MULTIPLE LOUD SPEAKER 



119 



The above discussion, together with Figs. 7.1, 7.2, 7.3 and 7.4, shows that 

 to obtain adequate power handhng capacity and uniform response over a 

 wide range (greater than 70 to 5000 cycles) requires a relatively large 

 diameter and heavy diaphragm and large coil at the lower frequencies and 

 a relatively light weight vibrating system at the higher frequencies. There 

 are a large number of direct radiator loud speaker systems which may be 

 built to satisfy these conditions. It is the purpose of the sections which 

 follow to consider a number of these systems. 



7.3. Multiple Single Cone, Single Coil Loud Speaker. — The character- 

 istics of Fig. 7.1 show that the low frequency efficiency may be maintained 

 to the higher frequency ranges by employing a small and relatively light 

 cone and coil. On the other hand, to obtain adequate power handling 

 capacity at the lower frequencies with tolerable excursions of the vibrat- 

 ing system requires a cone of relatively large area. To insure operation 

 below the elastic limits of the materials a cone of large area must be of a 

 sturdy construction. As shown in Fig. 7.1 and by equation 7.4 a large 



FRONT VIEW 



AMPLIFIER 

 A SIDE VIEW 





FRONT VIEW 



AMPLIFIER 

 B SIDE VIEW 



Fig. 7.5. Multiple single cone, single coil loud speakers. J. Large low frequency unit, small 

 high frequency unit and filter system. B. Seven small units connected in parallel. 



cone of this type must be driven by a relatively large coil to obtain a toler- 

 able efficiency. The efficiency of this system is low in the high frequency 

 range. 



Adequate power handling capacity and response over a wide frequency 

 range may be obtained by employing single coil, single cone loud speaker 

 units in two different arrangements, as follows: First, a large diameter 

 cone driven by a heavy coil for the reproduction of the low frequency 

 range, a small diameter cone driven by a light coil and a filter system for 

 allocating the power in low and high frequency ranges to the two respective 

 low and high frequency loud speaker units, Fig. 7.5A. Second, a sufficient 

 number of small diameter cones to satisfy the low frequency power require- 

 ments and of light construction to satisfy the high frequency response 

 requirements. Fig. 7. SB. 



