>>Qtc = 0.707This rule isn't written in stone. I have midrange drivers optimized
for small boxes but they will sound bad because the box is too small
and there is too much sound chaos inside the chamber. It would be
better to just violate the rule and make a deep box with good fill
to get a cleaner midrange sound.
If this is confusing, then make a test box to see what I mean.
Get some cheap particle board and make a small midrange box,
then make a deeper one with good fill. Listen to the driver
full range or high pass the driver to keep the bass out so you
don't damage the driver. Compare the sound and see what you like.
There is no guarantees that you will prefer the bigger box, but
you should at least explore that option and verify it.
Deep cabinet.
http://www.speakerbuilding.com/content/1044/09_sanded.jpg