SYSTEM DESCRIPTION AND PHILOSOPHY
A loudspeaker design naturally splits into various parts: cabinet, lower frequency, higher frequency, and crossover which, for the System 600A, is integrated in the amplifier assembly. The design of these parts cannot take place in isolation, as they are all interdependent.
The integration of all the features described below is what makes the whole loudspeaker system even greater than the sum of its individual parts.
Drive unit.
The drive unit used in the System 600A monitors is part of the latest generation of Dual Concentric units designed by Tannoy. Amongst many other features, this range of drivers incorporates a dual magnet assembly, ‘tulip’ HF waveguide and injection moulded polypropylene LF cone.
The design of the HF waveguide has been arrived at by making extensive use of CAD (computer aided design). It matches the acoustic source impedance at the HF diaphragm into the acoustic environment, shaping the wavefront as it travels down from the diaphragm ensuring equal path lengths to achieve a spherical wavefront. Wavefront shaping begins at the diaphragm surface and, because the compression ratio can be kept relatively low with this design, the distortions due to air
The HF diaphragm is made from aluminium and magnesium alloy, with optimised shape and thickness, suspended by a precision moulded, inert nitrile rubber surround. Its very narrow roll eliminates resonances below 25 kHz and provides a very stable and consistent mounting. The roll form ensures high excursions can take place if necessary yet provides a
The HF voice coil assembly incorporates a high temperature copper wire chemically bonded onto a kapton former fitting onto the outside of the HF diaphragm skirt. The thermal power handling of the voice coil is greatly increased thanks to its ferrofluid filled magnetic gap.
The LF unit uses a CNC precision injection moulded polypropylene cone, terminated by a nitrile rubber,
The shape of the LF cone has been calculated to match the HF hyperbolic waveguide ensuring the wavefront remains spherical and perpendicular to the cone surface throughout the propagation.
The heart of the LF unit is the motor system comprising the magnet and voice coil. The choice of magnet operating point parameters, air gap flux strength, voice coil details (number of turns, resistance, winding length, diameter etc.), moving mass, dynamic compliance and drive unit radiating area presents a very complex mathematical problem where the solutions can take many different forms. Reaching the correct answers is much easier if computers can be called on to assist with solving the equations, as Tannoy do for its drivers.
Cabinet.
As well as the drive units, cabinet design plays a major role in the acoustic performance of a speaker system. Among the problems which can contribute to the degradation of the emitted sound field, diffractions and reflections caused by the cabinet boundaries are too often overlooked although they are the cause of most of the irregularities heard and measured in the higher frequency areas.
In that respect conventional rectangular, sharp corner boxes perform especially poorly. On the other hand, the shape of the System 600A has been designed with careful