TRANSDUCERS
The 1501AL Low Frequency Driver
See Figure 2
The 1501A L Low Frequency driver is very similar to the 1500A L used in the S9800 system. It incorporates a new high impedance voice coil to allow a pair of woofers to be used while still maintaining an 8 ohm system impedance. The voice coil length has been increased to 30.5 mm (from 20.3 mm) and its milling width has been reduced slightly. This was done to allow greater clearance from the outer diameter of the coil to the laminated top plate and to provide a larger surface area of coil surface for heat dissipation. These coil improvements allow the 1501A L to handle up to 25% more power than the 1500A L.
Figure 2 – 1501AL section view
The 1500AL LF driver is a 380 mm diameter device with a 100 mm voice coil completely immersed in a radial field generated by an Alnico 5DG magnet. Alnico was chosen because of its stable operating point. This material is insensitive to temperature changes and back EMF from the coil. JBL has overcome the tendency of Alnico to demagnetize with high drive by utilizing a massive shorting ring at the base of the motor assembly. The top plate is constructed of alternating
The outer suspension is made of EPDM foamed rubber, which has the longevity and frequency response characteristics of traditional rubber surrounds, but with a low density very close to that of foam surrounds. Low loss EPDM material was chosen so that the transient detail of musical signals could be preserved. Dual inverted Nomex spiders are employed for the cancellation of
