Adding a second sub question

Would it be worthwhile adding a second sub in this case or would the money be better saved for future updates?

Right now I have a pair of LS50s and a single KEF KUBE 1. A small, very modest sub. I see one on eBay for $150. But given the specs, I wonder if adding a second one really gains me anything.

  • Amplification Type. active.
  • Speaker Driver Diameter. 7.87"
  • Speaker Driver Diameter (metric) 200 mm.
  • Nominal Output Power. 150 Watt.
  • Frequency Response. 38 - 150 Hz.
  • Output Level (SPL) 111 dB.
  • Crossover Frequency. 40 - 140Hz.
  • Audio Amplifier. integrated.

Low power. 38 Hz.

Do I skip it and wait until I can add a pair of those Syzygy monsters Wally at Underwood is so high on at a grand or so?


Why wait? I can’t think of a down side. A second sub, identical to the one you have, should give you better placement options and improve things over all. IMO, “stereo subs” are the way to go – i.e., you should place these close to you main speakers and try to blend them in as part of full range signal at a cross-over setting that works with your LS50’s.

For a “buck-fifty”, worst case is you sell both of the KEF KUBE’s for a couple of hundred dollars after you have saved up for your KEF KUBE-killer sub(s). FYI, in July a KEF KUBE (MKI) went for $190.00 on Audiogon.


I second that. More fun for a buck fifty is rarely to be had. You can also experiment with putting them 1/4 or 1/3 of the way along the side walls (assuming a regular-shaped room), which can be fun if you’re cool with sorta artificially widening the image, while at the same time, depending on your setup’s seat-to-speaker distance it may put the subs in better time alignment with the mains.

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My biggest concern was that I’m not gaining a whole lot of low end down to 38 Hz. But I take your point. Odds are I’ll probably jump on it.

With some careful integration, I am willing to bet you will be surprised at the improvement. If nothing else, there should be a better sense of “smoothness” across the frequency range.

Let us know how it goes if you pull the trigger.

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As cool as it is to have identical subs, I personally have used two different sizes before, and by noodling with placement and crossover point, it is possible to get them to work in their sweet spots and gain some extension. Some will likely be offended by that suggestion due to lack of symmetry, either visual, aural or imagined.

I strongly encourage you to do it. Even if they are small, fart boxes, the farts will be better distributed throughout the listening space…exciting the nodes and cutting the peaks in half (give or take).

I think a pair of Rythmik L12 sealed servo subs are tough to beat for ~$1k/pair.

3 db down at 18Hz and little phase shift.

Good point. The $150 may be better applied to a more expensive sub with the intention of getting a 2nd better sub in the future.

Many say identical is best, and I agree, but two different will still be better than one in my opinion and experience.

Two identical can work together (doubling headroom) and not fight each other, allowing for careful placement in the room to defeat the evil.

I own JL Audio d110 Dominion subs. I recently added a second for a stereo pair. While my d110s aren’t KEF KUBES, I can tell you the benefit of adding a second is worth every penny. Assuming you like the KUBE you’ve got.
Makes sub integration easier by helping break up standing wave room modes that a single sub will inevitably cause. One other tip, while it might be aesthetically less pleasing, seriously think about asymmetric placement of a stereo pair of subs relative to your room boundaries. Breaks up standing wave modes better than just about any other trick I’ve ever tried, including bass traps which I’ve never liked.


Okay. I bid on it. We’ll see what happens.

Thanks for the advice.


Big fan of asymmetrical placement. In my space I have one just behind the left speaker and it’s mate just to the left of my seated position, both driven high level from left channel. Magical.


I have seen sub opinions stating that most of low end benefits happen above 38. But I suspect the performance of the sub in the 38 to up to as high as 300 hz is the key. I think investing $150 to hear what happens is the first way to go. I recently, personally, learned (heard) the effect that a sub can have on soundstage and openness. This came from the result of Syzygy’s firmware update on my 12" power sub. I too am trying to decide on a second but need more time to evaluate the firmware update. I would recommend one, their DSP reallys works and well beyond my expectations. I have no idea what two subs would do for sound quality.

If you are an obsessed sub nut then, little will stop your buying. However, you did not write what your current set up does for you now and what you expect to gain from a 2nd. That may help those who want to advise you. As enticing as the phrase “stereo subs” sound, I have never experienced such a set up and would only try if I could get a 30 day trial. Because the subs have to work in your paricular room and support your LS50s, not overpower. I am not being negative, just reminding you of what you probably know well.


It’s not about stereo subs at all. There is very, very little if any distinction between L and R bass. Many mixes simply mix bass below some threshold to mono.

Multiple subs helps smooth the effect of room modes and as a side benefit increases headroom.

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Subwoofers, a pair beats a single easily. The science behind it is clear enough, I’m not going to try to explain it. Accept or reject…

I would advise you look for a pair of REL subs. I have T/9I subs. Available for around 2k for the pair. Highly recommended. You can go lower, but the T/9I is a pretty sweet spot to live. Everyone I know who owns REL subs loves them, and they also have larger subs than mine.
Someone here is convinced and will try to convince you that you only really need one sub. They / this is wrong and they just don’t know any better yet.
I have full range speakers with the subs located behind each. It is amazing how well this works when you have it dialed in.

My two cents…

( I had a single sub for a long time, knowing all you need is one. I learned)

Thanks Brett for offering two points which appeal to me. The mix of bass below some threshold to mono and the smoothing the effect of room modes. I will add those to my expectations list. When I trial a second sub, these will test my ears.


In rock and other pop music the bass is often mixed to the middle which is the equivalent to mono. This is especially true for vinyl as its is physically easier for the cartridge to track. There are, of course, exceptions.

Moreover, sound waves behave differently in a room than they do in a free field (outside). In a room, a bass wave will hit a wall or other surface, reverse direction, and then mix with the source wave coming from the speakers. (This is what makes speakers sound louder inside than outside due to these reflections as sound is not “lost” to the outside limitless space). Thus low frequency sounds appear to be coming from many directions and different intensities and cannot be localized. In most rooms this occurs at ~80Hz and below.

For these reasons (and more, such as our inability to detect phase differentiation in low frequencies) one can place a subwoofer essentially anywhere in the room without impacting soundstage, as long as the sub is reproducing only low bass.

100% support for adding a second subwoofer.

umiami91, one of the potential benefits in your situation (since the subwoofers are not super high quality) is… adding the second sub will allow the volume level of the subs to be turned down, relative to a single sub. This may help to reduce the expressed limitations of a single sub turned up louder…and give you a better sound.

just a thought…


Should I win the auction (likely, he’s had it up twice before) I’ll have my two subs soon enough. I won’t have reports soon though because my listening room is down until I’m not so sick anymore (in the basement and I can’t get down the steps so easily).

I have my LS50s on Target stands full of lead shot with iso acoustics apertas on them. They sound pretty darn great. Looking forward to the next level.

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The LS50 is a speaker that hits way above its price point. I bought a set of these and a Sprout to drive them for my son as a Christmas gift. We set them up on 3 kitchen chairs (2 for the speakers and one for the amp) to make sure everything worked and I was thoroughly impressed. That is about as bad of a setup as you could get and they sounded marvelous. I am sure adding a second sub - even a small one will help your system. Good luck with the auction.

This is critically important…and, I am afraid, many fall prey to the conventional wisdom that all bass is omnidirectional so you can pretty much slap a subwoofer down anywhere.