Sidebar I: The Joy of Measurements

When I measured the Royer mics for frequency response, I ran into a problem, in that my measurements didn’t quite match the factory published response curve. Specifically, I found a deep notch in the response around 14 kHz. After MUCH head-scratching and trying to figure out how I’d screwed up the testing once again, I finally satisfied myself that the notch was probably really there, so I called up Royer to talk about it. They were friendly, helpful, open and concerned. Seems they had jobbed the formal measurement out to a lab with an anechoic chamber, and were perfectly happy with the results they got back (which they should have been). I spent a lot MORE time, then, trying to figure out what was really going on, including some reading, research and consulting with my personal favorite audio guru, Neil Muncy.

What I finally concluded was this: there is in fact a frequency (ca. 14 kHz.) whose half-wavelength (.48 inches) makes it around to the back side of the ribbon and causes a very narrow null at that frequency (the response comes right up again, so that the output is almost as high at 17 kHz. as it is at 12 kHz). Now this looks awful on a response plot. In fact, the audible effect is negligible, for several reasons, and you shouldn’t worry about it. First, us humans are comparatively insensitive to narrow resonances and notches, due to the nature of the critical bands in our hearing. Second, the frequency involved is extremely high, and comparatively little energy is present there in most cases. Third, because it is an interference effect occurring at the ribbon, as the angle of arrival of the sound goes off-axis, the notch begins to go away. In actual production, the notch is less critical than the on-axis measurement would make it appear.

What about the lab’s anechoic measurement? I wasn’t there, don’t know how they set things up. I’m convinced the notch is there in anechoic space. Neil and I speculated that the sweep speed of the test oscillator, the writing speed of the chart recorder and/or an octave smoothing function may have taken the notch out.

To test my thesis about the notch being inaudible (er, not significantly audible might be a better way of putting it), I dialed in a complementary peak on the Yamaha 02R EQ and managed to pretty much smooth the notch out. I then compared, by listening, the sound of the mic with and without the notch. To my ears, listening to a variety of program sources, the notch just wasn’t an issue.

So here’s yet another case where we need to think through the meaning of what we are trying to measure. Ain’t audio fun?

Sidebar II: The Joy of Accuracy? - Not!

How can it be that a mic sounds “better” than the source it is trying to record? If we think about recording in terms of accuracy of reproduction, such a concept is nonsensical. However, when we CAREFULLY think through what we’re trying to accomplish, it makes a bit more sense. Think of it this way: we’re trying to coax music out of loudspeakers. An essential ingredient of music is tonal quality, and it is a very subjective ingredient. In the final analysis, we really have to ask ourselves how “musical,” how “beautiful,” something sounds. Doesn’t matter where it comes from. Doesn’t matter how accurate it is. Just “how beautiful.”

So, in this case, the Royer plus my loudspeakers combined to yield a subjective tonal quality that I preferred, slightly and unscientifically, in comparison with the original sound sources I studied. This is pretty fuzzy, of course, and you might not find the same thing to be true (you aren’t me, of course, and you aren’t using my loudspeakers).

Nonetheless, the observation suggests that there is something pretty special going on with these microphones. They manage to yield a very beautiful and convincing tonal quality that is distinctly (if subtly) different than what other microphones yield. And it is entirely possible that you may find it as attractive as I do. Time will tell.

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