Sx300PI and Sx300PIX 300-Watt Two-Way Weather-Resistant Speaker Systems
Frequency Response
The combination of a 12-inch woofer, wide bandwidth high-frequency driver and an equalized crossover results in the wide and smooth overall response shown in Figure 1. This response was measured at 10 feet, us- ing a 4-volt input in an anechoic chamber, and was measured using a swept sine-wave input. No external equalization was used. Figure 1 has been averaged and corrected for 1 watt at 1 meter.
Port Covers
The four ports surrounding the woofer may be "sealed" in order to add further weather protection to the system. Optional port cov- ers may be used in situations where in- creased weather resistance is needed. This will aid in the prevention of any moisture that may protrude through the foam-backed grill under extreme weather conditions to accumulate inside the enclosure. The op- tional port cover "kit" is supplied along with instructions with each system. However, once the aid of the port covers are installed, a difference of frequency response will change as shown in Figure 2.
Constant-Directivity Speaker System
The crossover frequency and speaker com- ponent geometries have been selected so that the directional characteristics of the woofer and constant-directivity horn match at the crossover frequency to create a special sys- tem type—the constant-directivity system.
Response within the 65° rated coverage angle is uniform, which means dependable audience coverage without “hot spots” or dead zones at certain frequencies. The 65° dispersion characteristic also helps avoid early reflections from nearby floor or side- wall surfaces which could degrade perfor- mance. The controlled directivity of the high- and low-frequency transducers also eliminates response irregularities caused by diffraction off nearby enclosure edges and, in combination with an essentially flat on- axis frequency response, produces a total acous- tic power output that is uniform with frequency.
Directivity
A unique feature of the Sx300PI is the con- stant-directivity dispersion provided by the 65° x 65° horn. The polar response of the system at selected one-third-octave band-
widths is shown in Figure 2. These polar responses were measured in an anechoic en- vironment at 10 feet using one-third-octave pink-noise inputs. The frequencies selected are fully representative of the polar response of the system. Beamwidth of the system uti- lizing the complete one-third-octave polar data is shown in Figure 4. Rq and directiv- ity index (Di) are plotted in Figure 5.
Suspending Sx300PI Enclosures
WARNING: Suspending any object is po- tentially dangerous and should only be at- tempted by individuals who have a thor- ough knowledge of the techniques and regulations of rigging objects overhead. Electro-Voice strongly recommends that the Sx300PI be suspended taking into ac- count all current national, federal, state and local regulations. It is the responsibil- ity of the installer to ensure the Sx300PI is safely installed in accordance with all such regulations. If the Sx300PI is suspended, Electro-Voice strongly recommends that the system be inspected at least once a year. If any sign of weakness or damage is de- tected, remedial action should be taken im- mediately.
When mounting the Sx300PI in a location where a weather-resistant system is required,
aminimum of a five-degree down angle is recommended. (See Figure 9.) This will aid in the prevention of any moisture protrud- ing through the foam-backed grille. A manual entitled Suspending System 200TM Loudspeakers is included with every Sx300PI system. It gives a summary of the suspension kits available and an idea of how each kit is used. A brief overview, which illustrates some approaches for single and multiple suspension, is given here for the benefit of the system designer. Please refer to individual suspension kit engineering data sheets for full details and safety information.
The first approach is to suspend an indi- vidual Sx300PI enclosure. The four metric M8 x 1.25 inserts (see Figure 6) which are built into the enclosure allow the system to be suspended using eyebolts (Mb100 Ac- cessory Kit). Typically it will be necessary to attach two cables to the top eyebolt and “pull up” on the rear. The Mb200 bracket (see Figure 8) encompasses the top and bot- tom of the enclosure and has additional fea- tures to make suspending the Sx300PI easier and more flexible. Electro-Voice recom- mends the use of the Mb200 in all but the
simplest situations. The Mb200 has supple- mentary holes to allow the Sx300PI to be attached to a wall or ceiling and aimed at an audience.
The Mb200 Installation Kit also allows the use of OmniMount® Series 100 mounting hardware by providing three-hole-pattern groups compatible with these support sys- tems. When OmniMount® Series 100 mounting hardware is specified, the Mb200 Installation Kit must first be attached to the speaker enclosure.
The second approach is to suspend multiple Sx300PI enclosures. The Sx300PI enclosure is not designed to suspend multiple enclo- sures from itself. If an “array” is required, then multiple Mb200’s must be used. Ar- rays may be constructed vertically by “daisy chaining” two Mb200’s from each other. The Mb300 array bracket allows the easy and secure construction of horizontal arrays, using Mb200’s to support the enclosure.
Power-Handling Capacity
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 in- put signal because it contains many frequen- cies simultaneously, just like real voice or instrument program. Second, our signal con- tains more energy at extremely high and low frequencies than typical actual program, adding an extra measure of reliability. Third, the test signal includes not only the overall “long term average” or “continuous” level— which our ears interpret as loudness—but also short-duration peaks which are many times higher than the average, just like ac- tual program. The long-term average level stresses the speaker thermally (heat). The instantaneous peaks test mechanical reliabil- ity (cone and diaphragm excursion). Note that the sine-wave test signals sometimes used have a much less demanding peak value relative to their average level. In ac- tual use, long-term average levels exist from several seconds on up, but we apply the long-term average for several hours, add- ing another extra measure of reliability.
Specifically, the Sx300PI is designed to withstand the power test described in the ANSI/EIA RS-426-A 1980. The EIA test spectrum is applied for eight hours. To ob- tain the spectrum, the output of a white-noise generator (white noise is a particular type
