A sealed enclosure designed to reduce the volume level of a guitar speaker. The speaker is mounted in the isolation cabinet, which closes up to isolate the sound the speaker produces from the rest of the world. Typically a microphone is mounted in the isolation cabinet to route the sound out to a mixing console, DAW, or PA system.
Isolation cabinets can dramatically reduce the volume level produced by a speaker. They are used for quiet recording in home and commercial studios, so that an amp can be cranked up without bleeding into other tracks or offending the neighbors, and they are also used onstage for controlling stage volume for better front-of-house sound quality and cleaner monitoring.