relatively recently in our theater setup with a pair of 15" subs (Dayton RSS390HF ported). I don't know whether I messed something up with calibration or had a setting wrong, but BR2049 is BY FAR the most bass heavy soundtrack I remember experiencing in our setup. Granted, we don't tend to do a lot of blockbusters, but it really was striking in the contrast. I'd think you'd want a pair of 15s

Just yesterday I received a pair of Rythmik FM8s to pair with Kef R3s in our new primary system (we just moved, and the 15s don't fit our space). The FM8s are obviously too small to meet your goals, but my 'quick take' is that they deliver on the reputation of Rythmik subs - very tight and articulate with deep extension - the FM8s are fantastic for music in a room about the same size as what you're in (a bit bigger, and with vaulted ceilings), but obviously sealed 8s aren't going to cut it for HT. Looking at the price list though, I'm not sure you can pull in the system you want under your budget if you go with Rythmik. I suspect what you really want is a pair of FVX15s, but that runs solidly over 2k. A pair of FVX12s is ~1800 and might be sufficient, but you'll certainly get more raw output for less $$$ from someone like SVS.
 

CDMC

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JL Audio D110
Better than the rest. Better drivers, better amps.

Do you have any evidence to support they are better? JLs have in the past been overpriced relative to their competition and had reliability issues.
 

CDMC

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If it were me, I would go with Rythmik, HSU or Rythmik in that order.

What you don't discuss is size limitations. All other things being equal a larger vented enclosure will net you more bass than a smaller sealed enclosure. To maximize the bass capability, I would target a pair of the Rythmik LVX12, Hsu VTF-3 MK5 HP, or SVS PB-3000.
 

theyellowspecial

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The Kef Kube subs are supposed to be really good. Some people on AVS prefer them to the sealed SVS subwoofers. Something to consider since you'd be getting a deep discount.
 

JohnnyHonda

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In my room of 12 x 21 x 9, the SVS SB3000 have been a great match to my KEF LS50 Wireless ii. Use the KEF digital crossover setting at 75hz. The parametric app works well, I had a high Q boost of 4 db at 63hz to deal with a minor room cancellation (Took care of most of the cancellations with front/side absorption, ceiling/back side diffusion/absorption from GIK Acoustics. Superb subwoofer.
 
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sfdoddsy

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I’ve owned LS50s numerous times.

I like them a lot but am firmly of the opinion that they should be crossed high to avoid stressing the woofer.

Or buy a 3 way like the R3 or Reference 1.

The LS50W may reach 50hz with EQ, but it shouldn’t unless you listen at late levels all the time.

You need to cross at 150hz.

Which means you need two subs. And they have to extend beyond 200hz.

Fortunately two on your list do. The SVS SB100 fits the bill very well.

Cheap, plays high, goes quite deep.

An even better choice for just a bit more is the Rythmik L12. It goes lower and louder than the SVS, and if you connect to the LFE input (bypassing the crossover) it actually plays higher. Mine doesn’t start rolling off until 500hz or so.
Plus it has selectable extension and EQ.

So I’d choose 2xL12s.

They are half the price of the F12, and give up the grand sum of 1db in volume.
 

kmurp

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Could one of you detail the detailed setup settings that you use in the KEF app as well as the settings you use on the sub itself?
I had a sub a couple of years ago with these speakers and got rid of it as it sounded bad. Perhaps it was my settings?
 

Trouble Maker

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I like them a lot but am firmly of the opinion that they should be crossed high to avoid stressing the woofer.

The LS50W may reach 50hz with EQ, but it shouldn’t unless you listen at late levels all the time.

You need to cross at 150hz.

Which means you need two subs. And they have to extend beyond 200hz.

At what frequency does most content go to stereo?
It seems like the LS50W only has a single (mono) sub out, and from what my quick google fu tells me the highest crossover point is 120hz. I can't seem to find the crossover slope, higher would help here, but that's almost always true right?
Owning the LS50Ws one of the most convenient parts is them being an all-in-one solution with no nee for any external boxes. So unless you start to look at more external boxes, which would defeat the purpose of some of the built in parts of the LS50Ws, you're 'stuck' with what they have built into them. But it is also limiting and part of why if I go to a full surround setup, which I very well may soon, I'm likely to ditch them.
 
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owl_of_minerva

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Why no KEF KF92 then? :p

Actually, the KF92 is intriguing. It has the same opposed driver that the popular Rhythmic one does and that's a glowing review. Right now I'm looking at 2x SB-2000 Pro's or 2x REL T/7is. Those and the KF92 all retail for about $2000. However, wouldn't it be better to have 2 subs with separation in terms of cancelling modes and whatnot? Or is a dual-driver KF92 just as good as a 2-sub setup? I suppose the smaller footprint of the KF92 can't be ignored.

I'm still torn- the idea of watching Blade Runner 2049 on the SVSs and music on the RELs both sound equally exciting.
 

detlev24

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A dual-opposed sealed subwoofer, like the KF92, has the following main advantages compared to a more "traditional" sealed build:
  • more compact enclosure at a similar cone area, which in case of the KF92 is double 9" drivers'
  • lower distortion than a single 9" subwoofer at any given SPL, due to double the cone area
  • less enclosure vibrations, as forces cancel [some relatively light subwoofers, otherwise, tend to "move" under higher cone excursions]
This is not a replacement for multiple subwoofers; which will be the better choice in most scenarios. Integration of multiple subwoofers is also trickier, compared to a single subwoofer set-up. In case of your options for dual subwoofers, I definitely would recommend to go for the SVS subwoofer(s), instead of REL.

However, you will only be able to "cancel" room modes, if you arrange both subwoofers to receive the same MONO signal, i.e., both subwoofers need to behave as if they were a single subwoofer - but they need to be spaced apart.

Some kind of DSP with bass management functionality, like the basic 'miniDSP 2x4 HD' [depending on the integration in your system], would be required - and (the 2x4 HD) could be equipped with filters created in 'Multi-Sub Optimizer' (MSO).
 

ishnish7

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A dual-opposed sealed subwoofer, like the KF92, has the following main advantages compared to a more "traditional" sealed build:
  • more compact enclosure at a similar cone area, which in case of the KF92 is double 9" drivers'
  • lower distortion than a single 9" subwoofer at any given SPL, due to double the cone area
  • less enclosure vibrations, as forces cancel [some relatively light subwoofers, otherwise, tend to "move" under higher cone excursions]
This is not a replacement for multiple subwoofers; which will be the better choice in most scenarios. Integration of multiple subwoofers is also trickier, compared to a single subwoofer set-up. In case of your options for dual subwoofers, I definitely would recommend to go for the SVS subwoofer(s), instead of REL.

However, you will only be able to "cancel" room modes, if you arrange both subwoofers to receive the same MONO signal, i.e., both subwoofers need to behave as if they were a single subwoofer - but they need to be spaced apart.

Some kind of DSP with bass management functionality, like the basic 'miniDSP 2x4 HD' [depending on the integration in your system], would be required - and (the 2x4 HD) could be equipped with filters created in 'Multi-Sub Optimizer' (MSO).
How critical would you say it is to have DSP for your subs? I am torn on deciding on subs for the LS50 wireless ii. I thought I was set on the Rythmik L12s, but being that they don't have DSP, I am stuck again. Does DSP make that much of a difference? I don't want to have to invest in a miniDSP if I could just get a very good sub with DSP already. I know SVS subs have DSP, but "musically", I hear they're not as good as the Rythmiks.
 

BigBeard

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In my room of 12 x 21 x 9, the SVS SB3000 have been a great match to my KEF LS50 Wireless ii. Use the KEF digital crossover setting at 75hz. The parametric app works well, I had a high Q boost of 4 db at 63hz to deal with a minor room cancellation (Took care of most of the cancellations with front/side absorption, ceiling/back side diffusion/absorption from GIK Acoustics. Superb subwoofer.
do you set the bass extension to speakers to low when using a subwoofer with the KEFs? Any benefit to not doing this?
 

JohnnyHonda

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Just standard, less pressure on the small KEF woofer (and I couldn’t hear or measure the difference).
 
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Ultrasonic

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How critical would you say it is to have DSP for your subs? I am torn on deciding on subs for the LS50 wireless ii. I thought I was set on the Rythmik L12s, but being that they don't have DSP, I am stuck again. Does DSP make that much of a difference? I don't want to have to invest in a miniDSP if I could just get a very good sub with DSP already. I know SVS subs have DSP, but "musically", I hear they're not as good as the Rythmiks.

You will struggle to find any sub with the DSP capability of a 2x4 HD or SHD I think. Whilst the likes of Arendal and SVS offer some DSP capability it is much more limited and harder to optimise. I use a PSA S1510 for music and am glad it doesn't offer any paramtric EQ as I'd basically be paying for functionality that I'd ignore in favour of using my SHD. I live in the UK where Rythmik subs sadly aren't available and so I can't comment from experience, but on reputation I think a Rythmik sub with external DSP sounds like a very good option. Provided you are happy to spend a bit of time learning how to use REW and making measurements.
 
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