Power Reference Dual Shallow 10? Loaded enclosures were developed to provide a simple solution to add bass in tight spaces. Solid MDF enclosures are designed to the exact T/S parameters of Power Reference shallow subwoofers to maximize the performance of the subs. The unique enclosure design allows for down-firing subwoofers making it ideal for under seat applications. These enclosures are sealed and ultra compact and produce tight and accurate bass.