Audiopulse

Our (Pat. Pend.) Linear Motor System Technology, is one of the newest and most innovative concepts that we have brought fourth to the continuing refinement and development of our low frequency transducers. LMS is a very elegant concept with highly effective results that can in fact be heard without any requirements for sophisticated measurement equipment. Applying LMS to an existing subwoofer platform yields a true three fold reduction in total harmonic distortion relative to the same subwoofer without the linear technology.

The trick to linear motor technology lies in the way in which the voice coil is wound. Typical voice coils consist of wire, either copper, aluminum or otherwise, wound around a cylindrical former. Electrical current traveling from the amplifier around the voice coil produces a electromagnetic field which creates a force in conjunction with a permanent magnet which accelerates the coil, former and diaphragm up and down. What the traditional method fails to account for is non linear behavior as the voice coil extends towards its extremities. As the voice coil moves, so do the fields, and the consequence is a reduction in the density of the electro-magnetic field strength generated from the voice coil as the speaker approaches its transversal maximum values in either direction. This effect is responsible for approximately a 40-70% reduction in the actual repulsive force generated between the current carrying conductor (voice coil) and the fixed magnet motor near peak excursions. This non linear effect is responsible for much of the total harmonic distortion found in a typical subwoofer. Because the magnetic field is generally inconsistent over the dynamic range of the driver, non linear motor behaviors ultimately cause severe distortion at high displacement.

Linear motor technology is able to correct this irregularity by redesigning the shape of the voice coil to permit a constant magnetic force even during maximum excursion. A computer aided model was used to shape the FEA optimized varying density voice coil to achieve dynamic linear force, and a Klippel analyzer measurement system was then used to test the drivers Bl product (magnetic force). The results showed that the liner voice coil’s magnetic force varied by a mere 2% on a true peak to peak stroke. Further tests showed that the linear motor was able to reduce the total harmonic distortion over an identical subwoofer without the linear voice coil by a factor a three holding the SPL constant at the same relative frequency. LMS technology is able to push drivers harder, and farther with less distortion than before.

LMS drivers are far more accurate and natural than traditional subwoofers and they have greater xmax displacements, so in fact they can displace more air with more accuracy and ultimately make for a more capable and higher fidelity subwoofer. Unlike many other linear methods used in the industry such as dual gap or split coil, LMS subwoofers are highly insensitive to coil alignment issues and also don’t suffer from motor B losses that other designs do. Secondly, because LMS coils are based off of an overhung coil design, they can typical handle far more power than conventional linearization subwoofers. Finally, LMS drivers have been proven to produce the flattest and most linear Bl graph of any subwoofers in the world even other claimed-to-be linear subwoofers which, a feat that others commonly said was impossible.