I gave up on a REL deal for a sunfire SDS12 cuz i wanted it for a 5.1 setup too. But it matches very well with my Monitor Audio silver. I can't tell where the impact is coming from. The perception of impact is always from the side where it's shown/recorded in the movies.REL was my first choice being sealed to keep up with my Heresy IIIs. I read somewhere (was it PS Audio?) that to keep the timing speaker level input is better and again sealed.
Duty for my system is only music.
REL is not sold in UAE so went in for a KEF Kube 12b. Again sealed and with speaker level inputs. Have been very happy since 2019.
Had to use an attenuator to avoid the sub getting cut (auto cut off) at low volume.
Speaker level to line level attenuator
When searching for a sub-woofer to augment Heresy IIIs in 2019 wanted it to be with Speaker Level inputs. The tube amp has only speaker out. Not keen to use a Y adaptor at it's input to feed subs with line level inputs only. Sealed sub was another aim. Primarily to match the fast Klipsch Heresy...www.hifivision.com
I did a phase match to 180 deg i guess.
Isn't phase control meant for the same purpose on all subs ?