macbook pro inverted phase?

[Zoran]

Hi
I connect Line-out to the Line-in with same 3.5mm stereo cable.
And get different results in phase and transfer measurements.
I used fuzzmeasure pro V333
And REW
.
Some apple lap top models showing inverted phase.
Step response on some laptop-s 2 model of MBP 17in showing opposite phase at input OR output by going first into negative region on Y axis
.
Mac mini have correct phase and step response. (High siera.)
15in MBP old model correct phase and step response. (Mavericks)
17in MBP old model opposite phase 180deg. (Mountain Lion)
17in MBP old model opposite phase 180deg. (Mavericks)
.
I am sure that we have more mac users. Please give some comments and personal experience on this issues?
.
Thanks

 

[Mario Pankov]

Comes from a company with upside down understanding of many things Just reverse it.

 

[Zoran]

It is strange that it occurs with 17in models?
different types with diferent OSX versions.
.
And I spot some roll-off (17in MBPs) at the HI end of BW with -1db cca. at 20KHz.
.

 

[Zoran]

Comes from a company with upside down understanding of many things Just reverse it.

how they understands upside down the things i can illustrate with facts:
I have these laptops more than 10 years. never I have had some problems or crash in OS. I have no issues with viruses. They are like new after more than decade. I have Windows on bootcamp working good and without issues but restricted from the internet... And the batteries are still good. As the keyboard keys still standing...
My wife burned down and throw to trash 3-4 pieces standard lap tops during the same period...

 

[Zoran]

negative step response indicating that
output is out of phase
or
input is out of phase
.

 

[mbrennwa]

Just use loopback and these issues are gone.

 

[Zoran]

In REW preferences interface "revert" button "fixed" the issue.
FuzzmeasurePro does not have that option. Maybe the new wersion have I didnt check.
I am wondering how many people did not checked simple and basic OUTPUT-LINEIN connection... Thats ommited almost in all guides for measurements sofware.

 

[Zoran]

Just use loopback and these issues are gone.

I am talking about loopback connection already?
I did like on this link first picture
Measure Frequency Response of an Audio Device
- MATLAB & Simulink

 

[mbrennwa]

By "use loopback" I meant to use dual channel measurement. One channel has your DUT (device under test), the other channel has the loopback. The loopback data is used to compensate the DUT measurement for the characteristics of the measurement chain outside the DUT. Using the loopback will compensate for the frequency response and the signal polarity of the sound card.

 

[Zoran]

I tried with enabling automatic correction with Out-In free pair and results are to good to be realistic and reliable? And differs regarding which pair used as measuremens/auto corr.

 

[mbrennwa]

What exactly did you measure? What was your measurement setup? Can you show the result?