645Chapter 18
Loudspeaker Cluster Design
by Ralph Heinz
18.1 Why Array?............................................................................ 647
18.2 Array Problems and Partial Solutions: A Condensed History..................................... 647
18.3 Conventional Array Shortcomings.......................................................... 647
18.4 Conventional Array Shortcoming Analysis................................................... 649
18.5 Coincident Acoustical Centers: A Practical Approach........................................... 650
18.5.1 TRAP Horns: A New Approach......................................................... 650
18.5.2 TRAP Performance................................................................... 651
18.6 18.6 Low Frequency Arrays: Beneficial Interference........................................... 652
18.6.1 Horizontal Woofer Arrays: Maintaining Wide Dispersion..................................... 652
18.6.2 Vertical Woofer Arrays................................................................ 653
18.6.2.1 Directivity at Frequencies Where Size Makes Horns Impractical............................ 653
18.7 Line Arrays and Digitally-Steerable Loudspeaker Column Arrays................................. 653
18.7.1 What Affects Intelligibility............................................................ 654
18.7.2 Measuring Intelligibility............................................................... 654
18.7.2.1 Subjectively..................................................................... 654
18.7.2.2 Objectively...................................................................... 654
18.7.3 Architecture and Room Acoustics........................................................ 655
18.7.3.1 Reverberation.................................................................... 655
18.7.4 Line Arrays......................................................................... 655
18.7.4.1 Digitally Steered Column Arrays.................................................... 656
18.7.4.2 Controlling High Frequency Beaming................................................ 656
17.7.4.3 Beam Steering....................................................................... 656
18.7.5 DSP-Driven Vertical Arrays............................................................ 657
18.7.5.1 Acoustical, Electronic & Mechanical Considerations..................................... 657
18.7.5.2 Point Source Interactions.......................................................... 658
17.7.5.3 Doublet Source Directivity............................................................. 658
18.7.5.4 Array Height versus Wavelength (Ȝ).................................................. 659
18.7.5.5 Inter-Driver Spacing versus Wavelength (O)............................................ 659
18.7.6 Multichannel DSP Can Control Array Height.............................................. 661
18.7.7 Steerable Arrays May Look Like Columns But They are not................................... 661
18.7.7.1 Beam-Steering: Further Proof that Everything Old is New Again........................... 6 62
18.7.7.2 DSP-Driven Arrays Solve Both Acoustical and Architectural Problems...................... 662
17.7.7.3 Variable Q.......................................................................... 662
17.7.7.4 Consistent Q with Frequency........................................................... 662
17.7.7.5 Ability to Steer the Acoustic Beam Independently of the Enclosure Mounting Angle............... 662
17.7.7.6 Design Criteria: Meeting Application Challenges........................................... 662
17.7.7.7 Horizontal Directivity is Determined by the Array Elements.................................. 663
17.7.7.8 Steering is Simple—Just Progressively Delay Drivers........................................ 663
18.7.7.9 BeamWare: The Software That Controls Iconyx Linear Array Systems...................... 663