[Wayne A. Pflughaupt]

My laptop isn’t the fastest in the world, but it’s certainly no dinosaur. In my experience, it’s perfectly normal to not get carbon-copy results with every measurement. Here are a few examples culled from my files. [Edit - traces are separated for the sake of clarity.]

4 rew graphs over 30-minute interval.jpg
Four REW Measurements Taken Over a 30-Minute Period

These were taken in the same session, over a 1/2-hour period. Notice that response between 20-40 Hz varies quite a bit. The depression at ~55 Hz varies in depth and the center shifts a little. With the sawtooth section between 55-90 Hz, the differential between the high and low points is a few dB greater with the lower two traces, especially the dark blue one. The 90 Hz peak is at least a couple dB lower in the gray trace compared to the others, as is the 100 Hz peak

The next graph shows measurements where each was taken two month intervals, in Sept. and Nov. last year, and Jan. this year.

3 rew graphs at 2-month intervals.jpg
Three REW Measurements Taken Over a 4-Month Period

The next graph shows two measurements taken on the same day, an hour apart. The two traces are “as is” readings, not separated by the Trace Offset adjustment like the graphs above. Notice that the light blue trace is at least 1-dB higher in overall SPL level.

2 rew graphs 1 hour interval.jpg
Two REW Measurements Taken 1-Hour Apart

Naturally, REW is going to offer different filter recommendations for differing traces, and different waterfall readings as well (another reason I don’t take much stock in them for filter setting purposes).

I’m using the RS digital meter. If some here actually are getting perfect carbon-copy results, I expect they’re using the Behringer mic? The latter has a much smaller diaphram, which I expect would make it less susceptible to variations in air pressure and other atmospheric changes, which can alter measured results.

Regards,
Wayne