Something like that. But, if you like to read about here;s the link.
http://www.silcom.com/~aludwig/Time_alignment.html
But, as I mention before, moving tweeter few cm back will make non flat front baffle what can be really serious problem in the MTM design. My experience tells me that DSP crossover is more flexible, you can change slopes , cross points in the second, and most important you can do usec delays and compensate driver misalignment. Also, additional eq for each band can be nice fine polish tool. :wink: At last, in the studio environment we are looking for accurate speaker, nor audiofool color 
Are we :?:
To fine tune some accurate passive crossover you must be real expert, and if you are, you will need some serious equipment to check the result. Just my 2 cent based on personal experience...
About tunning the sealed box Qtc is the parameter you are looking for.
Certain values of Qtc [The total Q of a driver and sealed enclosure] have specific response characteristics, which can be characterized as follows:
Qtc= 0.5 Critically dampened; Transient perfect.
Qtc= 0.707 Butterworth response-max amplitude response with minimum cutoff.
Qtc >0.707 Chebychev response-equal ripple response; max power and handling efficiency.
Qtc=0.5 is usually regarded as excessively taut and over dampened, however some standards still consider this value to be optimal.
Check this...http://www.geocities.com/kreskovs/Box-Q.html
Personally I will make calculations for both and choose to make bigger volume box, then fill the inside to fit into smaller volume calculation and finally choose by ear
:wink:
