KEF Subwoofer Sale

I am no expert on dialing in a sub woofer and I will not pretend to be. Others can probably answer this better than me. In my experience I think the reason you start at 80Hz is to allow the speakers to play as deep as they can before the sub takes over the deep bass regions. I don’t want the sub playing music above 80Hz because the LS50W does such a great job in the lower regions that the sub is there to help the speakers so deeper. Frankly I probably want to dial the crossover down as low as possible without causing the sound to dip in between whee the LS50W roll off and where the sub begins.

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It’s to do with directivity of the sound. Have the sub producing too high a frequency and you may start noticing it’s location in the room. The passive LS50s start to roll off at 100hz downwards and the ls50w at 80hz. Ordinarily that’s where you want the sub to compensate for the reduced output from the Kefs.

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Understood thank you guys. this is helpful.

I picked up the Kube-1 and it definitely “fills out” the sound of the LS50w nicely. I don’t feel I have them well integrated yet so tonight I will play with crossovers based on what’s been said above. I’m just starting to understand the topic a bit but far from experienced, having never owned a sub before, so thanks for all that good info @Rik_Carter !

I’m not a fan of Big Booming Bass so was concerned the Kube-2 would overwhelm the small LS50w’s and my room, which is an odd shape/size as I live in a 2-story loft where the living room is mostly open to the second floor but extends back to the kitchen, dining area and beyond on floor 1. As of now I’ve got the Kube-1 at about 1 o’clock but I’ve been thinking it’s too much and plan to dial it down a bit.

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Good to know Jon and nice move. The Kube-1 is a very nice sub :slight_smile:

Also nice to know that you already feel they can go down a notch or two on the gain. Perhaps the 11 or 12 o’clock position?

Placement of the sub is key. Where have you got the K1 in the room?

Directly to the right of the right speaker, on an IsoAcoustics stand on the floor, about 8-10" off the front wall. Sort of the middle point of the room up against the wall more or less, facing into the room.

I want to move it to the other side of the console, which puts it in the corner, between console and wall, next to the left speaker, so will have to see how that works out sound-wise. It sort of stands out too much where it is now.

In the corner could work out to be ideal as the sub tends to find it easier to pressurise the room. Don’t be surprised if you have to knock the vol down to 10-11oclock

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Are you sure the Kef Kube Subwoofers are going to do the LS50W’s justice? The base from the LS50W’s is so tight that it will be hard pressed to replicate. I am playing with an SVS SB-2000 and not sure it’s tight/musical enough to crossover at anything very high. Thinking of trying a rhythmik F-12 or Rel (though they are bad value for $). I would think that the Kef Kubes would a step down in the quality of bass. If you are going to try them I would suggest a low crossover to use as much of the tight LS50 bass as possible.

I agree that a sub will be hard pressed to match the speed of the Kefs above 60hz. Anything below that and, frankly, I can’t tell the difference in my setup. For me the Kefs without any room correction were too bassy so I used my sub up to 70hz and the Kefs from thereon. Sounds fantastic.

Going off topic a bit here, but I find that aside from incredible imaging/soundstage and space/air - which was always the primary strength of the passive LS50’s - the bass is one of the best parts of the LS50W’s. Tight/musical/and surprisingly deep. As you say, it can be strong if not controlled for - not flabby but just too much. I still need to run through REW and create frequency curves and convolution. No doubt I will see a big bass hump.

My biggest issue with replacing my much more expensive and convoluted main system are the highs … I just think there is a bit too much grain/off-timbre compared to my Raal Ribbon tweeters on my floor standers, which sound so silky and beautiful. But it could be that it’s just the extra detail in the LS50’s is coming through as less ‘smooth’ and silky … I know some others are put off by the hyper detail of the LS50’s.

You know your stuff but I will ask just to clarify: have you tried rolling off the higher frequencies (aka a Dirac Live house curve profile)? One other suggestion put to me by Thierry of HAF was a -2dB dip at 3.5khz (with Q=2)… now not sure if that’s just a perculiarity or my room setup or something to do with the speaker crossover (but seems quite high for a crossover from LF to HF).

Finally I read on another forum that having the Kefs a couple of inches below ear height also reduces their brightness a little.

If the xover is set higher than 70-80hz I’d agree that ANY subwoofer would struggle to do the Kefs justice. FWIW, and to clarify my setup, now that I have HAF room correction, I have the xover set at 65hz which is a nice sweet spot. Incidentally the LS50Ws roll off sub-80hz (not that you’d notice!).

Well, I have already have -2dB treble trim via the Kef app due to my lively room. I have to try adding further treble trim via Roon dsp/convolution/etc. Regardless, I am trying to compare to my other speakers, not the room, at this moment. They too have a small treble trim.

  1. if the LS50W’s are rolling off at 80Hz then how do they get their claimed -3dB responses of 45/50/55Hz (depending upon bass config)? Or is there a big bass hump above 80Hz? (Which is what I am starting to suspect and think I saw posted on another forum. A frequency response curve from Kef would be nice).

  2. My concern with HAF is that you have to pick you xover before taking measurements and sending to him. If you want to change your xover point then you need to remeasure and then get HAF filters regenerated (for more $). Of course, using REW you always need to remeasure after changing xover. The difference here is that you need to get HAF to regenerate convolution filters each time at an incremental cost.

I don’t understand the technicalities but from what I can deduce Kef dynamically adjust driver loading using a combo of the DSP and onboard amps.

Yes, in the interview on WhatHifi here Kef’s “Head of Acoustics” says that the software is dynamically adjusting bass response on the LS50W, depending on how loud and what kind of material you are listening to.

Interestingly, there are two sections in the app for setting the crossover. “Basic” for those with little understanding, where the app picks the crossover and bass “extension” settings of LS50W’s… and “Expert” that allows you full control to both the high pass and low pass points independently. Anyway, when you allow the app to choose for you it sets high pass at 95Hz and low pass at 80hz. Also goes into “Wall” mode that cuts bass extension by -3db. This all would seemingly mimic the response curve of the passive LS50. To have the staggered crossovers would seem to indicate different slopes in the two crossovers. IIRC, the low pass is second order and the high pass is 4th?

I’m also very curious about the high and low pass crossover slopes. It’s curious to me that the app defaults to staggered crossovers and a lot of folks seem to set them the equal.

For those of you who’ve done room analysis and correction, do you use equal high and low pass?

I just can’t quite get over that the default might (should?) be close to an ideal for the speaker, but it’s far from what I’ve heard people running them at with a sub.

One rationale behind an asymmetric and/or staggered crossover is the contribution of natural low frequency roll off.

For example, a sealed enclosure inherently has a second order (12 dB/oct) roll off. Combining that with a second order high pass filter approximates the roll off of a fourth order filter.