OS o a. 



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t, (U c« 



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S 



LOUD SPEAKER BAFFLES 127 



fabricate. Two suitable corrugations are 

 pressed into a single voice coil form. 



D. Loud Speaker with a " T " Type Filter 

 Connecting the Voice Coil Mass and the Cone 

 Impedance. — This system, Fig. 7.7D, con- 

 sists of two parallel resonant circuits, or a 

 S^^ 2'o<u ^Js'iS parallel resonant circuit m^ and Cui con- 

 >'S o§8 SpS^o. nected to the bottom of the voice coil of 



£^£ i)«-5 i'c'^"^£ ^he system of Fig. 7.7C. The equivalent 

 ° u ° -S S electrical circuit is also shown in Fig. 7.7D. 



rt ^ "^ tj c 



>- i S c^ The system then is a " T " type low pass 



-a 1".| 8 g filter connecting the coil and cone. See Sec. 



^ ° ^ .1 ^ 4.10. Very high attenuation is obtained at the 



^_g-S§S)0 resonance frequency of the arms. The re- 



H^Srt S^j'^'n^^-^^"^ sponsefrequency characteristic of this system 



%%\ S^^c^s-^g^^- is shown in Fig. 7.7D. Comparing with 



;^^;;; £'|8^:!^'^:!8 Fig. 1.1 A the attenuation at 10,000 cycles 



■| "c ^ -58.2 ^-f ^ cu y -f is 35 db. The attenuation is also quite high 



"^ ^ <u '5 -5 Sd c u _. § 5 c above 10,000 cycles. As in the other sys- 



cO^ oq'SpC-o^.Sc . .' ,1-1 • .u 



'Z -o t= ^ o S"'^ " £ ^ -B ^'^"^^ ^^ ^^ made by simply pressmg three 



-^^^ j3-^ij'7-^-g8i3Si corrugations into a single voice coil form. 

 oj'-'£-^rt"£2^'j>2i-"P 0^1 1 -1 1 c 



^V.'Z S-«-S&'aj-£S^ Several mechanical networks tor con- 



J" •£ 13 Oh ^ o %^^ -5 C-, J 8 ,,. , . 1 r 



-n,. u "■cjy^s^^Sjaj.y trolhng and suppressing the response or a 



•c loud speaker at the high frequencies have 

 ^ p ';, § ^ o been described. The cost of the system is 



Q ^ dJ O 2 ... 



^ _5 <o ^ i _^ very small compared to an electrical circuit 



uS" fe.>^uiu_^.2t^o-' i-i- 1 11 



■> .. S £ u ^ -S ■> « u "a-'s? >. for accomplishing the same result because 



't'?,^ -^^'^g::8o— § the networks are made by simply placing 



•i: -o ^ u § « c -S -f^ o ^ ^ -5 S" corrugations in the voice coil form. These 



^S'^-gSE e'o.^"'^ S-l"^ examples also illustrate the value of equiv- 

 «"s^S"?yc"?e^c^c^c , ^, •, • • • J- • J 



e.>^oi?'£^ bjDg_iJ_H_ £ o alent electrical circuits in designing and 



S'SJuS^eS ■gu'*^^ in predicting the action of mechanical 



^■^'o^^^.ti^ .^"""qJSd systems. 



^-^gjl-gE-S.f.JI ' 7.8. Loud Speaker Baffles. — A baffle is 



f« -s c^ Oh ^ partition which may be used with an 





■ 2 



(U 



C OJ -C H- ( 



S o-^'^^-^-^"c5__^ g'_u S-S acoustic radiator to increase the effective 



<U 13 03 C <u •= 0, 



D :^ ? S J " ^1 J -5 i) I .^"^ between the front and back of the radiator. 



length of the acoustic transmission path 



«5 u -c K ^ "" -c &-Ci v t ^.y ^ The term baffle is commonly applied to a 



plane surface. When a direct radiator 



j: rt d C c3 £ j= 



