Comparison of four subwoofer measurement techniques

Acoustic measurements of loudspeakers are difficult to perform at very low frequencies, and therefore their interpretation is often tricky. Four subwoofer measurement techniques are compared in terms of frequency response and directivity. The methods were selected with an attempt to avoid assumptions about the behavior of the loudspeakers: anechoic room, pseudo free field, reference chamber, and field separation. Three subwoofers were tested: two closed-box systems and an active/passive system. Discrepancies between the results are discussed and explained where possible.