Mordaunt-Short Avant Architect In wall speakers in-wall speakers are offered have optional back boxes available. They feature a self-sealing cable entry grommet at each end and the entire box is gasketed for a consistant volume enclosure. These custom-designed units are supplied with acoustic wadding which increases the apparent volume of the cabinet, controls standing waves and adds a primary layer of damping to the acoustic enclosure. The back-box surface features a water resistant coating to facilitate installation in almost any environment.