Topic: How Matched is Matched?

[beenjammin]

And back to the original question in the thread: For coincident or near-coincident recording with directional microphones, even matched pairs of condenser microphones from a good manufacturer aren't necessarily matched as well as one might ideally want. If you have a stereo recording that you've made using X/Y or ORTF or the like, try bringing it into your favorite editing software, selecting your favorite 30-second passage, and listening to it a few times. Then reduce the gain in one channel by, say, 3/4 dB and listen again. It's different. Perhaps it will be equally pleasing or maybe even more so--but it won't sound the same, because our brains are extraordinarily sensitive to differences between what our left and right ears are hearing. Try the same thing by restoring the balance to what it was originally, but this time try adding 1.5 dB at 100 Hz in just one channel and not the other, then listen again.

Thanks, DSatz! I've done just as you suggest and the differences are immediately noticeable if I have a loop running and make the gain adjustment while running. The effect is much less audible to my ears if I stop playback, adjust, and restart.

Yesterday I set up an ORTF with the caps to capture an afternoon ambience in my backyard. This included birds, a highway, an alley and some construction work. While I could notice differences in the stock matching and a 1.3dB offset, the difference wasn't especially meaningful in that setting. That is to say: each setting was as pleasant as the other. (Well, in fact, neither setting was better or worse, as the recording was pretty boring!)

I'll set up ORFT and DIN this weekend and record some cello to see how much difference I can detect in a less ambient setting.

[MIQ]

The effect is much less audible to my ears if I stop playback, adjust, and restart.

Auditory short term memory only lasts a few seconds.  To hear subtle differences, an instaneous switching arrangement works better than one with a delay between samples. 

And our brain's ability to hear even fractional dB level differences over wide freq bandwidths is pretty good (like full bandwidth channel differences).  Narrowband differences are much harder to hear.

Miq

[DSatz]

I agree with the last two posts; I should have recommended some way of listening to the results that would get around the lack of reliable auditory memory longer than a few seconds.

The experience is instructive; it's very good to realize how limited our perceptual abilities are in that respect. Plenty of self-styled "golden ears" render judgments as if they had that ability, when (being human) they don't. And for those of us who live at ordinary altitudes, it reminds us to make careful comparisons, not just "microphone X sounded better last Thursday than microphone Y sounded the week before in another location." I mean, that's a perfectly valid statement, but it says nothing one way or the other about the quality of either microphone.

--Back to the topic of microphone matching: I'd like to quote some bullshit that I just read on a manufacturer's Web site, but I don't want to give them any publicity by identifying them. This is, however, a manufacturer of equipment intended for use by professionals, who should instantly know better if they read any such claim:

Manufacturing tolerances have been minimized thanks to highly precise calibration of the capsule and the electronics – which means that any two microphones from this series, set identically, will always form a matched pair at +/- 0 dB!

[aaronji]

Yes, and some of their other marketing claims are a bit over the top, too...

[beenjammin]

Well, I confess that I lack the courage and experience to keep the mikes as is and have sent them in so that the experts may have a look at them.

I have two other sets of mikes, one matched and one non matched, and each pair is spot on. The manufacture set me the measurement charts of the pair I sent in and they are dead, dead on. It was the discrepancy between these charts and what I'm seeing on my end that motivated me to send them in to see if anything is going on.

What's most likely the case is that I'm being overly neurotic and am thinking about this too much. At least when I get them back, I'll have peace of mind. And in the case that there is something the matter, then I'll get that sorted.


 

[Gutbucket]

I just posted PDFs of the calibration charts for a DPA matched pair of their 4061 omnis (measured with the ~ +5dB 'low-boot' short grids installed on them), over in TS Knowledge Base / Microphones & Setup.  These provide a good example of what actual measured response charts look like, for a well-matched pair.

Link- http://taperssection.com/index.php?topic=175013.msg2163073#msg2163073



[Edit-]
And a few years ago I posted calibration charts for a well-matched pair of Microtech Gefell cardioids provided by the factory when I sent the mics back for service and repair.  A single PDF showing the response of both mics can be found attached to this post in the Team Gefell thread-  http://taperssection.com/index.php?topic=144869.msg1974932#msg1974932