What does impedance mean?

handfree headphones

What does impedance mean?

The impedance in ohms represents the resistance of the headphone and tells how easily a headphone can be driven by an amplifier. Conclusions about the volume can only be drawn for a given (amplifier) ??performance and taking into account the sensitivity of the headphones . A headphone with a low impedance (eg 32 ohms) therefore achieves the same volume with less voltage than a headphone with a high impedance (eg 600 ohms).

An example:

We connect two headphones with different impedances to a tablet via a mini jack. This tablet can (fictionally) deliver a level of 1 volt.

Headphone I has an impedance of 32 ohms.
Headphone II has an impedance of 600 ohms.
We calculate the power:

Headphones I:PI = (1V)2/32? = 31mW
Headphone II:PII = (1V)2/600? = 1,6mW

The advantage of high-impedance headphones is better resolution and better sound, but headphones with low impedances of around 16 to 80 ohms are recommended for mobile use (with smartphones, MP3 players, laptops).

Why is that? Batteries and accumulators of these devices deliver only very little voltage and thus also limit the maximum output voltage at the headphone output. This means that low-impedance headphones (such as those included with the Apple iPhone or Samsung Galaxy) are louder than high-impedance ones when used on the same mobile device.

On the other hand, if you only want to listen to music at home in the living room with your hi-fi system (amplifier) ??or if you use the headphones in the studio, then you should buy high-impedance headphones. The amplifier can and may then output a higher maximum voltage and can use this to “serve” the headphones with a higher resolution than low-impedance ones.

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Headphones with higher resistances can also be connected in parallel to the same headphone output using a Y-split cable – when using headphones with little resistance, you run the risk of exceeding their load capacity with the amplifier turned up loud, which can lead to damage (see ohmic Resistances in parallel circuits and Ohm’s law ).

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