Loudspeaker and manufacturing method thereof

The present invention provides an improved loudspeaker enclosure comprising two opposing end sections arranged at a distance from each other and enclosing sections which connect the end sections over said distance, wherein the inner volume of the enclosure is defined by said sections. The enclosure also has a reflex port which comprises a reflex opening which is provided to the enclosure and adapted to exhaust internal pressure from the inner volume to outside the enclosure. The reflex port further comprises an inner reflex port former which connects the inner volume of the enclosure to the reflex opening for forming the reflex port. The reflex port former is formed by molding as an integral inner wall section which extends inwards from the inner surface of either or both end section. On the other hand the reflex port former extends adjacent to an enclosing section which at least partially surrounds the reflex port former such that the reflex port is formed to a space between the reflex port former and the adjacent enclosing section.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a national stage application filed under 35 USC 371 based on International Application No. PCT/FI2013/050355 filed Apr. 2, 2013, and claims priority under 35 USC 119 of Finnish Patent Application No. 20125374 filed Apr. 2, 2012.

BACKGROUND

The present disclosure relates to loudspeakers. In particular, the disclosure relates to injection molded loudspeaker enclosures.

Loudspeaker enclosures are typically somewhat prismatic chambers provided with openings for receiving drivers. Most commercial loudspeaker enclosures can be divided into two main categories: junction structures and molded structures. Junction structures are typically assembled from laminar wall sections that form a prismatic loudspeaker enclosure. The front panel forms a mounting portion of the loudspeaker to which portion the drivers are attached. The panels of junction structure loudspeakers are typically made of natural wood or wood materials such as MDF, which comprises wood fibers combined with wax and a resin binder. Other materials are also known.

However, junction structures are limited to prismatic shapes without extensive manufacturing efforts to create arched shapes. Furthermore, junction structures require a considerable number of assembly steps to complete an enclosure. In most cases, junction structures also require additional enforcement members for establishing sufficient rigidity.

Accordingly, molded structures have been developed for establishing a rigid enclosure with fewer parts. Molded structures typically feature an enclosing mounting portion, which has a front section and integral side, bottom, and top sections extending rearward from the front section. The mounting portion therefore defines a volume that forms part of the inner volume of the loudspeaker. A molded structure also comprises a supplementary portion, which is attached to the rear end of the mounting portion for closing the loudspeaker enclosure. The supplementary portion may be a flat panel but it may also be shaped to define a volume that that forms a part of the inner volume of the loudspeaker when the two portions are assembled. The supplementary portion is typically provided with terminals for the loudspeaker cables as well as heat sink protrusions for cooling the enclosure in active loudspeaker applications. Indeed, molded structure enclosures are common in active loudspeakers as it is convenient to shape the enclosure to conduct heat away from the embedded amplifier. Pressure casted aluminum and alloys thereof are considered as preferred materials in the field of molded structure loudspeaker enclosures due to strength and heat conductivity of aluminiferous materials.

Conventional molded loudspeaker enclosure structures are usually provided with reflex ports in subsequent manufacturing steps. Reflex ports are formed, for example, by forming a hole to the back plate of the loudspeaker and attaching a tubular member to the hole extending inward for exhausting internal pressure shocks and for extending the response curve in low frequencies. It has been considered preferable to direct the reflex port emissions away from the sound fronts emanating from the drivers of the loudspeaker. Accordingly, reflex ports are designed to open to the rear of the loudspeaker, which yields several benefits compared to front baffle installations. The front baffle is usually designed to be as small as possible for aesthetic reasons but also because the area is needed for drivers. It is therefore beneficial to place the port somewhere other than the front baffle. Placing the reflex port at the front baffle would create a hole close to the sound sources, i.e. drivers, thus forming an acoustical discontinuity which would cause diffraction. Furthermore all tubes have a half wave resonance. Placing the port near the drivers maximizes the excitation of the tube resonance. For high sound pressure levels, the high air velocity in the port causes wide spectrum noise caused by turbulence of the air. It is beneficial to direct the noise source away from the listener.

Because reflex ports require subsequent manufacturing steps, attempts have been made to manufacture them as an integral part of the baffle portion of a molded loudspeaker. In known structures, the reflex port opens to the front of the loudspeaker, which is not especially advantageous for reasons explained above.

SUMMARY

Disclosed is a novel loudspeaker enclosure comprising two opposing end sections arranged at a distance from each other and enclosing sections which connect the end sections over that distance, wherein the inner volume of the enclosure is defined by the sections. The enclosure also has a reflex port that comprises a reflex opening provided to the enclosure and is adapted to exhaust internal pressure from the inner volume to outside the enclosure. The reflex port further comprises an inner reflex port former connecting the inner volume of the enclosure to the reflex opening for forming the reflex port. The reflex port former is formed by molding as an integral inner wall section which extends inwards from the inner surface of either or both end section. On the other hand, the reflex port former extends adjacent to an enclosing section that at least partially surrounds the reflex port former such that the reflex port is formed to a space between the reflex port former and the adjacent enclosing section.

Also disclosed is a novel method for manufacturing a baffle portion for a loudspeaker. In the novel method, a mounting section for receiving a driver is formed by molding a frontal wall section. In the same manufacturing step, enclosing sections are formed by integrally molding rearward extending and interconnected wall sections to the mounting section such that the enclosing sections protrude rearward from the inner surface of the mounting section and define therebetween a volume, which forms at least part of the inner volume of the loudspeaker. A reflex port is further formed in the same manufacturing step by molding an integral reflex port former as an inner wall section which extends from the inner surface of the mounting section rearward as a substantially parallel protrusion to the side enclosing sections. Accordingly, the reflex port, which is formed to a space between the reflex port former and an adjacent enclosing section, opens to the outside of the baffle portion and away from the mounting section.

Considerable benefits may be gained using the teachings of the present disclosure. Because the reflex port is formed during the molding of portion of the loudspeaker enclosure, no subsequent manufacturing steps are required. Simultaneously, the reflex port may also be directed to open away from the drivers removing the above explained disadvantages caused by exhausting reflex pressure in front of the loudspeaker.

With the novel construction and method, it is possible to produce a reflex port that is curved, wherein the port may have a dimensioned long length, which helps the acoustics of the loudspeaker. Moreover, the construction provides improved sound reproduction in low frequencies, as the reflex port may be dimensioned with a length sufficient to significantly extend the response curve.

The novel design yields yet another benefit in that the reflex port former protruding from the end section of the enclosure acts as an auxiliary stiffening bar that makes the enclosure more rigid, further improving sound characteristics of a molded loudspeaker enclosure.

The foregoing and other objectives, features, and advantages of the disclosure will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION

In this context the term forward direction refers to the direction to which sound waves primarily radiate from the speaker. Conversely, the term rearward direction refers to the opposite of forward direction. Respectively, the terms front and rear represent the sides of the speaker that are in the direction of forward or rearward directions, whereas sides are orthogonal to the front and rear faces of the enclosure. Furthermore, the term axial is used herein to describe the dimension in which the sound waves radiate either forward or rearward.

The baffle portion100according to one embodiment of the invention extends backward such that it forms at least part of the total inner volume of the loudspeaker1, e.g., at least 50 percent. In the embodiment presented in the appended figures, the baffle portion100encloses the entire inner volume of the loudspeaker1, whereby the loudspeaker1is closed by a planar closing section300. A bordering ridge122has been provided to the rear of the enclosing portions for creating an embedding for a rear plate300for closing the baffle portion100and forming the loudspeaker1. The closing section300may also form part of the inner volume, whereby the rear plate would be provided with forward-extending wall sections (not shown), which enclose an inner volume and which engage with respective wall sections of the baffle portion100.

The baffle portion100comprises a mounting section110, which is provided with an opening for receiving a driver200. The mounting section110is in the illustrated embodiment provided to the front end of the baffle portion100and has two openings for forming a two-way loudspeaker. While the disclosure is explained and illustrated in the drawings as a two-way loudspeaker embodiment, the disclosure is also applicable to loudspeaker enclosures designed for only one driver, a coaxial driver, or any other setup comprising at least one driver. Accordingly inFIGS. 1 to 3, the first opening is provided with a mid-frequency driver201and the second opening is provided with a high-frequency driver202. The baffle portion100is made by molding, such as by injection molding. Accordingly, the baffle portion100is an integral piece having a frontal wall section and lateral wall sections extending backward from the frontal wall section. In particular, enclosing sections120,130, and140are integrally formed to the mounting section110such that said sections110,120,130, and140, enclose the inner volume of the loudspeaker1or at least a portion thereof. The enclosing sections include enclosing top and bottom sections130and140, which extend rearward from the mounting section110. The substantially parallel top and bottom sections130and140are spaced-apart to create a height for the loudspeaker1. The enclosing sections further include two mutually and substantially parallel side sections120which extend rearward from the mounting section110and are spaced apart to create a width for the loudspeaker1. When viewed from the top enclosing section130of the baffle portion100, the enclosing side sections120extend beyond the enclosing bottom section140and are bent toward each other. Resulting bottom extensions121of the enclosing side sections120create stands for providing a gap between the bottom section140and the platform on which the loudspeaker1is to be placed. The bottom extensions121are therefore flat and wide enough to provide sufficient support.

As can be seen fromFIG. 2, the baffle portion100comprises an inner reflex port former150, which is formed integrally by molding as an inner wall section that extends from the mounting section110rearward to the inside thereof. The reflex port former150is formed similarly to the enclosing sections120,130, and140, which extend rearward from the inner surface of the frontal mounting section110. Accordingly the reflex port former150is molded as a substantially parallel protrusion to the side enclosing sections120at a distance on the inside thereof. Accordingly, the reflex port former150forms a reflex port160that opens to the outside of the baffle portion100and away from the mounting section110. The reflex port160is therefore formed to a space between the reflex port former150and an adjacent enclosing section120. It would be possible to provide another parallel reflex port former (not shown) between the reflex port former150and the side enclosing section120, wherein the reflex port160would be formed between the two reflex port formers. The reflex port160would however in any case be formed to the space between the reflex port former150and the adjacent enclosing section with or without an extra reflex port former.

In the illustrated embodiment, the baffle portion100comprises two reflex port formers150, which form two respective reflex ports160. The driver opening in the mounting section110has a plane that has a normal axis. The inner reflex port formers150are shaped to at least partially surround the normal axis of the driver opening. This results in curved reflex ports160, which follow the inner surface of the side enclosing sections120and surround the rear part, i.e. the inner components such as magnets, of the drivers201,202. The curvature of the reflex ports160is further amplified by starting camber151in the free top end of the reflex port former150. The reflex port former150terminates to another camber at the other end thereof where the former150merges to the bottom enclosing section140. The reflex ports160thus open to the outside of the loudspeaker1. As described above, bottom extensions121of the enclosing side sections120create stands, which provide a gap between the bottom section140and the platform on which the loudspeaker1is to be placed. Accordingly, the reflex port160opens, i.e. terminates, to the gap. In other words, the reflex ports160open to the inner flanks of the stands formed by vertical overhangs of the side enclosing sections120. More precisely the reflex port formers150terminate to the inner surface of the bottom enclosing section140, whereby the reflex port160terminates to a slit between the extension121of an enclosing side section120and the bottom enclosing section140(FIG. 3).

As mentioned above, the loudspeaker enclosure1according to the present disclosure may also be established in manner deviating from the construction illustrated inFIGS. 1 to 3. For example, according to one embodiment, the rear portion of the enclosure may also form part of the inner volume, whereby the rear plate would be provided with forward-extending wall sections (not shown), which enclose an inner volume and which engage with respective wall sections of the baffle portion100. In such an embodiment (not shown) a supplementary portion is formed, whereby the enclosure1has two opposing portions: a baffle portion100and a supplementary portion. The baffle portion may be similar to that described above. The supplementary portion would therefore also be made by molding, such as by injection molding. By contrast to a mere planar back plate, the supplementary portion according to the embodiment not shown comprises a closing section as described, but which comprises integral lateral wall sections extending forward therefrom. In particular, enclosing sections are integrally formed to the closing section such that the sections enclose an inner volume of the loudspeaker enclosure1or at least a portion thereof. The enclosing sections correspond to those explained above. The supplementary portion also comprises a reflex port former, which is an integral extension of the closing section opposing the mounting section. The reflex port former therefore protrudes inwards from the closing section, i.e. forward.

The supplementary portion may form a portion of the inner volume of the loud-speaker enclosure, whereby the baffle portion forms the remaining portion of the inner volume. It is also possible to form the entire inner volume with the supplementary portion, whereby the baffle portion consists of a front plate. According to one embodiment, the baffle portion and the supplementary portion each form about 50 percent of the inner volume of the enclosure. In some embodiments, where both portions define the inner volume of the enclosure, the reflex port is formed by two mating reflex port formers, wherein one reflex port former is provided to the mounting section and the other is provided to the closing section. The mating reflex port formers are designed to engage such that the reflex port is formed through a tight enough joint to prevent pressure shocks from escaping the reflex port through the interface of the mating reflex port formers.

As mentioned above, the baffle portion100is made by molding, injection molding. The enclosing sections120,130, and140as well as the reflex port former150are formed by feeding material into the mold through the mounting section110, wherein the enclosing sections120,130, and140and the reflex port former150protrude from the mounting section110to the inside of the baffle portion110. The feeding gate is therefore provided to the mounting section110in the molding process. As a result, the sections of the baffle portion100are integral parts of the piece rather than individual components thereof. It is therefore particularly possible to favor roundings between the enclosing sections120and130as well as in the extensions121. Furthermore, the substantially parallel side enclosing sections120as well as top and bottom sections130and140are slightly angled for promoting the ejection of the baffle portion100from the mold. The baffle portion100may be made of any material suitable for injection molding. However, it is particularly possible to use a composite material comprising thermo wood powder or pulp and polymer, reducing the need for finishing steps in the manufacturing process since such a material makes it possible to achieve adequate surface quality directly in the mold.

It is also possible to use other materials or composites in addition to, or instead of, the materials presented above. For example, it is possible to exploit composites having a combination of gypsum or talc, and polymer. Alternatively, potstone, cellulose, thermo wood and glass fiber may be used as a combination as such or combined with materials listed above.

FIGS. 4 to 7show a further embodiment where reflex ports160are formed to respective spaces that are defined by a reflex port former150, an enclosing side section120and a terminating plate400. The reflex port formers150preferably extend rearwards from the inner surface of the mounting section110to about half-way along the axial direction of the baffle portion100. The baffle portion100forms substantially the entire axial reach of the enclosure1, whereas the closing section300is a mere back plate. Alternatively, it could be possible to construct a similar terminating plate arrangement such that the enclosure1would comprise two axially extending halves, wherein the mounting section100together with the reflex port formers150would extend to about half-way along the axial dimension of the enclosure1, and the closing section300would feature a corresponding axial reach, i.e. corresponding enclosing side, bottom and top sections120,130,140(not shown). Also other axial proportions are possible.

The reflex ports160are therefore in the illustrated embodiment not closed by the closing section300but by the terminating plate400, which is parallel to the closing section300and arranged within the enclosure1to close the reflex ports160in the axial direction. The reflex port openings are provided to the bottom of the enclosure as in the embodiment ofFIG. 2. The terminating plate400enables adjustment of the volume of the reflex port160by limiting its axial length while maintaining the overall inner volume of the enclosure. This yields the benefit of being able to use one baffle portion design for a variety of different diaphragms that can be adapted to the enclosure by fine tuning the reflex port with aid of said terminating plate.

FIG. 4shows the structure of the reflex port former150without the terminating plate400. The illustrated embodiment features two opposing reflex port formers150a,150barranged adjacent to opposing side sections120and thus provides two opposing reflex ports160a,160bthat open to the space between the bottom extensions121of the opposing enclosing side sections120. The reflex port former150comprises a similar starting camber151similar to the first embodiment shown inFIGS. 2 and 4, where the starting camber151forms the inner opening for the reflex port160.FIG. 4also shows that the reflex port former150extends rearwards from the mounting section110to approximately the midpoint of the loudspeaker in the axial direction. As the reflex port160in this embodiment does not terminate to the closing section (not shown inFIG. 4), fixing points152have been provided for connecting the terminating plate400to the reflex port former150. The fixing points152may take the shape of axial bulges made to the inner surface of the reflex port former150. As the reflex port former150is molded simultaneously with the entire baffle portion100, so are the fixing points, which is advantageous in the manufacturing process. The fixing points152are threaded after molding. Alternatively, screws such as PT screws or self threading screws may be used.

FIG. 5shows the baffle portion100ofFIG. 4from a lower isometric view, and shows in greater detail the outer opening of the reflex port160. As explained above, the outer opening of the reflex port160is formed into the space between opposing bottom extensions121of the opposing enclosing side sections120. In other words, the enclosing bottom section140of the loudspeaker enclosure is upwardly recessed for providing integrated stands and creating clearance for the outer openings of the reflex ports160. Because the baffle portion100is created as one integral piece, distinguishing between different sections is a matter of semantics. Indeed, the enclosing sections120,130,140form a continuous enclosure profile (cf.FIG. 6), wherein there is a central upper recess in the bottom section140, and openings provided to the upward extending flanks of the bottom section140create the outer opening of the reflex port160.FIG. 5also shows similar bulges to those on the reflex port formers150formed to the inner surfaces of the side enclosing sections120for fixing the closing section300to the baffle portion100.

FIG. 6shows the structure of the terminating plate400. The terminating plate400is adapted to be fixed to the fixing points152of the reflex port former150. The terminating plate400therefore may have been provided with through-holes that accommodate screws. Also, the terminating plate400has been dimensioned such that it fits tightly between the opposing side sections120of the baffle portion100for avoiding leaks in the reflex port160. Once installed, the terminating plate400together with the enclosing side sections120and reflex port formers150define the profile of the reflex port160. As can be further seen fromFIG. 6, the terminating plate comprises two aligned flat rear flange portions401and a front portion402in front of the rear flange portions401as well as two corresponding beveled connecting portions403connecting the front portion402to the rear flange portions401. The terminating plate400is fixed to the reflex port former150from the rear flange portions401, whereas the connecting portions403provide frontal extension such that the front portion402engages with the driver201arranged between the reflex port formers150.

According to an alternative embodiment, the terminating plate400is substantially planar.

The assembly of the loudspeaker enclosure1is illustrated in the cross-sectional view ofFIG. 7. As illustrated, the mounting section110accommodates a high-frequency driver202and a low-frequency driver201, which is secured to the enclosure by the terminating plate400. More specifically, the low-frequency driver201is attached to the inner surface of the opening in the mounting section during assembly, when the terminating plate400is fixed to the reflex port formers150. The front portion402of the terminating plate400pushes the magnet of the low-frequency driver201forwards. An assembly spring203may be used between the low-frequency driver201and front portion402of the terminating plate400to ensure tight positioning. Also, depending on compliance of the spring, there may be a further effect of removing the resonance caused by the combination of basket and magnet.FIG. 7also shows how the rear flange portion401of the terminating plate400is aligned with the rear end of the outer opening of the reflex port160. When used to support a driver, the terminating plate400is perforated (not shown) for allowing rearward impulses created by the driver diaphragm to flow through the plate400such that the plate400induces minimal reflections or pressure peaks. The perforation also prevents division of the internal volume of the enclosure, which eliminates unwanted reflections or resonances or both.

The terminating plate400may be used for achieving further benefits. As can be seen fromFIG. 4, the plate may be used to secure the low-frequency driver201to the mounting section from the inside of the enclosure. By dimensioning the driver201, the axial length of the reflex port formers150and the plate, as well as possible additional spacers (not shown), the driver201is simultaneously locked into place when the plate is fixed to the baffle portion100during assembly. Accordingly, no fixing means are visible to the outside of the enclosure and there is one less assembly stage compared to conventional assembly.

The terminating plate may also act as a fixing point for absorption material500, such as polyester or glass wool, which is used to eliminate reflections within the enclosure that could cause coloration to the sound. The optimal placement for absorption material is at and below the horizontal plane of the port openings151inside the enclosure, as is the case in the example ofFIG. 7, wherein the terminating plate400is used for supporting the absorption material. Placing absorption above the port opening151horizontal plane would add damping to the air flow of the port. Therefore the beneficial gain of the Helmholtz resonance would be reduced. Placing the absorption at the bottom of the enclosure is not efficient because the particle velocity maxima of the first order internal modes in enclosure volume are at the center of the volume. An additional benefit of having the absorption material at the terminal of the port opening is the added damping of the air column resonance formed between the two port openings.

According to a further embodiment (not shown), the driver201and terminating plate400are both locked into place during assembly by an axial extension of the closing section300. In this embodiment, the driver201and terminating plate400are assembled into place without additional fixing means, whereby the axial extension of the closing section pushes the terminating plate400and therefore also pushes the driver201forward into correct position. It is therefore possible to assemble three components by using only one set of fixing means, such as screws, to attach the closing section300to the baffle portion100.