User manual ELECTRO-VOICE DX34A

[. . . ] 5 EV Business Audio Product Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 EVID Surface Mount Speaker Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Innovation in Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Innovation in Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] The overwhelming majority of paging and background systems are relatively small, however. With the margin on many installations running in the $400 to $600 range, there's not much room for error or misunderstanding, since the cost of a single callback can eat up most of the profits. To succeed with distributed sound systems, the professional contractor needs to be able to count on his jobs going in smoothly and efficiently. In this article, we'll explore some of the "nuts and bolts" issues that affect profitability in the distributed sound system market, and offer suggestions for improving your chances of success in the business. Ceiling vs. Surface Mount Systems Several factors will determine the choice of surface mount or flush mount (ceiling) speakers for a given job. The most common criteria are: · · · · Audio coverage requirements Audio performance needs Building structure design Esthetic requirements of the environment Evaluating the choices among these primary criteria will often determine the format which is required for a listening area. It is important to note here that any installation may employ both types of products for different areas or to meet certain performance needs. For example to gain more control over sound coverage surface mount speakers may be employed but ceiling mount subwoofers may be utilized to keep the esthetic "footprint" or design impact of the speakers on the space relatively small. Selecting & Positioning Ceiling Loudspeakers In the traditional approach to overhead-distributed systems, loudspeakers are located in a grid arrangement whose dimensions are dictated by the room height and the directivity of the speaker elements. Two basic placement patterns prevail: square spacing, and hexagonal (or crisscross) spacing. In addition to the spacing pattern, the designer must choose between three density types, designated respectively as edge-to-edge, minimum overlap and center-to-center (see Figure 1). The greater the overlap, the more uniform the coverage -- and the higher the cost. In fact, the level at the edges of a 140° pattern is actually more than 15 dB down compared to on-axis -- not 6 dB down. It's interesting to note that the same proportions hold true for any ceiling height: No matter how high the ceiling is, the off-axis distance is even farther away by the same proportion. So for the loudspeaker in this example, whether the ceiling height is 8 feet or 20 feet, the listener who is at the edge of the 140° pattern, who you might think is at the 6dB down point is really 15 dB down. The actual listening-plane coverage depends on the polar plot of each speaker. On average, the coverage of the listening plane from a speaker with a 140° polar coverage is usually between 90° and 110° . ElectroVoice/Dynacord BGM Guide Page 18 Converting Coverage Specs to A Layout How do you convert polar coverage to listening-plane coverage as you design sound systems?One is to use the EV ceiling speaker layout program that does the conversion for you. Ease can determine intelligibility and map the SPL output of your entire installation. Usually that's not necessary however, as you can easily do a little bit of math and figure out what the real listening plane coverage angle of the speaker is. The second way to compute the listening-plane coverage is to start with the exact polar plot of the speaker and use a conversion table. (Real polar plots directly from test equipment are more accurate than an artists' redrawing. ) Polar plots are usually normalized to the on-axis value, which is usually labeled "0 dB. " For every angle off-axis, there is a "difference-figure" between this normalized on-axis value and the volume at that angle. To convert to listening-plane coverage, add the 3dB Correction Factor figure from Table 1 for that angle off-axis to the figure from the polar plot. [. . . ] If we need to develop a total of 70 volts across the line, then, we can use an amplifier, which delivers half of that, or 35 volts, for each channel. Using the previous equation: P = E2/R = (35 volts)2/8 ohms = about 150 watts Professional amplifiers of this power class are today quite common and relatively inexpensive. It is important to note that amplifier bridging should only be done when the amplifier is specifically designed for this purpose. The manufacturer's instructions should be followed when using this technique. [. . . ]