Thanks for the link...
Regarding the speaker placement, most if not all the designs have the speakers mounted higher than the centerline. Does this affect the sq or they just raised it?
Theoretically, the location of the driver on a sealed enclosure doesn't really matter (in a perfect world so to speak). However, on vented enclosures, there is a minimum and maximum distance for the driver and the port so that the port does not unload the driver below the port's resonant frequency. This is just for the location of the port wrt the driver.
As for being above the centerline, here's what I can remember from memory.
1. Being above the centerline provides the least baffle plane resonance occuring being more reinforced as it approaches the edges of the enclosure.
2. Diffraction. Mounting the driver/s with an offset from the centerline changes the time and frequency domains of diffraction, however, this does not reduce the amount of energy re-radiated by the internal walls.
This is where stuffing is mainly used - unfortunately, most builders I see use stuffing as if it is a band aid to change the box frequency response.As sound waves like to bounce from hard surfaces, stuffing is supposed to aid in eliminating reflection, diffraction, or bounce NOT to change the box frequency response. If you are using stuffing like that then that means you have designed the wrong box for that particular driver.
In FR drivers/enclosure designs, the design and volume of the box most certainly dictates the lowest frequency possible to be reproduced. But overdoing it will result in unloading the driver below the lowest frequency the driver and box is designed for, thus, instead of the box reinforcing the driver and having more bass, you actually reduce the amount of bass because the driver sees the unwarranted increase in the box size as if it were in free air.
3. Mounting the driver with an offset from the centerline also introduces a change in the phase angle of the mids and highs wrt the low frequencies. Distribution that aids directionality is what we're after here. This my friend is what gives height, depth and imaging to the music we hear coming out of the driver/box combination.