At the talk Bill Woodman provided interesting snippets:
Good sound in a stadium is rarely possible with line arrays, far better use directional drive units. The acoustics in the Walt Disney hall in LA caused concerns for Keith Jarrett in a 2003 concert “It was like being in the center of a big bowl, with the sound stirring around and never finding any sort of focus,” Jarrett said of playing in Disney Hall. http://www.lsionline.co.uk/news/story/ATC-for-Walt-Disney-Concert-Hall/YGKL6R
Symmetrical Field Geometry is a big improvement in driver motor design. The hysteresis in the pole price and plate is about 6 to 8mm deep. A ring of small oxide coated particles on the front plate is used to control the eddy current for a ‘super linear magnet’.
Ed May, JBL’s designer uses short voice coils on a long gap for his cones. ATC have long or short coils for the cone drivers, because the 3″ dome is used on the flat part of its curve a short coil is not needed. Short coil drivers have a Q of 0.4 or more, good for reflex boxes whereas long coils work best as sealed boxes. All ATC sub’s are in sealed boxes. Bill emphasises that there should be no leaks, or say goodbye to bass.
Speaker Placement- Bill says across the short dimension of the room, about 1/4 or 1/3 of the way out. Subs should be sealed.