Korky, rather than considering an acoustically transparent(supposedly)screen, I'd suggest that you use a regular screen and position the M80s entirely to its left and right. As to the center speaker, since it's unlikely that the screen would be positioned high enough for a vertical M80 beneath it, you might consider using the M22 vertically positioned there for a closer match to the M80 mains(except low bass, of course, which the sub will handle anyway).

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Enjoy the music, not the equipment.