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RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition)

Posted by JBen (A) on October 6, 2010 at 23:07:31

In Reply to: RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition) posted by pictureguy on October 5, 2010 at 08:13:24:

Good Qs, Pix-G.

If you repeat the same test, say 5x, what are the results? What is the spread of values of each parameter measured?

[Despite what I'll say below -- and even without all the care I take -- the Cool Edit Statistics tool is very forgiving as far as the "clipped samples" relative figures are concerned. All one needs to have is a little discipline and apply common sense. Now, its associated SPL/RMS figures are more sensitive.]

Initially, my test sessions would have as many as 6 different pieces of music, all sharing the same settings. So, each piece was played exactly the same via each of the variables under evaluation. Lately, I use only 3 or 4 because it takes time to do it right. In all instances the results MUST say the same thing before I accept them as true indicators. So far they do and they also correlate to what I perceive.

For example, in the case of my Razored MMGs, the Cool Edit test has shown that P-Frames will always increase the amount of clipped samples by over 50%+ depending on the music in my test set. So, the percentages are relative, and they depend on:

• 1. Each music piece's dynamic profile & volume. The power amplifier is always at the the same setting. I chose music that -AT MY NORMAL LISTENING LEVEL - already falls in the area where some of it will overload the recording past "0" relative to...  


• 2. ...where I always leave the mic input level. The mic level setting always "stays put" in my case. This way I avoid disturbing the mic amplifier (E-mu 0404 USB) settings as calibrated for other measurements. I hate moving analog knobs nowadays, for fear of non-linearities. My new Windows 7 allows an improved option for this, though I have to test it properly)

In addition, with P-Frames, the average reported "RMS Power" goes up by close to 1db. This reported RMS Power difference is actually understated because digital samples that went over "0" (got clipped) are not quantified for strength. They simply get "counted" for having gone past the mark, as "possibly clipped" but the energy beyond that point isn't.

At first, I was more focused on the count of "clipped samples". Recently, I began to notice that the reported "RMS Power" figures could be useful for a different measuring perspective. I will have to keep note of certain things AND adjust input levels to within "digital limitations". In other words, avoid going over "0". The problem is that I would have to mess with the analog/mechanical knobs on the mic box (the E-mu ), which I am avoiding. Again, using Windows 7 controls may allow me to do it.

Have you run the test....or any tests on a SINGLE speaker at a time?...
Yes, the first times, later in Stereo. In any event, the results correlated. For the purposes of what I was trying to find out the stereo set did, arguably, a little better. BTW, I did fear that comb filtering would have a bearing but it did not (again, for my limited purposes).*

Other types of testing objectives may require that only one Maggie be used at a time.

*While the microphone is firmly anchored in the tripod, there still is the impossible task or repositioning an MMG "precisely" in the same place & angles. One gets very close but it is never "totally precise". Therefore, I measured with the same settings through a few consecutive practice repositionings. With a little care the same results were repeatable. Ironically, larger -- but usually inconsequential -- changes happened because of the variable noise floor. Touch nothing for 10 minutes and somebody's A/C unit will kick in. Measure with some music then and, if you look HARD, you MAY see it in the Cool Edit graph but still not see a meaningful difference in the numbers. (These noises do have more effect on the frequency scans and at times have caused me to cancel testing).

Edits: 10/06/10

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