Nominal impedance

The nominal impedance in electrical and electro-acoustic (audio) the frequency-dependent impedance at the input and / or output of an electrical appliance that is specified in the middle frequency range at a frequency of 1 kHz in the specifications in the datasheet. Your unit is the ohm.

• With headphones is an industry standard has developed, which recommends a nominal impedance ( input impedance ) between 50 and 600 ohms.
• For speakers are 4 ohm, 8 ohm, 16 ohm rarer than nominal impedance ( input impedance ) ( at f = 1 kHz) common even 6 ohm can still be found.
• In studio microphones the industry standard is a nominal impedance (output impedance) at 200 ohms. With microphones, the minimum load impedance ( input impedance ) should be expressed more than five times the value of the microphone Rated impedance or otherwise, the input impedance of the following microphone amplifier should have at least five times the value of the microphone nominal impedance, in order not to unnecessarily attenuating the microphone signal in the voltage.

Amplifiers have an input impedance and an output impedance whose values ​​are very different. Therefore, there are many problems when standard home and studio standard meet; not to speak of balanced and unbalanced and a wide variety of connector standards.

The name of the impedances is quite different and confusing. Thus, the input impedance of a device is called in the parlance also external resistance Ra, input resistance, load resistance and terminator ( such as speakers ) and the output impedance of a device (eg microphone ) is also called internal resistance Ri, output resistance and source resistance. There are problems, when Ra as an external resistor to the " output resistance " Ri is confused, because these are two different " impedance ".

For the studio technology the impedances in the IRT specifications 3/5 set for mixing consoles.

A transformer itself has no nominal impedance; It translates a connected impedance of the primary side to the secondary side and back.

The impedances with different names

In the engineer - language is usually chosen the word resistance for the word impedance.