In part 2, we present an alternate simplified design technique that is based not on Part 1’s specification of frequency responses at arbitrary off-axis vertical angles, but on specification of the total shape and coverage angle (vertical beamwidth) of the polar patterns generated by pairs of separated point sources. Here we show that when only a single pair of drivers is operating at a specific frequency (Part 1 called these the “critical frequencies”), the spacing of these drivers is a constant distant apart in terms of acoustic wavelength. The design procedure of Part 2 simplifies that of part 1 by restricting the level of the forced-to-be-flat off-axis angle to -6 dB thus making it equal to the level of the polar beamwidth specification, i.e. beamwidth is defined as the angle between the 6-dB-down points from on axis. Thus restricted, Part 2 shows that the spacing of each pair of drivers at their critical frequencies should be in the range of 0.4 to 0.6 wavelength to yield well-behaved polar shapes with beamwidths in the range of 67º to 113º. Part 2 also shows that that spacing ratios between successive pairs of drivers should preferably be in the range of 2:1 to 2.5:1, but can extend out to 4:1, but at the expense of polar uniformity at angles beyond the 6-dB-down points.
https://www.aes.org/e-lib/browse.cfm?elib=14208
Click to purchase paper as a non-member or login as an AES member. If your company or school subscribes to the E-Library then switch to the institutional version. If you are not an AES member and would like to subscribe to the E-Library then Join the AES!
This paper costs $33 for non-members and is free for AES members and E-Library subscribers.
Learn more about the AES E-Library
Start a discussion about this paper!
