The linked pictures relay upper frequency response issues related to edge diffraction and loss of bass response also due to diffraction. I am confused with the post’s reference to "resonance" and "in the box".
http://www.aes.org/aeshc/pdf/how.the.aes.began/olson_direct-radiator-loudspeaker-enclosures.pdf
http://www.aes.org/aeshc/pdf/how.the.aes.began/olson_direct-radiator-loudspeaker-enclosures.pdf