User manual ELECTRO-VOICE ADVANCED LINE ARRAY DESIGN WITH LAPS II SELECTED TECHNIQUES

[. . . ] Advanced Line Array Design with LAPS II Selected Techniques Version 1 Electro-Voice, Burnsville, Minnesota, USA © Bosch Security Systems Inc. April, 2009 Advanced Line Array Design With LAPS II SELECTED TECHNIQUES Jeff Berryman Rev. Introduction EV's LAPS II line array prediction program includes several advanced features that help you design better line array systems. This note explains how those features work, and how you can use them to get better sound. 2. Feature: Three-frequency Prediction LAPS II predicts line array coverage for up to three frequency bands at once. [. . . ] 1 / SEPTEMBER 18, 2009 Figure 7 shows the frequency response of a theoretical line array of loudspeakers, each with perfectly flat frequency response. The loudspeakers in this example are 10. 5" high, approximately the size of an EV XLD-281, and are curved and flown in a typical arrangement. the point at which the frequency response is measured) is on the central axis of the array, 100 feet distant. Figure 7. Axial frequency response of a curved line array. From this curve, it is apparent that for good tonal balance, equalization will be required. For typical line arrays, the equalization curve will take the form of a fairly smooth ramp that rises from low to high frequency. With practical arrays, the total rise from 100Hz to 10kHz will be between 6dB and 18dB, depending on length and curvature of the array. Part of this equalization may be provided by the loudspeakers themselves, since line array loudspeakers are often engineered with built-in high-frequency boosts, but the rest of it must be provided in the drive chain, prior to the crossover filters. 4. 2. LAPS II Equalization Calculation For all line arrays, the specific equalization required will depend on: · · · · Array height and tilt angle Incremental vertical angle of each box Gain shading (i. e. gain of drive signal to each box) Frequency response of individual loudspeakers. LAPS II calculates a recommended equalization curve that takes all of these factors into account. While the LAPS EQ curve does not include any venue effects (reverberation, room resonance, surface reflections, etc. ), it is an excellent starting point for room tuning. Experience has shown that starting with the LAPS curve leads to clean-sounding system tunings that have fewer narrowband equalization points, and that suit a wide range of program types with surprisingly little adjustment. In use, LAPS computes an equalization curve each time it does an acoustic prediction. This curve applies to a specific point in the venue called the Acoustic Reference Point (ARP). You can 5 ADVANCED LINE ARRAY DESIGN WITH LAPS II · SELECTED TECHNIQUES REV. 1 / SEPTEMBER 18, 2009 specify the position of the ARP on the LAPS "Venue" page, where all the venue size and shape parameters are entered. Normally, the ARP is situated at the front-of-house mix position. The LAPS EQ curve is computed to provide a defined target frequency response at the ARP. The target frequency response curve has been chosen to provide good tonal balance in most applications. It is flat up to approximately 7kHz (depending on loudspeaker model), then gently rolls off above. [. . . ] Horizontal scale is 25 feet per division. Blue Red Teal 500 Hz 3000 Hz 8000 Hz Figure 10. In fact, these curves are fairly good already. But look what happens with a bit of gain shading. Figure 11 shows the same array, with Box 1 (the top box) turned down 3dB, Box 9 turned down 2dB, and Box 10 turned down 4dB. Blue Red Teal 500 Hz 3000 Hz 8000 Hz Figure 11. [. . . ]