The P4 is the smallest speaker in the P Series, in order to achieve sufficient bass extension the design engineers at B&W came up with a unique solution. ● The key difference, which is not visible from the outside, is the internal cabinet construction. A folded tapered duct has been used, which is selectively damped to give bass reinforcement similar to a reflex enclosure, without the danger of pipe resonances that would otherwise arise in the tall narrow enclosure. T echnical highlights Kevlar®: B&W developed and patented the method of using Kevlar® for loudspeaker cones to reduce unwanted standing waves. DuPont originally created Kevlar® for use in bulletproof vests.