Is it better to have two matched subs or one

They don’t have to match, but it’s better if they do. Any difference is more likely to make localization of the subwoofers more apparent.

The Velodyne SMS-1 bass manager shows the in-room response of my KEF Reference 1s to be pretty flat to 30 Hz before sharp roll-off, so it's no surprise the location of jazz bass players is well imaged even without the subs.  But the location of jazz bass players is also well imaged by my LS50s.

db

@dbphd I've had the same experience with all the speakers I've had in my room, I didn't mean to imply that the Ref 1s were doing something others couldn't, although they do image better than any other speakers I've owned.

big_greg -- I agree the Ref 1s image splendidly.  I use mine mostly for Roon via ethernet to an Ayre QX-5/20 digital hub with balanced analog to a KX-5/20 preamp and VX-5/20 amp.  For surround and movies I add a DX-5 DSD disc player, Bryston SP3 processor, and 4 LS50s.  A pair of HGS-15s with acoustic room correction extend LF to below 20 Hz.

db