The Model 2447H/J is a 38 mm (1 1/2) exit diameter addition to JBL’s family of professional quality compression drivers. The 38 mm exit allows the Coherent Wave™ phasing plug to directly couple with Optimized Aperture™ Bi-Radial® horns to provide lower distortion and better coverage control to 20 kHz than previous designs. In addition to improving performance the 38 mm design also reduces size and weight.
The Coherent Wave™ phasing plug structure has four equal length passages to provide in-phase summation of diaphragm output at the 38 mm exit. This optimized configuration produces coherent acoustical power up to much higher frequencies than more conventional designs.
The diaphragm design includes JBL’s exclusive three-dimensional diamond pattern surround¹ tuned to reduce fatigue inducing stresses in the membrane and support structure. This provides predictable normal resonance modes, and radial reinforcing ribs increase diaphragm stiffness. This diaphragm design combined with the Coherent Wave™ phasing plug increases the 2447’s output in the 5 kHz to 20 kHz range.
High temperature voice coil former materials and adhesives enable the 2447H/J to handle high power levels over extended periods of time. The voice coils themselves are identical to previous JBL models, so that impedance and network matching will be the same. After manufacture, the frequency response of each transducer is tested for conformity to JBL’s rigid performance standards.
The model 2447H/J is ruggedly constructed to withstand the rigors of both fixed installations and touring applications. All tolerances are held to the same high levels traditionally associated with JBL designs. The JBL manufacturing process permits the use of rim centered diaphragms for instant interchangeability and ease of field service.