An extended bandwidth folded well diffusor extends the diffusion bandwidth of a shallow, asymmetric diffusor by incorporating maximum-depth, folded L-shaped, half-width wells on both ends (sides) of a diffusor, thus providing increased maximum well depth without increasing the physical depth of the diffusor. When the inventive diffusor is placed in an array, the folded L-shaped, maximum-depth, half-width end wells form a novel T-shape, which offers a favorable impedance lowering the resonant frequency, thus extending the diffusor diffusion bandwidth. T-shaped recesses may also be located within a single diffusor. The front surface of the diffusor may be flat or curved or angled.