Technology Highlight

Ultra High Symmetry™ Magnet Structures

The loudspeaker magnet structure and voice coil assembly work together to produce the force necessary to move the cone back and forth. It is critical for high performance loudspeakers that this force and resultant motion be the same in both directions. The result of a non-uniform force is harmonic distortion and reduced product quality.

All P.Audio Design magnet structures feature a Ferrite based high energy permanent magnet. The magnetic assembly utilizes an Ultra High Symmetry design™ design in order to greatly minimize harmonic products at high mechanical displacements and at high input power levels.

Figure 1 is a cross-section of the P.Audio Design magnet structure assembly. This assembly consists of the permanent magnet and low-carbon steel sections designed to "focus" the magnetic energy associated with the permanent magnet in the "magnetic gap".

The grey portion of the magnetic cross section is the permanent magnetic. The section highlighted in red is the pole piece/back plate, also known as the "T-Yoke". The section highlighted in blue is referred to as the front plate. The front plate and pole piece/back plate act as a "magnetic circuit" to conduct the magnetic energy and concentrate that energy in the magnetic "gap”.

Figure 2 is an expanded version of Figure 1 and shows a close up view of the magnetic gap. It is important to note that the geometry of the magnetic gap shown in Figure 2 is the same above the magnetic gap as it is below the magnetic gap. This ultra high symmetry presents the same magnetic environment regardless of whether the voice coil has moved up or down in this gap. The loudspeaker voice coil assembly is positioned in the "gap" and develops an electromagnetic field when energized by the amplifier. This electro-magnetic field interacts with the magnetic field produced by the permanent magnetic assembly and produces the force available to move the loudspeaker cone assembly. The net result of the ultra high symmetry permanent magnetic assembly is a very linear interaction of the voice coil's electro-magnetic field and the permanent magnetic field of the magnet structure. This symmetry will ensure that a very well controlled and constant force is available to move the loudspeaker cone assembly.

Figure 3 shows the P.Audio Design voice coil suspended in the magnetic gap. Figure 3 is the same image as Figure 2 but with the loudspeaker voice coil assembly added. (Note: Figure 3 is an image of the P.Audio design showing an Inside Only TM voice coil design. The P.Audio Design 18 inches also uses a UHS design but utilizes a Square Wire Technology voice coil geometry.)

Multiple Symmetrical Demodulation Rings

All P.Audio Design UHS magnet structures utilize dual demodulation rings designed to substantially reduce both the harmonic distortion and intermodulation distortion associated with voice coil displacement. There are two demodulation rings in every UHS magnet structure, as shown in Figure 4. The symmetrical demodulation rings not only reduce the magnetic flux (energy) modulation but also act to make the variation of system inductances more linear as input current.