For our 8 inch speakers we designed a motor that is powered by both ferrite and neodymium magnets. The hybrid magnet system and unique geometry of the pole piece enabled us to create motors with magnetic filed strength of 2.0 Tesla. Not only that, but the magnetic gap height is equal to 9 mm. That allowed the speakers to be a completely underhung voice coil design. Since the voice coil practically does not leave magnetic gap with uniform field strength along all the gap height, the raw power, linearity and reduction of distortions are at their best. In order to maintain 0.01 mm tolerance of all elements, magnetic motor components are manufactured using computer controlled CNC lathes.
Our magnetic motors were further enhanced by the most advanced Faraday Ring system that was ever used in 8 inch speakers. The elimination of eddy currents, reduction of voice coil inductance which translates to higher cut-off frequency and reduction of distortions is well worth the resultant complexity of the magnetic motor. We experimented with galvanisation of pole pieces with thin layers of various non-magnetic metals and combinations of CNC milled elements made of aluminium, brass and copper. The combination that we decided to go with, is in our opinion is the most optimal one.
After conducting many tests the solution was found and it turned out to be even better than we expected. It is 100 % linear within the maximum excursion of the speakers ( + - 6mm). It behaves like a spring. It does not consume the energy by damping, it just positions the voice coil in the magnetic gap. The downside of such technology is that each spider has to be milled with precise CNC machine. Nevertheless the advantages are obvious and totally worth it. In order to measure the actual compliance (amount of excursion under known force) of the suspensions, we designed and custom a made special device. You can see the graph with measurement comparison of our suspension and classical (resin soaked cloth) spider below.
The cones used in the drivers are made of paper. We tested countless cone materials (including t-shirt cotton soaked with hardening solution that was so rigid that you could crack and crush it just like an eggshell). Whatever we tested, the cellulose (paper) ended up as the best way to go. After many attempts to find the best sounding paper we finally got it. Nevertheless we still had to find a coating solution. Paper that isn’t protected from atmospheric moisture will, as time pass, absorb it into the its fibres. That results in huge sound changes. The thing that suffers the most are high frequencies. Month after month they will get more blunt, blurred and in the end - not present. We developed a lightweight organic resin solution, that completely penetrates paper and seals all pores, so that no moisture will ever enter the paper.
Solutions and technologies used in F8 Magus fullrange driver:
Copper & Aluminium Faraday Ring System
Mixed magnet motor (Neodimium + Ferrite)
Ultralinear low dumping spider
Underhung voice coil
Multicoated waterproof paper cones