The p-4 15 stuffs a lot of material in a realitively small enclosure. What would be the effect of changing the dimensions to approximately 28x20x14. This is still smaller that the JBL SR4725X which uses the same drivers and larger cone. The SR4725X is 28x24x16, I believe. Would tweaking the cabinet size compromise the overall speaker design and performance?
The net effect should be almost negligible. The increased volume will reduce damping very slightly and increase response between 60 and 80 hz or so by about 1db. If this is a concern, it can be offset by tuning the box just a bit lower. This driver allows substantial freedom with the cabinet.