Analyse a speaker with a mic that was calibrated with a calibrated speaker

[Hardy Heinlin]

This is a historical chicken-egg-question.

Regarding the frequency linearity of speakers and microphones: In the history of acoustic engineering, which device's output was measured first and what was used as a reference?

Honest question. I don't know the answer :-)


)-)ardy

[Jeroen Hoppenbrouwers]

I don't know but I assume it was a chicken and egg cycle. As equipment became better and better, a weapons race developed and eventually the wobble became more linear.

When developing something, I tend to focus on the transmitter first, as the receiver cannot be tested without a transmitter, but the transmitter can, using a cruder way of measuring output.

[Hardy Heinlin]

For example, for the volt unit, i.e. for the question "what is 1 volt?", I see factors like the units joule and newton and so on, and from there I can go back to three basic units that I can define mechanically: 1 gram, 1 meter, 1 second. That is, a defined piece of mass, a bar, and an observed astronomic orbit. Just mechanical tools. – Now, regarding speakers and mics, the difficult part in the measurement is the conversion from volt to membrane deflection length and vice versa.

Maybe there's a mechanical sine wave generator, a mechanical wheel or something, that indicates its amplitude optically on a metric scale, so that the mechanical amplitude at each frequency can be adjusted exactly, and that same amplitude may also actuate the membrane of a microphone whose output voltage is to be measured.

Similarly, a speaker input might get a constant AC voltage at a rising sweeping frequency, and the speaker's membrane deflection might be optically projected on a scale by a mirrored light beam.

You assume it was a cycle. You mean they improved the speaker side and the mic side alternately so they became finer and finer? But what was the reference? :-)

[Jeroen Hoppenbrouwers]

Yes I meant that improvement cycle. The reference would be whatever method of measurement, ranging from mechanical (in the time of the old phonograph) to electrical to electronical to possibly digital. Linearity is not necessarily just physics, I assume that with audio equipment there is also significant subjective human "measurement". Like with coffee or wine. Chemical analyses don't cut it.

The goal of audio reproduction linearity is to reproduce the original sound, right? That can be a way to introduce human specialist observation.

[Hardy Heinlin]

The goal of audio reproduction linearity is to reproduce the original sound, right?

Yes. Actually, one could generate pink noise with mechanical things and another pink noise with electronic tube noise or transistor noise and feed that into the speaker. Then use your ears and compare the mechanically produced pink noise to the noise coming out of the speaker ...