Taperssection.com
Gear / Technical Help => Microphones & Setup => Topic started by: tim in jersey on February 13, 2021, 01:00:25 AM
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I get the fact that each is purpose-built to do different jobs. I have no idea how they differ though. Construction, powering etc.
Anyone care to explain or point me to a resource where I can read up on it?
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measurement mics are meant to be flat on response
studio mics are meant to sound good (which isnt necessarily flat)
a measurement mic can be EQ'd to sound good before a studio mic can be EQ'd to be flat
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Construction (except for certain physical parameters such as size) and powering aren't the issue. The main point of a measurement mike is that its frequency response has been carefully measured at the factory, and is reliably traceable to a known reference standard. It should ideally be flat under the particular conditions (free-field or diffuse-field) in which it will be used--but to any extent that it's not, the deviations must be charted and made known explicitly to the end-user acoustician so that they can be taken into account while working with the mike.
Most stereo music recording isn't done under either free-field or diffuse-field conditions, however, but something in between. Free-field conditions are sometimes approximated in studio and live work to a certain extent (i.e. with close miking)--but diffuse-field omnis basically became obsolete for music recording (at least for the main microphones) when stereo took over in the 1950s. Practically the only people who record music from such distances any more are those making ambience recordings for the rear channels of a surround mix.
As a result it's a fallacy when anyone assumes that measurement microphones must also be the best main microphones for music recording. The most-preferred omni mikes for stereo music recording have response characteristics that no measurement microphone would ever have, because the recordings sound better to most people that way. In addition, music recording generally requires a high signal-to-noise ratio that measurement microphones don't necessarily offer--particularly the smaller ones.
Please let me know if anything I've said here isn't clear, or if you need an explanation of free-field and diffuse-field conditions / microphones.
--best regards
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Construction (except for certain physical parameters such as size) and powering aren't the issue. The main point of a measurement mike is that its frequency response has been carefully measured at the factory, and is reliably traceable to a known reference standard. It should ideally be flat under the particular conditions (free-field or diffuse-field) in which it will be used--but to any extent that it's not, the deviations must be charted and made known explicitly to the end-user acoustician so that they can be taken into account while working with the mike.
As always, DSatz lays out excellent knowledge for us here. Thanks.
Earthworks makes a series of measurement mics which are designed/manufactured with consistent omnidirectional polar pattern in mind, among other things.
Their line of measurement mics includes some which extend a little beyond 20 kHz and some which go up to 50 kHz.
https://earthworksaudio.com/measurement/m50/
As DSatz mentioned, the measurement mics will come with a calibration chart or a file. The details of these files are rather simple, and are the measurements of the exact serial numbered mic compared to a listed reference mic. I believe the contents of the file are literally the measurement at frequency, listed in the value in +/- dB. I'm attaching a sample image I found on the internet, from a place which calibrates mics.
You can purchase inexpensive measurement mics new and used, which lack calibration files. (usually cheaper than the same mic with the data)
In order to best utilize mics for frequency analysis, they should be calibrated, and the chart or file saved along with the mic, so it can be transferred to a future owner, or in case your computer crashes.
For advanced measurement applications, a series of matched mics may be needed. Meyer Audio in Berkeley has a set of matched calibration microphones which they use in their anechoic chamber where they measure each loudspeaker they build. Evidently, the higher number of mics you need factory-matched, the more costly it becomes. A set of 8 precision-matched mics costs a lot more than 4 pairs, from DPA.
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You don't see much crossover between measurement and recording mics, but there is one instance I am aware of where a microphone manufacturer markets the same capsule for both measurement and recording applications: The Gefell MK 221 omni capsule. It is sold as a free-field measurement capsule (https://www.microtechgefell.de/mikrofonkapsel?wl=463-MK221#start), but the same capsule is used for the M 221 studio microphone (https://www.microtechgefell.de/mikrofon?wl=257-M221). Josephson also uses the capsule with their c617set microphone (http://www.josephson.com/pdf/c617setds05.pdf). I read somewhere a while back that Gefell does special runs of the MK 221 for Josephson with even tighter tolerances than normal.
Well, OK two instances. The other one is the B&K 4006 capsule, which was originally a measurement capsule until B&K liked how it worked for recording. I believe they still manufacture the 4006 capsule for the current DPA 4006 mic.
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Practically the only people who record music from such distances any more are those making ambience recordings for the rear channels of a surround mix
..and concert tapers making audience recordings from a position far from the stage, significantly back toward the rear area of the audience, often behind the soundboard, where the "taper's section" is frequently located.
In other words, it is actually more common for folks on this forum than most any other types of recording. Granted, the oddity of recording the output of a PA system designed to project direct sound and effectively extend the critical radius of reverberation futher out into the audience than would be the case in a non-PA reinforced scenario complicates the acoustical situation.
[edit] Maybe not fully diffuse back there, but predominantly
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Practically the only people who record music from such distances any more are those making ambience recordings for the rear channels of a surround mix
..and concert tapers making audience recordings from a position far from the stage, significantly back toward the rear area of the audience, often behind the soundboard, where the "taper's section" is frequently located.
In other words, it is actually more common for folks on this forum than most any other types of recording. Granted, the oddity of recording the output of a PA system designed to project direct sound and effectively extend the critical radius of reverberation futher out into the audience than would be the case in a non-PA reinforced scenario complicates the acoustical situation.
[edit] Maybe not fully diffuse back there, but predominantly
This is why I always enjoy running my schoeps mk3 (mk2xs).
It's the only Schoeps capsule actually designed to be employed in something the way I run them....
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> It's the only Schoeps capsule actually designed to be employed in something the way I run them....
Thank you for the "something" part. The terms "free-field" and "diffuse-field" come from the lexicon of acoustics rather than from audio recording, and the basic design of the capsule dates back to a time before stereo recording was at all common.
When stereo recording did eventually become a major influence on microphone buying habits, there was increased use of directional microphones, and for omnis, somewhat closer mike placement overall--which in turn meant that microphones with moderate rather than full diffuse-field equalization tended to be preferred. For example today, people who want to use Schoeps mikes for Decca Tree setups tend to buy the MK 2 S (or sometimes even the MK 2 H)--plus spheres for the capsules, of course.
(I'm just now posting more arcane details over in the "Team Schoeps" area.)