The use of SMC (Soft Magnetic Compound) in the PHANTOM M-250 has many advantages, but by introducing SMC into the area close to the magnet gap, the overarching result is a significant reduction of distortion from losses in the magnet motor.
SMC’s unique ability to deliver a high magnetic conductivity and a very low electrical conductivity, gives us all the desired qualities of a really good speaker magnet, without the traditional disadvantages.
When using iron-based magnets in speakers, the magnetisation and demagnetisation introduced by the shifting current directions does not happen at the same pace. The demagnetisation process is slower than the magnetisation. This phenomenon is called hysteresis, and is a known problem in almost all speaker magnet motor systems.
The problem with hysteresis is that it introduces an unintended resistance to the voice coil, resulting in unwanted distortion. The reason hysteresis occurs is that iron is not only magnetically conductive, but also very electrically conductive.
SMC on the other hand is very highly magnetically conductive, but has a very low electrical conductivity (approx. 1/10,000’s of iron). The result of using SMC is almost no hysteresis, and therefore no distortion.