[yooss]

I believe that this question is repeated(I cannot be the first to think of this), but I'm not very good at English and I don't seem to be able to find the right word to put into the search function nor am I familiar with Google.
 
So here's the situation:
 
I was looking at the ER4S FR graph, and thought how do they create the graphs?
 
Simple: they would just use reference microphones.
 
How do they know they are reference microphones and have a flat FR graph?
 
They would use reference speakers
 
How do they know the reference speakers are truly flat?
 
They would use an older reference mic
 
How do they know the mic is flat?
 
They would use another speakers... and so on.
 
Will somebody please give me a clarification?

 

[nick_charles]

For mics you can provide a set of inputs at different frequencies and take electrical measurements. viz supply a 1khz tone of a given amplitude and record the electrical output from the mic and run it through freq analysis software, repeat for different frequencies. The combination of electrical outputs for each frequency shows the FR of the mic , it should be very similar at all freq points if it is a good mic.

 

[yooss]

Aha, that explains! Thank you

 

[Pio2001]

Err.. what ?
 
Yooss was wondering how frequencies "of a given amplitude" could be generated without first knowing the frequency repsonse of the speaker.

 

[Yoga Flame]

Tuning forks?

 

[Uncle Erik]

Quote:

Err.. what ?
 
Yooss was wondering how frequencies "of a given amplitude" could be generated without first knowing the frequency repsonse of the speaker.

You use a signal generator of some type to generate a tone or a particular waveform.  Tones and waveforms can be defined mathematically and you can measure the response of the test gear against known formulas.
 
Once you know the signal generator is accurate, you can put a tone or waveform through something and compare what comes out the other end to the original signal.
 
The difference between the original signal and what comes out the other side tells you how to plot the frequency response chart.  The "0" on the chart is the original input and the line going up and down across it show how the driver responds when given a signal at that frequency.

 

[Pio2001]

Quote:

You use a signal generator of some type

These are voltage generators. But we are talking about acoustic measurements. How do you generate a given acoustic pressure if your pressure measurement device, the microphone, is not calibrated yet ?
 
There must be some kind of microphones that have a flat frequency response by design and that are used to calibrate the others.