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Default setting crossover KEF LSX ii??????

Peerke007

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Jan 19, 2023
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Last week I got myself some green KEF LSX ii to replace some old monitors on my desk. The wife likes the look of these little handy speakers.

When I connect my KEF Kube 10b and use the app to set the system up, the crossover is set to almost minimize the use of the Kube 10b and I don't understand that. As soon as I move the slider to a crossover frequency in order to give the Kube 10b more LF signal, the app does not "recognize" the Kube 10b any more and tells me I have a custom subwoofer.

I always thought it would be wise to have a subwoofer work with a crossover between 80-100 Hz, in order to "relief" the LSX (or what ever you use) from the lowest frequencies. Why is the KEF app setting the crossover so low and make the LSX ii work so hard on the LF?
 
The sub choices are just presets if you change the setting it is ofcourse ”custom” :)

There is no regognition of any kind its an analog output .

What does it suggest for xover ?
 
High pass 67,5 Hz and Low pass 80 Hz.

I understand changing the setting is "custom", but the app shows Subwoofer model KEF Kube 10B/10MIE, but that will change to custom as soon as you change (one of) the frequency.

Why would the LSX ii have to cover 67,5-80 Hz also? Why not e.g. HP at 80 Hz and LP at 92,5 Hz and still show the subwoofer is a Kube 10B?

I know it is not a big deal, specially if the automated wake up of the Kube 10B is not affected, but I am just curious why KEF make the LSX ii work hard on low frequencies?
 
High pass 67,5 Hz and Low pass 80 Hz.

I understand changing the setting is "custom", but the app shows Subwoofer model KEF Kube 10B/10MIE, but that will change to custom as soon as you change (one of) the frequency.

Why would the LSX ii have to cover 67,5-80 Hz also? Why not e.g. HP at 80 Hz and LP at 92,5 Hz and still show the subwoofer is a Kube 10B?

I know it is not a big deal, specially if the automated wake up of the Kube 10B is not affected, but I am just curious why KEF make the LSX ii work hard on low frequencies?

And that's why its shows custom as soon as you change the settings :) there is only those two values .

When you select a Kef subwoofers the only things that happens is that it selects two suitable values for you as a starting point .
They have done some inhouse testing and thinks these are good values to start at .

I'm also curios to know how they arrived at this .

Also the filters are not infinitely steep these are just 3dB inflection points .

Test different kef subs what do they suggest for those it migth not be the LSX but the sub they think needs this .

And its only a starting point they cant possibly know anything about your room acoustics which matters more .
 
Fyi they (Kef) explained to us in another tread that there is no "secret sauce" ie other hidden stuff going on in the speaker when you choose a kef sub , they just suggest these two values based on some testing .
 
Fyi they (Kef) explained to us in another tread that there is no "secret sauce" ie other hidden stuff going on in the speaker when you choose a kef sub , they just suggest these two values based on some testing .
Thanks. I will experiment some, to begin with the suggestion of Zolalll. I hope that the automated activation of the subwoofer by the LSX ii would still be there. The app tells me that it works for KEF subwoofers, but when I change the crossover, the app might think the subwoofer is not a KEF????????

Confusing how people (in this case me of course) can think.
 
Thanks. I will experiment some, to begin with the suggestion of Zolalll. I hope that the automated activation of the subwoofer by the LSX ii would still be there. The app tells me that it works for KEF subwoofers, but when I change the crossover, the app might think the subwoofer is not a KEF????????

Confusing how people (in this case me of course) can think.
Why do you care what app might think?
Get a measurement microphone (UMIK-1 +REW) and PEQ the room mode spikes.
You have to adjust input levels and gain on the sub in order to auto on/off works properly. Higher input levels and lower gain (volume) knob will do the trick that it comes on on moderate SPL listening levels but in order to that sounds correct you need equal loudness normalisation (which by it self will substantially rise input level on the sub in such conditions). Those are small speakers that pass calibration point with satisfactory THD levels only on near field (1m) but you use them like that already anyway.
 
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Why do you care what app might think?
Get a measurement microphone (UMIK-1 +REW) and PEQ the room mode spikes.
yes its a desk setup i would use EQ apo for this :)

My opinion this a very close listening distance , sitting behind a desk with speakers close to you . So they may not be that strained by 70Hz content ?
 
Why do you care what app might think?
Get a measurement microphone (UMIK-1 +REW) and PEQ the room mode spikes.
I cared because first I did not understand why a small speaker like the LSX ii would have to take a bigger amount of LF than I would have expected. That is solved now, because the app gives a suggestion.

Second issue now is the automated waking up of the Kube 10B. The Kube 10B needs a decent amount of volume to wake up normally and sometimes I just don't want to play that loud.

In the setting menu of the LSX ii, under Speaker preferences, you can turn on the "Wake sub on start-up". The info button tells: "This function will wake up subwoofer simultaneously when speakers turns on. Please note this function is only supported for KEF Subwoofers only. It may not be compatible with other subwoofer."

So if I change the crossover and the app changes the type of subwoofer from Kube 10B to "custom", will that affect this Wake sub on start-up function?
 
yes its a desk setup i would use EQ apo for this :)

My opinion this a very close listening distance , sitting behind a desk with speakers close to you . So they may not be that strained by 70Hz content ?
EQ-APO has ISO 226 2003 equal loudness also. Ideal would be placing sub about one m ahead centered (for pretty much any sub and room) to fully concel the first peak of the room mode. Guess it's possible to do that in near field setup (and only there).
 
@Peerke007 look it's a small speaker (4.5" woffer's) to meaningfully stres it out crossover should be very high at 200 Hz (woffer peak output) but you don't want to do that as you would need two sub's one per each chenel and speaker and sub's would bleed to much to lower mids. So 90 Hz is your best bet and uper limit with one sub for relatively normal summing of low long length waves.
 
@Peerke007 look it's a small speaker (4.5" woffer's) to meaningfully stres it out crossover should be very high at 200 Hz (woffer peak output) but you don't want to do that as you would need two sub's one per each chenel and speaker and sub's would bleed to much to lower mids. So 90 Hz is your best bet and uper limit with one sub for relatively normal summing of low long length waves.
Will try. Thanks.
 
these are the settings I have settled on after several months of listening and fine tuning.
 

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