Subwoofer xover settings for KEF LS50W (orig model)

@jbs, go higher if you can. The Little woofers in the LS 50 carry the bulk of the midrange and unloading them will clean them up even further. I cross over with ESLs at 125 Hz. Try 100 Hz if you can. Roll off the LS50s a little earlier then you roll into the subwoofer say set the LS 50s to roll off at 110 Hz and set the subwoofer to 100 Hz. Also move the subwoofer so it is right against the wall between the LS50s then take the measurement from the front of the sub to your listening position and set the LS50s to exactly the same distance which should keep them off the wall a foot or two (on the radius of a circle).

The reason low crossover points are being recommended is because most sub manufacturers expect their clients to run the sub without a high pass filter on the main speakers. They are trying to bring the sub in under the main speakers. It is also much less noticeable way down and easier to integrate without screwing things up. You also have more flexibility in placement. But the improvement in distortion levels coming from the woofer more than make up for any disadvantage particularly with smaller loudspeakers that use the woofer as the principle midrange driver.
Your LS50s will grow to three times the size. 

@mijostyn +1

Thx, the highest setting on the sub REL B1 is 95 hz. Yes, you read that right. That is where I have it now so the LS50W DSP settings do not interfere and I don't have two notches in play. I was trying to stay away from that area to keep it simple given this is a temp setup and goign way higher seemed problematic due to the sub xover. Maybe I'm all wrong about this. 

Normally I'd be running the sub at speaker level (unsing the differential hookup) but that'll wait until I put the REL with some other speakers and electronics.  

Download a sound level meter app like db on your smartphone, and stream some whitenoise (available on Spotify, elsewhere).

Then turn the sub level up and play with the crossover control. adjust level up and down until flattest in the bass region. That will give you a reasonable estimate of where your exact level and crossover settings should be. Adjust phase if available for best impact from percussion, etc. then fine tune level and xover settings from there as needed.

You might be surprised what you find this way compared to doing it by ear alone. Probably more good sound out of your sub than expected.

I had original ls50s crossed over at ~ 60-80 hz. WIth new metas, I ended up with crossover on same sub set at lowest point ~ 40 hz and higher levels than prior. Everything sounds fuller and more alive now, and just the right amount of bass on all recordings. Room is 12X12’ square which many will say is horrible for bass, but fact is it sounds really good. BEst bass I have had ever.  Sub is Klipsch sw-308, a little 8" dynamo.