Need some help interpreting unexpected Distortion changes

tony22

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I've had no changes to my system since my last set of "reference" measurements. But after a rather nasty electrical incident I decided to run new sweeps and compare them to my references. I set up my UMIK-1 in its standard position (it's always in the same place, +/- 1/4-1/2"), and set the Calibration level at the same amplitude (75 dB(C), +/- a tenth or so). The SPL sweeps looked about the same. I did Trace Arithmetic subtraction of one from the other and got pretty much nothing. But when I looked at the Distortion graphs I was surprised (and now worried). Here's what it looked like before the incident:

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and here's what it looks like after:

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To me this looks like something happened, but I'm not an expert in interpreting distortion data. I don't know if slight mic position differences could cause this, or anything else for that matter other than some potential damage. Audibly, the music sounds the same as always... I think. My room is well treated acoustically and there was no outside noise or other intrusions when I did any of these sweeps.
 
Oh, that was with my REL Carbon Special sub on. Here are the same before and after with sub off.

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Nothing of concern in distortion, all well below the noise floor. Noise floor is a bit higher and those spikes at multiples of 1 kHz are USB clock breakthrough, if using a laptop they may change depending on whether the charger is connected. Check the UMIK volume setting, if it has been set to 100% turn it down to the unity gain (0 dB) setting. You can get the windows input volume control to read in dB by right clicking it.
 
Thanks John. I will check as instructed.

What worries me is that there's such a significant appearing difference. Nothing has changed in my system between these two measurements.
 
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