Once upon a time on usenet Dave Plowman (News) wrote:
A mid range unit - say about 4" - in a suitable sealed box. Remind me
of the difference between mounting it on the rear of the baffle,
front, or recessed flush to it? I've seen all done on commercial
designs.

It's all about time alignment with the tweeter. My rule of thumb with my
previous home-made speakers is if it's a flattish cone I rear mount it but
if it's a deep cone I front mount it. I try to keep the respective
voicecoils of the tweeter and squawker as close as possible to the same
plane relative to the front baffle.

But there's not much science behind that, just experience and gut feelings.
Hopefully someone more knowledgeable will chime in.
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)