Speaker frequency response charts

Other than how the cab design affects the bass response with a given speaker, SPL graphs are misleading in that they don't show how the speaker impedance curve interacts with a tube amp or how cone resonances and internal cab modes and early reflections color the sound. I still find the graphs somewhat useful.

I believe guitar players generally base their opinions on what makes a good cab sound on what we hqve heard thus far. I think the original Marshall 4x12" design has some drawbacks that are in no way beneficial. Jim Marshall had admitted that the idea was just to fit as many speakers into the smallest size possible with little consideration for how it affected the sound. Disregarding the beaming effect, It's actually not that bad tonally. Some benefit might be achieved with rear padding in upper-mid smoothness with some speakers by eliminating various resonant peaks and cancelations, if the resulting dryer sound is acceptable, and stronger punch may also be achieved with a thicker rear panel. A simple alteration which may eliminate the ~700Hz dip would be to add a separator to raise the cancelation above 1kHz where it wouldn't generally be noticed, but that might be more trouble than necessary.