EVI-28 250-Watt Two-Way Compact Vari Intense® Speaker System
responses were measured in an anechoic environment at 20 feet using one-third-oc- tave pink-noise inputs at 2 degree resolu- tion (over 870,000 data points). The fre- quencies selected are fully representative of the polar response of the system. Beamwidth of the system utilizing the com- plete one-third-octave polar data is shown in Figures 5 and 6. Rθ and the directivity index (Di) are plotted in Figure 7.
Constant Directivity and Variable Intensity
Constant-directivity systems are specially tuned to provide a consistent, smooth tran- sition from the low-frequency subsystem through the high-frequency horn’s oper- ating range. These systems nearly always have symmetrical vertical dispersion pat- terns and a constant horizontal dispersion versus elevation. When a constant-direc- tivity system is installed above a surface, the SPL on the floor varies significantly from front-to-back and left-to-right. The front-to-back variation can be minimized by tilting the horn further back, but this always results in a large amount of slap echo, less dynamic range and poor intelli- gibility as a result of excessive energy dis- persed into the reverberant field. The so- lution is Electro-Voice’s revolutionary patented1 Vari Intense® horn that throws
a6- to 10-dB hotter signal to the back of the room while providing a wide nearfield angle and a narrow farfield angle. The vari- able horizontal angle ensures a rectangu- lar floor pattern, and the intensity change compensates for the drop in SPL over the longer distance to the back of the room (13 feet for the short throw and 55 feet for the long throw in a typical underbalcony application such as Figure 7). This single horn replaces a short-throw/long-throw horn combination, cutting materials and labor time while increasing performance with higher intelligibility and more uniform coverage. The system is provided with a 2,000-Hz passive crossover featuring tweeter protection and a proprietary pas- sive equalization circuit that provides fre- quency-shading, amplitude-shading and time delay to the two woofers. An Acous-
1.The use of Vari Intense® horns is protected by U.S. patent #5,020,630.
tic Lens Filter (ALF) on the grille helps to eliminate spurious lobes and provides a degree of acoustic loading. These features heavily modify the polar response of the two woofers, providing an extremely uni- form polar pattern with a shape that matches the VI horn’s unique SPL profile. They also smooth the transition between woofers and the horn to minimize horizon- tal lobes, providing amazingly even cover- age through the crossover point. This ex- tends the VI characteristic down to 500 Hz in an extremely compact enclosure.
Installation Tactics
The EVI-28 is designed to provide sub- stantially even SPL over a floorplan of a size that is determined by the height of the system above the floor and the vertical aim- ing angle of the system relative to the floor. The recommended operational vertical angle is minus 5 degrees from the top sur- face of the enclosure to minus 45 degrees, defining a maximum used vertical disper- sion of 40 degrees. The standard aiming of the system when it is mounted above a flat floor is with the top of the enclosure parallel to the floor. In this orientation, the system will provide even SPL over a floorplan that is approximately twice as wide as the mounting height, and five times as long. Tilting the enclosure down by approximately 10- to 15-degrees relative to the slope of the floor will produce a floorplan twice as wide as the mounting height and approximately three times the depth. At the standard aiming, the 45-degree nearfield operational angle defines an approximate offset to the first useable row of one-half the height of the speaker system above the listening plane.
In a typical installation, the top surface of the loudspeaker will point slightly above the head height of the furthest targeted seating or standing area. This will ensure the minimum amount of slap echo from the back wall. In an under-balcony situation, the sharp cutoff above the zero degree axis prevents early ceiling reflections from caus- ing interference patterns in the listening area. Since the EVI-28 has a very smooth and rapid drop-off towards directly below
the cabinet, you can actually stand right in front of the speaker (see Figure 10) with- out ear strain or microphone feedback. The remarkable absence of lobes to the rear al- lows the system to be mounted directly overhead to target a particular area with- out disturbing the audience below or be- hind the cabinet.
For example, Figure 9 shows a typical un- der-balcony application that has a floor with an upward slope of 5 degrees. The speaker is mounted 10 feet above the seated head height, so the horizontal width is fixed at approximately 20 feet. The en- closure is tilted back by 5 degrees to pro- vide a 50-foot throw, with the outskirts of the pattern filling in the rear aisle area with tonally accurate but reduced overall SPL. If the under-balcony seating area is only 35 feet deep, then the enclosure should be tilted down by about 10 degrees relative to the floor in order to prevent excess slap echo and preserve intelligibility.
Figure 10 shows a typical small-room ap- plication, perfect for a 20-foot by 30-foot boardroom or meeting hall. In this case, the head height is actually defined by a standing height of approximately 6 feet, so the long-throw axis should be very close to vertical. Then the included 40 degree angle points directly towards the entire lis- tening area, minimizing slap echo while re- taining a full width, high intelligibility and even SPL throughout the listening area.
Power Handling
To our knowledge, Electro-Voice was the first U.S. manufacturer to develop and pub- lish a power test closely related to real-life conditions. First, we use a random-noise input signal because it contains many fre- quencies simultaneously, just like real voice or instrument program. Second, our signal contains more energy at extremely high and low frequencies than typical actual pro- gram, adding an extra measure of reliabil- ity. Third, the test signal includes not only the overall “long-term average” or “con- tinuous” level - which our ears interpret as loudness - but also short-duration peaks which are many times higher than the av- erage, just like actual program. The long-
