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International Tonmeister Symposium
Oct. 31, 2005 Schloss Hohenkammer

Improving 5.1 and Stereophonic Mastering/Monitoring
by Using Ambiophonic Techniques

By Ralph Glasgal, Ambiophonics Institute, 4 Piermont Road Rockleigh, New Jersey 07647 USA

Establishing a Crosstalk Cancelled Monitoring Station

To avoid such pitfalls we suggest a monitoring facility that uses a binaural technology. That is one that allows the ITDs, ITDs and pinna directions to be heard as in Figure 7.

Fig 7
Figure7 - Ambiophonic monitoring preserves the true ITD and ILD captured during a recording session.
Figure 8 - early monitoring session using barrier.

In figures 8 and 9a you can see an early version of such a monitoring station. Putting a simple physical barrier between two speakers directly in front of the monitoring position eliminates the crosstalk and most of the pinna confusion particularly in the central 60 degree stage area. The speakers should be head spaced on each side of the panel. The center channel in the 5.1 case is fed equally to both of these speakers. Today one uses crosstalk canceling software, which is readily available, to do the same thing without the physical barrier. Figure 9b. This method of 5.1 monitoring makes it much easier to see what happens when the center speaker is engaged. There is also no chance of a delay error between the side and the center speakers to cause errors in judgment. You can hear easily if the center channel information is compressing the width of the stage or if there are phasing effects. You can also switch to 60 degree stereo speakers plus center for a quick comparison at any point in the process.

Fig 9a
Figure9a - inexpensive monitoring station preserves ITD and ILD

Fig 9b
Figure 9b Software Based Monitoring Station Preserves ITD and ILD

Our experience is that musicians, listening in a binaural environment, can more easily appreciate what has been captured and are less likely to request changes, especially those that are irrational, as is quite possible, when monitoring just in stereo or 5.1.

If it sounds fine monitored this binaural way and is subsequently released without too much processing will it sound better on all those subpar stereo systems out there? I believe so but this is a subjective opinion not susceptible to proof. But common sense indicates that the great variety of systems out there will insure that the percentage of good reviews will remain about the same whether the mix is psychoacoustically pure or psychoacoustically eccentric. However, if the mix keeps the cues relatively intact, it is then possible, in years to come, for a home listener to recover this data and hear the stage with all the depth and width that the microphones did capture.

Robin Miller of Filmaker Studios has devised a coder, Figure 10 that can convert a purist four channel recording into a 5.1 equivalent. Then at a future time a decoder can be used to fully recover the original unprocessed 360 degree surround recording. Thus one could use an advanced recording surround technology such as Ambiophonics, monitor it with full binaural realism, please the client, but still release the performance in 5.1. We believe that the 5.1 recordings made this way are superior to the recordings made the conventional way using the typical methods reviewed in the first part of the next section.

Fig 10

Figure10. Four Purist Microphone Channels Convert to 5.1 and Back Again