Thiele-Small parameters
Thiele Small Parameters (TSP) describe the behavior of an electrodynamic loudspeaker . On the one hand, the physical quantities that characterize a driven, damped harmonic oscillator are specified in practically easy-to-use units ; on the other hand, parameters are also included that describe the drive system ( voice coil and magnet ). A loudspeaker in a bass reflex housing represents an electrical high pass of the fourth order in terms of its acoustic transmission behavior .
General
The basics for describing the acoustic transmission behavior of an electrodynamic loudspeaker in a housing were described by Leo L. Beranek in Acoustics as early as 1954 . The Australian Albert Neville Thiele and the US American Richard H. Small presented the interaction between the loudspeaker and its housing, especially bass reflex boxes ("vented boxes") as the basis for sound transmission from loudspeakers from 1961 onwards . Most of the parameters are already through the The design of the loudspeaker is specified (this can only be changed by the manufacturer), the developer of a loudspeaker system can only optimize its transmission behavior through the size of the box and, in the case of a bass reflex system, by tuning the Helmholtz resonator (bass reflex channel). The Thiele Small parameters were named after their two discoverers.
The Thiele-Small parameters
- Equivalent volume V as
- Resonance frequency F ms
- Electrical quality Q es
- Mechanical quality Q ms
- Overall quality Q ts
- Moving mass M ms
- Membrane area S d
- Suspension compliance C ms
- DC resistance R e
- Inductance of the voice coil L e
- Displacement volume V d
- maximum deflection X max
- Force factor B × l
- mechanical loss resistance R ms
This data set is necessary and sufficient for calculating loudspeaker enclosures. It should be noted that all sound converters that do not work as a driven mass-spring system are not meaningfully described by the Thiele-Small parameters (e.g. electro- and magnetostats , bending wave converters).
The Thiele-Small parameters are also characterized by the fact that they - with the exception of the equivalent volume V as - can be measured completely "on the electrical side" of the complex equivalent circuit diagram. For the measurement of the electrical impedance required for this at the voice coil connection of the driver (cf. Gaedtke 1985) only a few and also inexpensive tools are required. The measurement of the equivalent volume is done either by coupling the loudspeaker to a closed housing with a known volume or by loading the membrane with a defined additional weight. A plasticine or, if necessary, chewing gum can be used for this.
literature
- Leo. L. Beranek. Acoustics , McGraw-Hill, 1954, Library of Congress Card Number 53-121246
- AN Thiele, "Loudspeakers in Vented Boxes", in JAES (Journal of the Audio Engineering Society), Part 1, JAES May 1971, Volume 19, Number 5, p. 382 ff (presented 1961 in Sydney at the IRE conference), Part II, JAES June 1971, Number 6, p. 471 ff
- Richard H. Small, "Direct-Radiator Loudspeaker System Analysis", in JAES, June 1972, Volume 20, Number 5, pp. 383 ff
- Richard H. Small, "Vented-Box Loudspeaker Systems Part I: Small Signal Analysis" in JAES June 1973, p. 316 ff, "VB Large Signal Analysis", in JAES July / August 1973, p. 326 ff.
- Wolfgang Josef Tenbusch: Basics of the loudspeakers. Michael E. Brieden Verlag, Lüdenscheid, 1989, ISBN 3-9801851-0-9 ( Sound and Sound Edition 1).
- Michael Gaedtke: Parameter measurements on loudspeaker chassis. The construction of coordinated housings using the Thiele-Small parameters , Franzis-Verlag, Munich 1985 Gaedtke 1985