Ah, the meeting the minds are touching on all the interesting points that at one time or another have been debated on and theorized as to what impact all the elements combined do or don't effect subwoofer/enclosure performance/bass response.
Bracing
I've always used " window type " for enclosure's, though, admittedly, I have used bracing with circular cutouts only form the standpoint of where this bracing would be located as to not impede air flow/movement while at the same time displacing the least amount of volume.
Given now that we realize how subwoofer function applies it's mechnical force to the static air volume, the air more or less is in resonance with that of the frequency of the subs excursion when it reaches a certain point.
The air is moving, but not to any great degree that would cause these " turbulence " issues that keep being brought up time and time again, I have always argued that bracing in any form doesn't hinder the function of the static air volume nor the port for that matter.
Slot Ports & 45's in corners
I cannot argue nor dismiss the effectiveness using 45 degree corners in the ports as to the impact of " bass response " whether it improves it over a 90 degree corner.
As mlstrass has already stated that two identical ported enclosure's would have to be built to prove this " theory " out as beneficial or not, speculation as this point provides nothing concrete.
And as also stated, it is highly doubtful that to the human ear, anyone would be able to distinguish such differences.
The smoke thing is very interesting as it would clearly show the forces at work and what is and is not happening.
Idea ( Something from watching Myth Busters )
Build a ported enclosure and use a Plexiglass top for the enclosure, that way it can be seen what is actually happening to air/smoke and more important, make a video of how the air/smoke is moving in the port and around bracing and what not.
This would answer alot of questions, clear up all doubts and either confirm or " BUST " the myths going around.
As to the 45 vs 90 degree corners in terms of the " Air Movement " and the " Trapped Vortex " created, I have rethought the physic's in terms of dynamic air flow vs static air being resonated as the frequency of the subwoofers full excursion .
The air is not reacting as " flow " in one direction, but being both pushed and pulled simultaneously at such an accelerated rate that what we have been referring to as " air blowing out the port " is nothing more than vibration of the air and what we are " feeling " is both compression and decompression of that static air in the same instant.
