The JBL 2242H low frequency transducer incorporates JBL's ongoing developments in improved thermal dissipation and linearity at both high and low cone excursions. To increase power handling while minimizing power compression, JBL's engineers have developed a patented voice-coil to-air heat dissipation method known as Vented Gap Cooling™. This process pumps air through the magnetic gap and directly over and around the voice coil to provide immediate heat transfer and reduction of operating temperature- a direct improvement in power compression.
The 2242H is built around a completely new motor structure with a pole piece extending both above and below the top plate to improve gap flux symmetry and increase thermal conductivity from the voice coil to the pole piece. In addition to the benefits of JBL's Symmetrical Field Geometry™,the 2242H also incorporates a copper shorting ring that is imbedded in the pole piece at the precise center of the gap and is in close proximity to the voice coil. The copper ring acts like a shorted secondary turn in a transformer,with the voice coil acting as the primary winding. The benefits of this are a reduction in third harmonic distortion and a reduction of the voice coil's inductance, which improves the transducer's transient response.
The 2242H can produce peak instantaneous outputs of 134 dB above 100Hz measured at one meter, greater than any other JBL low frequency transducer.The new voice coil-magnet circuitry is referred to as Super Vented GapTM technology.
The 2242H is intended for use in applications where large amounts of low distortion low frequency acoustical power is required, along with excellent mid-bass transient behavior. A typical application is as a subwoofer for cinemas,with extension down to 25 Hz. The total peak-to-peak excursion of the moving system is 18 mm, within 10% linearity.
The 2242H carries a power rating of 800 watts, as compared with the 600watt rating of its predecessors. This is accomplished through the use of a voice coil with one-third more surface area than in the earlier designs, allowing the 2242H to dissipate heat more effectively to the surrounding metal parts, The higher power rating, reduced power compression, and increased efficiency give the 2242H a net continuous output capability that is 3 dB greater than that of the 2241H.
Careful attention has been paid to the design of the moving system. The cone used in the 2242H is reinforced with fiberglass for added strength. The inner suspension is a JBL design whose "stress-strain" curve has been chosen to produce better control of cone motion at the highest excursions.