142 



DIRECT RADIATOR LOUD SPEAKERS 



the response to transients is usually very poor because the internal me- 

 chanical resistance is not sufficiently large. Of course, the steady state 

 response with respect to frequency is usually not very smooth and the 

 nonlinear distortion is quite large in these receivers. As a consequence, 

 the poor transient response is masked by these distortions. 



7.17. Diaphragms (Cones) and Voice Coils. — The diaphragm or cone 

 of practically all direct radiator loud speakers in use to-day is made of 

 paper. The cone shown in Fig. 7.18^ is made by a felting process and the 

 cone and corrugated suspension are made in one piece. The corrugations 

 in the conical portion of the diaphragm act as compliances. The portions 

 between the compliances vibrate essentially as a whole. The resultant 

 structure is then similar to that of a low pass filter. See Sec. 4.10D. The 



-•»-».,<, CORRUGATED 



CORRUGATIONS SUSPENSION " 



EDGEWISE 

 WOUND 

 RIBBON 



Fig. 7.18. Cones and voice coils. Sectional views. A. Felted paper cone. B. Developed 

 paper cone with leather outside suspension. C. Voice coil wound with round wire. 

 D. Voice coil with edgewise wound ribbon. 



compliances serve to reduce the effective mass of the vibrating system. 

 The corrugations also add rigidity to the cone in a radial direction. The 

 cone shown in Fig. 7.185 is developed from a flat sheet of paper. A leather 

 outside suspension is used with this cone. For voice coil and centering 

 systems two general classes are used, namely: inside and outside sus- 

 pensions. The inside suspension is some form of slotted disk. The outside 

 suspension shown is a corrugated disk. Slotted disks are also used for 

 outside suspensions. 



The simplest voice coil construction consists of round enameled wire 

 wound on a paper cyhnder (Fig. 7.18C). The ends of the voice coil are 

 soldered to flexible leads anchored to the cone. The ratio of the volume of 

 the conductor in the air gap to the air gap volume should be as large as 

 possible to make efficient use of the air gap flux. Certain reasonable 



