A personal listening device including at least one direct-radiating balanced-armature audio transducer and at least one substantially enclosed, indirect-radiating, or tube-coupled balanced-armature transducer. The tube-connected transducer emits sound waves which pass through a hole, slot, tube or bore before entering an airspace near the eardrum of a user, while the direct-radiating transducer emits sound waves directly into the airspace adjacent the indirect-radiating transducer or tube, which airspace is contiguous with the airspace near the eardrum of the user.

FIELD

The invention relates to electro-acoustic audio transducers in the nature of headphones and earphones. More specifically, the invention relates to configurations of in-ear monitor components featuring improved acoustic rendition characteristics.

BACKGROUND

Traditional personal listening devices utilize one or more drivers as audio reproduction sources. The sound waves from these drivers are commonly carried from an enclosed, sub-miniature electro-acoustic transducer or driver, through a tube or sound bore connected thereto, to an opening near or within the user's ear canal. In such earphones, the device's overall frequency response is affected by the length and inner diameter of the tubing or bores used to direct the output of the drivers to the earpiece or tip of the device. This use of tubing or bores introduces tube resonance, affecting the frequency response of the driver connected to the tubing or bore. Tubing or bores also constrict the sound waves passed from the driver through the tube or bore, often complicating the acoustic design of the device or exerting a deleterious effect on the overall fidelity of the system.

Alternate arrangements of transducers and other components in earphones can simplify the design or construction of the device, or improve its sound-reproduction fidelity. These benefits may be of significant value in this field.

SUMMARY

Embodiments of the invention are multi-transducer in-ear monitors, earphones or canalphones, where at least one audio transducer is an indirect-radiating balanced armature that delivers its sound waves through a hole, slot, tube or bore, and at least one other audio transducer is a direct-radiating balanced armature that radiates its sound waves directly into a closed and substantially sealed airspace adjacent the first balanced armature's hole, slot, tube or bore. A main chamber of the earphone shell contains at least one front-vented driver placed with no direct coupling to other such drivers or to the ear canal. A ported chamber containing a front-vented driver may be connected to the main chamber; such ported chambers may be used to tune the response of particular drivers and frequency ranges. Sound combines in the main chamber before passing into the ear canal through a hollow sound stem. One or more front-vented high-frequency drivers may also be placed in the hollow sound stem for high-frequency emphasis. An embodiment may also contain one or more dynamic (moving coil) drivers.

DETAILED DESCRIPTION

FIG. 1is a simplified cutaway drawing of an embodiment of the invention, shown in place in a user's ear. An embodiment comprises a housing100(shell shown in crosshatching), generally with an enlarged portion105that rests in the user's outer ear (auricle cross-section at110), and with a protrusion or stem115extending into the user's outer ear canal120. The protrusion115is substantially sealed to the outer ear canal (it is typically either custom-molded to fit or provided with a compressible foam covering around the protrusion) to form a closed volume including the inner portion of the ear canal125and the airspace inside housing100(e.g. at130). The volume is closed on the other end by the user's tympanic membrane (eardrum),135. The volume may be vented by an acoustically opaque vent140which allows air to enter or escape slowly, improving insertion and removal comfort while not appreciably affecting the sound reproduction capabilities of the system.

The housing100may include interior partitions145to improve structural integrity and provide secure mounting points for components such as an electronic crossover network150, which separates an electrical audio signal into sub-parts suitable for driving multiple audio transducers (“drivers,” “speakers”) contained within the housing. In prior-art earphones, and in embodiments of the invention, a driver155may be of the balanced-armature type, where the electromechanical mechanism is mostly or fully enclosed within a modular shell, said shell having a small “snout” or “spout” through which sound is emitted. (Instead of a spout, some balanced armatures emit sound through a hole or slot in the casing. A spout, as shown here, facilitates the attachment of a tube to carry sound waves from the transducer to another location within the housing.)

In the illustrated embodiment, sound from transducer155enters a tube165(or, in some embodiments, a bored channel or “bore” formed through portions of the housing). Tube165may terminate short of the end of the protrusion (170, end of protrusion at175); or may extend near the end of the protrusion (dashed extension180). The end of the protrusion may be covered by an acoustically-transparent mesh or screen185to protect the components inside housing100from damage or debris.

In an embodiment, at least one balanced armature190is disposed within housing100, and emits its sound waves directly into the airspace130(as indicated by arrow195)—these sound waves do not escape from the balanced armature's shell through a hole, slot or spout, and are not carried through a tube or bore. The sound-emitting diaphragm of this balanced armature is exposed and visible. This direct-radiating transducer may be within an enlarged portion of the housing and directed toward the ear canal and eardrum, as shown here, or one or more direct-radiating transducers may be placed within the protrusion and directed transversely across the ear canal. Some embodiments may include multiple tube-connected acoustic drivers and multiple direct-radiating acoustic drivers. Embodiments may also include acoustic transducers of other types, such as a moving-coil or “dynamic” driver, or an electrostatic driver.

Typically, the multiple audio transducers of an embodiment reproduce different audio frequency ranges, such as high frequencies, mid-range frequencies, and low frequencies. An input audio signal is separated into a suitable number of frequency ranges by the electronic crossover network, and the sub-portions of the signal are coupled to the appropriate audio transducer. An embodiment may use direct-radiating drivers for one frequency range and indirect-radiating drivers for another range. Alternatively, a frequency range may be supplied to both direct-radiating and indirect-radiating drivers. It is understood that the frequency ranges are not entirely distinct—for example, some sound energy at the upper or lower end of the middle frequency range may be produced by a transducer that is principally relied upon for high- or low-range reproduction.

FIG. 2shows a partial cutaway, perspective view of an embodiment of the invention.FIG. 3is a shaded view of substantially the same embodiment from a slightly different angle, shown inserted in a user's ear. InFIG. 2, the outer shell205holds several audio transducers: direct-radiating balanced armature250, dynamic (moving coil) bass driver290, and tube-coupled balanced armature255. The direct-radiating balanced armature250emits sound waves from its exposed-and-visible diaphragm252directly into the interior airspace230(which is contiguous with the airspace adjacent the user's eardrum, refer toFIG. 1, 125). (It is appreciated that dynamic bass driver290also radiates sound from an exposed-and-visible diaphragm surface [although that surface is not visible from this vantage point]. But bass driver290is of a different type; it is not a balanced armature.)

In contrast to the direct-radiating balanced armature250, tube-coupled balanced armature255emits sound through a snout at260, and the sound travels through tube265before entering the interior airspace230. As mentioned with reference toFIG. 1, tube265may extend most or all of the way down the stem, as shown here, or it may terminate short of the end of the stem. Thus, the sound waves in tube265travel adjacent to, but separated from, the sound waves radiated directly into airspace230by direct-radiating balanced armature250. The portion of airspace230in the stem that is adjacent to tube265is identified by reference character275. At the far end of the stem, nearest the user's eardrum, a ring or collet285carrying an acoustically-transparent screen snaps into place to protect the drivers and electronics inside the earphone housing from debris and moisture.

FIG. 2also shows an interior partition245(dashed line), and the outside orifice240of an acoustically opaque vent that helps equalize pressure between the interior airspace230and the ambient atmosphere outside the user's ear. The back of bass driver290(i.e., the side opposite the radiating diaphragm) is also vented to the atmosphere through an orifice293. The vent tube may be provided with a tuned filter (e.g. at296), to control the low frequency response of the device.

InFIG. 3, some corresponding elements are visible: the outer shell305, the outer orifice of the acoustically opaque vent340, a direct-radiating balanced armature350and the back side of bass driver390(and also its vent orifice393). Also visible in this Figure is an electrical connection320through which electrical power and/or audio signal can be coupled to the earphone. (Note that bothFIGS. 2 and 3are shown without the back cover that mostly closes the shell and creates the enclosed airspace within the earphone and adjacent airspace within the user's ear canal.

FIG. 4shows another embodiment, similar to that ofFIG. 2(e.g., housing205; direct-radiating balanced armature250; dynamic driver290), where another direct-radiating balanced armature450is placed in the open airspace of the stem so that the sound waves it radiates from its exposed diaphragm455, across the stem airspace, combine with the sound waves from other audio transducers250and290. In this embodiment, indirect-radiating balanced armature255emits sound waves through a short tube260, so they enter the open airspace sooner than inFIG. 2. This Figure also shows that a mounting fitting or fixture445may be used to hold direct-radiating and tube-coupled transducers in a predetermined spatial relationship.

FIG. 5shows a typical modular balanced armature500, which comprises a case510, electrical contacts520&530, and a radiating surface (diaphragm)540from which sound waves are emitted. Some modular balanced armatures further comprise a cover over the radiating surface540, which contains the sound waves within the module and directs them to a predetermined exit orifice, such as a hole, slot, spout or snout. This latter type is generally referred to as a “closed” or “indirect-radiating” balanced-armature driver.

FIGS. 6A and 6Bcompare open and closed balanced-armature audio transducer modules. InFIG. 6A, likeFIG. 5, the radiating surface640is exposed and visible, and sound waves are radiated roughly perpendicularly to the surface (650). InFIG. 6B, radiating surface640is covered by a cover or shell660, which confines the sound waves radiated from640and forces them to travel through an opening in the shell at spout670(and through optional tube extension680), as shown by dashed line690. In the module ofFIG. 6B, cover660conceals radiating surface or diaphragm640completely, so that it is not visible through spout670. However, an embodiment may comprise a balanced-armature audio transducer module where cover660includes a hole, slot or perforations. In such a module, the sound-radiating diaphragm640may be partially visible, but the sound waves must still pass through the hole, slot or perforation to exit the module. In contrast, in an open and direct-radiating balanced-armature audio transducer, all (or substantially all) of the diaphragm is visible (FIGS. 5 & 6A). An embodiment of the invention is a headphone or earphone comprising both types of balanced-armature transducers (direct-radiating and slot-, hole-, tube- or bore-coupled).

FIG. 7shows a partially cut-away view of another embodiment700, being worn by a user. The headphone in this figure is provided with a cover705that substantially seals the airspace inside. The enlarged portion of the embodiment rests, at least in part, in the user's outer ear710. The protrusion or stem720extends into an outer portion of the user's ear canal and seals thereto, creating a substantially sealed airspace inside the user's ear canal (730). At the far end of the ear canal, the user's tympanic membrane740and middle/inner ear anatomical structures750are found. Within embodiment700, both direct-radiating and tube- or slot-radiating balanced armatures (transducers) convert electrical signals into sound waves, which enter the user's ear canal and can be heard. Since the ear canal is substantially sealed, sounds and noise from the external environment are attenuated or blocked.

It will be appreciated that whileFIG. 8shows one personal listening device29, a pair of devices29may be worn by a user in order to reproduce sound in both ears. The two devices may be physically identical, but more often they will be constructed as complementary, roughly mirror-image pairs to suit the user's left and right ears.

In an embodiment, personal listening device29does not include any sound tubes or bores extending from the one or more drivers3,9,13to the tip16of the device29. By eliminating the sound tubes or bores used in traditional personal listening devices, personal listening device29reproduces sound to the user's ear drum without the undesirable effects of tube resonances, such as those shown in prior artFIG. 11(curved arrows inside tube44).

In an embodiment, the housing1may be divided into two or more chambers6,2via one or more walls7. In an embodiment, wall25may also be included which separates chamber2from stem12, forming another chamber40. Housing1may have as many walls7,25as necessary to produce the desirable frequency response from the personal listening device29. In another embodiment, the housing1may be one single air space, without any walls, such that only one chamber is present.

In an embodiment, the one or more chambers6,2,40may hold one or more drivers3,9,13. Furthermore, changing physical dimensions of these the one or more chambers6,2,40and the location of these chambers6,2in respect to chamber40give each driver(s) that are contained in that chamber preferred sound characteristics. For example, for a driver9that insufficiently reproduces frequencies above 4 kHz, a chamber6of proper dimensions may be formed by placing a wall7in housing1with a thin opening8to a passive radiator19(as shown inFIG. 10). Wall7and any additional walls used in the housing1may either be integrated with the housing1or may be formed from a separate piece that is attached to housing1. Opening8may be created by a gap between wall7and the passive radiator19, as shown inFIG. 10, or it may be created by a gap between wall7and any side of housing1. In an embodiment which does not include passive radiator19, opening8may be created by a gap between wall7and faceplate28, or it may be created by a gap between wall7and any side of housing1. In an embodiment, opening8may be created by perforating less than an entire portion of wall7with very small perforations.

Vent20may be a predetermined size or be a variably sized port that allows for introduction of ambient sound into the system.

In an embodiment, housing1includes driver3, which may be of any frequency response. In an embodiment, driver3is a low frequency driver. Driver3may be any type of driver, such as balanced armature, moving coil, dynamic, piezoelectric, planar, electrostatic, or any other type of driver. In an embodiment, driver3is a dynamic driver.

In an embodiment, the one or more chambers2,6,40of housing1may be lined with acoustically absorptive or dampening material such as foam, silicone, fiber, or the like. In an embodiment, the acoustically absorptive or dampening material may be open cell foam. By lining the one or more chambers2,6,40with this material acoustically absorptive or dampening material, the amount of reflections and resonances within the lined chamber2,6,40may be controlled. In an embodiment with two or more chambers, fewer than all of the chambers may be lined with said acoustically absorptive or dampening material. In another embodiment with two or more chambers, all of the chambers may be lined with said acoustically absorptive or dampening material.

In an embodiment, a personal listening device29with two or more chambers2,6,40, the output from the one or more drivers located in a particular chamber may bleed or exit into another chamber via an opening or slot8between the chambers. For example, in the embodiment personal listening device29shown inFIGS. 8-10, the output from driver9located within chamber6may bleed or exit chamber6into chamber2via opening8. That output from driver9may then combine in chamber2with the output from driver3, and the combined output from both drivers9,3may then bleed or exit opening41through cone11and into sound stem12. From sound stem12, the combined output may then exit the personal listening device29and, when the personal listening device is worn by a user, enter the user's ear canal.

In an embodiment, filter15is made of a soft screen with very tight weave. Filter15may be waterproof to prevent sweat and other moisture from entering the system. In an embodiment, personal listening device29further includes an external screen26placed at or near the tip16of the device29. External screen26may be included to protect filter15from punctures, earwax and other elements. External screen26may be rigid and may be made of plastic, stainless steel, or similar material capable of protecting filter15from being damaged or punctured.

In an embodiment, one or more drivers in the housing1may be back-vented. In an embodiment, driver3is a back-vented driver. To back-vent driver3, tube4is attached to the back vent of the driver3and “exhausted” through vent5to the outside environment of the housing1. By back-venting driver3, the diaphragm of the driver3is able to move more freely. In an embodiment, back-vented driver3is a low frequency driver, such that back-venting driver3allows for the diaphragm of the back-vented driver3to move more freely at low frequencies and therefore improve the low frequency response of back-vented driver3.

An embodiment personal listening device29may use one or more front-vented drivers, one or more back-vented drivers, or any combination of front-vented and back-vented drivers. A driver may be both front-vented and back-vented.

According to various aspects of the invention described above and illustrated inFIGS. 8-10, an embodiment personal listening device29is capable of reproducing sound via one or more drivers to a user without the use of any sound tubes or bores running from the one or more drivers to the tip16of the device29. By omitting any sound tubes or bores, the sound quality of the device29is improved, and the linearity to the frequency response of the drivers is restored, reducing resonant peaks and distortion.

Turning back to the prior art combination43shown inFIG. 11, when a tube44is connected to a driver45, even with small lengths, the tube introduces tube resonance, which is a multitude of peaks and valleys in the frequency response of the driver45connected to the tube44. Furthermore, tubes increase the velocity of the sound pressure traveling through them. The sound is concentrated down a small tube and is only released after it escapes from the tip of the tube. This constriction on the sound waves in the tube has a negative effect on the overall fidelity of the system, and is audible. Tubes may also easily get clogged with ear wax and other debris.

However, according to various aspects of the invention described above and illustrated inFIGS. 8-10, the open-air system of the personal listening device29embodiments described herein allows for the sound to immediately scatter or fan out once it leaves its origin, i.e., the surface of the driver diaphragm18. By omitting all sound tubes or bores, tube resonance is eliminated.

Also disclosed is a method of tuning a personal listening device29according to aspects of the invention. The method includes selecting the one or more drivers to be placed in one or more chambers in the housing1. In another embodiment, the personal listening device29may have more than one driver, which are all placed within a single chamber in the housing1. In another embodiment, the personal listening device29may have more than one driver3,9,13which are each placed within their own chambers6,2,40in the housing1. In another embodiment, the personal listening device29may also include one or more drivers13placed within the stem12of the personal listening device29; the stem12may either be integrated with the housing1or may be formed from a separate piece that is attached to housing1. In an embodiment, the device29may include wall25such that the one or more drivers13located in stem12are in an additional chamber40.

In a personal listening device29including two or more chambers2,6, the method may further include using the size of the one or more chambers2,6to tune the one or more drivers9,3and to tune the overall personal listening device29. For example, in an embodiment personal listening device29, chamber2may be sized to be larger than chamber6, thereby lowering the high frequency extension of that chamber (seeFIG. 9). In another embodiment, chamber2may be sized to be smaller than chamber6, thereby raising the frequency response cutoff point of that chamber. Just like speaker boxes require proper dimensions for a given transducer, changing the physical dimensions and reflective properties of the chamber will have a direct impact on the frequency response of the one or more drivers contained in that chamber.

In a personal listening device29including two or more chambers2,6, the method may further include using the location of each chamber within the housing1to tune the one or more drivers9,3and to tune the overall personal listening device29. The location of each chamber is determined by how close the chamber needs to be to the last chamber40to produce a desired frequency response.

The method may further include orienting the one or more drivers3,9,13in a direction within the one or more chambers6,2,40that yields a sonically pleasing result. For example, in an embodiment personal listening device29which includes drivers3,9and chambers6,2(FIG. 9), driver3may be positioned in chamber2such that the output of driver3is aimed toward the stem12, and driver9may be positioned in chamber6such that the output of driver9is aimed toward wall7. By positioning drivers3,9in this manner, one is able to correct for frequency response deficiencies inherent in the driver.

In an embodiment wherein one or more drivers13are placed in the stem12of the personal listening device29, the method may further include partially sectioning off the stem12with wall25to create an additional chamber40for the one or more drivers13placed in the stem12(seeFIG. 8). In an embodiment, driver13may be a high frequency driver and that is placed directly in stem12, and stem12may be partially sectioned off with wall25to create a dedicated high frequency chamber to improve the high frequency driver performance.

Acoustical tuning may alternatively include, or may also include, placing damping material such as open cell foam on or over the front vent10of one or more drivers, lining one or more chambers with this damping material, or tensioning or loosening the passive radiator19. The passive radiator19acts as a controlled transducer as it transfers sound from one chamber to the next. In an embodiment device29which includes a faceplate28(seeFIG. 10), passive radiator19also prevents resonances from building up in the device29because of the close proximity of the faceplate18, which sits over the one or more chambers2,6, to the one or more drivers3,9.

The method may include changing the overall size of the housing1. For instance, if the housing1is decreased in size, the individual components in the housing1are positioned closer together, whereas if the size of the housing1is increased it will cause the individual components to be more spaced apart. Changing the spacing of the individual components within the housing will have an effect on the frequency response, phase response, and overall sound presentation of the personal listening device29.

The method may include using the height of the one or more walls8,25to tune the one or more drivers3,9,13and the overall system. For instance, in an embodiment personal listening device29with chambers6,2and drivers9,3(seeFIG. 9), driver9may be tuned by including an opening8between the chambers6,2. In an embodiment personal listening device29further including driver13positioned in stem12(seeFIG. 9), drivers9,3may be tuned by including an opening41between chamber2and cone11(seeFIG. 9). Openings8and/or41act as a frequency shaping wave guide, and thus may be used to tune the frequency response of the driver or drivers that output sound through the opening8,41. In another embodiment, walls7may instead be coextensive with passive radiator19, i.e., there may be no opening8between chamber6and chamber2.

In an embodiment, opening8may be a relatively long and narrow slot created by the gap between wall7and passive radiator19(seeFIG. 10). Alternatively, opening8may be a slot created by a gap between wall7and any side of housing1. In an embodiment, opening41may be a slot created by the gap between wall25and the side of cone11(seeFIG. 8). In an embodiment, opening8may be created by perforating less than an entire portion of wall7with very small perforations. In an embodiment, opening41may be created by perforating less than an entire portion of wall25with very small perforations. In an embodiment with more than one wall7,25, each of the more than one walls7,25may include an opening8,41. In another embodiment with more than one wall7,25, less than each of the walls7,25may include an opening8,41. In an embodiment, the one or more openings8,41may be covered or stuffed with acoustical foam or other similar material to further control the frequency. In another embodiment, there may be no opening8between chambers6and2.

The method may further include shaping the overall frequency response of the system using a filter15inserted in stem12or attached to stem12. In an embodiment, once the one or more individual drivers have been tuned, filter15can be inserted close to the tip16of the stem12. Filter15can be used to further eliminate any resonances that have been created in the system and to control the mid, mid-high and high frequencies. The method may further include adding an external screen26with which to protect filter15from damage.

The method further includes placing a passive radiator19in the housing1such that the passive radiator19is positioned over top of all chambers6,2and can ultimately deliver sound to the sound stem12of the device29.

The method further includes covering the housing1with a faceplate28, the faceplate included to reject external sounds and noise from the system and also protect the passive radiator19from damage.

The method may further include using one or more of the chamber size, the wall height, and/or the location of each chamber within the housing to tune the drivers9,3,13. The method may further include changing the overall size of the housing1to affect the frequency response, phase response, and overall sound presentation of the personal listening device29.

The method may further include tuning driver9by including an opening8between chambers6and2. The method may further include tuning drivers9and3by including an opening41between chamber2and cone11. The method may further include covering or stuffing one or more openings8,41with acoustical foam or other similar material to further tune the drivers.

An audio reproduction device according to an embodiment of the invention may include several distinguishing features, such as a housing suitable for positioning near a user's outer ear, said housing comprising a protrusion configured to extend at least partially into an outer portion of the user's ear canal and to substantially seal the ear canal; a first balanced armature configured to emit first sound waves, said first sound waves conducted to the substantially sealed ear canal by a tube within the protrusion; a second balanced armature configured to emit second sound waves, said second sound waves radiated directly into an interior of the housing; and an electronic crossover network to receive an electrical signal and deliver a first portion thereof to the first balanced armature, and a second portion thereof to the second balanced armature. Such a device might optionally be characterized by the second balanced armature being positioned to emit said second sound waves toward the user's eardrum. Such a device might optionally be characterized by the second balanced armature being positioned to emit said second sound waves transversely across the user's ear canal. Such a device might optionally be characterized by the tube carrying the first sound waves being adjacent the interior of the housing where the second sound waves travel. Such a device might further comprise at least one additional acoustic driver configured to emit sound waves into the substantially sealed ear canal. Such a device might optionally be characterized by the at least one additional acoustic driver being a dynamic driver. Such a device might further comprise an acoustically opaque vent to allow air to enter or escape the substantially sealed ear canal. Such a device might further comprise a wall to divide the housing into at least one chamber containing the second balanced armature, said at least one chamber lined with an acoustically absorptive material.

Another audio reproduction device according to an embodiment of the invention may include several distinguishing features, such as a housing having a protruding stem suitable for entering and substantially sealing to a user's outer ear canal, an interior volume of said housing and protruding stem thus forming a substantially closed airspace adjacent the user's eardrum; a first balanced-armature audio transducer module to emit first sound waves, said first sound waves exiting the transducer module through an opening in a casing thereof; a second balanced-armature audio transducer to emit second sound waves, said second sound waves emitted directly into the interior volume of the housing from a diaphragm that is exposed and visible; and an electronic crossover network to receive an electrical signal and deliver a first portion thereof to the first balanced-armature audio transducer module, and a second portion thereof to the second balanced-armature audio transducer. Such a device might optionally be characterized by the first sound waves traveling through a tube coupled to the first balanced-armature audio transducer module before entering the substantially closed airspace adjacent the user's eardrum. Such a device might optionally be characterized by the first sound waves traveling through a bore formed in the housing before entering the substantially closed airspace adjacent the user's eardrum. Such a device might optionally be characterized by a diaphragm of the first balanced-armature audio transducer not being visible through the opening in the casing. Or the device might optionally be characterized by a diaphragm of the first balanced-armature audio transducer being visible through the opening in the casing. Such a device might optionally be characterized by the housing being divided into at least two chambers by at least one wall, a configuration of at least one chamber chosen with respect to a sound characteristic of a driver disposed within the at least one chamber.

Yet another audio reproduction device according to an embodiment of the invention might include several distinguishing features, such as a housing having a protruding stem suitable for entering and substantially sealing to a user's outer ear canal, an interior volume of said housing and protruding stem thus forming a substantially closed airspace adjacent the user's eardrum; a first balanced-armature acoustic transducer to emit first sound waves from a radiating diaphragm and into an enclosed shell, said first sound waves exiting the first balanced-armature acoustic transducer through an opening in the enclosed shell; a direct-radiating balanced-armature acoustic transducer to emit second sound waves, said second sound waves emitted into the interior volume of the housing adjacent the first balanced-armature acoustic transducer; and an electronic crossover network to receive an electrical audio signal and deliver a first portion thereof to the first balanced armature acoustic transducer and a second portion thereof to the direct-radiating balanced armature acoustic transducer. Such a device might further include a moving-coil audio transducer within the housing, said moving-coil audio transducer receiving a third portion of the electrical audio signal from the electronic crossover network and emitting corresponding third sound waves into the substantially closed airspace adjacent the user's eardrum. Such a device might optionally be characterized by the moving-coil audio transducer comprising a back vent communicating with an atmosphere outside the substantially closed airspace adjacent the user's eardrum. Such a device might optionally be characterized by the back vent including a tuned filter to control a low-frequency response of the moving-coil audio transducer. Such a device might further include an acoustically-opaque vent to permit air to enter or escape slowly from the substantially closed airspace. Such a device might further include an acoustically transparent screen at an end of the protruding stem.

The applications of the present invention have been described largely by reference to specific examples and in terms of particular arrangements of components and structures. However, those of skill in the art will recognize that earphones comprising direct-radiating transducers can also be constructed in various alternate forms and arrangements. Such variations and alternate arrangements are understood to be captured according to the following claims.