Strange curve while calibrating focusrite 4i4

[Ofer]

Hi all,

I switched to an asio interface Focusrite 4i4 3rd gen. To calibrate the line output (not headphone) output was connected to input with either a TRS to TRS cable or TRS to XLR. The gain was matched to -12db. The measurement looks strange with 4db difference between 20hz and 24khz. I didn't see anything like this in my web search. I did make a cal file from the measurement yet it seem strange that the card has this strange response.
No listen to this device is ticked.
Loopback is through the phone jack that is not used.
The input was set to instrument (no phantom power).

Thanks

 

[jtalden]

Possibly "Air" is active?

 

[sam_adams]

If you use a TRS to XLR cable to loop from the rear output to the front input, the device detects the XLR connection and assumes it is a mic input. If you use a TRS to TRS to loop from the rear output to the front input, the INST selector should be off so that input is seen as a line level input not a Hi-Z instrument input. Rear outputs 1 and 2 are line level outputs controlled by the front panel Monitor volume control. Rear outputs 3 and 4 are fixed, line level outputs whose level is set internally by using the Focusrite Control app.

The easiest configuration to use for line level testing is to use the fixed line outputs 3 and 4 as the source and control the output level using the Focusrite Control app. Use the rear panel line level inputs for capture and adjust the levels using the Focusrite Control app. Setting the levels for these inputs and outputs using the Focusrite Control app will set the levels internally on the device and these settings should remain set from session to session. Once those levels are set internally, you can use the output level setting in REW to set your test signal level.

Additionally, you should familiarize yourself with the settings in the REW Signal Generator for the different signal types paying close attention to the peak level and the crest factor to keep from clipping either the inputs or outputs.

 

[Ofer]

Possibly "Air" is active?

That was it! Thanks a lot. Why did "air" cause that?

 

[jtalden]

" Air" just changes the SPL response to accentuate the high frequencies so they are more easily heard.