KEF LS50W2 - force subwoofer on function

The latest firmware upgrade for KEF wireless speakers (LS50W2, LS60, LSX) took place overnight and includes the intrroduction of a ‘Force Subwoofer On’ function. When activated in the settings part of the KEF connect App this ensures that your subwoofer switches on when your speakers do. KEF note that it is only supported for KC62 and KF92 but I have found that it works perfectly with my JL Audio subwoofer. It switches it on even when the voilume is very low and it seems to stay on. Worth checking out for those of you who have had ongoing problems with your (KC62) subwoofer not switching on unless the volume is turned well up. Just mentioning here as it would be easy to miss unless you are a nerd like me and read the firmware release notes!!


Updated overnight – tried it this morning.

Pretty uneventful – it just works: when the speakers are turned on (regardless whether music is playing or not), the sub follows suit after a second or two.

Thanks for sharing, @Ben_Patana !


IRT: your JL Audio/ither subs, we cannot guarantee that it will turn on other brand’s subs. That’s why there is the disclaimer.

Can you please describe how the function works? Does it generate something like a 5hz signal out of the speaker sub-out that kicks on the subwoofer’s auto function, but then that signal is then filtered out by the DSP, hence no one hearing or seeing anything from the sub driver?

It’s a higher frequency tone which is filtered out by a low pass filter on the sub itself. The signal sensor sits before the filter. At a fundamental level its actually no different to how the normal wake-up function works, we just send out a signal that we know will wake the sub up at the point the LS50WII is turned on.

Ah. I was thinking so low it wouldn’t be played, but it’s so high it won’t be played! Interesting.

This is of course cold comfort for all of us who have a KC62 without wireless KEF system to send this signal. And the fact this rudimentary software fix exists is pretty much admission that things went wrong in producing the sub. But I guess no further hardware fix is coming our way.

Next time? Include a 12v trigger. Please.

Please reach out to your local KEF service center. There is also an update for improving the wake-up behaviour in general.