Thanks guys.

I usually use 8" but what you say still rings true, re not to expect subwoofer like bass. My thought here is just to get maximum performance without including a subwoofer.

Previously I thought it wouldn't be much use as I thought most in-wall/in-ceiling speakers were designed as infinite baffle (with the exception of higher end speakers that have optional full enclosures to be installed during rough in), but with a manufacturer publishing recommended enclosure sizes for an entire line of speakers, that changes things. KEF even offers the same for their more value oriented speakers.

In the case of the 2x4 truss, fitting an enclosure in between the trusses is a great idea as I could make them in an assembly line fashion (at home or on site) vs custom fitting each one. Give my self a 1/4" of room for variance and used wedges to fit.

Adding a rigid baffle would add time as now I have to cut circles, but, would also eliminate the need for a new construction ring so the time spent would be saved there. I think that's a good idea.

Also the enclosure idea eliminates any complication added if resilient channel is used.

I just finished my last two distributed audio system for the year so I won't have an opportunity to try this out soon,but I'm planning to add two ceiling speakers in my kitchen when I can and I have attic access so I think I'll do a before and after type test. I can even run some sweeps with Room EQ Wizard and post results.

I'll revisit this later.

Thanks for your input.

Craig.