Thanks for your reply.The output level and the input level can be adjusted. If you make loopback at input 3, then point it where Loopback input. If you are measuring not a subwoofer, select at 'Levels' 'use main speaker'.
That's most likely the case. Thank you very much, John. Great tool too.If you are planning to use a different input for measurement (e.g. Input 1 or 2) that's the one that should be used for the loopback. Interfaces may not have the same input and output sensitivity, so the gain difference may be normal. If the Motu comes with a mixer app you may be able to adjust gains there.