Kef LS50 Wireless II - sub integration and other optimizations


Feb 5, 2021
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Newb here, signed up to reach out as ask for some advice.

Here's my setup:
Kef LS50W II + S2 stands + Kef Sub (Kube 10b).
Pro-ject X2 turntable for analog and Tidal Connect for digital.
Generally great set up, simple, lovely sound. Now just trying to optimize a few things.

High pass / low-pass questions
1. I used to have both the High-pass and the sub out low-pass frequencies at 80Hz (in the Kef app). Now experimenting with 95Hz for both. Is it recommended/necessary to have both frequencies be the same? They are 2 different sliders in the Kef app, so I can choose say 80Hz for the High-pass and 100 Hz for the low pass.
2. Any recommendations on setting up the high and low pass frequencies? I feel that I hear more detail in the bass when the low-pass is at 110Hz. Anything wrong with that?
Side note on the Sub's physical dials. The volume is set to max and the crossover to LFE. Anything I should change here or just make changes in the app?

Adding an extra sub
The Kef LS50W II (unlike the original version) accepts 2 subs. Would I be improving the bass response by adding another Kube 10b? I know that adding a 2nd sub improves the general distribution of the bass in the room, but will the quality /detail/tonality also improve?

Room correction
Outside of the EQ settings in the Kef app, are there easy ways to do some basic room correction? I have no room treatment for the moment, but the room they're in has 2 big rugs and lots of books. Not real acoustic treatment, so looking to see if I can improve on that somewhat. I don't use Roon and feel somewhat intimidated by that process, is there an easier way?

Other recommendations
Outside of the questions above, are other ways I can extract more quality from this system? open to ideas and thoughts.

Thanks for any thoughts can help me continue to improve the set up!


Well-known member
Apr 27, 2011
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You actually want to have the HPF at a higher frequency than the LPF - try something like 50Hz and 80Hz (LPF and HPF respectively). Filters are not brick wall, so the chosen frequencies are where the signal starts to roll off. The idea is that both speaker and sub plays some of the same frequencies at lower volumes, but add together to create a nice straight line in frequency response. Set the frequencies too close, and you'll get a bump entered around the middle of that region, set them too far apart and you'll get a hole instead. Your sub is set just fine, being in LFE mode.


Well-known member
Mar 7, 2011
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I've been messing around with a similar setup (with some help from forum members such as @Deliriumbassist ). LS50 wireless IIs and a REL T5i Subwoofer. KEF have a 'White Paper' detailing some of the specs and design features of the LS50s. The section on adding one or more subs:

"A crossover between the LS50 Wireless II and the subwoofer is provided and the crossover frequency is set within the app. There is no choice of filter shape - it is always a 4th-order Linkwitz-Riley giving -6dB at the cut-off frequency and a flat in-phase total response. If there is any low-pass filter supplied with the subwoofer, it should be bypassed if possible or, if not, the frequency should be set to the highest possible. The choice of crossover frequency is something of a compromise. The higher it is, the less the excursion demands on the LS50 and the louder the whole system can play. However, if a mono subwoofer output is selected and the crossover frequency is too high, some of the stereo information is lost. 80HZ is usually considered the highest to avoid any perception of loss of stereo information and the lower it is the better in this respect. In Basic setup mode, the cut-off frequencies of the high-pass to the LS50 Wireless II and the low-pass to the subwoofer(s) are always the same and this is normally the course to follow. However, some subwoofers do not have a flat response and different cut-off frequencies may give better results. Having different frequencies requires the user to use Expert mode for setup."

As time playing went by I have drifted towards a lower crossover and also set the high and low-pass filters to be equal. I *think* this is due to the -6dB at the crossover. That is a significant drop in audio volume at the crossover freq. I'm now at 60Hz for both. The integration, to my hearing, is pretty seamless and having the crossover relatively low prevents any loss of the tonal quality of the LS50s which I like.

FWIW the active LS50s go lower than the passive LS50 Meta with KEF recommending the use of the extra setting in normal circumstances.

Frequency Range (-6dB)
47Hz - 45kHz (Less)
43HZ - 45kHz (Standard)
40HZ - 45kHz (Extra)
Frequency Response (±3dB)
53HZ - 28kHz (Less)
48HZ - 28kHz (Standard)
45HZ - 28kHz (Extra)
Frequency Range (-6dB) 47Hz - 45kHz
Freguency Response (±3DB) 79Hz - 28kHz

PS still waiting on my S2 stands in titanium grey. Nearly 3 months and counting....
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