To operate passive speakers an external amplifier is needed. They are widely used in both domestic as well as professional audio systems. Because passive speakers offer flexibility in configuration they allow customers to select an amplifier that suits their hearing preferences economically as well. In a home audio setup, passive speakers can be an efficient listening system when used with a stereo amplifier. In professional audio systems, passive speakers can be integrated into an elaborate multi-speaker arrangement with a single or multi-amplified system. To suit different listening preferences passive speakers are available from bookshelves to large floor standing models all engineered to reproduce specific ranges of frequencies and varying levels of sound quality.