FWIW, with my stereo pair of S/510’s the settings in my 28’x15’x8’ room are:
Five clicks from 20 hz on the crossover and 12 clicks clockwise on the high level input for use with a pair of Thiel 3.6 speakers;
3 o’clock in the crossover and the same setting on the high level input as the Thiels for use with Tannoy Autograph Minis.
The Thiel 3.6’s, according to the book, is flat to 31 hz and -3db at 29hz. But in my room it starts going downhill at 50 hz. The Autograph Mini drops off at 100 hz and the bass completely disappears at 60 hz.
I personally don’t have the patience to listen, get up and adjust, sit back down and repeat the process the way the REL manual suggests.
The way I dialed them in is with the Stereophile Test CD2 bass decade test tones and a dB meter from an RTA app. I ran the tones for the speakers and the subs separately. I noted the bass fell -3db at 50 hz on the Thiel and set the crossover on the REL until 63 hz was -6db lower than 50 hz. That turned out to be 4 clilcks. I then adjusted the high level input until the REL put out at 50 hz and below the same level as the Thiels at 63 hz and above (15 clicks). I then set the other sub to the same settings.
Both subs are wired with the red/yellow together.
For the Autograph Mini’s I repeated the same procedure only I cranked the crossover to 3 o’clock beforehand -- and it sounded damn good so I left it there. Makes it easy to switch between speakers with the crossover at those settings (I can eyeball the 3 o’clock setting and it’s easy to count to five).
The final adjustment was with a couple of test tracks, mainly "Bass Room" Nenad Vasilic (Galileo Music) and PS Audio’s playlist, both on Qobuz.
