JBL/Harman Professional - Northridge, CA, USA
A theory of dual compression drivers was described earlier and the design was implemented in several JBL Professional loudspeakers. This type of driver consists of two motors and two annular diaphragms connected through similar phasing plugs to the common acoustical load. The new concept is based as well on two motors and acoustically similar phasing plugs but the diaphragms are mechanically “tuned” to different frequency ranges. Summation of acoustical signals on common acoustical load provides extended frequency range compared to the design with identical diaphragms. Theoretically maximum overall SPL sensitivity is achieved by the in-phase radiation of the diaphragms. Principles of operation of the new dual asymmetric driver are explained using a combination of matrix analysis, finite elements analysis, and data obtained from a scanning vibrometer and the electroacoustic measurements are presented. Comparison of the performance of these dual drivers and the earlier fully symmetric designs is provided.