259:
74:
420:
unfortunate tendency to soften when hot. Hisco P450, developed in 1992 to address the softening issue in professional speakers, is a thermoset composite of thin glassfibre cloth, impregnated with polyimide resin, combining the best characteristics of polyimide with the temperature resistance and stiffness of glassfibre. It withstands brutal physical stresses and operating temperatures up to 300°C, while its stiffness helps maintain the speaker's 'cold' frequency response.
456:
424:
response is required from a loudspeaker, aluminium wire may be substituted, to reduce the moving mass of the coil. While rather delicate in a manufacturing environment, aluminium wire has about one third of the mass of the equivalent gauge of copper wire, and has about two-thirds of the electrical conductivity. Copper-clad aluminium wire is occasionally used, allowing easier winding, along with a useful reduction in coil mass compared to copper.
144:
33:
375:
a portion of the coil remains within the gap at all times. The power handling is limited by the amount of heat that can be tolerated, and the amount that can be removed from the voice coil. Some magnet designs include aluminium heat-sink rings above and below the magnet gap, to improve conduction cooling, significantly improving power handling. If
401:
In the earliest loudspeakers, voice coils were wound onto paper bobbins, which was appropriate for modest power levels. As more powerful amplifiers became available, alloy 1145 aluminium foil was widely substituted for paper bobbins, and the voice coils survived increased power. Typical modern hi-fi
374:
is related to the heat resistance of the wire insulation, adhesive, and bobbin material, and may be influenced by the coil's position within the magnetic gap. The majority of loudspeakers use 'overhung' voice coils, with windings that are taller than the height of the magnetic gap. In this topology,
446:
Voice coils can be used for applications other than loudspeakers, where time force linearity and long strokes are needed. Some environments like vacuum or space require specific attention during conception, in order to evacuate coil losses. Several specific methods can be used to facilitate thermal
423:
The actual wire employed in voice coil winding is almost always copper, with an electrical insulation coating, and in some cases, an adhesive overcoat. Copper wire provides an easily manufactured, general purpose voice coil, at a reasonable cost. Where maximum sensitivity or extended high frequency
397:
Many hi-fi, and almost all professional low frequency loudspeakers (woofers) include vents in the magnet system to provide forced-air cooling of the voice coil. The pumping action of the cone and the dustcap draws in cool air and expels hot air. This method of cooling relies upon cone motion, so is
410:
Aluminium was widely used in the speaker industry due to its low cost, ease of bonding, and structural strength. When higher power amplifiers emerged, especially in professional sound, the limitations of aluminium were exposed. It rather efficiently but inconveniently transfers heat from the voice
419:
plastic film which did not suffer from aluminium's deficiencies, so Kapton, and later Kaneka Apical were widely adopted for voice coils. As successful as these dark brown plastic films were for most hi-fi voice coils, they also had some less attractive properties, principally their cost, and an
438:
coatings on other voice coil wire. This creates lightweight, low-inductance voice coils, ideally suited to use in small, extended range speakers. The principal power limitation on such coils is the thermal softening point of the adhesives which bond the wire to the bobbin, or the bobbin to the
379:, the area of the voice coil windings is proportional to the power handling of the coil. Thus a 100 mm diameter voice coil, with a 12 mm winding height has similar power handling to a 50 mm diameter voice coil with a 24 mm winding height.
367:
which assists in cooling the coil, by conducting heat away from the coil and into the magnet structure. Excessive input power at low frequencies can cause the coil to move beyond its normal limits, causing distortion and possibly mechanical damage.
406:
up to 150°C, or even 180°C. For professional loudspeakers, advanced thermoset composite materials are available to improve voice coil survival under severe simultaneous thermal (<300°C) and mechanical stresses.
317:
is produced. This magnetic field causes the voice coil to react to the magnetic field from a permanent magnet fixed to the speaker's frame, thereby moving the cone of the speaker. By applying an
297:, which produce a larger force and move a longer distance but work on the same principle. In some applications, such as electronic focus adjustment on digital cameras, these are known as
471:
design which is used mostly in high-end speakers has the coil's height smaller than the gap's. The differences, advantages and disadvantages of both methods are listed below.
351:), voice coils are usually made as light weight as possible, making them delicate. Passing too much current through the coil can cause it to overheat (see
411:
coil into the adhesive bonds of the loudspeaker, thermally degrading or even burning them. Motion of the aluminium bobbin in the magnetic gap creates
562:
that positions the heads: an electric control signal drives the voice coil and the resulting force quickly and accurately positions the heads.
103:
531:
Both topologies attempt the same goal: linear force acting on the coil, for a driver that reproduces the applied signal faithfully.
398:
ineffective at midrange or treble frequencies, although venting of midranges and tweeters does provide some acoustic advantages.
415:
within the material, which further increase the temperature, hindering long-term survival. In 1955 DuPont developed Kapton, a
382:
In 'underhung' voice coil designs (see below), the coil is shorter than the magnetic gap, a topology that provides consistent
488:
This method keeps the number of windings within the magnetic field (or flux) constant over the coil's normal excursion range.
459:
Overhung and underhung voice coils. Light grey is soft iron, dark grey is permanent magnetic material and the coil is in red.
394:
it may leave the gap, generating significant distortion and losing the heat-sinking benefit of the steel, heating rapidly.
359:, provide a higher packing density in the magnetic gap than coils with round wire. Some coils are made with surface-sealed
208:
554:. In this application, a very lightweight coil of wires is mounted within a strong magnetic field produced by permanent
463:
The image above shows two ways in which the voice coil is immersed in the magnetic field. The most common method is the
286:
cone. It provides the motive force to the cone by the reaction of a magnetic field to the current passing through it.
180:
245:
227:
125:
60:
96:
17:
187:
550:
In particular, it is commonly used to refer to the coil of wire that moves the read–write heads in a moving-head
610:
165:
440:
194:
583:
161:
46:
176:
86:
90:
82:
154:
107:
258:
615:
403:
431:
8:
467:
design where the height of the voice coil is greater than the magnetic gap's height. The
383:
201:
318:
555:
328:
275:
310:
298:
594:
376:
294:
52:
559:
427:
371:
314:
283:
604:
510:
435:
430:
flat wire may be used, providing an insulating oxide layer more resistant to
412:
352:
571:
540:
513:
that the coil experiences, constant over the coil's normal excursion range.
290:
551:
391:
364:
455:
416:
143:
591:, 7th Edition, August 2001. Hisco, Anaheim, CA 92807. 714 777 2665.
544:
321:
348:
279:
360:
271:
539:
The term "voice coil" has been generalized and refers to any
402:
loudspeaker voice coils employ materials which can withstand
344:
325:
340:
547:
to move an object back-and-forth within a magnetic field.
262:
A 7.5 cm diameter dual voice coil from a subwoofer driver.
339:
Because the moving parts of the speaker must be of low
168:. Unsourced material may be challenged and removed.
363:and collar materials so they may be immersed in a
355:). Voice coils wound with flattened wire, called
282:) is the coil of wire attached to the apex of a
602:
95:but its sources remain unclear because it lacks
506:Gap's height is greater than the coil's height.
450:
324:to the voice coil, the cone will reproduce the
519:Hard non-linearity as the coil exceeds limits.
494:Soft non-linearity as the coil exceeds limits.
331:, corresponding to the original input signal.
485:Coil height is greater than the gap's height.
491:Higher coil mass, sensitivity low to medium.
293:such as those used to move the heads inside
61:Learn how and when to remove these messages
558:. The voice coil is the motor part of the
534:
516:Low coil mass, sensitivity medium to high.
386:over a limited range of motion, known as X
589:The Hisco Loudspeaker Voice Coil Handbook
246:Learn how and when to remove this message
228:Learn how and when to remove this message
126:Learn how and when to remove this message
454:
343:(to accurately reproduce high-frequency
334:
257:
585:, A good paper on Voice Coil Actuators.
14:
603:
289:The term is also used for voice coil
474:
377:all other conditions remain constant
166:adding citations to reliable sources
137:
67:
26:
24:
25:
627:
347:without being damped too much by
42:This article has multiple issues.
142:
72:
31:
153:needs additional citations for
50:or discuss these issues on the
13:
1:
577:
543:-like mechanism that uses a
451:Overhung and underhung coils
304:
7:
565:
10:
632:
597:, Principle and Practice.
313:through the voice coil, a
81:This article includes a
535:Other uses for the term
110:more precise citations.
509:This method keeps the
460:
404:operating temperatures
263:
611:Electromagnetic coils
458:
335:Design considerations
261:
595:Voice Coil Actuators
432:dielectric breakdown
162:improve this article
384:electromotive force
556:rare-earth magnets
461:
428:Anodized aluminium
264:
83:list of references
528:
527:
390:. If the coil is
299:voice coil motors
270:(consisting of a
256:
255:
248:
238:
237:
230:
212:
136:
135:
128:
65:
16:(Redirected from
623:
475:
295:hard disk drives
251:
244:
233:
226:
222:
219:
213:
211:
170:
146:
138:
131:
124:
120:
117:
111:
106:this article by
97:inline citations
76:
75:
68:
57:
35:
34:
27:
21:
18:Voice coil motor
631:
630:
626:
625:
624:
622:
621:
620:
601:
600:
580:
568:
537:
529:
453:
389:
337:
307:
252:
241:
240:
239:
234:
223:
217:
214:
171:
169:
159:
147:
132:
121:
115:
112:
101:
87:related reading
77:
73:
36:
32:
23:
22:
15:
12:
11:
5:
629:
619:
618:
613:
599:
598:
592:
586:
579:
576:
575:
574:
567:
564:
536:
533:
526:
525:
521:
520:
517:
514:
507:
501:Underhung coil
497:
496:
495:
492:
489:
486:
473:
452:
449:
387:
372:Power handling
336:
333:
329:pressure waves
315:magnetic field
306:
303:
254:
253:
236:
235:
150:
148:
141:
134:
133:
91:external links
80:
78:
71:
66:
40:
39:
37:
30:
9:
6:
4:
3:
2:
628:
617:
614:
612:
609:
608:
606:
596:
593:
590:
587:
584:
582:
581:
573:
570:
569:
563:
561:
557:
553:
548:
546:
542:
532:
524:
518:
515:
512:
511:magnetic flux
508:
505:
504:
503:
502:
498:
493:
490:
487:
484:
483:
482:
481:
480:Overhung coil
477:
476:
472:
470:
466:
457:
448:
444:
442:
437:
433:
429:
425:
421:
418:
414:
413:eddy currents
408:
405:
399:
395:
393:
385:
380:
378:
373:
369:
366:
362:
358:
354:
353:ohmic heating
350:
346:
342:
332:
330:
327:
323:
320:
316:
312:
309:By driving a
302:
300:
296:
292:
291:linear motors
287:
285:
281:
277:
273:
269:
260:
250:
247:
232:
229:
221:
210:
207:
203:
200:
196:
193:
189:
186:
182:
179: –
178:
174:
173:Find sources:
167:
163:
157:
156:
151:This article
149:
145:
140:
139:
130:
127:
119:
109:
105:
99:
98:
92:
88:
84:
79:
70:
69:
64:
62:
55:
54:
49:
48:
43:
38:
29:
28:
19:
616:Loudspeakers
588:
572:Galvanometer
560:servo system
549:
541:galvanometer
538:
530:
522:
500:
499:
479:
478:
468:
464:
462:
445:
426:
422:
409:
400:
396:
381:
370:
356:
338:
308:
288:
267:
265:
242:
224:
218:January 2008
215:
205:
198:
191:
184:
177:"Voice coil"
172:
160:Please help
155:verification
152:
122:
113:
102:Please help
94:
58:
51:
45:
44:Please help
41:
357:ribbon-wire
284:loudspeaker
108:introducing
605:Categories
578:References
552:disk drive
443:and coil.
392:overdriven
365:ferrofluid
268:voice coil
188:newspapers
47:improve it
469:underhung
417:polyimide
305:Operation
116:June 2017
53:talk page
566:See also
545:solenoid
465:overhung
322:waveform
447:drain.
349:inertia
311:current
301:(VCM).
280:winding
202:scholar
104:improve
523:
441:spider
436:enamel
361:bobbin
345:sounds
278:, and
276:collar
272:former
204:
197:
190:
183:
175:
434:than
326:sound
319:audio
209:JSTOR
195:books
89:, or
341:mass
181:news
388:max
164:by
607::
274:,
266:A
93:,
85:,
56:.
249:)
243:(
231:)
225:(
220:)
216:(
206:·
199:·
192:·
185:·
158:.
129:)
123:(
118:)
114:(
100:.
63:)
59:(
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
