Frequently Asked Questions
What was the signal chain for each microphone in the main testing scenario?
Each microphone went through its own cable to the studio wall panels, which led to the control room through an approximately 200' conduit run. They arrived at a patchbay in the control room where they were normalled to the input section of the studio API Legacy console with API 212L mic-preamps. Group #6 (small diaphragm omni condensors) was tested using 4 channels of the Millennia HV-3D, because of the Earthworks OM-1's adverse reaction to the transformer front-end of the API preamps. All preamp outputs fed the input (fader 2) section of the console, where all the faders were set to unity gain by the consoles automation section. Individual outputs from each microphone were bussed through the console to an SSL AlphaLink Madi AX into Nuendo 5, running at 24/88.2 khz. Monitoring was handled through the API channel path, and the studio SLS monitors.
Why didn't you run each microphone through the EXACT same signal path (cable, conduit run, patch cable, preamp, converter, etc)?
This would have prevented our testing of multiple microphones recording a single performance, so while an unfortunate variable in this testing scenario, we hope the tested signal path is representative of a standard studio recording session where the microphones might actually be in practice.
How was the signal chain calibrated for each recording?
A 400hz tone was generated through a single point-source powered loudspeaker and measured to be 85 dB(A) at the location of the "control" microphone in each group. Each preamp was adjusted to represent an input level of -10dBvu into the converters, with the hopes that any effects of the preamp, console channel section, and A/D converter would be represented equally for each transducer. Because deliveries varied slightly at each station, each of the collected audio files were peak normalized to -1.0dB by the DAW, resulting in accurate level similarity within each microphone group, however differences in levels may be apparent when comparing microphones across different performances.
These tones were also recorded after calibration for the researchers to graphically observe for phase differences and anomalies. As a result, it was interesting to note that all of the Alesis/Groove Tubes transducers have reversed absolute phase: generating a negative voltage when positive pressure is applied to the front of the diaphragm, contrary to all the other microphones tested (and general microphone design practice).
What care was taken in setting up the microphone groups for each artist?
Each artist came in for a 2-3 hour session, of which about 45 minutes of that session time was spent delivering their performances. Their head-height was measured, and the point-source speaker was adjusted to represent this height. The research team moved the speaker around to each station and adjusted each microphone in the group to the talent's height. Calibrations were conducted at the 1st station to be tested, with the point-source precisely 12" in front of the "control" microphone placement. After calibration, the talent was asked to present in precisely the same location (12" away from the "control" microphone) with a pop-filter 4" from their mouth. It is important to note that this is outside of the range of noticeable proximity effect for most directional transducers. Once the talent completed takes at the given station, a single microphone stand with a pop-filter and headphone monitoring system, along with the "control" microphone, which maintained the same transducer and signal path throughout every test, moved with the artist to the next station. The process was then repeated at each station.
How were the microphone groups selected?
Groups were designed to directly compare similarly designed microphones and/or a change in polar pattern on the same microphone (when matched pairs were available) or a physical change in the configuration (like the addition of an Acoustic Pressure Equalizer, or the testing of the front and rear of the Royer R121).
How was the microphone "array" configuration decided upon?
The array configuration was developed with respect for understood propagation patterns of the human voice (Olson, 1955), the on-axis polar patterns of each transducer, possibilities of physical placement, angle of sound impingement (Eargle 2004) and consideration of the potential diffraction effects caused by multiple microphones occupying a small area (Woszczyk, 1989). Each microphone in the array occupies a slightly different position, and is thus subject to receiving slightly different acoustical energy than the other transducers in the group. To determine the "maximum" amount of microphones that could be used at each station, arrays were tested (LINK) in configurations of three, four, five, and six similar microphones (once with DPA 4006s, once with Shure SM-58s) with talent reading from a distance of 12". Four microphones was determined to offer the most microphones and least amount of coloration.
Why are some microphone samples missing from certain performances?
Certain samples were disqualified if their recordings seemed to not be representative of the transducers specified function. For instance, the cable on the control microphone became faulty during the Male Voiceover tracking session, so we did not include the effected samples.
Why can't I see or play the WAV files on the "listen" pages?
You need to use a browser that supports HTML5 to see/play the WAV files. Please upgrade your browser to the most recent version. Unfortunately, IE does not play WAV files - please use Firefox 3.5+ or Chrome 3+ instead.
Can I just download all the files and compare them on my own?
All the session materials will soon be available for download as 24 bit/88.2khz WAV files.
I hear a constant background noise or hum in some of the voiceover recordings - What the heck?
Good ears! Once upon a time, video cameras used tape media - and with this came moving heads and rotating transport motors that make annoying sounds. We used two of these "vintage" pieces to carefully monitor and record the movement of the performers as they delivered each performance. We were monitoring the incoming audio at low levels in the control room and didn't notice the noise of the cameras leaking into the microphones until after all the sessions were complete. Very sorry for the distraction!!