The Ideal Surround Speaker Many listeners have found that built-in speakers are the perfect solution for side and/or rear channel surround speakers. They take up no floor space and virtually disappear from view. We specifically designed the DI 5.5BPS for surround channel duties. You can install them in walls or ceilings for enveloping surround effects with smooth natural response and precise detail retrieval. Every sound effect and musical note will be revealed with exact accuracy while you are enveloped in a life-like bubble of sound. Definitive's Disappearing® In-Wall series speakers feature near-invisibility thanks to their small area, hidden flange design, and low profile micro-perf grilles. They are as easy to install as traditional flanged flush-mount speakers, and don't require custom sheetrock/spackle skills to install yet they are practically invisible.