I bought a second EMM-6. Different batch, so it should give an idea of variation between random samples of the mic, and also the small electret capsules on which it is based. From 35 Hz to 3 KHz, the variation is a small fraction of a decibel. One has a low frequency rise, the other falls off slightly at very low frequency. Above 3 KHz, there are small random bumps which could easily be due to comparison on different days between the test mic and Dayton’s calibrated B&K mic. Here’s Dayton’s calibration data for the two mics. Sound sample here.