Low TCR voice coil wire
Thermal Coefficient of Resistivity (TCR) Maintains constant impedance
For electric coil windings, particularly in moving coils such as the voice coil of a heavy duty bass loudspeaker or other electro-acoustic transducer, the present invention has found metallic materials, as alternatives to copper or aluminum in the voice coil wire, that can provide increased available maximum SPL (sound pressure level) exceeding an empirical limit, just under 120 dB/1 m, that has been found to apply to various loudspeakers of known art regardless of efficiency and structural differences. Through study of known art regarding this limitation and theoretical analysis of the factors in voice coil structure and design that limit the maximum attainable SPL, a novel basis for selecting voice coil wire material has been developed. By selecting wire material for low TCR (temperature coefficient of resistance) along with suitable resistivity and density, rather than for low resistivity alone which has conventionally dictated copper or aluminum, the present invention has led to the identification of new wire materials that can increase the available SPL. Such materials include alloys of aluminum containing between two and five component basic metals selected from the following group: magnesium, silicon, manganese, zinc and copper. The alloy Al Mg(3.5%) in extruded form yields maximum SPL 1.5 dB above that of pure aluminum and 3.32 dB above that of pure copper.
Patented 1994 JBL Incorporated.
First use of Alnico magnets.
Composed of Aluminum, Nickel and Cobalt, JBL was the industry leader in introducing this strong permanent high power alloy in professional speaker systems.
Alnico magnets produce magnetic field strength at their poles as high as 1500 gauss (0.15 tesla), or about 3000 times the strength of Earth's magnetic field.
First introduced in the D130, 15-inch transducer.
First to introduce titanium in high-frequency diaphragms
JBL’s titanium diamond diaphragm structure combines the ruggedness of phenolic and composite-type diaphragms with the outstanding frequency response of fragile aluminum and exotic metal diaphragms.
First neodymium-magnet Pro Audio compression driver and woofer
Neodymium magnets and dual voice coils provide peak performance at a fraction of the weight of conventional drivers. JBL’s next generation neodymium compression drivers deliver stunningly accurate high frequencies through a new 1.5" annular polymer diaphragm design.
Neodymium's magnetic properties allow a few ounces to replace pounds of conventional magnet material. While other speaker manufacturers may use neodymium, JBL engineers created a design that reduces the massive (and heavy) steel top plates,back plates, and pole pieces that complete the "magnetic circuit".
Typical Neodymium Configuration