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Applying Williams' Stereophonic Zoom
Old 27th February 2014
Gear Addict
🎧 5 years
Applying Williams' Stereophonic Zoom

With respect to Williams' Stereophonic Zoom.....

I realize that it doesn't necessarily need to be applied down to an accuracy of three decimals and perhaps should be seen more as a good rule of thumb. But I am wondering about something.

From what I gather Williams himself apparently judges the orchestra angle from eye height, by using what he calls a "crocodile". So strictly speaking using Sengpiel's orchestra angle calculator:

Extension angle of the orchestra ensemble scene calculation SRA stereo recording angle distance to microphone system - sengpielaudio Sengpiel Berlin

the "distance to the microphone system" would be the hypotenuse of the average height of man and the distance across the floor to the orchestra. For example, if Mr. Williams is 1.75m tall and standing 3 meters in front of the orchestra, then Pythagoras tells us that the "distance to the microphone system" would be 3.47m. Strictly speaking the sound is probably not being produced on the floor but at a height of around 1 meter or so. Taking that into account by subtracting 1m from the height of the mics above the floor, and assuming the width of the orchestra is 8 meters. You end up with a hypotenuse of 3.09 meters and an angle of 104.63 degrees.

However, here is what bothers me slightly. Most of us don't have our main pair 6 feet above the floor. Perhaps more like 12 feet. Do the same math for 12': height =3.65m, distance 3m. Sound is 1 meter above the floor so adjust mic height down to 2.65m. So a hypotenuse to the microphone system of 4.00m. Plug that into the same 8 meter orchestra width and it gives an orchestra angle of 90 degrees.

At a 90 degree angle between the mics that is the difference between a mic spacing of about 20cm or 25cm.

To make my life a bit easier I created a PDF file from a spreadsheet I have made that has two tables to calculate the orchestra angle from a combination of mic height, distance and orchestra width, followed by a bunch of Williams' graphs for the various microphone patterns (cardioid, hyper, etc.).

Am I crazy?

Regards, Christine
Old 2nd March 2014
Here for the gear
ebs's Avatar
🎧 10 years
Originally Posted by connloyalist ➡️
From what I gather Williams himself apparently judges the orchestra angle from eye height, by using what he calls a "crocodile". So strictly speaking using Sengpiel's orchestra angle calculator:
Extension Angle of the Orchestra or the Scene (Orchestra Angle) - That is the total angle seen from the point of the microphone setup.
To this visible orchestra angle from the microphone setup always belongs the invisible Stereo Recording Angle SRA which the microphone system is producing; see:

The often unknown Stereo Recording Angle SRA of stereo microphone systems (arrays) with two microphones.

Using the ORTF microphone system you get this nice interactive visualization:
Visualization of ORTF Stereo microphone system Cardioid/cardioid 110° Mic spacing 17 cm Equivalence stereo.

Don't calculate the visible and invisible angles too close. In the end your ears have to decide if it sounds like you want.

Cheers ebs
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