GB2085694A - Balanced armature transducers - Google Patents
Balanced armature transducers Download PDFInfo
- Publication number
- GB2085694A GB2085694A GB8031747A GB8031747A GB2085694A GB 2085694 A GB2085694 A GB 2085694A GB 8031747 A GB8031747 A GB 8031747A GB 8031747 A GB8031747 A GB 8031747A GB 2085694 A GB2085694 A GB 2085694A
- Authority
- GB
- United Kingdom
- Prior art keywords
- armature
- yokes
- transducer
- speech
- coil
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R11/00—Transducers of moving-armature or moving-core type
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
- Signal Processing (AREA)
- Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
Abstract
An electro-acoustic transducer of the balanced armature type, for use as a telephone earpiece or microphone, has its magnetic circuit formed by two parallel magnetic material yokes (1, 2), between which is located a speech coil (9). A ceramic permanent magnet (5) is located between the ends of the yoke at one end of the transducer. At the other end the yokes are angled inwards (4) to define a short narrow gap in which a flat reed-like armature (10) of ferro-magnetic material is secured. This is held in place with spacers (11) of a weakly magnetic material e.g. nickel, to facilitate welding. The armature extends through the speech coil (9) and into another narrow gap defined by inward-angled portions of the yokes. This, the main gap, is of relatively large area. Between the main gap and the speech coil a drive rod (7) is secured, preferably not by welding to avoid distorting the armature, and this drive rod drives a conical diaphragm. <IMAGE>
Description
SPECIFICATION
Telephone receivers
This invention relates to an electro-acoustic trans
ducer of the balanced armature type.
A known example of a balanced armature trans
ducer is the so-called rocking armature transducer
currently used in the earpiece of the standard British
Post Office telephones. This, which follows the prin
ciples of our British Patent No. 606012 (J. S. P.
Roberton - 18), has a drive unit which consists
essentially of an E-shaped magnetic structure, the
central leg of which is a permanent magnet and the
outer legs of which carry the operating coils. The
armature is a plate-like structure pivotted about the
central leg and which as it vibrates due to speech
currents in the coils drives the diaphragms via a
drive rod. Thus the functions of the armature
and the diaphrams are separated andthe alternating
speech flux does not pass through the magnet.
However, both the alternating and the steady fluxes
share paths in the yoke and the armature.
An object of the invention is to provide a trans
ducer of the balanced armature type which is an
improvement on known transducers such as the
type referred to.
According to the present invention, there is pro
vided an electro-acoustic transducer of the balanced
armature type, which includes two yokes of ferro
magnetic material which extend parallel to each
other and between which is a speech coil, a perma
nent magnet between the ends of the yokes at one
end of the transducer, and a ferro-magnetic arma
ture of flat-strip like form mounted by one of its ends
between the ends of the yokes at the other end of the
transducer, wherein at the other end of the trans ducerthe yokes are angled inward to produce a
short and narrow gap between which the end of the armature is secured, wherein between the magnet
end of the transducer and the speech coil the yokes
are angled inwards and then extend parallel to their
length and are then angled outward to define a main
gap which of larger area than the first-mentioned
gap and is a narrow gap, wherein the armature
extends from its said securing point through the
speech coil and into the main gap, and wherein the
armature is coupled by a drive rod to a diaphragm so
that when the armature is driven it drives the diap
hragm via the drive rod, the arrangement being such
that speech currents in the coil vibrate the armature
and hence the diaphragm or that speech waves inci
dent on the diaphragm vibrate the armature and
induce currents in the speech coil.
An embodiment of the invention will now be
described with reference to the accompanying draw
ing, in which Fig. 1 is a sectioned view of a trans
ducer embodying the invention, Fig. 2 is a top-plan
view of the transducer of Fig. 1, and Fig. 3 is a plan
view of a metallic blank from which one of the two
yokes ofthe transducer of Fig. 1 is made.
On the accompanying drawing, the dimensions of one example of a transducer embodying the invention have been shown, from which it will be seen that the figures are on an enlarged scale. The actual dimensions shown are those for a transducer which could be a direct replacement in a telephone earpiece for a rocking armature transducer. The upper and lower yokes 1,2 are identical piece-parts, each of which is a blank such as shown in Fig. 3 bent to the shape shown in Figs. 1 and 2. The blanks are of a suitable ferro-magnetic alloy. The yokes are shaped with inwardly bent portions such as 3 and 4, of which the portions 3 of the two yokes define as relatively long active pole gap. The other gap is a short back gap.
The magnet 5 is a ceramic permanent magnet, and is between the left-hand ends of the yokes, poled as shown. Note that the active gap has a short magnetic path length of 1 mm and a large area, of 36 sq mm.
Each yoke has a hole such as 6 via one of which holes passes a drive rod 7, which drives the transducer's diaphragm (not shown). Note that the hole is not strictly necessary in both yokes, but from the production aspect it is convenient for the yokes to be identical.
Between the widened out portions of the yokes is a coil former 9 on which the speech coil is wound: terminals for this coil are conveniently mounted on extensions of the cheeks of the coil former. The space between the yokes in which the coil former is located is longer than the former length so that its position can be adjusted if necessary before it is fixed in place.
The armature 10 is a flat thin reed, 0.8 mm thick by 6 mm wide by 24 mm tony, clamped by nonmagnetic spacers 11 in the back gap. This back gap also has a short magnetic path length, 1 mm, but is of relatively small area, 9 t,o 12 sq mm. This armature passes freely through the eye of the coil, and through the centre ofthe active pole gap. It also carries the drive rod 7 which is suitably secured to it. Note that the armature 10 is accessible from the sides so that the pole air gaps can be adjusted.
Since the active pole gap is larger in area, by two or three times, then the back gap, most of the steady flux passes across it so that there is little left to pass along the length of the yokes to the back gap. Hence the parts of the yokes near to the magnet may be near to saturation, while the rest of the yokes carries that value of steady flux needed for optimum AC permeability.
Little of the AC flux due to the speech coil passes through the magnet since its reluctance, and the reluctance of the parts of the yokes near it can be greaterthan the reluctance to AC of the active pole gap. As the magnet is close to the pole gap, some of its leakage flux adds to the fringing flux of the gap: to exploit this the end of the armature projects through the gap towards the magnet.
The flat reed armature is virtually in the neutral
magnetic plane for the steady flux, so very little of it
passes along its length, its cross-sectional area
being 4.8 sq mms. The main flux crosses the arma
The drawings originally filed were informal and the print here reproduced is taken from a later filed format copy.
ture in the pole gap, where it passes through a grea
ter area, 25 to 36 sq mm. This enables it to be made
of a higher permeability material, which saturates at
a lower flux density, so that its negative stiffness due
to magnetic pull weakens enough to prevent it hold
ing itself poled.
As can be seen from the drawing, the blank for the
yoke is widened at the magnet end: this widened
portion becomes a flange which stiffens the yoke
near the pole gap. If the spacers used to define the
back gap 11 are a weakly magnetic alloy they should
be compatible with the yoke and armature, and
enable final fixing to be done by welding.
The pole gap face and back gap face are coplanar,
and are parallel to the magnet sealing. The air gap
shown at the pole gap is 0.1 mm, and may provide
some damping resistance due to air viscosity.
To ensure that the flatness of the reed like arma
ture, which can be maintained during any annealing
needed, is not spoilt on assembly of the drive rod 7, this latter should be stuck or clipped to the armature,
rather than being welded or soldered. If the armature
is truly flat, the amount of adjustment needed is
minimised.
The magnet is not attached to the yokes, being
held in place by slight depressions in the yokes until
magnetised. Note that although the magnet in the
example shown is of a ceramic, a metallic magnet
can also be used.
To consider the magnetic structure again, it will be
noted that to a very large extent the AC and DC flux
paths have been separated. As will be seen this per
mits the use of relatively high DC flux without upset
ting the AC efficiency.
The AC permeability of a soft magnetic material
rises from its initial value to a blunt maximum at a
DC induction of around 0.5 Tesla. As the DC flux
increases further, the AC permeability falls, more
rapidly as saturation is approached. For good effi
cieney the product of the square of the DC flux and the AC flux must be maximised. Thus a high AC
permeability enables the magnetising ampere-turns
in the coil to induce a high AC flux in the active gap.
With the arrangement described above, the parts of the yoke which carry the DC flux due to the magnet
can be near to saturation without regard to the AC
permeability. Hence the DC flux can be very large without spoiling the device's response to AC flux.
The above indicates why the yokes are widened at -the magnet end:this allows the yokes to carrythe high DC flux to all of the main gap and thus stiffens
the yoke nearthe main gap where the magnetic pull
is considerable. The space provided beyond the coil
former is to allow adjustment of the reed armature
so that its free end can be set to the most sensitive
position in the main gap.
The yokes can be made of such material as a
grain-oriented silicon steel, using some ofthe
increased efficiency to reduce cost or difficulties in
manufacture.
Although the transducer which has been described herein is intended for use as a telephone
earpiece it wilt be understood that transducers
embodying the invention can also be used as mic- raphoneS.
Claims (5)
1. An electro-acoustic transducer of the balanced armature type, which includes two yokes of ferromagnetic material which extend parallel to each other and between which is a speech coil, a permanent magnet between the ends of the yokes at one end of the transducer, and a ferro-magnetic armature of flat strip-liked form mounted by one of its ends between the ends of the yokes at the other end of the transducer, wherein at the other end of the transducer the yokes are angled inward to produce a short and narrow gap between which the end of the armature is secured, wherein between the magnet end of the transducer and the speech coil the yokes are angled inwards and the extend parallel to their length and are then angled outward to define a main gap which is of larger area than the first-mentioned gap and is a narrow gap, wherein the armature extends from its said securing point through the speech coil and into the main gap, and wherein the armature is coupled by a drive rod to a diaphragm so that when the armature is driven it drives the diaphragms via the drive rod, the arrangement being such that speech currents in the coil vibrate the armature and hence the diaphragm or that speech waves incident on the diaphragms vibrate the armature and induce currents in the speech coil.
2. An electro-acoustic transducer as claimed in claim 1, wherein the drive rod is secured to the armature at a point between the main gap and the speech coil, and extends substantially at right angles to the armature through a hole in one of the yokes.
3. An electro-acoustic transducer as claimed in claims 1 or 2, wherein at its securing point the end of the armature is spaced from the two yoke ends by spacers of weakly magnetic material, being secured thereat by welding.
4. An electro-acoustic transducer of the balanced armature type, which includes two yokes of ferromagnetic material which extend parallel to each other and between which there is a speech coil, a source of direct current magnetic flux between the ends of the yoke at one end of the transducer, and a ferro-magnetic armature of flat strip-like form mounted by one of its ends between the ends of the yokes at the other end of the transducer, wherein between the first-mentioned ends of the yokes and the speech coil the yokes are so shaped as to define a narrow main gap which is of relatively large area, such that the direct current flux due to the source and the alternating current flux due to the speech coil are conveyed via separate magnetic flux paths,4 wherein the armature extends from the point at which it is secured to the yokes through the speech coil and into the main gap, and wherein the armature is coupled by a drive rod to a diaphragm so that when the armature is driven it drives the diaphragm via the drive rod and vice-versa, the arrangement being such that speech currents in the coil vibrate the armature and hence the diaphragm or that speech waves incident on the diaphragm vibrate the armature and induce currents in the speech coil.
5. An electro-acoustic transducer of the balanced armature type substantially as described with referpence to the accompanying drawing.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8031747A GB2085694B (en) | 1980-10-02 | 1980-10-02 | Balanced armature transducers |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8031747A GB2085694B (en) | 1980-10-02 | 1980-10-02 | Balanced armature transducers |
Publications (2)
Publication Number | Publication Date |
---|---|
GB2085694A true GB2085694A (en) | 1982-04-28 |
GB2085694B GB2085694B (en) | 1984-02-01 |
Family
ID=10516432
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB8031747A Expired GB2085694B (en) | 1980-10-02 | 1980-10-02 | Balanced armature transducers |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB2085694B (en) |
Cited By (31)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1994010817A1 (en) * | 1992-10-29 | 1994-05-11 | Knowles Electronics Co. | Electroacoustic transducer |
US5647013A (en) * | 1992-10-29 | 1997-07-08 | Knowles Electronics Co. | Electroacostic transducer |
WO2000032013A1 (en) * | 1998-11-19 | 2000-06-02 | Microtech Corporation | Electric-acoustic transducer having moving magnet and transducing method thereof |
US6075870A (en) * | 1996-12-02 | 2000-06-13 | Microtronic B.V. | Electroacoustic transducer with improved shock resistance |
US6658134B1 (en) | 1999-08-16 | 2003-12-02 | Sonionmicrotronic Nederland B.V. | Shock improvement for an electroacoustic transducer |
US20100312040A1 (en) * | 2009-06-05 | 2010-12-09 | SoundBeam LLC | Optically Coupled Acoustic Middle Ear Implant Systems and Methods |
US20130272564A1 (en) * | 2012-03-16 | 2013-10-17 | Knowles Electronics, Llc | Receiver with a non-uniform shaped housing |
US8611969B2 (en) | 2004-01-29 | 2013-12-17 | Surefire, Llc | Cable assembly with earpiece |
US8625834B2 (en) | 2004-09-27 | 2014-01-07 | Surefire, Llc | Ergonomic earpiece and attachments |
CN104247458A (en) * | 2012-03-16 | 2014-12-24 | 美商楼氏电子有限公司 | A receiver with a non-uniform shaped housing |
EP2897380A1 (en) * | 2014-01-21 | 2015-07-22 | Rion Co., Ltd. | Electromechanical transducer and electroacoustic transducer |
US9277335B2 (en) | 2009-06-18 | 2016-03-01 | Earlens Corporation | Eardrum implantable devices for hearing systems and methods |
US9544700B2 (en) | 2009-06-15 | 2017-01-10 | Earlens Corporation | Optically coupled active ossicular replacement prosthesis |
USD839243S1 (en) | 2017-09-22 | 2019-01-29 | Surefire, Llc | Earpiece |
US10286215B2 (en) | 2009-06-18 | 2019-05-14 | Earlens Corporation | Optically coupled cochlear implant systems and methods |
US10492010B2 (en) | 2015-12-30 | 2019-11-26 | Earlens Corporations | Damping in contact hearing systems |
US10511913B2 (en) | 2008-09-22 | 2019-12-17 | Earlens Corporation | Devices and methods for hearing |
US10516951B2 (en) | 2014-11-26 | 2019-12-24 | Earlens Corporation | Adjustable venting for hearing instruments |
US10516950B2 (en) | 2007-10-12 | 2019-12-24 | Earlens Corporation | Multifunction system and method for integrated hearing and communication with noise cancellation and feedback management |
US10516949B2 (en) | 2008-06-17 | 2019-12-24 | Earlens Corporation | Optical electro-mechanical hearing devices with separate power and signal components |
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US10779094B2 (en) | 2015-12-30 | 2020-09-15 | Earlens Corporation | Damping in contact hearing systems |
US11058305B2 (en) | 2015-10-02 | 2021-07-13 | Earlens Corporation | Wearable customized ear canal apparatus |
US11102594B2 (en) | 2016-09-09 | 2021-08-24 | Earlens Corporation | Contact hearing systems, apparatus and methods |
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US11516603B2 (en) | 2018-03-07 | 2022-11-29 | Earlens Corporation | Contact hearing device and retention structure materials |
-
1980
- 1980-10-02 GB GB8031747A patent/GB2085694B/en not_active Expired
Cited By (60)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1994010817A1 (en) * | 1992-10-29 | 1994-05-11 | Knowles Electronics Co. | Electroacoustic transducer |
US5647013A (en) * | 1992-10-29 | 1997-07-08 | Knowles Electronics Co. | Electroacostic transducer |
EP0784415A1 (en) * | 1992-10-29 | 1997-07-16 | Knowles Electronics Co. | Electroacoustic transducer |
EP0924961A1 (en) * | 1992-10-29 | 1999-06-23 | Knowles Electronics Co. | Electroacoustic transducer |
US6075870A (en) * | 1996-12-02 | 2000-06-13 | Microtronic B.V. | Electroacoustic transducer with improved shock resistance |
WO2000032013A1 (en) * | 1998-11-19 | 2000-06-02 | Microtech Corporation | Electric-acoustic transducer having moving magnet and transducing method thereof |
US6658134B1 (en) | 1999-08-16 | 2003-12-02 | Sonionmicrotronic Nederland B.V. | Shock improvement for an electroacoustic transducer |
US10440459B2 (en) | 2004-01-29 | 2019-10-08 | Surefire, Llc | Ergonomic earpiece |
US8611969B2 (en) | 2004-01-29 | 2013-12-17 | Surefire, Llc | Cable assembly with earpiece |
US9042947B2 (en) | 2004-01-29 | 2015-05-26 | Surefire, Llc | Multiple input acoustic coupler |
US9479856B2 (en) | 2004-01-29 | 2016-10-25 | Surefire, Llc | Ergonomic earpiece |
US9560436B2 (en) | 2004-09-27 | 2017-01-31 | Surefire, Llc | Ergonomic earpiece and attachments |
US8625834B2 (en) | 2004-09-27 | 2014-01-07 | Surefire, Llc | Ergonomic earpiece and attachments |
US10231048B2 (en) | 2004-09-27 | 2019-03-12 | Surefire, Llc | Ergonomic earpiece with attachment mount |
US10200778B2 (en) | 2004-09-27 | 2019-02-05 | Surefire, Llc | Earpiece with ergonomic extension |
US11483665B2 (en) | 2007-10-12 | 2022-10-25 | Earlens Corporation | Multifunction system and method for integrated hearing and communication with noise cancellation and feedback management |
US10516950B2 (en) | 2007-10-12 | 2019-12-24 | Earlens Corporation | Multifunction system and method for integrated hearing and communication with noise cancellation and feedback management |
US10863286B2 (en) | 2007-10-12 | 2020-12-08 | Earlens Corporation | Multifunction system and method for integrated hearing and communication with noise cancellation and feedback management |
US11310605B2 (en) | 2008-06-17 | 2022-04-19 | Earlens Corporation | Optical electro-mechanical hearing devices with separate power and signal components |
US10516949B2 (en) | 2008-06-17 | 2019-12-24 | Earlens Corporation | Optical electro-mechanical hearing devices with separate power and signal components |
US10516946B2 (en) | 2008-09-22 | 2019-12-24 | Earlens Corporation | Devices and methods for hearing |
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US10511913B2 (en) | 2008-09-22 | 2019-12-17 | Earlens Corporation | Devices and methods for hearing |
US20100312040A1 (en) * | 2009-06-05 | 2010-12-09 | SoundBeam LLC | Optically Coupled Acoustic Middle Ear Implant Systems and Methods |
US9055379B2 (en) * | 2009-06-05 | 2015-06-09 | Earlens Corporation | Optically coupled acoustic middle ear implant systems and methods |
CN102598712A (en) * | 2009-06-05 | 2012-07-18 | 音束有限责任公司 | Optically coupled acoustic middle ear implant systems and methods |
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US9277335B2 (en) | 2009-06-18 | 2016-03-01 | Earlens Corporation | Eardrum implantable devices for hearing systems and methods |
US10286215B2 (en) | 2009-06-18 | 2019-05-14 | Earlens Corporation | Optically coupled cochlear implant systems and methods |
US11323829B2 (en) | 2009-06-22 | 2022-05-03 | Earlens Corporation | Round window coupled hearing systems and methods |
US10555100B2 (en) | 2009-06-22 | 2020-02-04 | Earlens Corporation | Round window coupled hearing systems and methods |
US11153697B2 (en) | 2010-12-20 | 2021-10-19 | Earlens Corporation | Anatomically customized ear canal hearing apparatus |
US11743663B2 (en) | 2010-12-20 | 2023-08-29 | Earlens Corporation | Anatomically customized ear canal hearing apparatus |
US10609492B2 (en) | 2010-12-20 | 2020-03-31 | Earlens Corporation | Anatomically customized ear canal hearing apparatus |
US20130272564A1 (en) * | 2012-03-16 | 2013-10-17 | Knowles Electronics, Llc | Receiver with a non-uniform shaped housing |
CN104247458A (en) * | 2012-03-16 | 2014-12-24 | 美商楼氏电子有限公司 | A receiver with a non-uniform shaped housing |
EP2897380A1 (en) * | 2014-01-21 | 2015-07-22 | Rion Co., Ltd. | Electromechanical transducer and electroacoustic transducer |
US9601980B2 (en) | 2014-01-21 | 2017-03-21 | Rion Co., Ltd. | Electromechanical transducer and electroacoustic transducer |
US11317224B2 (en) | 2014-03-18 | 2022-04-26 | Earlens Corporation | High fidelity and reduced feedback contact hearing apparatus and methods |
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US10531206B2 (en) | 2014-07-14 | 2020-01-07 | Earlens Corporation | Sliding bias and peak limiting for optical hearing devices |
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US11516603B2 (en) | 2018-03-07 | 2022-11-29 | Earlens Corporation | Contact hearing device and retention structure materials |
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Also Published As
Publication number | Publication date |
---|---|
GB2085694B (en) | 1984-02-01 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PCNP | Patent ceased through non-payment of renewal fee |