Thanks, Bill. I did think of the out of phase possibility. I like you have been considering the tuned speaker cabinets, my son and I used to build speaker cabinets years ago at Speakers Kits and Crossovers. I looked for some of the old computer design files in my old disks only to find I do not have a computer that will read the original floppy disks.
Yes we used to tune the speaker boxes with PVC pipe and acoustics insulation. Although the many many boxes of my kids stuff is still stored here in the garage, the one thing I can't find is the Db meter we use to use for tuning. Oh well.