Our 5 1/4" works well in a 1/3 cu. ft. sealed box. This has been used successfully in a built-in 7.1 home theater system. It creates a wide and deep sound-field where there are no bad seats in the house. This speaker will surprise you with its full-range capabilities. This speaker could be used in outdoor environments (boats, spas, etc) or in the best home audio / theater system. As a high efficiency midrange / tweeter with a capable woofer, this would be a system to be reckoned with. Only a simple crossover, if any, is needed for a multi driver system.