Hi romavictor,
I have owned two REL Stadium IIIs for years. Keep in mind that I use them along with Thiel CS5i’s (already relatively flat down to 20hz) and significantly large corner bass-traps in my room, so YMMV.
FWIW, here are my experiences:
1) They will not provide "thump or oomph" (except when used for HT via the XLR low-level inputs) when connected through the hi-level inputs. RELs are designed to integrate into your existing system seamlessly via the hi-level inputs from your amp(s). They load the room with ultra-low sound pressure that, when the REL(s) is set up correctly, will improve imaging and sound staging of your speakers as well as provide a more solid bass foundation below (and above, see 3 below) the crossover-point setting. If you are looking for "punch", JL Audio Fathoms are a better choice IMO.
2) The best (only?) way to judge the REL’s contribution is to listen with it engaged and then quickly shut it off mid-cut. A helper is useful here. You should notice (a sometimes subtle) loss of spatiousness of the soundstage and less extreme low bass. Switch it back on and listen. Switch off, listen. Over and over as you tune its placement and settings.
3) My RELs provide significant output above the selected setting for the cross-over point. Ignore the labeled settings on the knob (use them only as reference points when comparing settings). Start much lower than you initially think in volume and cross-over setting (60 hz in your case) and listen to musical material that you are familiar with, creep the setting up notch by notch until you "hear" the sub (see 2 above) and then back it off a notch (or two or three) on the fine adjustment knob.
4) Once you have the volume level and cross-over setting tweaked in (possibly wearing a path in your floor/carpet by this point), the effect of the REL should only be evident when switching it off, but you should definitely hear what is missing when you do so.
5) Try the REL with the phase switch in both positions (in-phase and out-of-phase) and listen to decide which works best in your situation.
6) The RELs also work to cancel standing bass-nodes in your room. I won’t get into that here, but following the above steps in tuning your REL to your system/room will encompass this as well.
Good luck and be patient.
Best to you romavictor,
Dave
