My mains, my center channel, and the side surrounds, are all having different mfgs frequency responses. I listen to DD movies. My AVR has calibrated all five speakers plus the woofer. Is it important that their frequency responses be closely matched, or not? What are your thoughts on speaker frequency response being miss matching? A concern? As long as they are closely matched in frequency response?
You have asked a question that has no precise answer, as there are variables. Frequency response errors are often related to significant underlying problems NOT correctable by EQ.
However there are some rules. The front three should match closely. However if they match in frequency response errors, then they are all equally lousy.
That is what timbre matching actually is. It means making sure the front three are equally lousy.
The other issue in addition to FR, is lobing. This is a serous problem as the ubiquitous center horizontal MTM configuration has precisely the wrong lobing pattern, and will by design have uneven distribution and only a good FR right in front of it. That is a design approach that really needs to stop.
As far as the others are concerned it is less of any issue. But having all speakers good neutral speakers with good on and off axis response really does make a superior system. This is especially true if you are using any multichannel format recorded in larger and especially ambient spaces. The ear is not fooled when the reverberant field does not match the direct field. I am absolutely certain of that.