Box size the issue Steve? FWIW, two things you might want to look at:Cressy Snr wrote: ↑Sun Mar 25, 2018 5:33 pm I'm not doing it - too small a room; but these drivers would IMO, do really well on an open baffle running wide open, with a 15, or better still, an 18 inch bass helper underneath them.
1/ Shift to a quasi-aperiodic load. I don't like the aperiodic term as it's not accurate but you know what I mean. Dates from the dawn of time, they were fooling with these in the '30s so novel it isn't. Get your sealed box (say, about 60 litres) with a reasonable amount of internal damping, drill about 40 holes in it & make sure they're covered internally with damping. That should bleed off enough pressure without resonanting to reduce the box Q a bit.
2/ Electrical equivalent. Well, not really, but it's sometimes done with woofers in an undersized box to damp down the LF. Not especially well-known, but it's been done for years. Same box size & stick a ruddy great cap in series with the driver. Probably about, oh, call it 150uF should be a reasonable compromise. Done right you end up with a response curve that follows a similar shape to an EBS vented box; the cap compensates for the rising response caused by the high box Q, until you reach the impedance rise at resonance, where the response will flattens out a bit as you'd expect before dropping away again. TBH, I don't recall seeing anybody do this with wideband drivers, just woofers, although it will certainly have been done at some point. Nothing new under the sun.