1. What type of speaker should be used? Yamaha has introduced speakers exclusively for AFC: the S8AFC and the S8AFC-D. Both models use the same driver. The S8AFC is an enclosure model and the S8AFC-D is a driver-only model, with which the contractor can choose a speaker to suit the architectural requirements. S8AFC 2. Where should the speakers be placed? There are set beyond Dc from the listening area to avoid the localization of the sound from speakers. Wall speakers should be facing directly horizontal. The height can be determined by the distance from the nearest seat which should be at or beyond Dc. Ceiling speakers should face directly downward. 3. How far apart should the speakers be? The distance between speakers should be 15 to 20 feet, which corresponds to Dc. Under a balcony, the distance between the seats and the speakers is often less than Dc. In that case, the speaker distance should be the same as or less than the ceiling height. 4. How many speakers does AFC use? To realize the continuous distribution of spatial impressions, the system requires many speakers distributed throughout the venue. We have determined the number of speakers by this way. When someone plays a musical instrument in a room, the listener hears the direct sound and the physical reflections of that sound. Turning on the system, the listener hears the direct sound from the source, direct sound from the nearest AFC speaker, and physical reflections from the source, including the sound of other AFC speakers. The energy of the direct sound from the nearest AFC speaker is shown in this formula.   Wa : The output of the AFC speaker On the other hand, when the system is turned off, the energy of physical reflections from the sound source is shown in this formula.   Ws : The output of the source Here, to realize twice the reverberation time, the energy should be twice because energy density increases with reverberation time. So, assuming the value of the output of the AFC speaker times the number of speakers equals the value of the output of the source, the number of speakers for AFC is shown in this formula.   Q : AFC speaker directivity including installation condition (=2)   r : Distance from a listener to an nearest AFC speaker   X : Correction Coefficient   S : Room Surface   a: Average sound absorption coefficient   R : Room Constant This figure shows the result of this formula, the correlation between reverberation time and the number of speakers. Each line is categorized by the capacity of the venue. Each closed square symbol corresponds to actual venues. The symbols from A to D are located on the line of 2,200 seats. Similarly, the symbols from E to H are located on the line of 700 seats. This way has one assumption. In consideration of the localization of speakers, the value of the energy of the direct sound from the AFC speaker is -22 dB against the value of the energy of physical reflections from the source. A: Wakayama Prefecture Culture Center 2,000 seats, 49 speakers B: Act City Hamamatsu, Main Hall 2,336 seats, 52 speakers C: Arkas Sasebo, Main Hall 2,000 seats, 48 speakers D: Sumida Triphony Hall 1,801 seats, 40 speakers E: Ritsumeikan University Lecture Hall 651 seats, 54 speakers F: Kyoto Bunkyo University Dosho Hall 847 seats, 36 speakers G: Kawaguchi Lilia Concert Hall 593 seats, 24 speakers H: Akita Atrion Concert Hall 700 seats, 24 speakers >> Back to "System configuration". Copyright (C)2012 Yamaha Corporation. All rights reserved.