Wednesday, July 12, 2006

How to Aim Loudspeakers

Cheat Sheet: How to Aim Loudspeakers (from Pro AV web site for AV Professionals)

High-quality professional loudspeakers can provide excellent pattern control, and modern software tools can accurately predict coverage based on specific hanging and aiming details. Here’s what you need to know to implement loudspeaker aiming in the field.

Loudspeakers aren’t like flashlights, and sound doesn’t behave like light.

New technology on the horizon will create practical aiming methods that require less guesswork and no actual physical aiming. Using columns of multiple DSP controlled drivers and software, users can vary the vertical coverage pattern from 15 to 120 degrees, as well as aim the pattern ±30 degrees.

The coverage pattern is a rough approximation of the geometry of the area of expected coverage. Because loudspeakers have varying degrees of pattern control, there can be significant energy “outside” the pattern. This problem is further complicated by erratic polar response; all frequencies aren’t necessarily produced with equal energy within the pattern. The best way to aim an individual loudspeaker is to align a laser aiming device on-axis, and aim it at the center of your listening area.

When more than one loudspeaker is used near another one, you can expand coverage, but there will be interaction effects. Most loudspeaker manufacturers now provide proprietary calculators to model arrays to minimize interaction effects and maximize coverage. Once optimal parameters are determined, the physical data (array height, angles between cabinets, and angles of the entire array) is given to the installers to implement in the venue, using various tools.

Using Array Calculators
The typical process for using an array calculator is:
1. Determine the rigging points for the array.
2. Determine where the vertical coverage starts and ends (the front rows to the rear of the venue).
3. Take physical venue measurements using a laser range finder and a clinometer.
4. Plug this data into the calculator software.
5. Adjust the software parameters (array height, array angle, inter-box angles, and number of loudspeakers) until a desirable solution is found for both SPL and coverage.

Line Array Calculators
Adamson,, Adamson SHOOTER

Alcons Audio,, Alcons Ribbon Calculator (ARC)

d&b audiotechnik,, Q-Calc

Duran Audio,, DDA

Eastern Acoustic Works,, KF730 Wizard, KF760 Wizard

Electro-Voice,, Line Array Prediction Software

JBL Professional,, Line Array Calculator

L-Acoustics,, Soundvision and Array 2004

Martin Audio,, Viewpoint

McCauley,, McCauley Line Array Calculator

Meyer Sound,, MD3 Placement Calculator, Array Calculator

Nexo,, GeoSoft

Renkus-Heinz,, Aimware

SLS,, Line Array Software Simulator (LASS)

Worx Audio,, EASE Focus

Integral Angles — Most professional loudspeakers intended for arrays have built-in angle indicators in the hanging hardware for cabinet-to-cabinet spacing.

Laser Level — Align the device on-axis and attach it to the loudspeaker to show where its coverage hits the audience. (Lists for approximately $70,

Pitch and Slope Locator — This device measures angles and altitude. (It lists for about $8.50,

Clinometer — This tool measures altitude. (It lists for approximately $189,

Range Finder — This device measures distance. (It lists for about $270,

Laser Vertex Hypsometer — This tool measures distance, height, or angles. (It lists for about $2,395,

Digital Inclinometer with Remote Readout — This device remotely provides angle information. (Prices start at $436,

Sources: dB Sound, EAW, Electro-Voice, Renkus-Heinz, Rieker Inc.

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