Impedance and Thiele/Small on Surface Pro 4

[AnalogBeforeDigital]

Morning - couple of quick questions:

Internal sound card on Surface pro 4 has two options - Which is preferred?
1. 4 prong audio out jack (Headphone and Mic combined)
2. USB to Audio converter (Headphone and Mic combined like a gaming headset)

Does Sound card above need to be calibrated? If so:
1. how is that done given the selection port selection above?
2. I'm on Linux desktop running on a surface pro 4- how are the defaults configured?

Calibrating the Impedance Rig -
1. Looks as if I remove sense resistor but connect those leads to "short" the circuit
2 Then run calibration as in https://www.roomeqwizard.com/help/help_en-GB/html/impedancemeasurement.html#calibrate
3. Do I also connect the clips +/- which normally attach to Driver - or can i LEAVE THEM ALONE?

From there I could:
1. Reconnect Sense Resistor and
2. Take Impedance measurement https://www.roomeqwizard.com/help/help_en-GB/html/impedancemeasurement.html
3. Take Thiele Small Parameters https://www.roomeqwizard.com/help/help_en-GB/html/thielesmall.html#top

Impedance with additional circuitry in place (Think crossover parts - all passive) - can this be done too?

Am I missing anything?

(as an aside - the Surface screen resolution makes app impossibly tine (and I'm old and my eyes failing)

 

[AnalogBeforeDigital]

Added Question - now that I've been trying this - I have not done SPL setup - Is that okay?

When I skip that step - proceed anyways - measuring the impedance rig seems way off - (525% from reference levels)

I think in the new versions of the options vs the documentation have become outdated (I'm running latest beta_28) so I'm not sure any of this is correct or that I'm selecting options properly - can someone help out?

 

[John Mulcahy]

The help files you linked are for V5.19, use the help in REW or the beta help files.

I doubt that you can use the Surface Pro's combined connector, it doesn't appear to have a stereo input. The USB audio interface might be useable if the "mic" input offers a stereo line input, but you would likely be better off getting a basic USB soundcard.

Regarding the application size, should be fine on Windows, if not change the display scaling or increase the font sizes in the REW View preferences. Not sure how Linux handles that.

 

[AnalogBeforeDigital]

Thanks John,

To the audio input - I have tested that something with a 4 prong audio jack that the input and output (headphone and mic) are recognized by the system. (images attached above.)

Can you recommend a fairly inexpensive USB sound card - and would that make the rest of this easier?

As to the steps above - which are strictly necessary to achieve impedance and T/S measurements?

 

[John Mulcahy]

There is a good thread on impedance measurement here. I don't have any personal experience of low cost cards for impedance measurement, but I have seen a post from someone saying they used a Behringer UMC22 without problems.

 

[AnalogBeforeDigital]

thanks - do I need soundcard and impedance rig calibration files prior to measuring, when try and calibrate impedance rig - I get flat 100 ohm - when application inputs have been cleared and physical leads shorted...

Any help?

 

[John Mulcahy]

No, there are no cal files for impedance measurements. Impedance calibration with the current beta version is done with the load open circuit. Just follow the help.