I have auto equalisation on the subwoofer, and it shows the results on my laptop, then I can further adjust the curve to be perfect, but that really pin points the listening position.
I prefer to tune by ear, so I use a tone generator, and I have found that using large dB/oct roll off's, that also puts the subwoofer out of phase at different frequencies, which makes sense, using inductors creates phase shift.
This is a sophisticated subwoofer, retailing around $6000au, so I expect it to perform, it's just learning all of it's idiosyncrasies first.
So generally speaking, where would you normally set the gain/master volume, as in, should the gain be set to zero, and master volume used alone?