DE10061734A1 - Loudspeaker with transition time correction element for achieving flat wavefront, has diameter of openings to sound channels less than wavelength of highest radiated frequency - Google Patents

Abstract

The device has a transition time correction element with full membrane coverage, equal distance between membrane (B) and correction element at all points and uniformly distributed openings in the cover connected to sound carrying channels (F), so that the diameter of the openings to the sound channels are less than the wavelength of the highest frequency to be radiated. All output surfaces end in a plane forming an outlet flange (G). Independent claims are also included for the following: the possibility of achieving a flat wavefront with loudspeakers and the possibility of coupling several loudspeakers to a large one to increase the positive characteristics further.

Description

1. Objectives of the invention

The aim of the invention is to avoid the overlapping of sound waves, that is to say interference, when several loudspeakers are connected together (with a cone-shaped diaphragm or conventional horn-driver combinations) ( Figure 8B). This eliminates the deletions and increases in the overlap area between the individual loudspeakers, which enables a substantially interference-free transmission of speech and music.

2. Description

All images shown relate to speakers with dome-shaped Membrane. All technical functions discussed also work with conical membranes and conical membranes with dome-shaped Voice coil cover.

The invention relates to a loudspeaker with a membrane that is electromagnetically excited to vibrate ( Figure 1B), this can be constructed in the form of a dome or cone, and to a time-of-flight correction element that is built into the front of the respective membrane to produce a completely flat (in vertical and horizontal, or only in one of these) Levels) acoustic wavefront. This is achieved through the special construction of the runtime correction element.

The runtime correction element consists of the following parts:

• - a complete cover ( Figure 1D) of the membrane ( Figure 1B). The distance between the membrane and the part of the transit time correction element (cover) facing the membrane should be as small as possible and be the same at all points. The minimum distance is determined by the maximum deflection of the membrane.
• - There are several openings in the cover (depending on the design) ( Fig. 1E). These openings are evenly distributed over the membrane surface ( Figure 2), so that each opening has its own area of the membrane surface that is as large as possible ( Figure 3). The cross-sectional shape of the openings can vary depending on the design. ( Photo 2). The edges of the openings are rounded to minimize flow noise ( Figure 4).
• - The openings form the beginning of sound guide channels ( Fig. 1F). The sound guide channels are all of the same length and expand exponentially or conically towards the outlet flange. The ends of the sound guide channels, here defined as exit surfaces ( Figure 1H), all end on one level and thus form an exit flange by joining them together. The exit surfaces always have a rectangular cross section so that they can be meaningfully coupled to one another. Some channels are straight and some channels are curved ( Figure 1F Roman channel 1) or tortuous ( Figure 1F Roman channel 7) to compensate for the not always equal distance between the membrane and the plane of the outlet flange.
• - The outlet flange ( Figure 1G) can be constructed as a line or block-shaped, rectangular ( Figure 5). Several outlet flanges can be combined to form a large outlet flange, just as the outlet surfaces form a flange. The large outlet flange created in this way can have the same linear or block structure as a single one ( Figure 6). The assignment of the positions of the openings in the cover ( Fig. 1D) to the position of the outlet surfaces in the outlet flange, i.e. the course of the sound guide channels, can vary depending on the design of the outlet flange ( Fig. 7, Fig. 2.2 to Fig. 5.2). The outlet flange can form the end of the loudspeaker ( Fig. 10C), serve as a pure diffraction slit or as a directional radiator or for connection to a horn funnel ( Fig. 10a and b).

3. Function and tasks of the individual parts Here, using the example of a tweeter with a dome-shaped diaphragm and an outlet flange in line form with connected horn cone, in comparison with a conventional tweeter with horn cone ( Figure 9)

The starting point and condition is that the membrane used has the function of a piston radiator is fulfilled, i.e. vibrates uniformly as a whole surface. The function is only when the membrane breaks up into partial vibrations still guaranteed to a limited extent because the phase oscillations are caused by the time correction element are also transmitted in opposite phases and on Outlet flange can lead to extinctions. So that is Transmission range of such a system to higher frequencies  limited. However, this only applies to systems with larger ones Membrane diameters (e.g. 10 or 12 inch loudspeakers as the basis). For tweeters with their relatively small diaphragm diameters (1-4 inches) this effect occurs only in the top end of the transmission range and is therefore negligible. Conventional systems are with the same defects. By cleverly arranging the openings for Membrane area as well as through the correct selection of the cross-sectional shape of the The effect of openings can be prevented or at least reduced.

A. Vertical level

If there is no other way, the sound waves generated by the membrane ( Fig. 1B) enter through the openings ( Fig. 1E) in the cover ( Fig. 1D) into the following sound-guiding channels ( Fig. 1F) and pass through these to the exit surfaces where the Sound guide channels form a common large exit surface, the exit flange ( Figure 1 D). Since all channels have the same overall length from the opening to the outlet flange, the sound waves also need exactly the same time to pass through them and arrive at the outlet flange at the same time (in phase), where they form a common, flat sound wave ( Figure 11). Each individual exit surface would behave like a spherical emitter due to its small area (Appendix 7. ). Only by combining all exit surfaces to form the exit flange does a radiant surface emerge that fulfills the conditions for the radiation of a flat (in the special case of a cylindrical shaft). The diameters of the sound guide channels are selected so that they are smaller than the wavelength of the highest frequency to be emitted, so that the sound waves follow the bends of the channels and no reflections can occur. This cannot be achieved with conventional tweeter-horn driver combinations ( Fig. 9A and B), more and less; curved sound waves emitted, since the diameter of the horn entrance surface is always too small for the emitted wavelength. The conditions for a spherical emitter are fulfilled and spherical waves are emitted. The horn funnel can control the propagation of the spherical waves to some extent (Appendix 7 ). If several conventional horn driver combinations are placed on top of each other, there is inevitable overlap in the radiation area of the individual loudspeakers ( Figure 8B), i.e. sound waves add up in some places, sound pressure increases occur, sound waves cancel out in other places, transmission holes occur. These effects (interferences) significantly impair the signal transmission (Appendix 6. JBL literature).

These effects can be avoided with the described invention ( Figure 8A). In theory, an infinite number of delay correction elements can be mounted one above the other or next to one another without causing interference. The more time-delay correction elements are installed one above the other, the lower the lower cut-off frequency of the entire combination, in which the conditions for an even sound wave propagation are given (Appendix 7.).

B. Horizontal plane

In the horizontal plane (in this example) the runtime correction link and conventional horn driver combinations behave identically; the opening width of the horn funnel used determines the spatial radiation ( Figure 9B and Figure 10A)

4. Function and tasks of the individual parts Here is the example of a combination for the medium and low Frequency range, consisting of 4 coupled delay correction elements units

The function of the individual parts corresponds exactly to that described in: A. The arrangement of 4 square outlet flanges to form a large square outlet flange ( Fig. 6C) fulfills the conditions for emitting plane sound worlds in both planes, vertically and horizontally, up to a defined lower limit frequency (Appendix 7.). The more runtime correction element elements are interconnected, the larger the in-phase radiating surface, the lower the lower limit frequency to be achieved. With such an arrangement, a very narrow directional lobe can be generated from sound waves, which means that very long distances can be covered. With several conventional cone speakers or horn driver combinations, this cannot be achieved without disturbing interference (see section 3, vertical level).

6. May be considered for the assessment of patentability pulling publications

• - German patent: DE 196 03 002 C1
• - from the USA: JBL Technical Notes Volume 1, Number 7
• - Springer textbook
  M. Zollner / E. Zwickner
  ELEKTROAKUSTIK
  Third improved and expanded edition in 1993
  ISBN 30-540-56600-7
  Page 62 Paragraph 2.3 Ball Shaft
  Page 58 Paragraph 2.2 flat wave
  Page 69 Paragraph 2.5 cylinder shafts
• - Franzi's publishing house
  Hans Herbert Klinger
  Speakers and loudspeaker housings for HiFi
  1987 14th edition
  Page 18 Paragraph 2.3 Diffraction and interference
  Page 62 Paragraph 4.1 horn or horn speakers

7. Appendix Technical information

• - a membrane emits sound waves, the Wavelength greater than the diameter of the Membrane, they spread out spherically
• - a membrane emits sound waves, the Wavelength smaller than the diameter of the Is membrane, these become with increasing Frequency bundled in the vertical axis of the Blasted membrane (see 6.)

Claims (3)

1. The claims relate to the delay correction element (phase correction element) connected upstream of any loudspeaker diaphragm and its special construction, the features of which are:

• - a complete covering of the membrane ( picture 1D)
• - The distance between the membrane and the time correction element is the same at all points
• - openings in the cover ( Fig. 1E)
• - The openings are evenly distributed on the side of the louse time correction element facing the membrane (defined here as a cover) ( Figure 2)
• - The openings can have different cross-sections ( picture 2)
• - The edges at the openings are rounded ( picture 4)
• - Sound guiding channels connected to the openings ( Fig. 1F) of the same or different cross-section ( Fig. 2 and 3) but always of the same length
• - The diameter of the openings to the sound guide channels is smaller than the wavelength of the highest frequency to be emitted
• - Some sound guide channels are straight, others are curved or curved to compensate for the not always the same distance between the curved plane of the membrane cover (and thus the membrane surface) and the plane of the outlet flange
• - The sound channels expand exponentially or conically
• - The exit surfaces form the end of the sound guide channels ( Fig. 1H)
• - All exit surfaces end on one level and form the exit flange by joining them together ( Figure 1G)
• - The outlet flange can be constructed as a line or as a rectangle ( Figure 5)
• - Several outlet flanges can be coupled to form a common larger outlet flange ( Figure 6)
• - The outlet flange forms the end of the loudspeaker or is used to connect a horn funnel

2. The possibility with speakers from claim 1 level sound waves produce. 3. The possibility of multiple speakers from claim 1 to a large one Coupling speakers to further increase the positive properties.