Here's a schematic for a simple dual channel measurement jig, which can be used with ARTA, REW, or SoundEasy. This jig is made with USB audio interfaces in mind, so the use of 1/4" TRS connectors is recommended for this purpose. Main reason is that the 48V phantom power on audio interfaces is only present on the XLR pins, so use of TRS will ensure that 48V will only ever be present when a mic is connected, not when using this jig even if you leave phantom power turned on.

R1 should...