JBL 2420 is a professional quality compression high frequency driver which has the widest range of flat response in the industry. It is built to typical JBL standards of precision. Mathematically determined phasing plugs are machined concentric exponential horns to eliminate phase cancellations. Magnetic assemblies are cast and machined to hold tolerances considered impractical by industry standards. Diaphragms of duraluminum alloy are pneumatically drawn to shape to eliminate stresses that cause fatigue. A ring machined from pure silver is added to the pole piece to counteract the inductive component in the voice coil at high frequencies. After manufacture, the frequency response of each driver is tested, and a peak or dip means it is rejected.
Link for PDF: JBL-2440-2-in-Comp.pdf