H 



DOUBLE COIL, DOUBLE CONE LOUD SPEAKER 123 



4J O 



c ji: .- •- ji: 



(U -M O O -tJ 



7.6. Double Coil, Double 



I "o :^ :^ "o ^ Cone Loud Speaker \ — 



The double coil, double cone 



loud speaker. Fig. 7.6D, 



"o "o o "^ consists of a light coil 



^ 1 ! I i i 1h 1 1 i 1 1 "^ coupled to a small cone, 



connected by a compliance 

 to a heavy coil and large 



J^, -c 



opcy,, t:_: _c^a,r^r5 



S'H 3'8 o-g i' -"I .y ^^ S J ^ cone. In this system an 



_c 



.^g -^ E 'S .^"^ c1- 



3 S 



US 



• • u aj > 

 t; >J " 



£! u >- f, _; ° "^ > i.^_.cj u increase in range is obtain- 



ed by reducing the imped- 



O '-' 



o ^ 



,-, . ^ g^-S H I ^1 '-^ "^ 2 g ^ 8 "S ance of both the coil and 



_c: <u " 5 i" -^ 

 "5 -c ■" c u <u fe 



the diaphragm at the higher 

 frequencies. At low fre- 

 quencies the electrical re- 



2 S^'o^S^^M^i "o.^ § M-« e S 0) g actance ot the capacitance 



g 'd-^-S^;;'d^^^^|^ Z:.:§^^i'^2 Cfiis large compared to 



<D ^j-i-'^oZ^^.-ji^ "^is^s' o.^'g the electrical impedance of 



^ ■S-d'g^"£S-^^ -^S— •••"—• ^ the large portion or the 



I ll ^ S || S ^l-^rd ^il II I I. voice coil L„ r^, and the 



^ 'I r. I ^ 1^ ^ -^ '^ : :^ S^^ ^-s ^ g ^ same current flows in both 



-2 u .. t; 



o-3^^^c'""Sg'^S "'"^gp^i coils. The mechanical re- 



actance of the compliance 



'" o " -S <u '3 jj ■- r5 jn 3 ■= o •? -f=, -d 



> i; — a, 



^ o ^ -* '1-' • ::; • — -^ 



o ^ .5 ^ -n c ^ " g ^ Cm separating the two por- 



l liill'-ilU'l ^lil^'-si ti°^^s o^ the coil is large 



-S ^°'S§_^'o^.Scjj2 ^^-oc^-g^ compared to the mechani- 



"^ •s-S-a^cSgjs 4-u >P" ":z:?i cal impedance ot ^i. Ihere- 



§ g^^_g1^||'8^8-^g-c'a'8|'-^« fore, at low frequencies the 



(u •B-c^£oduM"'^'S'i^c=^bca)"'2 system behaves as a single 



<^ J 1^1 § l>^ .1^^- ^ :^ 1-;^ §^ coil, single cone loud speak- 



y'ii^'S^^ SSI- I Si 2 11-5 . a^S, er. Both parts of the voice 



l^-^^^^-^^ltlS S-^l i^'g'^ § 1"^^^ quencies; no air gap flux is 



•" "5 K i ^ -i ^ ^ '1 ^ "^ •- -^ ^^ 'i ^ "^ -^^ -S ^ wasted as would be the 



•sM-E^^-g^i^^B.yas^'S,^^g-?S= case if two separate units 



I g.^- ^ E 8-j^ ^-Gi-g a^^ ^"el - i ^^^^ "s^^- ^t '^^g'^ ^^^' 



l^l^-t^^lS)!;^^. g-|_^g|£^. g-gg^ quencies the electrical capa- 



" §.a^ ^ ^-:: -^ c^S fe ^ " ^n i n "3 g "^ :: 5 '-n ' Olson, H. F., 7o«r. Jcous, 



I r JlLi^l 15 lll^l |o« i 8 S ^^- ,^7^-. Voi/lO. No. 4, 



p. 305, lyjy. 



