Waveguide electroacoustical transducing

The Invention relates to loudspeaker systems with an acoustic waveguide, and in particular those with waveguides which have uniform cross sectional areas. For the Background is on the <patcit><text>US 4628528</text></patcit>. <patcit><text>US 5373564</text></patcit> and <patcit><text>US 6278789</text></patcit> based.

It is an important objective of the present invention, an improved wave guide provide.

WHERE 96/11558 discloses a wave guide system for radiating sound waves, comprising: a source of sound waves; a low-loss acoustic waveguide for transmitting sound waves, wherein the wave guide comprising: a first terminal, which is configured with the source of sound waves to be coupled; a second terminal which is adapted the sound waves into the external environment radiate; a center line that runs along the length wave guide runs; and walls, the cross section surfaces in planes perpendicular to the center line enclose, with the walls in such a way are tapered in that the cross-sectional area at the second terminal is smaller than the cross sectional area at said first terminus is.

According to the present Invention is such a wave guide system by the features of Claim 1 characterized.

More Features, objects and advantages will become from the following detailed Description clear that refers to the following drawings, in the:

<figref idrefs="S8">1</figref> a cross-sectional view a speaker system with waveguide according to the invention; and

<figref idrefs="S9">2a</figref> and <figref idrefs="S9">2 B</figref> computer simulated curves of acoustic Performance or driving deflections versus frequency for a waveguide according to the invention and for a conventional wave guide are.

Referring to the drawings and in particular <figref idrefs="S8">1</figref> is a speaker and a waveguide assembly according to the invention shown. A wave guide<figref>14</figref> has a first end or a terminal <figref>12</figref> and a second End or a terminal <figref>16</figref> on. The wave guide<figref>14</figref> lies in the form of a hollow tube with tapered front cross-sectional area. The walls the wave guide <figref>14</figref> are tapered, so that the Cross sectional area the wave guide at the first end <figref>12</figref> greater than the cross-sectional area at the second end <figref>16</figref> is. The second end<figref>16</figref> can from acoustic or cosmetic reasons be slightly widened. The cross-section (along the line AA of <figref idrefs="S8">1</figref>, Perpendicular to the center line <figref>11</figref> of the wave guide <figref>14</figref>) may be circular, oval or rectangular or a regular or irregular be polyhedron or any other closed contour. The wave guide<figref>14</figref> can be a closed end or an open end. Both ends can radiate into the open air, as shown, or an end can in an acoustic enclosure radiate as a closed volume or a volume with an opening or a tapered or non-tapered waveguide.

Out clarity the walls the wave guide <figref>14</figref> straight shown, and the wave guide <figref>14</figref> is uniform tapered over its total length shown. In a practical embodiment, the waveguide may be curved, to any desired having shape in order to in a housing fit, or about one end of the waveguide relative to the other end the wave guide acoustic reasons to arrange. The cross section of the wave guide<figref>14</figref> can a have different geometry, that is, a different shape or straight or curved Sides, at different points over the length thereof. In addition, the rejuvenation of Wave guide on the Length of the waveguide vary.

On electroacoustic transducer <figref>10</figref> is in the first end <figref>12</figref> of the wave guide <figref>14</figref> arranged. In one embodiment, the invention, the electroacoustic transducer <figref>10</figref> on 65 mm cone driver with a ceramic magnet motor, he, however, a Converter with any other cone or magnet or any be another way elekroakustischer converter. Both sides of the electroacoustic converter <figref>10</figref> can in the first end <figref>12</figref> the wave guide <figref>14</figref> appropriate his, or the electroacoustic transducer <figref>10</figref> in a wall the wave guide <figref>14</figref> near the first end <figref>12</figref> be appropriate and sound waves in the wave guide <figref>14</figref> radiate. In addition, the surface of the electroacoustic transducer <figref>10</figref>That of the waveguide <figref>14</figref> away is addressed, radiate directly into the environment, as shown.

Inner walls of the wave guide <figref>14</figref> are substantially acoustically lossless. can in the wave guide a small amount of acoustically absorbing material <figref>13</figref> available be. The small amount of acoustically absorbing material<figref>13</figref> can near the transducer <figref>10</figref> be arranged, as in <patcit><text>US 6278789</text></patcit> described, so that the shaft guide at is low frequency loss, with a smooth frequency response at high frequencies. The small amount of acoustically absorbent material dampens undesirable Resonances and provides a smoother output over the range of from wave guide radiated Frequen&lt;?page 3?&gt;zen, but does not prevent the formation standing waves at low frequency in the wave guide.

In one embodiment, the invention, the wave guide a tapered waveguide, in which the cross-sectional area at points along the waveguide is described by the following formula: <img img-content="mf" img-format="tif" he="12" wi="49" file="00040001.tif" />wherein A is the area, and y = the the (wide) inlet end measured distance, and <img img-content="mf" img-format="tif" he="10" wi="24" file="00040002.tif" />and x = the effective length of the Wave guide, and<img img-content="mf" img-format="tif" he="11" wi="23" file="00040003.tif" />The first resonance or tuning this embodiment is good through the first solution nonzero of αf = tanβf_i approached, in which <img img-content="mf" img-format="tif" he="11" wi="48" file="00040004.tif" />and c₀ = the speed of sound. After approximation by the above formulas the wave guide be modified empirically to end effects and other factors be taken into account.

In one embodiment, the length x of the wave guide <figref>14</figref> equal 660 mm (26 inches). The cross-sectional area at the first end<figref>12</figref> is 4130 mm² (6.4 square inches) and the cross-sectional area at the second end <figref>16</figref> is 581 mm² (0.9 square inches), so that the defined area ratio ( than the cross-sectional area the first end <figref>12</figref> divided by the cross sectional area of ​​the second end <figref>16</figref>) Is about 7.1.

Referring on <figref idrefs="S9">2a</figref> and <figref idrefs="S9">2 B</figref> are computer-simulated Curves of radiated acoustic power and the driving deflection opposite to the frequency for a sound speaker system with wave guide according to the invention (curve<figref>32</figref>), Excluding acoustically absorbent material <figref>13</figref> and having a length of 660 mm (26 inches), and for undamped wave guide with straight walls of similar Volume and length of 914 mm (36 inches) (curve <figref>34</figref>) Shown. As from<figref idrefs="S9">2a</figref> and <figref idrefs="S9">2 B</figref> it can be seen to extend the Bass range up to about the same frequency (70 Hz) and the frequency response the Wel lenführungssystems according to the invention is shallower than that of the non-tapered waveguide system. Narrowband peaks (the "spikes" called) in the two curves can significantly by using the acoustically absorbent material (<figref>13</figref> out <figref idrefs="S8">1</figref>) Can be reduced.