CURVED SURFACE SOURCE 



33 



to the wavelength. When these conditions are satisfied for all frequencies, 

 the response characteristic will be independent of the position within the 

 solid angle. 



A loud speaker ^^'^^-^^ consisting of a large number of small horns with 

 the axis passing through a common point will satisfy, for all practical 

 purposes, the requirement of uniform phase and amplitude over the spheri- 

 cal surface formed by the mouths of the horns. A cellular or multihorn 

 of this type is shown in Fig. l.WA. This particular horn system consists 

 of fifteen horns arranged in five vertical rows and three horizontal rows. 

 The mouth opening of each horn is 8 X 8 inches. The horizontal and ver- 

 tical angle between the axis of the individual horn is 17°. 



The directional characteristics of a multihorn loud speaker may be 

 predicted theoretically " from the directional characteristics of an in- 



Fig. 2.11. A — a spherical radiating surface consisting of 15 individual exponential horns. 

 5 — geometry for predicting the directional characteristics of a cluster of small horns. 



dividual horn and the geometrical configuration of the assembly of horns. 

 Assume that the point of observation is located on the OF axis, Fig. 2.115, 

 at a distance several times the length of the horn. The amplitude of the 

 vector contributed by an individual horn for the angle ^ can be deter- 

 mined from its individual directional characteristic. In this illustration, 

 the plane XOZ is chosen as reference plane for the phase of the vector. 

 The phase angle of the vector associated with an individual horn is 



-360° 

 X 



2.29 



"Wente, E. C, and Thuras, A. L., Jour. A. I. E. E., Vol. 53, No. 1, p. 17, 1934. 

 isHilliard, J. K., Tech. Bull. Acad. Res. Council, March, 1936. 

 " Olson, H. F., RCA Review, Vol. 1, No. 4, p. 68, 1937. 



