Nominal impedance
In electrical engineering and electroacoustics (audio), the nominal impedance is the frequency-dependent impedance at the input and / or output of an electrical device, which is specified in the technical data in the data sheet in the medium frequency range at a frequency of 1 kHz. Your unit of measurement is the ohm .
- An industry standard has developed for headphones that recommends a nominal impedance ( input impedance ) between 50 and 600 ohms.
- For loudspeakers , 4 ohms, 8 ohms, less often 16 ohms, are the nominal impedance (input impedance) (at f = 1 kHz), and 6 ohms can still be found.
- The industry standard for studio microphones is a nominal impedance ( output impedance ) below 200 ohms. The minimum terminating impedance (input impedance) of the microphone should be more than five times the value of the nominal microphone impedance or, in other words, the input impedance of the following microphone preamplifier should be at least five times the nominal microphone impedance in order not to unnecessarily attenuate the voltage of the microphone signal.
Amplifiers have an input impedance and an output impedance whose values are very different. That is why there are many problems when the home norm and the studio norm meet; Not to speak of symmetrical and asymmetrical and the most diverse connector standards.
The designation of the impedances is quite different and confusing. The input impedance of a device (e.g. loudspeaker) is also called external resistance R a , input resistance, load resistance and terminating resistance and the output impedance of a device (e.g. microphone) is also called internal resistance R i , output resistance and source resistance. Problems there when R a as A ußenwiderstand with the " A usgangswiderstand" R i is mistaken, because those are two different "impedances".
For the studio equipment , the impedances are IRT - specifications 3/5 set for mixing consoles.
A transformer itself has no nominal impedance; it translates a connected impedance from the primary side to the secondary side and back.
The impedances with the different names
| R i | R a |
| Internal resistance | External resistance |
| Source resistance | Load resistance |
| Output resistance | Input resistance |
| - | Terminating resistor |
In sound engineering language, the word "resistance" is usually chosen instead of "impedance".
See also
literature
- Gustav Büscher, Alfred Wiegelmann: Little ABC of electroacoustics. A practical arrangement and explanation of the basic terms, numerical values and tables (= RPB-Electronic-Taschenbuch . Volume 29 ). 7th, revised and expanded edition. Franzis-Verlag, 1976, ZDB -ID 996632-8 .
- Michael Dickreiter, Volker Dittel, Wolfgang Hoeg, Martin Wöhr (eds.): Manual of the recording studio technology . 2 volumes. 8th, revised and expanded edition. Verlag Walter de Gruyter, Berlin / Boston 2014, ISBN 978-3-11-028978-7 or e- ISBN 978-3-11-031650-6
- Thomas Görne: Sound engineering . Fachbuchverlag Leipzig by Carl Hanser Verlag, Munich a. a. 2006, ISBN 3-446-40198-9 .
- Berndt Stark: Loudspeaker manual. Theory and practice of box building . 7th, completely revised edition. Pflaum, Munich 1999, ISBN 3-7905-0807-1 .
- Wolfgang-Josef Tenbusch, Richard Small: Basics of the loudspeakers (= Klang & Ton Edition . Band 1 ). 2nd Edition. Michael E. Brieden Verlag, Oberhausen 1995, ISBN 3-9801851-0-9 .