Sound reproduction acoustic enclosure

[57] ABSTRACT

The present invention refers to an acoustic enclosure comprising a horn having resonant portions flexibly mounted, and deflecting means at a horn end.

Claims, 6 Drawing Figures

<img file="US3687221A_D0001.tif" />

PATENTED AUG 2 9 1972

3,687,221

<img file="US3687221A_D0002.tif" />

Fig.4

Fig. 5 //V ven £!4/C HE/- PtfC/L β£/Υ£ SO/V/VARO

2y

<img file="US3687221A_D0003.tif" />

/rr/J.

3,687.221

SOUND REPRODUCTION ACOUSTIC ENCLOSURE

The present invention has reference to the technical field of sound reproduction and relates more particularly to a novel type of acoustic enclosure for a vibrating element such as a loud speaker or the like.

Known sound reproduction devices generally comprise a series or chain of members performing different functions, namely reading of the sound information as registered on a carrier, emission of a modulated signal, amplification and finally actuation of a vibrating element adapted to deliver sound radiations.

Obviously the final quality or “faithfulness” of the reproduction is in terms of the several members of which the “chain” is made up. It is therefore important that each of the elements of one and the same chain should have homogeneous functional characteristics. Now while considerable progresses have been achieved in the manufacture of recording carriers (such as records having microfurrows or stereophonic carriers) or in the production of reading or amplifying members, difficulties are encountered as regards vibrating elements to which so far no satisfactory solutions have yet been found.

Such difficulties are due to various causes among which one may cite those interferences between radiations emitted by the opposite faces of vibrating elements, also the formation of stationary waves in the enclosures and parasitic resonance phenomena which are generated in the walls of the casings or horns associated with the vibrating elements.

Known solutions for remedying such disadvantages (baffles, closed housing, anti-resonance enclosure, etc.) lead to complicated constructions the manufacturing cost of which is high or to very simple and cheap constructions the acoustic quality of which is generally poor. Moreover the quality of such equipments is always in terms of the volume of those enclosures that are used, which leads to fairly cumbersome stock.

The present invention has for its chief object the provision of an improved acoustic enclosure based on a complex conception but lending itself to an easy and cheap manufacturing possibility and which permits, moreover, with a limited volume to obtain a sound reproduction the quality of which is equal or better than the results that may be now obtained when using the best known equipements i.e., those having the largest size and of maximum costs.

Another object of the invention is to provide an acoustic enclosure or chamber permitting the achievement of a better efficiency and “brightness” of the vibrating elements by comparison with the characteristics obtainable with the same vibrating elements as used on conventional acoustic enclosures.

A further object of the invention considered according to its most general principle, is to provide an acoustic enclosure essentially characterized by the combination of at least one vibrating element, a horn and at least a deflecting member all located within the enclosure having at least one vent and so mutually arranged that the radiation emitted by the face of the vibrating element directed toward the inside of the enclosure undergoes from said deflecting member a change of shape and direction permitting said radiation to travel through the horn and to escape through the enclosure vent as an audible wave in phase with the radiation emitted by the face of the vibrating element directed toward the outside of the enclosure.

A more specific object of the invention is to provide an acoustic enclosure as above-stated wherein the horn is constituted by a blade of great length wound spirally and yieldingly or flexibly fitted between two opposite 5 faces of the enclosure, the horn thus shaped being preferably exponential, its flexible mounting enabling it freely to acquire a resonant condition so that such horn fulfills three separate functions, namely first to amplify the sound wave by shaking step by step an increasingly ¹⁰ large air volume, second to function like a resonator permitting by generating resonances mostly of audible frequencies to eliminate parasitic resonances, and third to slow down the wave owing to its reflection against the walls.

¹⁵ A still further object of the invention is to provide an improved acoustic enclosure wherein the deflecting member may be situated either between the inner face of the vibrating element and the neck (or input) of the 20 horn or between the mouth (or output) of the horn and ^u the enclosure vent whereby in the first case the deflector permits the wave emitted by the inner face of the vibrating element to penetrate into the horn while in the second case the deflector directs the horn wave 25 outwards, the possibility being afforded in both cases, so to influence the deflector shape and the horn length as to cause the wave emitted through the vent to be in phase with the wave emitted by the outer face of the vibrating element.

With these and such other objects in view as will incidentally appear hereafter, the invention comprises the novel construction and combination of parts that will be now explained with reference to the accompanying drawings exemplifying the same and forming a 35 part of the present disclosure.

FIG. 1 is a front sectional view of a first embodiment of an acoustic enclosure according to the invention.

FIG. 2 is a side sectional view of the enclosure shown in FIG. 1.

FIG. 3 is a detail view of a constructional form of the deflecting member.

FIG. 3a is a sectional view on the line a—a of FIG. 3.

FIG. 4 is a front elevational view of an enclosure representing a modified embodiment of the invention.

FIG. 5 is a side view of the enclosure shown in FIG. 4.

In FIGS. 1 and 2 is represented an acoustic enclosure or chamber 1 of parallelepipedic shape carrying centrally of its front face 2 a loudspeaker 3 mounted upon ³® a baffle 4. Inside the enclosure 1 is positioned a blade S which is spirally wound. Said spiral blade 5 is flexibly or yieldingly mounted upon the front face 2 and the rear face 6 of the enclosure 1 with interposition of a sheet of a supple material 7 to which it adheres to a sufficient ⁵⁵ extent to preserve its shape in spite of the vibrations, such material being for example cellular rubber, plastic foam or the like. The blade 5 and the walls 2, 6 of the enclosure 1 define an acoustic horn 8 the neck or input ₆₀ of which is located behind the loud speaker 3, said horn being directed toward a vent 9 provided on a side face 10 of the enclosure 1.

Preferably though not necessarily the shape given to the horn 8 will be that of an exponential horn. It is im₆₅ portant to notice that in an enclosure of reduced volume a blade 5 of great length may be accommodated and that the flexible mounting of said blade permits it freely to acquire a condition of resonance.

3,687,221 «J

Between the face 11 of the loudspeaker 2 directed towards the inside of the enclosure 1 and the neck of the horn 3 is arranged a deflecting member 12 which is illustrated in detail in FIGS. 3 and 3α.

This arrangement permits the rear wave of the loudspeaker 3 to be reflected by the deflector 12 in a direction at right angles to its original direction and thus to be introduced into the horn 8 through which it travels before going out through the vent 9.

In the constructional form shown in FIGS. 4 and 5, the loud speaker 3 is situated on a side face 10 of the enclosure 1 adjacent the upper part of said face. However the vent 9 is situated on one face or on the two front and rear faces of the enclosure. The deflecting member 12 is situated adjacent the mouth of the horn 8 near the vent 9.

In this arrangement, the rear wave from the loudspeaker 3 flows directly through the neck of the horn 8 and after having travelled through it undergoes a change of direction owing to the deflector 12 whereby it comes out through the vent 9.

It will be easily understood that the use of the wave emitted by that face of the vibrating element which is directed towards the inside of the enclosure, after it has travelled through a horn of great length, permits the achievement with an enclosure of reduced volume of a very strong amplification and consequently a considerable increase of the efficiency of the vibrating element.

The shape of the horn input and that of the deflector or deflectors is so calculated as to impart an adequate acoustic load to the vibrating element.

Furthermore the continuous variation right along the spirally wound blade of those variations that are undergone by its constitutive material permits the blade to behave as a continuous resonator which takes a resonant condition for all frequencies within the audible range. All these resonances partake in a substantial increase of the enclosure efficiency by blanking off all parasitic resonances.

It should be noticed that the enclosure according to the invention may be made of miscellaneous materials ranging from the heaviest ones (metals) to the lightest ones (expanded polystyrene). The blade which constitutes the horn may be also made of a very light material such as a polyvinyl compound, or an impervious or other fabric.

Obviously the above-described embodiments of the invention merely constitute examples among others in the field of the combination of means according to the invention and numerous modifications in the shape of the several elements, their nature or their relative arrangement may be conceived without departing from the ambit of the invention and the scope of the subjoined claims.