LOUDSPEAKER ENCLOSURE CONSISTING OF STONE AND METHOD FOR MANUFACTURING SAME
FIELD OF THE INVENTION
The invention relates to the loudspeaker enclosure consisting of stone defined in the preamble of claim 1 and to a corresponding method for manufacturing the loudspeaker enclosure. BACKGROUND OF THE INVENTION
Stone as a loudspeaker material has already been known for years. Its good properties include large mass, ability efficiently to damp oscillation and large density. Stone loudspeakers are known for example from publications CN2371745, CN2324737 and CN230182 . In the two first-mentioned publications, the loudspeakers are manufactured traditionally to the form of a rectangular parallelepiped from thin stone slabs having a uniform thickness. Acoustic waves do not, however, op- timally function in rectangular boxes containing sharp corners. In addition, manufacturing from slabs having a uniform thickness does not provide for the possibilities of varying the appearance that is essential to loudspeakers .
The third publication predominantly describes a theoretical possibility of manufacturing a stone loudspeaker from one monolithic piece of stone. The manufacturing thereof, i.e. grinding, at least on an in- dustrially profitable scale, is not possible.
OBJECTIVE OF THE INVENTION
An objective of the invention is to eliminate the drawbacks of the prior art referred to above. In par- ticular, an objective of the invention is to disclose
a structurally new type of a stone loudspeaker and a method for manufacturing same to provide optimal acoustic properties for the loudspeaker.
SUMMARY OF THE INVENTION
The loudspeaker enclosure consisting of stone according to the invention includes a front cover, a back cover and an edge circulating around the borders thereof and connecting them to each other to form a substantially sealed structure. According to the in- vention, the loudspeaker enclosure consists entirely of two stone parts to be joined to each other, which together form the loudspeaker enclosure, i.e. a front part and a back part. The front part includes the front cover and substantially half of the width of the edge along the entire length thereof. In the same way, the back part includes the back cover and substantially half of the width of the edge along the entire length thereof. This way, the front part and the back part are both substantially similar and mutually cor- responding cup-type and monolithic pieces of stone, the edges of which are perpendicular to the planes defined by the front cover and the back cover.
As the corresponding edges of the borders of the front part and the back part include mutually corresponding fittings, such as grooves or the like, in order tightly to join the parts to each other, and as the edges are exactly parallel to each other, the edges of the loudspeaker constitute straight, smooth and almost seamless surfaces. In addition, gasket tape can be used between the front part and the back part in order to secure the tightness of the seam.
Since the loudspeaker enclosure is formed from two parts, they are open and easily machineable, i.e. groundable. This way, the casing of the front part and
the back part can be machined to have a substantially- uniform thickness over the entire area thereof. When high-quality and homogenous, easily machineable soap- stone, such as the Finnish soapstone from Nunnanlahti, is further used as the stone, the front part and the back part can be machined to have a thin wall thickness, and the entire structure can be made relatively light. Depending on the desirable properties to be constructed for the loudspeaker and on the applications, the front cover includes one or more openings, in general round holes, to the edges of which the loudspeaker is mountable. To the edge of the opening on the front cover there may be bored a set of holes to which the loudspeaker can be screwed or bolted.
In one embodiment of the invention, the back cover includes a reflex tube being the same piece of stone therewith and opening outwards to the back surface of the back cover and inwards to a distance from the inner surface of the back surface. In other words, the reflex tube is ground to the same integral stone with the back cover and may extend within the back cover in the direction of the edges thereof from the outer surface of the back cover inwards, all the way to be flush with the edges.
The loudspeaker manufactured from two pieces according to the invention provides for a structure wherein the inner surfaces of the front part and the back part are round-shaped and free of sharp corners and edges throughout . The invention also relates to a method for manufacturing the loudspeaker enclosure consisting of stone. In
the method, two substantially homogeneous pieces of stone of the same size, a front stone and a back stone, are first provided. The stones need not necessarily be named front stone and back stone immediately from the start, but can be made similar at first, because the front stone and the back stone may be identical to each other in many respects. In the invention, the outer surfaces of the pieces of stone are ground to correspond to the desired outer surface of the loudspeaker enclosure. In the same way, the shape of the front part of the loudspeaker chamber is ground inside the front stone, as well as at least one opening for the driver, penetrating the front surface of the loudspeaker. Furthermore, the shape of the back part of the loudspeaker chamber is ground inside the back stone, as well as the reflex tube opening to the back side of the back part. Furthermore, corresponding surfaces of a similar shape are ground to the edges of the front stone and the back stone. Finally, the front stone and the back stone ground to a cup-type shape are joined to each other to form an integral loudspeaker chamber. It is to be noted that it is also possible in the method according to the invention that the inside shapes of the different parts of the loud- speaker are ground first and the outer surfaces of the parts last. In the same way, it is possible that parts ground to be complete in the inner parts thereof only are joined to each other, whereafter the outer surfaces thereof are ground jointly to the final shape and appearance.
Preferably, the inner surfaces of the front part and the back part are ground in the method according to the invention to a substantially round shape, to be smooth and free of sharp corners and edges. As the front part and the back part are further ground to
have a substantially homogeneous and relatively thin structure throughout, the loudspeakers are provided as structures corresponding to the traditional loudspeakers manufactured from stone slabs in weight but having superior sound reproduction properties.
The loudspeaker enclosure consisting of stone and the corresponding manufacturing method according to the invention provide important advantages compared with the prior art. The structure and the method according to the invention provide for the use of a non-resonant and soundproof loudspeaker material for industrially produced loudspeakers in such a way that a flat frequency response as well as the desired sensitivity and lightness can be optimized therein without limiting the freedom and diversity of design.
LIST OF FIGURES
In the following section, the invention will be de- scribed in detail with reference to the accompanying drawings, in which
Fig. 1 illustrates the stone loudspeaker according to the invention as seen obliquely from the front,
Fig. 2 illustrates the loudspeaker of Fig. 1 as seen from the back,
Fig. 3 illustrates the front part of the loudspeaker of Fig. 1 as seen from the inside and
Fig. 4 illustrates the back part of the loudspeaker of Fig. 1 as seen from the inside.
DETAILED DESCRIPTION OF THE INVENTION
The loudspeaker enclosure manufactured entirely from soapstone, illustrated in Fig. 1 to 4, includes only two pieces of stone, i.e. a front part 1 and a back part 2. The front part includes a substantially planar front cover 3 and edges 4 turning perpendicularly in-
ward in a rounded fashion from the border areas thereof. This way, the front cover 3 and the edges 4 thereof form together a cup-type structure shown in Fig. 3, the internal volume of which constitutes approximately half of the volume of the loudspeaker. Machined to the front cover 3, there are also two round openings 8, and a set of mounting holes 10 with threaded sleeves have additionally been bored to the edges of the larger opening. Lastly, suitable loudspeakers can be mounted to the openings 10.
It is essential of the front part of Fig. 1 and 3 that it is ground from one piece of stone and that there are no sharp edges or corners on the inner surface thereof, but the surfaces curve in an even and round- shaped fashion between the front cover and the edges.
Fig. 2 and 4 more specifically illustrate the back part 2 of the loudspeaker, including a substantially planar back cover 5 and edges 6 turning perpendicularly inwards in a round-shaped fashion from the border areas thereof. In the manner corresponding to the front cover 3, the back cover 5 is ground from one piece of stone to a substantially round shape and to be free of sharp corners and edges of the inner surface .
The outer surfaces of both pieces, i.e. the front cover 3 and the back cover 5, are also machined to be evenly smooth and round-shaped in such a way that the round shape of the inner surfaces gives the loudspeaker its optimal acoustic properties, and the round shape of the outer surfaces gives the loudspeaker its characteristic appearance. Together, the similar round shape of the surfaces provides for the fact that it is possible to machine both pieces of stone to a substan-
tially uniform thickness and to be thin throughout the entire area of the covering thereof. This way, they are provided relatively light, despite of the heavy manufacturing material.
To the back part 2, there has also been machined a reflex tube 9 being the same stone therewith. The reflex tube 9 opens to the back side of the loudspeaker, to the upper part thereof, and extends inside the loud- speaker approximately to the same distance from the back cover 5 as the edges 6. Also, the reflex tube 9 is ground to a round shape without sharp edges. Furthermore, it is shaped to have a curvingly elliptical cross section, whereby it serves as a good carrying handle, in addition to serving as the reflex tube.
To the back part 2, there are additionally provided two through holes 11 for electric cables and four mounting holes for mounting bolts 12 by which the front part 1 and the back part 2 can be mounted to each other.
The essential feature in the mutually corresponding shapes of the front part 1 and the back part 2 is the fittings 7 of their edges, by which the parts are tightly sealed against each other. Another essential feature is the parallel orientation of the edges 4 and 6 of the front part 1 and the back part 2, i.e. the inner surfaces of the edges, when the parts have been joined together, form even and straight surfaces over the seam without discontinuities of the surface. This even and smooth continuity of the surface of the seam area can be secured further by a thin gasket tape 13 to be used on the seam.
The invention is not limited merely to the examples referred to above; instead, many variations are possible within the scope of the inventive idea defined by the claims.