Subwoofer for Kef LS50 Wireless II?

OP,  Auralex Subdude platform under the sub will help to get the bass under control away from one note and more articulate.  Especially if you are not at foundation level and room has suspended plywood floors.  

How are you going about it?

I have Ls50 metas and a Klipsch sw308 sub in a smaller 12x12 room. Larger rooms are likely more of a challenge in that the sub will have to do more. Listening to my ls50/sub combo as I type. To get the sub set up right I used a sound meter app (decibel) on my iPhone to fill in the lowest octave that was missing in my case mostly below 40hz or so. You need to measure to get it right. I had crossover set way too high by ear. Using a white noise streamed internet channel as the source I Turned up sub level then adjusted crossover point and tweaked those two until low end was leveled with the rest. Then tweaked phase with some good percussion recordings for best dynamics. Could not have done it right by ear alone. Sounds awesome. Sub needs to be able to go down to 20hz or so in your room to fill in the bass completely. Check the specs. The new KEF sub is designed to go with the ls50s. I’d look at that first.