The vertical angles of the speakers which cover the orchestra seats are adjusted so that the line representing the upper limit of the 15 degree vertical angle strikes just above the last row of seats. If the theatre has a balcony which is not too close to the speakers, the orchestra and balcony may be covered with one pair of speakers in the same horizontal plane. In this case the vertical angle of the speakers is adjusted to give approximately equal intensity and intelligibility in both the orchestra and the balcony. When the balcony is too close to the speaker to be covered adequately in this manner, it is necessary to use separate speakers for orchestra and balcony. The speaker used to cover the orchestra is placed in the usual manner, below the center line of the screen. The balcony is covered by

speakers placed just above the center of the screen, and adjusted vertically to properly cover the balcony without directing any sound into the orchestra. The number of speakers used depends upon the size of the balcony. Very high theatres which have a second balcony may require a third tier of speakers if the upper balcony is to be well covered. This is, however, an exceptional case.

The choice of location and number of loudspeakers to be used in a theatre depends upon so many variable factors that fixed rules for such choice cannot be laid down, but each theatre must be considered as an individual case and all variable factors must be considered separately and in combination.

For a further discussion of the problems involved in the location of loudspeakers, see Chapter XII.

Copyright 1930 RCA Photophone, Inc. 8