Of all the variables in subwoofer setup, physical placement has the greatest influence on low-frequency performance. More than driver size, amplifier power, or cabinet design, where a subwoofer sits in a room determines what it sounds like — because at low frequencies, the room and the subwoofer form a coupled system in which position controls everything.
Low-frequency wavelengths are long relative to room dimensions. A 60 Hz tone has a wavelength of approximately 5.7 metres — longer than many listening rooms. At these frequencies, the subwoofer and the room’s boundaries interact to create standing wave patterns in which certain positions have greatly elevated output and others have deep cancellations. Moving the subwoofer by even half a metre can produce changes in frequency response at the listening position of 10 dB or more — a difference far larger than any amplifier or driver characteristic.
Corner placement is the most commonly recommended starting position, and for good reason: corners provide maximum boundary reinforcement, producing the highest output for a given input. This is efficient and useful for maximising low-frequency extension and level capability. The drawback is that corners also represent the worst positions for room mode excitation — modal resonances are most strongly driven from corners. Corner placement maximises output and maximises unevenness simultaneously.
The subwoofer crawl — placing the subwoofer at the intended listening position and moving around the room at floor level while playing a bass test tone — identifies positions where the bass is most even and extended. The position that sounds best from the listening position while the subwoofer is at ear level is the position where the subwoofer should be placed when the listener is in their chair. It is a simple and effective technique that costs nothing and consistently outperforms arbitrary placement.
Multiple subwoofers — typically two or four, placed symmetrically — distribute bass energy more evenly throughout the room by exciting different modal patterns that partially cancel each other’s unevenness. This is the most effective approach to achieving consistent bass response across a wide listening area, and it is why professional cinema and music reproduction facilities use distributed subwoofer arrays rather than a single unit.