The larger BA-71 uses four 160mm woofers while the BA-31 employs two woofers. The B71 employs two 160mm midrange drivers in a D'Appolito array around a single front-firing air-motion-transformer tweeter, the B31 a single midrange unit. These speakers differ from the rest of the Burmester loudspeakers because they incorporate a user-adjustable air-motion-transformer tweeter on the upper rear panel of the cabinet.
Part of the reason Burmester’s future is assured is products like the new BA31, the second device in the company’s new Ambience line of loudspeakers. The term Ambience is more than just marketing speak – at the back of the BA31 (and the original, larger BA71) is a second rear-firing Air Motion Transformer (AMT) folded ribbon tweeter, with a large level control, designed to introduce an extra degree of ambience into the system.