Measurement examples

The following polar animation shows the directivity of a conventional cone drive unit compared to the directivity of a Distributed Mode Loudspeaker (DML).

The directivity of the 8" cone conventional bass driver (shown in red) is compared with a ~400mm² DML panel (freely mounted). Both devices are horizontally mounted, radiating down into free space (on-axis= 270°). The panel has a coincidence frequency (Fc) at ~6kHz. The in-plane coincidence lobe is visible at this frequency, then rotating forward with frequency.

A study undertaken into diaphragm material and its effect on directivity at high frequency.

The 17kHz polar image shows a comparison of two different plate materials on linear (roll) surrounds (on-axis= 0°). The first plate has an Fc at 7.5kHz and the second has less stiffness with Fc at 24kHz.  A wider, forward coverage can clearly be seen in the directivity from the plate with the lower Fc.