What JL Subs to pair with Harbeth SHL-5 Speakers?

I have a single F113 in my 19 by 20 ht room and it is more than enough and never feels pinpointed bass wise

If you can go larger, do

I run. reL b2 and it's awesome. Compact 7es3's

Your room seems to be plenty large enough for the 40.1. As far as total cost and space needs, wouldn't the 40.1 without the subs be a better choice. I use a REL Strata iii sub with my 30.1's, but even then I find integrating the two can be a challenge to get the sub set for every type of music.

Valinar makes a good point that in a your relatively large room, perhaps the 40.1 is the better choice. But if you stick with SLH-5, a pair of JL F113 should be plenty -- provided you split the signal and relieve the SLH-5 of the bass work. If you have spoken to JL Audio, you know they strongly recommend crossing over to relieve the mains of the work that is the sub's specialty. True, integrating subs can be a challenge, but it is doable; and when done right, its terrific. Also, integration is far less difficult when using a cross-over, rather than having the mains rull full range and overlapping the sub in the mid-bass.