Using KEF LS50 Wireless II with a Subwoofer

I’ll forward the suggestions - I can at least promise they will be looked at in regards to feasibility.

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Thanks, Ben
That’s much appreciated.

The sound level from the LS50 WII speakers via ethernet cable is so much higher now. I think I will do some a/b comparisons of the sound quality (cable vs wireless) but from what I hear right now, Roon Ready status has been a major plus for your kit. Well done you :grin:

Hey @Ben_Hagens

Just got home and tried the your settings – all appears to be working fine and sounding great. Thanks! (Same goes for the RoonReady FW, but no surprise there… ;-)).

Given the highpass at 70Hz – am I right in thinking the Bass Extension setting (Less/Standard/Extra) doesn’t really matter anymore?

You would be correct, HPF overrides.

You could consider the bass extension option to be preset HPFs for LS50WII when a sub isn’t being used (the idea is that, in a smaller room, room gain starts at a higher frequency, so the bass rolls off higher to compensate for what you gain from the room)



Quick update: i have a list of issues with the kc62 that i am sharing. Link to follow.

Kef is working in a firmware update to fix the pop in rca out. Info below. Quick q: is there a way that users can update firmware themselves or does this require Kef to step in?



The engineering team will be investigating the KC62 to make sure it is not sending a signal out after going into standby. If for some reason this is happening in the KC62 you could experience the noise you have described. That would also mean it would happen in a new unit.

Before we move forward with getting you a replacement unit let’s wait for confirmation from engineering.

Thank you,
Fred Cobb

The development team has confirmed that the issue is due to the KC62. They are currently working on firmware to fix this issue.

Thank you,
Fred Cobb

Here is the link:

Hi Pascal,

I’ll be able to give more info as I receive it, I’m not sure what any rollout would look like as of yet.

I confess that this auto-standby issue is causing me to hold back on my plan to get a KC62. For the people who have implemented Ben’s suggested fix to essentially shift the crossover from the LS50W to the KC62 how is that working out for you? I tend to listen to my LS50W (currently v1 but might upgrade to v2 later this year) at about 38 to 40 on the Roon volume setting so not at all loud.

Also for Ben a couple of questions…

1 - Is there some level of firmware control over the level of signal coming into the LTE port at which the KC62 comes out of and goes back into standby or is that controlled by analog circuitry to detect the threshold so not adjustable short of actually changing components on the PCB? Essentially I’m asking if this issue might ever be able to be addressed via a firmware update, maybe with an option for the user to select the sensitivity themselves or even disable auto-standby altogether. Maybe disabling it altogether wouldn’t be great because as far as I can tell there is no remote for the KC62 which is a bit of a shame at least for me because I use a universal remote so it would be no big deal for me to add KC-62 power-on/off commands to my power-on/off routines on my remote but if the KC62 has no IR capability then clearly that is impossible.

2 - If the KC62 is fed via the wireless connection kit is that handled any differently? I assume (maybe wrongly) that the audio is transmitted between sender and receiver digitally but is it then converted to analogue in the receiver so that the KC62 still sees an analog signal as it does with the LTE input or does that socket on the back of the KC62 see the digital signal? If the latter then might a firmware update be possible on the wireless sub connection even if it’s not possible on the LTE input?

In one word: great – it’s a whole different ballgame. The sub now auto wakes even with light use and stays awake whenever music is playing. I have only had it fall to sleep with low volume, talk-only TV and very low-volume classical chamber music – as it should. I play at about the same volumes as you mention.


I have collected most know issues + remediation (if any) + Kef’s response here >> Link << I have enabled comments so anyone can provide these.

In addition you need to be aware of the 2 following things Kef is/has been working on:

  1. inverted polarity at sub out - this was the case in the initial production run and has apparently been fixed in later production runs
  2. pop/signal send on RCA-out around 10 mins after this sub goes to standby. Kef is working on a firmware fix.

That being said: i really would like Kef to confirm that they are working on a fix as mentioned work arounds are a bit odd for a sub at this price level. Can anyone @Kef please confirm?

Note that i have already ordered a KC62 + KW1 module but holding off delivery as i rather not send it back to get the firmware updated/fixed/whatever have you…

At Julian: no-one has been able to confirm whether this issue gets solved using a KW1. I know 1 user who has this combination - i’ll check with him to see if got any results.

@Kef employees / @Ben_Hagens - we would really like to have a platform supported by Kef to report and discuss these issues (and fixes/workarounds) as it is now dispersed across several social media platforms - i believe this will help both Kef as well as their customers

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Good morning/afternoon Ben,

Rollout would depend on whether the KC62 is user-updateable - that would greatly simply things. Unfortunately i do not see a USB port or similar. Would you be able to shed some light on this matter?

Re the KC62 i do have serious concerns - it’s a wonderful product (i have one on order and more might follow) but there are also some issues (wake-up issues, pop, inverted polarity) that owners might find unaccepable at this price point and some of them are returning their KC62.

I guess marketing or engineering might need to step in here and issue a formal statement on how to address/solve these problems (or provide a draft timeline).

Just to be clear: Kef makes wonderful products - please keep doing so - and i don’t mind spending a small fortune on them - And although we all understand that every product has it’s issues communications from Kef must really improve here.

Hi Pascal,

I can confirm that the reported issues are being worked on as a matter of urgency, and I will update here when I can. Don’t take this as me being short, after all I can only provide information that I have.

Hi Ben,

No problem and i fully understand. I’ll wait until further update from your side.



Hi Ben thanks for all your support on here. I just got a single KC62 to pair with my new LS50 IIs. The settings as you suggested seem to work very well and sound is awesome. I do have one question. Pascal noted in his issues list and I just read form another user that the phase needs to be inverted when switched to MANUAL instead of LFE.

Can you please confirm if this is accurate, does the phase need to be inverted when running in MANUAL?


Hi Julian,

I checked with the other owner - he did not yet tried the KC62 with the KW1 - so no update yet (unfortunately).



Hi @Ben_Hagens — I appreciate you being active on this thread.

I am the owner of the LS50 Metas, one KC62, and a miniDSP device.

Your instructions for LS50WII owners to switch from LFE to Manual from post #17 are clear to me. I have two follow-up questions though:

First, is it a problem to tackle this problem slightly differently? Ideally I would like to 1) set the sub to Manual mode, 2) set the sub chassis LPF dial all the way up to 140hz, and 3) on my miniDSP to set the LPF to a conventional Linkwitz-Riley 24db/octave slope at 80hz? I would be using both RCA outputs of my miniDSP into both RCA inputs on the KC62.

It is my hope that this would address the issue of lack of LFE mode sensitivity to wake-up, and give me control over the LPF exactly the way I want it on the miniDSP rather than on the sub chassis like in your method. Your official method already has cascading filters, with the 140hz LPF on the output of the LS50WII being fed into the 70hz LPF of the KC62. My suggested solution would have the 80hz LPF from the miniDSP first, followed by the 140hz LPF on the KC62.

Second, can you please disclose the type and slope of the default LPF and HPF crossovers that KEF is using for the LS50WII and KC62? I think it’s only fair to your Meta+KC62 customers to allow us to set our speakers to your exact specifications, especially for the Metas since there is no way for us to replicate your HPF crossover unless we know the type (LR or BW) and slope. I don’t see any reason why that should be proprietary info.

I hope I’ve been clear here. Thank you!

Forgive the extra post, but I don’t think I can edit.

My two questions remain, but I wanted to acknowledge that I got the LS50WII+KC62 prescribed frequency incorrect. The official KEF numbers are 45hz for the LPF and 70hz for the HPF, as I’m sure just about everyone but me has straight right now. Apologies for any confusion created.

This sort of makes my point, however. Those are very unconventional numbers to use, so for those of us with the passive Metas and KC62, we really do need the extra information about the crossovers to replicate what KEF recommends.

What gets me is that Jack Oclee-Brown, KEF’s VP of Tech and former Head of Acoustics, was just on the Darko Audio podcast and discussed the default LPF/HPF settings and twice (at 40:40 and 54:48) said stuff like these settings “just work” and have been “carefully considered” and him and Darko go on about how hard it is for end users to get the right integration, but with an all-KEF system that they can offer this sort of customized recommendation. With a bit more information provided I hope Meta+KC62 users can achieve this same effect via their own DSP. Thanks.

Do you think that you have those numbers reversed? Based upon those settings the sub will only work BELOW 45hz and the LS50 would only work ABOVE 70hz. So you would have no sound reproduction between 45hz and 70hz where there is plenty of action on many recordings.

You probably want to have at least a little overlap for the LPF and HPF to avoid either a dip or a complete dropout.

Due to wildly individual home room acoustics there is no “one setting fits all” for sub integration. I would experiment with various settings in your own environment.

I had a pair of SVS SB2000 subs with my Mark2’s. I set the sub turn on frequency to well over 100 so it would always be on with most music, ready to go. On the sub itself I set the LPF to something like 50hz. I set my LS50 HPF to around 45hz. I tuned by ear.

No, those are indeed the numbers, and that’s why it’s so important to have the type and slope of the crossover.

In general (this is true beyond the W2/KC62 settings), the “crossover frequency” set is never the frequency where all sound from that filter stops. E.g. we can easily assume the KC62 plays frequencies well above 45hz, but at what sort of slope is it attenuating? We don’t know. Same with the W2, it’s definitely playing below 70hz, but we have no idea about how it’s playing below 70hz.

KEF’s own VP of Tech in that podcast says 1) he’s wasn’t really a believer in sub-sat systems until this project, 2) he thinks it’s a lot to ask end-users to develop a crossover themselves by ear hence the need for tested crossover presets matched to the W2 and KC62, and 3) that these presets went through rigorous testing and deliver the best integration across any room type. Therefore I think the crossover specs are relevant information for any Meta+KC62 owner in any room.

Sorry for the delay, folks. I’ve not been as active for a little while because reasons.


Firstly, the slopes are 4th order LR, so 24dB/octave.

The output from the LS50WII is actually 250Hz, not 140Hz, so you have a lot more signal bandwidth (actually going into vocal fundamental range) heading out to the KC62. I’m not so sure your method would have the intended effect, though. The cascading filters are sequential - so the one in the miniDSP would affect the signal first, so you’re already rolling a bunch off above 80Hz. This would reduce the audio bandwidth reaching the input of KC62. The 140Hz of the KC62 filter would do pretty much nothing (audible, anyway). The idea behind setting the LS50WII output to 250Hz is that now you have a much wider audio bandwidth hitting the KC62’s input, which is where the sensor for triggering them on is. The higher the bandwidth, the more chance of a triggering signal there is. The way I would use the miniDSP would follow the same line of thought - higher filter frequency for the first filter, intended filter frequency for the one on KC62.

However (and there’s always a however, isn’t there?), when it comes to the passive vs the active, one has to remember that the LS50WII has a whole bunch of DSP to allow the extension of LS50WII to push further south, meaning the frequency response is at the bottom end is different between the two - one would probably need to bump the filter frequencies up a bit (or even consider not using a high-pass filter at all, the FR is pretty damn smooth at the low end on LS50 Meta).


The numbers are correct - as a starting point. In terms of what Dr Jack and his team put together, they are pretty damn spot-on - for my ears and all the different rooms I’ve tried them in, anyway. In general, though, there are several things that need to be considered with crossovers:

  1. A crossover is not a single thing. It is made up of filters. The entire signal will be sent into the filter for each driver.
  2. A filter will then attenuate the signal. How it does so depends on the type of filter (high-pass, low-pass, band-pass, notch).
  3. Either ways, in order to get a nice blend/integration between drivers, loudspeaker filters are not ‘brick wall’ type. As an example, a high-pass filter here doesn’t just stop everything below, say, 70Hz. It lets everything above 70Hz through to the driver just fine, but from 70Hz (or maybe slightly higher, it depends on the actual style of filter) and downwards, the filter starts to roll-off/attenuate.
  4. The effect of the slope is applied to the frequency response of the driver.
  5. The idea of a crossover is that you want a smooth transition between the two drivers. So after you apply the filters to the respective drivers, they will have a final frequency response. In the crossover region, they add together because they are playing the same frequencies as each other, so the final result, if applied correctly, is a nice, smooth transition.
  6. Generally, If the filter/driver combinations are too close together, or overlap you’ll get a bump in response in the crossover region between the two drivers, if they are too far apart, you’ll get a dip. But again, refer to point 4, as the frequency response of the driver itself is also to be taken into account.
  7. When you see a crossover frequency, all that is describing is literally where the filter slopes ‘cross over’ each other. In an A/V receiver, you’ll see only a crossover frequency - the high-pass (going to the main speaker) and low-pass (going to the sub) filters are prescribed to achieve that crossover value. I think this is where a lot of confusion comes from.

In all, I would actually argue that the 45/70Hz figures are not unconventional figures to use - they take into account everything that needs to be taken into account for, minus the room and personal taste because we don’t have control of that. I think the confusion arises from misunderstanding what crossovers actually are, and the labelling of 'low-pass filters as ‘crossover.’ With KEF Connect, we’re giving more control over the constituent parts of the crossover network, control which isn’t generally given. We COULD have given a ‘crossover’ control, which would have given prescribed crossover implementations, with preset low and high-pass filter settings that would have been invisible/uneditable, but that would have reduced the level of control - these settings are not ‘one-size-fits-all’ due to point 4, the room, and personal taste.