Yeah, but something like that is only decent for home theaters and what not. "Room correction" makes the room less of an issue by making the system even less accurate than it was before.
And of course, the room problems remain.
That really doesn't help unless you also get the little granite cable isolators and $1000/meter cables.
And don't forget the special green felt-tip pen to mark around the edges of your CD's!
. Let us simplify matters by ignoring anything over, say, 200Hz. Yes, there's a lot of hash up there, but it's more appropriate to deal with that sort of thing by using room treatments.
..Above that first resonance, you're going to see more resonance modes at integer multiples of 28 Hz, so expect potential problems at 56, 84, 112 Hz, etc.
As a general starting point, the sum of R5 and V3 should be about six times the sum of R4, V2 and R6. The values given will give the circuit a frequency range from roughly 30 to 200 Hz.