First speaker to reproduce a 60hz sq wave

[Deleted member 48726]

That's what I was wondering a while ago. But this is what I like about ASR, one just needs to start a conversation just passing by and be gone

That's actually okay. The meat is in the discussions. And sometimes a topic is explained in a new way so I actually end up getting (some of) it eventually. I save bookmarks of different topics explained in different ways.

 

[KSTR]

Now comes the crucial point, if the measurement conditions are not changed (the mic and the measurement software are left completely unchanged), a phase shift occurs due to the time offset (because of the difference in the speed of sound at 20°C and 30°C) which "distorts" the plot of the square wave.

I think that's where your misunderstanding is. As long as the speed of sound is constant vs. frequency -- which it is to almost 100% perfection -- it doesn't matter if it is not constant vs. temperature or humidity or whatever. The plot of the square stays exactly the same, except for the different time-of-flight offset.

To avoid this, a fixed time of flight (reference point) is assumed for all measurements (then the correct relative sound generation off-set between the drivers is in the measurements) - for example, the time of flight of the on-axis measurement of the tweeter (and tweeter voice coil as rotation axis for all measurements).
If measurements of the tweeter are carried out and then the measurements of the midrange driver, phase deviations between the tweeter and midrange driver may occur if the temperature of the measuring room increases, as the time of flight is a fixed value.

Obviously you get errors when assumed time-of-flight does not stay constant during measurements with regard to inter-driver phase relationships. But that's either easily avoided in practice or irrelevant vs other errors. IME wind is your worst enemy for far field measurement, especially outdoors.

 

[René - Acculution.com]

Exactly what @KSTR just wrote. If there is no dispersion, you will have your square wave, since a constant time delay does not cause distortion. The only problem you have if there is no dispersion is to assume an incorrect sound speed when eliminating the phase associated with the time of flight.

 

[Adis]

Actually there are conditions where odd amplitude harmonics are all aligned. Certain places are known for this due to currents, wind, and boundary conditions like profile of the shore.

If I did not know that a square is a geometric shape, I would think that it is physical...

 

[Adis]

A real square wave is a mathematical abstraction. To actually make one you would need infinite bandwidth.

It's an oxymoron, in my book.

 

[fpitas]

It's an oxymoron, in my book.

Lol. Well, it is used sometimes in mathematics. No one ever said you can produce one in real life, any more than you can produce the unit impulse function.

 

[ctrl]

Thank you @Hayabusa @Zapper @René - Acculution.com @KSTR for the tutoring...
Will later correct my wrong statements... nobody is perfect

The only problem you have if there is no dispersion is to assume an incorrect sound speed when eliminating the phase associated with the time of flight.

In my example above no one corrects the time of flight after the 10°C temperature rise - it stays always the same, the measurement equipment is not aware of the temperature change, same as my ear.
As I said, first measurement and calibration at 20°C at 5m distance, a nearly perfect square wave is measured. Then 10°C temperature increase and measurement without changes and as you all have now made more than clear to me, nothing changes in the measured square wave.
Because "a constant time delay does not cause distortion".

 

[René - Acculution.com]

There will be a change in the phase related to the change in time delay from a change in sound speed. But it is not really relevant as the square wave is retained. You just go from one constant delay to another (assuming no dispersion) which has the same effect as measuring at a different distance on axis, where the square wave is also seen. This is why the phase related to distance is often desired eliminated to get to the transducer phase.

 

[ctrl]

There will be a change in the phase related to the change in time delay from a change in sound speed. But it is not really relevant as the square wave is retained. You just go from one constant delay to another (assuming no dispersion) which has the same effect as measuring at a different distance on axis, where the square wave is also seen.

Yep, that's where I was totally wrong, as you all kept trying to make me realize, my error in reasoning.
I thought because the time of flight is not corrected after the temperature increase, the phase frequency response is no longer linear (in the measurement) and therefore the square wave is displayed distorted.