Among other things it talks about the 2k to 10k droop on most cantilever types:
A prior art cantilever for a pickup cartridge is made of a pipe of an aluminum alloy. In order to obtain required strength, the pipe must have a large diameter and a thick wall and consequently is very heavy, so that the effective mass of avibrator is increased. In order to solve these problems, there has been proposed to use a pipe made of titanium because the latter has excellent mechanical strength so that both the diameter and wall thickness may be reduced and consequently the weightmay be reduced. However, even with the titanium pipe sufficient strength and rigidity cannot be attained.
In order to attach a stylus tip, one end of a cantilever is pressed flat, a hole is formed through the flattened portion and the stylus tip is forcibly fitted into this hole. In this case, the cantilever is annealed so that the decrease instrength and rigidity results. In order to solve this problem, the cantilever with the stylus tip is subjected to the oxidation process, but satisfactory strength and rigidity still cannot be attained because the oxidation process results in theincrease in rigidity and Young's modulus only by 10%. Furthermore the control of oxidation of the cantilever is difficult and in the extreme case the cantilever becomes brittle.
Because of these unsatisfactory cantilevers, the conventional pickup cartridges exhibit the so-called drooping phenomenon. That is, their frequency response drops in the range between 2 and 10 KHz below the high resonance frequency f.sub.0(which is in general between 10 and 40 KHz). Thus the flat frequency response curve cannot be obtained. Furthermore their transition characteristics which determine the degree of trackability are not satisfactory.
So far the only company I have found who still seems to be using Boron tube cantilevers is Steinmusic with their Aventurion 6 cartridge - which appears to be a custom modified Benz LP-S with boron tube cantilever (?).
Anyone know of any other currently made boron tube cantilever cartridges?