Floyd Toole Quotes

(Quotes taken with permission from his book: "Sound Reproduction, Loudspeakers and Rooms"
by Focal Press, Copyright 2008, an excellent book!)

Pages 370 – 372:

"Keele culminates a series of papers on constant-beamwidth transducers (CBTs) in collaboration with Button, in which they examine the performance of several variations of truncated lines: straight and curved, "shaded" (drive power reduced toward the end), and un-shaded (all transducers driven equally), all standing on a plane reflecting surface (Keele and Button, 2005). It is a masterpiece of predictions and measurements that provide many answers and suggest many more possibilities."

"Figure 18.3 shows a small sample of the informative sound field simulations in the paper. (……….) How did (e) and (f) sound? Excellent—at least that is the author's opinion from a biased, sighted test. It was distinctive in how little the sound level and timbre appeared to change with location in the room and how the loudspeaker did not get "loud" as one walked up to it."

Pages 368-372 Sound Reproduction Loudspeakers and Rooms

The Perfect Surround Loudspeaker? "Figure 18.3 showed sound-level contour plots for several variations of truncated, curved, and shaded-line loudspeakers. The two on the bottom (e and f), versions of the constant beamwidth transducers (CBT), were of special interest because they exhibited constant directivity (potentially good sound), and some of the contours held nearly the same sound level over long distances. Inspired by this, Figure 18.21 shows a family of contours taken from the same paper (Keele and Button, 2005) but inverted, placing the loudspeaker at the ceiling interface. The row of "heads" across the width of this imagined room intersect with only one line; they are at a nearly constant sound level from 200 Hz to 8 kHz. And as one moves even closer to the loudspeaker, at the same height, the sound level goes down." (…………)

"If a variation of this design or something else entirely, can come close to this performance target in a real room, the result would be a remarkable improvement in spatial and directional effects for the entire room. It is probable that fewer surround loudspeakers would be needed for large audiences."

(Note by Don Keele Oct. 2011: The CBT36 would work superbly in this application. The pair of systems should be mounted upside down on the ceiling on either side of the video room and aimed cross fired into the room. For optimum results, the ears of the listeners should be in an approximate range that extends from the bottom of the hanging array (its top) to a point two feet lower. This would effectively equalize level variations across a 10 to 15 foot wide listening room!)

Pages 407-409, Sound Reproduction Loudspeakers and Rooms