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It is extremely gratifying to have accurate 3D prediction software confirm and validate tried and tested loudspeaker selection, positioning, and aiming techniques, some of which predate prediction software all together.

Industry legend Bob "6o6" McCarthy created simple but reliable methods such as Forward Aspect Ratio and Lateral Aspect Ratio which minimize variance over listening‑space, that empower audio professionals to deploy loudspeakers without computer aid.

 

"If I have seen further it is by standing on the shoulders of Giants."

- Sir Isaac Newton -



The Triangle (Lateral Aspect Ratio)Figure 1Figure 1 shows such a method known as Lateral Aspect Ratio (LAR). LAR provides the available width, between two -6 dB‑points (relative to on‑axis), perpendicular to a loudspeaker, based on the on‑axis distance normal to that loudspeaker and its coverage angle.

This solution is key for, e.g., determining the spacing between loudspeakers that live on a line (uncoupled line source) such as frontfills, under- and over‑balcony loudspeakers, surrounds and ceiling loudspeakers.

Having successfully adopted these techniques myself for over 15 years now, it is extremely gratifying and comforting to observe the validity of these techniques in accurate 3D prediction software.

Forward Aspect Ratio & Minimum Variance Line (3 dB /div)Figure 2Proof of Concept (6 dB / div)Figure 3Figures 2 and 3 show all major landmarks for aiming a single loudspeaker. Notice the beautiful trapezoid keystone shape in the top right viewport (plan view) of Figure 3, proving that lateral width is proportional to distance, as well as the two triangles in the top left viewport (isometric view) of Figure 3.

If these concepts are alien to you, be sure to pick up a copy of the latest edition of Bob McCarthy's seminal book "Sound Systems: Design and Optimzation". They served me very well!