solderdude
Grand Contributor
The ratings from the Df metric look to me like a random number generator.
For example, the Sony NWA105 got a median Df of -71.4 dB and the E1DA 9038 got -42.2 dB.
That's what OP found to be the case and all the 'perhaps' in his post points to OP wondering about the why. It looks like OP did not find an explanation but wanted 'ASR' to know.
I wonder if the same thing would occur with PK metric ?
Would also be nice if someone else repeated the measurements to see if it is generic or a single device.
In any case it is a 'null test' with a poorer result than most others and it is unknown why.