If you are designing a system to work in a large room, say 50 feet x 90 feet x 20 feet high, or a room volume of 90,000 cubic feet, the use of components is the only practical way to get proper coverage and sound quality. Please don't forget that stacking several self-contained, full-range systems (such as used in smaller rooms) will not produce good results in a large room!
The system shown in Figures 16 and 17 uses separate short- and long-throw high-frequency horns whose narrow coverage angles give good, intelligible coverage in the entire room. As illustrated in the elevation view of Figure 16, the highly directional HR4O 400 x 200 horns are aimed straight back to fill the back of the room. The HR90 900x400 horns are aimed down slightly to evenly fill the front of the audience. You may want to refer to the "Double Distance Rule "and "Room Reverberation Swamps Your Voice" sections which start on page 4 to refresh your memory.
The system block diagram is shown in Figure 18. This system uses an electronic crossover (such as the E-V XEQ-l) as described in detail in the "Medium Size Room" section on page 12. Only one XEQ-l is required since it can drive many amplifiers as long as only one crossover frequency is necessary. Once again, the TAPCO 6001-RB mixer was chosen for illustration. A TAPCO C-12 mixer with the addition of another XEQ-l crossover could give you a stereo system with more channels and flexibility if you so desired. Remember, a PA system with stereo capability must be used with intelligence and care, since you run the risk of having part of your vocals on one side, and part on the other, with only the people near the middle of the room hearing it all. The stereo system can, however, be used for special directional effects which serve to enhance the basically monaural vocal mix.
Since the large room system shown in Figures 16, 17, and 18 is bi-amplified, you will have to balance the level of the high-frequency horns against the low-frequency speakers. A simple way of accomplishing this can be done by ear, while speaking or singing into the microphone you usually use. First - with the amp driving the short-throw high-frequency horns turned down or off- balance the long-throw horns against the low-frequency speakers. Start with the gain controls of the low-frequency and long-throw high-frequency amplifiers all the way up and the high4requency level control on the crossover all the way down. (If the crossover has no such control, use in its place the gain control on the high4requency power amp.) Then, speak or sing into the microphone and bring the high-frequency level control on the crossover up until a natural, balanced sound is heard in the last half of the room served by the long4hrow horns. Finally, move into the front half of the room served by the short-throw horns and advance the gain on their amplifiers until a similarly balanced sound as achieved. The appropriate high-frequency low-frequency balance may also be obtained in a more scientific manner by employing a one4hird-octave real-time spectrum analyzer which will display the frequency response of the system in the audience area. Adjust the gain and level controls for smoothest response in the crossover frequency region (800Hz).
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