In a traditional loudspeaker, the diaphragm acts as a “rigid piston” at low frequencies, but turns into a multimodal object when approaching its so called “breakup region”.
In a BMR, there is no “break-up region”. Instead, a limited number (usually 2 – 4) of evenly spread modes are carefully positioned within the frequency band. The modal, bending-wave operation starts in the frequency range where the piston-like operation of the panel would otherwise cause the driver to beam. The result is a drive unit that operates like a piston at low frequencies but becomes a bending wave device at high frequencies. Thanks to the bending wave operation, the drive unit demonstrates wide dispersion even at high frequencies. Acoustically, the behaviour of a BMR approximates to the ideal “point source”.