REL R328 & R305 -- are these two REL subwoofers close enough as a match?

John Hunter (REL Acoustics) 2018-Jul-17, 9:46 AM PDT

"it CAN be done but it’s very tricky. If you’ve not done it before you can easily get confused. Room acoustics can be quite different from one side of your system to another and this shows up most in the bass. Add in the quite different voices of S versus R and you could easily get very confused and frustrated. Questions such as "can I expect differences in reproduction between them, to the extent I’d need to compensate with different settings on each?" are extremely intelligent, but minimize the real world experience necessary to have confidence in attempting this.

If you still want to, we’ll guide you through it but know that it’s real work--assuming your current unit is properly set-up, you’ll need to re-wire it to become a monoblock sub dealing only with, say, the left channel.
Then you’ll need to carefully dial-in the right channel new S/3. If one side or another seems predominatnly louder you will want to swap subs because you may need to re-balance the system (room acoustics can swamp the differences between these two subs instantly--the 328 will sound thicker heavier--you may experience it as "louder"--but it’s generally the overshoot you are hearing, the S/3 doesn;t have any of that).
Then dial-in the S/3 (assuming you didn’t need to swap, in which case if you did find swapping was beneficial you’ll need to dial both subs in). Pay zero attention to any setting except phase, which does have to be identical, and simply listen for perfect blend and gain.

Then plug both in and slightly re-tune, fine tune for best performance when using both.

It can be done, just a question of whether you feel comfortable with your own set-up chops."