Wayne Parham Messages: 18783 Registered: January 2001
Illuminati (33rd Degree)
The sealed center channel offers no advantage - It's done purely for aesthetics. It actually reduces LF extension; however, having the extra extension in the left and right channels is probably enough overlap for the subs. So while the sealed centar channel provides no advantage, I don't see it causing any real disadvantage either, provided the right and left channels are vented as designed.
As for the braces, glue and a small amount of preload is enough. I actually prefer not to use screws except in places where clamping force is needed and a removable brace is impossible or impractical. For this reason, I only use screws on the 12π hornsub, where they provide holding/clamping force on some panels and internal structures.