Meeting Topic: Stereo Mic Technique for Augmented Ambience Gradient
Speaker Name: Jamie Tagg, Assistant Professor of Recording Arts, Indiana University
Meeting Location: Shure Incorporated, 5800 W. Touhy Ave, Niles, IL 60714
A video recording of Jamie Tagg's presentation can be viewed here:
Jamie Tagg has developed a microphone configuration called Stereo Mic Technique for Augmented Ambience Gradient (STAAG) which has proved to be a useful tool for meeting the challenges of working on-location. One of those challenges is the tradeoff between a detailed stereo image as well as rich spatial envelopment. Another challenge is that monitoring is typically done with headphones, which often impart much more timbral detail and a wider stereo image than would be experienced listening over loudspeakers.
Jamie reviewed some of the popular existing microphone techniques and what their strengths and weaknesses are. A Blumlein pair (coincident bi-directional mics) has excellent stereo imaging, but can sound "flat" or one-dimensional. ORTF (cardioid mics spaced 17 cm apart, at an angle of 110 degrees) mimics the way we hear. It favors the front and has a reduced capture of reverberation. Spaced omnidirectional mics provide relatively little directional detail, but good spatial envelopment.
In developing STAAG, Jamie wanted good localization and the ability to adjust the amount of reverberant sound after the fact. In addition, it was crucial that adjusting the mix of reverberant energy didn't affect localization. It was also important that he have independent timbral control of the sound source and the ambience.
The STAAG solution is essentially two ORTF pairs facing forward and backward, with the capsules being coincident in the front to back direction. In addition, the backward facing pair uses shotgun mics instead of cardioid to reduce overlap between front and back.
After proving successful in his own recording, Jamie wanted scientific evidence that the desirable characteristics of STAAG are consistent from listener to listener. One of the experimental challenges was to have a consistent sound source across many different mic choices and placements. His solution was to reproduce the instruments of a string quartet using multiple loudspeakers.
Test subjects listened to the recordings and were asked to rate different mic scenarios on how accurately they could localize the sound sources as well as the sensation of envelopment. STAAG performed very well in these double-blind tests, and often scored higher on spatial envelopment than even a widely spaced pair of omni mics.
Jamie concluded his presentation with a number of recorded examples, which unfortunately could not be included in the video due to copyright.
Written By: Ross Penniman