The WM-BF40 was a similar model to the WM-BF28, the difference being that the “mega bass” loudness system was included. The controls for this were fitted on the cassette door, and included two small sliders that enabled the amount of extra bass and treble to be adjusted. Although the BPC-700K rechargeable battery could be used with the WM-BF40, it was not included as standard equipment. Text copyright © Walkman Central. Unauthorised reproduction prohibited.