Installation procedures for any conventional loudspeaker are fairly well-defined and easy to un- derstand: find an appropriate hanging height and position that affords a clear path to the listening area (such as above the center of a stage or above the lectern in a church), and aim the loudspeaker to- wards the center or just to the rear of center of the room. With this method you hope to cover the majority of the room with fairly consistent sound, but the mid and high frequencies never seem to fill perfectly. It is frequently aimed a little too far back and there is a large amount of slap echo, or the front row is too loud, the back row too soft and the front and back row corners sound muted due to a lack of high-frequency energy. Other solutions to filling the room have been suggested and imple- mented, including a dual-horn format (one long throw and one short throw). This method works fairly well, but encounters several problems: the added expense of another horn/driver combination; the vastly increased time to physically install and then tune the level and aiming of two horns; the in- evitable destructive interference patterns through- out the listening area; the expense of another ampli- fier channel to achieve correct impedance match- ing; and the need for a very aesthetically clean in- stallation, with no odd-looking (to the customer) dangling horns. Another solution is to have a horn that is variable angle, in order to throw a narrow pattern to the back of the room. The problem with this concept is that this doesn’t take into account the drop in SPL between the near throw (about 25 feet) and the far throw (about 70 feet), so the high frequencies are about 10 dB down in the back of the room. To solve all of these problems, the Vari In- tense® horns were invented, yet another innovation in the long tradition of Electro-Voice. When properly aimed, the Vari Intense® horns can provide extremely even SPL throughout an entire room, filling in the corners without pushing too much energy at the back wall, thus avoiding slap echo. The rules of fixed installation have just changed...
The Electro-Voice EVI-12, EVI-15 and EVI-28 enclosures are the first in a new generation of problem-solving systems. The new systems are designed as a package, with easy mounting, refin- ishing ability, lightweight, compact and unobtrusive size and shape and the classic musical sound that Electro-Voice is known for. The new small-format VI horn maintains consistent directional control down to 2,000 Hz. In the EVI-12 and EVI-15 the VI horn is optimally crossed over to an specially
angled woofer. Note: the 12-in. driver in the EVI- 12 is at a different angle than the 15-in. driver in the EVI-15, optimizing the floor pattern with the differ- ing directivities of the two drivers. In the EVI-28, the VI horn is crossed over to a pair of vertically- arrayed 8-inch woofers with a proprietary technique that provides delay, amplitude and frequency shad- ing to the two woofers.
The EVI-12, EVI-15 and EVI-28 systems are installed just like any conventional loudspeaker, keeping in mind a few simple guidelines. Let me preface these guidelines with a simple but impor- tant comment: the VI systems are extremely versa- tile and will work in a large variety of applications. They will work well with tall ceilings, short ceilings, rectangular rooms, slightly trapezoidal rooms and a whole host of odd shapes so long as the coverage area is fairly close to rectangular. The larger EVI-12 and EVI-15 have been tested in rooms with 12-foot ceilings and performed very well, although with reduced width of throw. A single EVI-12 was installed in a room 75-foot by 150-foot and an average RT60 of 4.5 in the mid band and performed very well with good intelligibility and a minimum of slap echo. It has been thought in the past that if the floor pattern does not fit the VI horn exactly, then it cannot be used at all. This is not the case, and if it were the case, we could not use standard constant- directivity horns in most applications either. The larger VI systems have an “optimum” room that is approximately twice the height in width and three times the height in length. This is the ideal condi- tion, but the figures and descriptions that follow should give you a good feel for the wide-range ca- pabilities of the systems.
EVI-12 and EVI-15 Installation:
The nominal floorplan that the system will cover with equal SPL is approximately two “units” wide by three “units” long, where the height of the loudspeaker defines the size of the “unit.” For ex- ample, if the loudspeaker is 18 feet above the floor, it will typically cover a floorplan of about 36 feet wide by 54 feet long. In this typical installation (see Fig- ure 1), the back panel of the loudspeaker is mounted approximately 0.6 units (about 11 feet) back from the first row and has a nominal angle of the top of the enclosure parallel to the floor or slightly tilted back (2 to 3 degrees). For rooms that are much longer than normal, the VI systems are very easy to aim and position to fill the entire length. Experi- ments in actual listening rooms have shown that with
