One AFC Enhance system utilizes four microphones for operation. If multiple AFC Enhance systems are needed for a single venue, each additional system will also require four microphones. For detailed examples of microphone and speaker arrangement of a single AFC Enhance system, please ask Yamaha subsidiaries or qualified AFC Enhance tuning partners.

In order to realize appropriate system, Yamaha recommends to use the microphone below.

Microphone Type / Modal Table

Microphones are fixed to or hung from the ceiling. They must be visible from the source point. They are set at or around the critical distance (Dc) from a representative source point. Environmental noise, especially from heating and air conditioning systems, has to be considered. The reverberation enhancement of AFC Enhance will also increase the SPL of back ground noise. This is not necessarily a problem because it is natural, e.g. if the reverberation time is increased by absorption decrease of absorptive materials, the noise level will increase. However, it is important to prevent excessive noise caused by a direct wind to the microphones or proximity to other mechanical noises. A length of 1.8 meters (6 feet) would be criteria for a sufficient distance between a microphone and a supply opening. For Early reflection enhancement, microphones have to receive the direct sound from a sound source, so they should preferably be set at or within the critical distance (Dc). Microphones must be visible from any point on or around stage area. If the microphone can be set at the Dc, the microphones can be used either for Reverberation enhancement or ER enhancement.

The microphones should be positioned so that the closest microphone-to-microphone distance is no less than half the length of the lowest wavelength you want to enhance. For example, if you want to enhance more than 125 Hz, the distance between the microphones should be greater than or equal to 1.4 meters (4.5 feet).


For AFC Enhance system, we recommend using Yamaha’s VXS series surface mount speakers, VXC series ceiling speakers, Installation series (IF/IS) loudspeakers, and also NEXO’s iD series and PS series point source speakers. For detailed description of products that are used for AFC Enhance, please refer to the “Lineup” section of the site.

For REV system, speakers should be placed beyond Dc from the listening area to avoid the localization of sound from the 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.

For ER system, speakers should be placed on the walls. The speakers should be faced to the audience. The distance between speakers should be between 4.6 to 6.1 meters (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 this case, the speaker distance should be the same as or less than the ceiling height.

What will AFC Enhance NOT do?

- For rooms with excessive natural reverberation, AFC Enhance cannot deaden the space’s reverberation.

- Acoustical anomalies such as excessive reverberation, focused echoes, slap-back echoes, diaphragmatic surfaces, noisy rooms, vibrating or shaking floors or structures, and standing waves or room modes cannot be corrected by AFC Enhance. Traditional acoustical means or solutions must be employed for these issues.

- While AFC Enhance can mask flutter echo, actual correction of the echo problem requires traditional acoustical solutions.

- The primary goal of AFC Enhance is to create natural sounding reverberation that correlates with the visual stimulus from the room. Thus, AFC Enhance will not make one room sound like another such as the Yamaha Artist Services, Inc Piano Selection Studio cannot be made to sound like Stern Auditorium at Carnegie Hall. AFC Enhance’s natural sound is assured because the reverberation tail used to start the AFC Enhance process contains the room’s impulse response signature which is then used to create the additional reverberation in the FIR filters which adds to the reverberant level and further lengthens the tail.