how many braces

[hmmmm]

About how many braces would you suggest for this speaker? 9"x 13" x 42" with 1 1/2" front baffle and bottom...the rest 3/4". The one "h" brace shown is not attached. These are two rs180 7" woofers. Thanks!
I'll eventually finish these in satin black and the bottom will be raised on spikes coming out of the black iron base (seen in photo one). The grill will fit in like a puzzle piece in the curve at the bottom.

[kexodusc]

I try for one shelf brace every 8" of height or so...Seriously, that's overkill most of the time, especially with 3/4" MDF, but I'd say 3 braces would be good for your cabinet. 4 if you can swing it. No less than 2...obviously not an exact science.