The Tannoy Monitor series loudspeakers use AlNiCo type magnets. These magnets are reputed to contribute to the sound of Tannoy Dual Concentric speakers as a result of the fact that cast iron-alloy magnets form an electrically conductive shorting-ring thus allowing for a reduction in flux modulation via the self-induced currents in the magnet. (Source: "Tannoy History"). The mix of materials used in an AlNiCo type magnets varies, depending on the type of AlNiCo. From http://mag-net.ee.umist.ac.uk/articles/a3.html the following mix of materials is quoted:
AlNiCo composition range (% by weight):
Aluminium Nickel Cobalt Copper Niobium Titanium IRON (Fe) 6 to 13 % 13 to 18 % 0 to 42 % 2 to 6 % 0 to 3 % 0 to 9 % Balance to 100%
The table above is a generalisation for the various types - note that there are other possible ingredients besides Aluminium, Nickel and Cobalt, as small traces of Copper, Niobium and Titanium are included in some types.
Tannoy sales literature refers to magnets for the Red and Gold series as "TiCoNAl" which is a trade-name for a particular mix of the above ingredients. The HPD-385 is quoted in Tannoy sales literature as using an AlComax-V magnet, also another trade-name for and AlNiCo style magnet. Note that for every type of AlNiCo magnet, Iron (Fe) is used to top the mix up to 100%, making AlNiCo an iron-alloy.
From another web site (http://yu-ra.tripod.com/motor.htm towards the bottom of the page ) AlNiCo-V is quoted as:
Aluminium Nickel Cobalt Copper Niobium Titanium IRON (Fe) 8 % 14 % 24 % 3 % 0 0 51 %
Tannoy Magnet Construction
Loudspeaker magnet systems have been, and still are constructed in two possible ways:
(i) With permanent-magnet as the centre-pole, and a rounded outer casing that forms the flux return path to the front of the magnet. This is how many JBL's are made.
(ii) The inverse of (i), with a soft-steel centre-pole, and ring-shaped cast iron-alloy (AlNiCo) outer-ring permanent-magnet. This is how all Tannoys (Black, Silver, Red, Gold, and HPD's) are made.
Pro-and-Cons of (i) and (ii) above
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