Feasibility of measuring headphones down to 0.01% THD

[DanWiggins]

I had forgotten to share that I had recently been pleased to find that I could measure down to 0.05% THD or less with my in-ear mics: https://www.head-fi.org/threads/mez...eadphone-official-thread.959445/post-17743506. Interestingly, the microphones' self-noise could decrease by 10 dB just from resting a hand on my DAC/amp's chassis. And this was before I had learned that you could decrease the noise floor with longer sweeps. I don't yet have an audio interface suitable for measurement averaging. Does anyone know if the Focusrite Scarlett 2i2 maintains sample synchronization?

It looks like you're using REW. I believe that will work fine for ASIO based products like the Focusrite, so it should be sample synch'd at least to 96 kHz. ASIO tends to get a bit "less reliable" above that.