Creating wall cabinet for flush mount speakers

[maurice53]

I am putting in a pair of Proficient Protege W682 in an existing interior 2x4 framed sheetrock wall. Wires are run, cutout made. I am thinking of creating an enclosure in the wall by placing a piece of 2x4 horizontally above and below the speaker. How would I determine the size of the in wall enclosure or is this even worth the effort at all? The wall cavity is empty, 16" wide, 7ft tall.

 

[maurice53]

Just spoke to tech support at the manufacture. They sell a pre construction sheet metal back box 14x 10x 5 3/4, I think he said it is lined with insulation. It's obviously too deep for a 2x4 wall. But mainly said it is sufficient to insert insulation in the wall cavity to cut down on sound reverberating in the wall cavity.