I can tell you from my experience with REL subs. I first considered both the T5X and the T9X but finally settled on the S510 with the thought of doing the same and getting a second one when my wallet recovered, the only problem with that is the recovery is still on going so I still have only the one. I can tell you for certain that I am glad I went with the S510, it add enough to the low end that sometimes I don't feel the need for another one that I would have to find room for. Oh well, maybe some day.
Adding an Sub that doesn't go well below speakers?
The backbone of my setup is based on a couple of Canor Monoblocks that feed a pair of Marten Oscar Trio. The trio are rated for 27hz (-3db), but I still feel that the system would benefit of having one or two subwoofers that help both of below 27 while also allowing more breathing space for the speakers.
I was considering a couple of REL T5X because of the little footprint as well as the high line connections (the amps don't have a dedicated low-level sub out). But just before pulling the trigger, I saw that the T5X is rated at 37hz (-6db).
Would it make sense to add them to the system? Doesn't sound right. I know probably the Martens roll off above 27, but perhaps 37hz sub is too high for my system.
Perhaps a T9X that goes to the same 27hz? Or do I definitely need to splurge and do for an S series, like the S510 that is rated at 20 hz? If I do an S510 I will do just one and add a second once my wallet recovers.
Well, would love to hear from you.