REW first scan - mystery

[1066]

Sweep length - is REW faulty on intel macbook?
My aim was to make a couple of PEQ settings to correct my room response in Wiim software.

At the beginning of this thread I was getting strange measurement drop-off going:

Mac > Airplay > Wiim mini optical out > SMSL M8 dac > Nord ICE 1200 > Revel 206 *1

I have tried changing the sweep length and it is giving quite different results.
I do also get some fails on the sweeps too.


1. Which of these setting for sweep can I trust?
2. Why is this difference occurring?
3. Will REW calculate PEQ settings, or do I have to rough estimate?
4. How would I verify the Wiim software PEQ is creating a more neutral response, do I save a sweep file and play it somehow from my iPhone Wiim app?


Very much appreciate if anyone has any ideas of best next step forward.

*1 I will also create a set not using Airplay and outputting from the headphone jack of the laptop straight into the Nord ICE 1200 amp which previously gave more believable result but have run out of time tonight.