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

[. . . ] Figure 2 shows the 3000 Hz plot of the main-floor SPL coverage of the original configuration. It's a bit rough, but still within a ±3dB window over the coverage area. 3000 Hz Figure 2. Figure 3 adds the 500Hz and 8000 Hz curves: Blue Red Teal 500 Hz 3000 Hz 8000 Hz Figure 3. Exposition center, 12 XLC-DVX, main floor, original configuration, This graph tells us that the tonal balance of the system will vary quite a lot over the listening area. [. . . ] 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. 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. Although the EQ curve is calculated at the ARP, it will apply well to the rest of the listening area as long as the array has been designed to provide even coverage. The ARP is located 100 feet downstage, a normal front of house mix position for such a venue. Figure 8. The light gray trace shows the frequency response of a single XLC-DVX box, as measured in the laboratory. Practical Advice: Creating the LAPS EQ Curve "Dialing in" a LAPS EQ curve usually requires three or four parametric sections. All EQ curves are different, but here is a starting point that we have found useful: # 1 2 3 4 Type 6dB low shelf Bell Bell or 12B high shelf Bell Freq 600 3kHz 7-12kHz varies Gain -6 +3 varies varies Q n/a 0. 5 varies varies Note LF rolloff Mid-high contour HF contour Optional, to fix small wiggles Table 1. Suggested starting point for setting up LAPS EQ 6 ADVANCED LINE ARRAY DESIGN WITH LAPS II · SELECTED TECHNIQUES REV. [. . . ] 10 ADVANCED LINE ARRAY DESIGN WITH LAPS II · SELECTED TECHNIQUES REV. 1 / SEPTEMBER 18, 2009 Delay shading may be used very helpfully with subwoofers, to control steering of bass radiation. For a comprehensive discussion of subwoofer arrays and steering, please see the EV white paper entitled Subwoofer Arrays. 6. Conclusion LAPS II's advanced prediction features, taken in conjunction with a bit of physics, can lead to bettersounding line arrays with no increase in cost. [. . . ]