Well that all makes more sense I think:
I don't think the hump is inherent to the driver, I think it's the enclosure size and port combination. For example, if I keep all else the same but double box size, We get something like this:
Which looks quite a bit closer to what my tuning looked like for the 8ohm shielded version.
I think you probably want a bigger box if you want these vented. Look around at other designs using the Rs225 (Curt Cambell has a ton, impulse audio has a video review
YouTube) they are using larger boxes tuned in the mid-lower 30s.
Your box will work, you're just leaving some performance on the table. If you don't want to change it, You can use EQ to bring the hump down and put a highpass below tuning frequency, which will give you a box that can play louder than the bigger alignments, but not as low. You could also try to stuff the port and test the sealed alignment, your box size gives a nice low Q sealed box which rolls off faster but extends into the 30s and below just as well.
The yellow line is your ported box, for reference, everything else is the same size sealed box. This would probably be what I'd do if a different box isn't possible, I'd take the reduced SPL capability for the better extension and SQ of the sealed version.
