How to set the cursor on the charts to the zero mark?

[Vladimir_1953]

Hello everyone!
How to tie the cursor position on the phase grid to the zero mark? It is not set quite accurately yet.
This is necessary to accurately determine the tuning frequency of the phase inverter port.

 

[sm52]

This is necessary to accurately determine the tuning frequency of the phase inverter port.

The accuracy you showed in the screenshot is already good for your purpose. Also, phase crossing through zero will not always be the frequency of port tuning.

 

[Vladimir_1953]

The accuracy you showed in the screenshot is already good for your purpose. Also, phase crossing through zero will not always be the frequency of port tuning.

What is the exact frequency of the port tuning?
I always thought that the zero crossing was the absolute indicator.

How and with what to determine the exact tuning frequency of the subwoofer phase inverter port?

 

[John Mulcahy]

How to tie the cursor position on the phase grid to the zero mark?

The zero position will depend on the number of grid lines and the grid interval. It can be forced by suitable choices of the Y axis limits for SPL and for phase, but you can also select the option in the Graph controls to draw a line at phase = 0.

 

[Vladimir_1953]

The zero position will depend on the number of grid lines and the grid interval. It can be forced by suitable choices of the Y axis limits for SPL and for phase, but you can also select the option in the Graph controls to draw a line at phase = 0.

View attachment 82455

Thank you, John!
I activated the options as you recommended.
But I can't set =0, only a little higher or a little lower.

Is it possible to enter the parameter =0 manually?

 

[Vladimir_1953]

I use REW 5.31.3

 

[Vladimir_1953]

The accuracy you showed in the screenshot is already good for your purpose. Also, phase crossing through zero will not always be the frequency of port tuning.

I would agree with you if we were talking about measuring the SPL.
I have provided an Impedance graph.
The measurement mode is 2-channel.

 

[sm52]

There is another reason because of which determining the exact frequency of the port setting according to the impedance graph can be compromised. This is a measurement voltage. With different input voltage, you will receive slightly different data. For example, at 0.2 volts and 2.2 volts. The difference can be up to 2 hertz.

 

[Vladimir_1953]

I always try to take measurements at a voltage of 2.83V on a 4 ohm load equivalent, which is indicated in the passport specifications.

 

[sm52]

This means that you assume that the driver will always run at 2.83V, and never at another.

 

[John Mulcahy]

Thank you, John!
I activated the options as you recommended.
But I can't set =0, only a little higher or a little lower.

Is it possible to enter the parameter =0 manually?

That's just the pixel resolution for that window dimension. You could zoom in on the phase axis if you feel you need more precision.

2.83V is an unusually high drive level for impedance measurements.

 

[Vladimir_1953]

The factory datasheet for Thiele/Small specifies exactly this voltage 2.83 volts.

*** SensitivityThe sound pressure, in dB, produced by a speaker in response to a specified stimulus. Usually this is specified at an input of 1 watt or 2.83 volts (2.83 volts = 1 watt into an 8-ohm load) at a distance of one metre. *** ( from WikipediA)

If I am wrong, please correct me and indicate the "correct" voltage when measuring impedance.

 

[John Mulcahy]

That figure is used for specifying sensitivity, as the text states. TS are small signal parameters, typically measured with a drive unit voltage around 1Vrms or lower.