U.S. patent application number 09/921175 was filed with the patent office on 2002-02-07 for system for integrating mid-range and high frequency acoustic sources in multi-way loudspeakers.
Invention is credited to Engebretson, Mark.
Application Number | 20020014369 09/921175 |
Document ID | / |
Family ID | 22830446 |
Filed Date | 2002-02-07 |
United States Patent
Application |
20020014369 |
Kind Code |
A1 |
Engebretson, Mark |
February 7, 2002 |
System for integrating mid-range and high frequency acoustic
sources in multi-way loudspeakers
Abstract
This invention provides a system for integrating sound radiation
from mid-range and high frequency sources enabling improved control
over the radiation of high frequency sound waves. This acts to
minimize the distortion, while enabling compression-loading of the
mid-range sound waves increasing acoustic energy. To do so, a
radiation boundary integrator ("RBI") having slots is positioned
over the mid-range sound sources acting as a smooth sidewall
wave-guide thus controlling the high frequency sound waves
emanating from the high frequency sound sources. To allow the
mid-range frequency sound waves generated from mid-range sound
sources to pass through the RBI, slots are formed within the RBI.
As such, RBI may have an outer surface area that may form an
acoustical barrier to high frequencies radiating across the outer
surface, yet be acoustically transparent to mid-range frequencies
radiating through slots in the radiation boundary layer. The RBI
may also serve as a volume displacement device to compression-load
the mid-range sound sources. To do so, the back surface of the RBI
may be contoured to the shape of the midrange sound source thus
reducing the space between the two, and loading the mid-range sound
sources generating greater mid-range sound energy.
Inventors: |
Engebretson, Mark; (Encino,
CA) |
Correspondence
Address: |
Squire, Sanders & Dempsey L.L.P.
14th Floor
801 S. Figueroa Street
Los Angeles
CA
90017-5554
US
|
Family ID: |
22830446 |
Appl. No.: |
09/921175 |
Filed: |
July 31, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60222026 |
Jul 31, 2000 |
|
|
|
Current U.S.
Class: |
181/199 ;
181/148 |
Current CPC
Class: |
H04R 1/26 20130101; H04R
1/30 20130101; H04R 1/403 20130101; H04R 1/288 20130101; H04R 1/323
20130101 |
Class at
Publication: |
181/199 ;
181/148 |
International
Class: |
A47B 081/06 |
Claims
What is claimed is:
1. A sound radiation boundary integrator, comprising: a top portion
adapted to provide a substantially flat surface to control high
frequency sound waves; a back portion adapted to be juxtaposed to
at least one mid-range frequency sound source; at least one slot
through the top and back portions, the at least one slot adapted to
be juxtaposed to the at least one mid-range frequency sound source;
and a porous material substantially transparent to mid-range
frequency sound waves within the at least one slot.
Description
CROSS REFERENCES TO RELATED APPLICATION.
[0001] This application is a non-provisional application claiming
priority to U.S. Provisional Patent Application, Ser. No.
60/222,026 filed Jul. 31, 2000.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention.
[0003] This invention relates generally to a system for integrating
radiation of sound waves from disparate mid-range and high
frequency sound sources. This is accomplished by providing a
substantially solid boundary to control angular radiation of high
frequency sound waves while allowing mid-range frequency sound
waves to emit through slots in the substantially solid boundary.
The system also acts as a volume displacement to create loading for
the mid-range frequency sound waves.
[0004] 2. Related Art.
[0005] Professional loudspeakers and sound systems are designed to
control the direction of the sound radiating from its sound
sources, or commonly referred to as drivers or transducers. Sound
radiating from a high frequency sound source, with the absence of
sidewalls or boundaries, will radiate in all directions and
possibly wrap around the sound source. This severely limits the
predictability and control of the direction of the sound radiation.
On the other hand, if boundaries or sidewalls are placed adjacent
to the sound source, forming an angle (where the sound source is
located at the vertex of the angle), the sound radiation will
generally conform to the angle between the boundary surfaces. Thus,
one of the advantages with using boundary surfaces is being able to
directionally control the sound radiation.
[0006] Another design objective of professional loudspeaker and
sound systems is being able to integrate a number of mid-range
sound sources adjacent to a number of high frequency sound sources
into a housing. To do so, for example, three high frequency sound
sources may be position vertically in between two mid-range sound
sources that are flushed in two adjacent walls. That is, the three
vertically stacked high frequency sound sources are at the vertex
of two adjacent walls that are at an angle with respect to each
other with two mid-range sound sources mounted into each of the
walls. As such, the cones of the mid-range sound sources are, in
part, part of the sidewall.
[0007] One of the problems with above design is that the cones of
the midrange sound sources form a recess or depression in the
adjacent sidewalls that serve as the high-frequency wave-guide. The
resulting irregular boundary prevents uniform angular radiation of
the high frequency sound waves that pass over these depressions.
Another problem with the above design is the limitation on the size
of the multiple mid-range sound sources that may be mounted into
the two adjacent sidewalls. That is, larger diameter sound sources
are desirable over smaller diameter sound sources because they can
generate greater acoustic power. However, the upper frequencies
generated by the larger mid-range sources can `lobe` or narrow in
radiation angle if sources are large compared to the wavelength,
due to the finite propagation velocity of sound. To avoid upper
mid-frequency narrowing, there is a limit as to the size of the
mid-range sound sources, which limits the acoustic output power of
the mid-frequency range sound sources.
[0008] Therefore, there is a need to integrate radiation from the
mid-frequency and high frequency sound sources to better control
the angular radiation of high frequency sound waves. Furthermore,
there is a need to improve the acoustic power or energy that may be
produced by the mid-range sound sources.
SUMMARY OF THE INVENTION
[0009] This invention provides a system for integrating sound
radiation from mid-range and high frequency sources. This provides
improved control of the angular radiation of mid-range and high
frequency sound energy. To improve this control, a radiation
boundary integrator ("RBI") having slots for mid-frequency
through-radiation is provided over the mid-range sound sources to
serve as a smooth, wave-guiding side wall thus controlling the
angular radiation of high frequency sound waves emanating from the
high frequency sound sources. In the past, this type of sound
control was done without the use of wave-guiding surfaces covering
the mid-frequency sound sources, such that the angular radiation of
high frequencies conformed to the contours of the cones or
diaphragms of the mid-range frequency sound sources, compromising
both the frequency-directivity and the quality of the high
frequency sound energy. The RBI is acoustically solid to high
frequencies radiated across the outer surface, yet acoustically
transparent to mid-range frequencies radiating through the outer
surface. To allow the mid-range frequency sound waves generated
from mid-range sound sources to pass through the high frequency
wave-guiding surfaces, slots are formed within the RBI.
[0010] Besides integrating the mid-range and the high frequency
sound waves, the RBI may be used to compression load the mid-range
frequency sound waves to improve the acoustic power output of the
mid-range sound sources. This is accomplished by providing a back
surface of the RBI such that it faces the mid-range sound sources
and may be contoured to conform to the shape of the mid-range sound
source or speaker. This reduces the space between the back surface
and the sound source. The reduced space compression-loads the
mid-range frequency sound sources, enabling greater mid-range
frequency sound output.
[0011] Other systems, methods, features and advantages of the
invention will be or will become apparent to one with skill in the
art upon examination of the following figures and detailed
description. It is intended that all such additional systems,
methods, features and advantages be included within this
description, be within the scope of the invention, and be protected
by the accompanying claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention can be better understood with reference to the
following figures. The components in the figures are not
necessarily to scale, emphasis instead being placed upon
illustrating the principles of the invention. Moreover, in the
figures, like reference numerals designate corresponding parts
throughout the different views.
[0013] FIG. 1 is a cross-sectional side view of two radiation
boundary integrators masking the respective mid-range frequency
sound source.
[0014] FIG. 2 is a front view of two radiation boundary integrators
according to the embodiment illustrated in FIG. 1, having three
vertical high frequency sound sources in between the two boundary
integrators.
[0015] FIG. 3 is a front view of a radiation boundary integrator
having foam in each of the slots.
[0016] FIG. 4 is a side view of a radiation boundary integrator
illustrated in FIG. 3.
[0017] FIG. 5 is a bottom view of a radiation boundary integrator
illustrated in FIG. 3.
[0018] FIG. 6 is a rear view of a radiation boundary integrator of
the embodiment illustrated in FIG. 3.
[0019] FIG. 7 is a cross-sectional view along line 7 in FIG. 6.
[0020] FIG. 8 is a cross-sectional view along line 8 in FIG. 6.
[0021] FIG. 9 is a front view of an alternative embodiment of a
radiation boundary integrator.
[0022] FIG. 10 is a front view of an alternative embodiment of a
radiation boundary integrator.
[0023] FIG. 11 is a perspective view of a radiation boundary
integrator incorporated within a speaker housing.
[0024] FIG. 12 is a perspective view of a series of speaker
housings illustrated in FIG. 11 stacked together.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] FIGS. 1 and 2 illustrate a Radiation Boundary Integrator
(RBI) 50 masking over two midrange frequency sources 40 on each
side. Three high frequency sound sources 41 positioned vertically
between the two RBIs 50. The RBI may provide a substantially solid
boundary for the high frequency sound waves produced by the sources
41 and may allow mid-range sound waves from the sources 40 to be
emitted through slots 43 in the RBI 50. This way, the RBI 50
integrates the sound waves radiating from both the high and
mid-range frequency sound sources for better control and to
minimize distortion of the high frequency sound wave front shapes
because the high frequency sound waves pass along a substantially
flat surface.
[0026] The high frequency sound sources 41 generate high frequency
energy or sound waves, which propagate across the two RBIs 50. The
surfaces of the RBIs 50 are angled relative to each other with the
exception of a leading section 45. The leading section 45 forms a
smooth transition to the substantially flat and solid portion 60 of
the RBI 50. This way, the two RBIs 50 are adjacent to each other
forming an angle relative to each other functioning a smooth
wave-guide for the high frequency sound waves generated by the
sound sources 41. That is, the two RBIs 50 are at a predetermined
angle to control and direct the high frequency sound waves
emanating from the sound sources 41. The predetermined angle
between the two RBIs 50 depends on an application, which may vary
from about 60.degree. to about 100.degree. and, in particular,
about 90.degree. for use in an auditorium setting. Depending on a
particular application, the predetermined angle may be chosen by
one of ordinarily skill in the art to optimize the performance.
[0027] As to the number and configuration of the slots 43, FIG. 2
illustrates four slots 43 formed within a RBI 50. Each slot may be
configured into an elongated rectangle and formed on each of the
four quadrants. For example, in the (1) upper right, (2) the upper
left, (3) the bottom right, and (4) the bottom left. With regard to
the width "W" of the slot 42, their size may range from one-half
inch to 1 inch. The distance "D" between the two slots 43 may range
from two to four times the width "W". Thus, an example
configuration have support D=W .times.(two to four). If W=1 inch,
then D may be between about 2 to 4 inches. In this embodiment,
width "W" is about {fraction (13/16)}-inch (about 2.0 cm) and
distance "D" is about 2-{fraction (9/16)}inches (about 6.5 cm). The
height "H" of the slots 43, may be configured to substantially
equal to the diameter of the mid-range frequency sound source
40.
[0028] Although the above example illustrates three high and four
mid-range frequency sound sources, any number of mid-frequency or
high frequency sound sources may be used. And by way of background,
a mid-frequency sound source 40 generally produces frequency energy
between approximately 200 Hz and 2000 Hz. The high frequency sound
source 41 generally produces frequency energy above 1000 Hz and may
refer to such devices as transducers, drivers, and speakers.
[0029] FIGS. 1 and 2 illustrate slots 43 running through the RBI.
However, the slots 43 may act as a cavity that may interfere with
high frequency sound waves passing along the top surface 60. To
minimize such an effect, as illustrated in FIGS. 3-8, each of the
slots 43 may be filled with a porous material 48 such as foam so
that the RBI 50 acts like a substantially solid boundary layer for
the high frequency sound waves generated by the source 41. That is,
foam pieces 48 may be shaped to fit the slots 43, and may be
inserted into the slots 43 in order to create a substantially solid
acoustic surface for the high frequency energy generated by the
high frequency sound source 41.
[0030] The foam 48 may be substantially transparent to mid-range
frequency sound waves, however, to allow such waves to pass through
the slots 43. This way, the foam 48 may be substantially solid
acoustically to high frequency sound waves to substantially block
high frequency sound waves normal passing across the foam from
passing through the same slots. An example foam piece may have
porosity between 60 PPI and 100 PPI. A foam section, having a
porosity of about 80 PPI, may be ideal for appearing transparent to
mid-range frequency. Besides foam, any porous material may be
used.
[0031] FIG. 3 illustrates the right side "R," the left side "L,"
and the base "B" of the RBI 50 that may be sized to substantially
mask or cover the mid-range frequency sound sources 40 and to
provide a substantially solid boundary layer for the high frequency
sound waves from the sound sources 41. In this example, the right
side "R" may be greater than the left side "L" so that the space
between the two RBIs 50 expand in the lateral direction and also in
the vertical direction. In one example implementation, the right
side "R" may range from 16 inches to 18 inches. The left side "L"
may range from 15 inches to 16.5 inches. And, the base B may range
from 7 inches to 9 inches.
[0032] In particular, as illustrated in FIG. 7, the skin of the RBI
50 includes a top portion 60 and a back portion 62. In between the
top and back portion may be foam 64 as well, so that the RBI 50
made of such assembly is acoustically inert for damping purposes.
This keeps the RBI 50 from being resonant and hollow sounding. One
of the advantages of using foam in the middle is that it reduces
the weight of the RBI 50. The foam in the slots further serves as a
low pass filter for the higher frequencies of the mid-range sound
source. These frequencies may pass through the slots and perhaps
interfere with the high frequency sound waves from the sound
sources 41. That is, the foam in the slots may prevent distortion
of the higher frequency sound waves generated by both the high and
mid-range frequency sound sources.
[0033] The top and bottom portions 60, 62 may be made of a variety
of materials providing an acoustical boundary to the high frequency
energy generated by the high frequency sound source 40.
Alternatively, as illustrated in FIGS. 3-8, the skin of the RBI 50
may be vacuum formed from plastic.
[0034] RBI 50 also serves as a volume displacement device creating
a loading for those midrange frequencies originating from the
mid-range frequency sound sources 40. This effectively attenuates
the higher frequencies, while improving the efficiency at the lower
mid-range frequencies. The back portion 62 of the RBI 50 may be
juxtaposed to the cone of the mid-range sound source 40 without
coming into contact with the cone. The space in front of the sound
source 40 may be substantially closed except for the transparent
slots in the RBI 50. As such, RBI 50 compression loads the
mid-range frequency sound source by making a substantial portion of
the cone surface oppose a solid surface leading to the slots 43
allowing for a transparency of the mid-range frequency sound waves.
In other words, the acoustic load in front of the cone is greater
with the RBI masking the sound source 40 when compared to operation
in open air without the RBI 50. This effectively transforms the
diaphragm surface to a larger equivalent air mass, thus increasing
the efficiency of the acoustic system at the lower frequencies.
[0035] In general, the mid-range frequency sound sources do not
operate at frequencies where it may not be efficient. That is, as
the effective size of the diaphragm becomes bigger it is less
efficient at high frequencies than at lower frequencies because the
total mass of the air load on the front of the diaphragm at higher
frequencies is substantially greater. As such, the mid-range sound
sources here generate more mid-range frequency to take advantage of
the improved efficiency.
[0036] In FIGS. 4-8, the back portion 62 may be formed to
substantially mirror the cone and the dome shape of the
mid-frequency sound sources 40. To minimize the interference at the
upper range of the middle frequencies, the back portion 62 may be
configured to be as closely adjacent as possible to the
mid-frequency sound sources 40 without the cone of the
mid-frequency sound sources 40 touching the back portion 62 when
the cone vibrates. For example, the back portion 62 may be
separated from the mid-frequency sound sources 40 by 0.2 to 0.4
inches. The distance between the back portion 62 and the
mid-frequency sound sources may be about 0.375 inch.
[0037] In FIG. 8, the slots 43 gradually expand from the back
portion 62 to the front portion 60 of the RBI 50. For example, an
acute angle .phi. may be formed between the two outer surfaces of
two slots 43, and the slot 43 may expand at an acute angle .alpha..
In this example, the acute angle .phi. may be between about
30.degree. and about 50.degree., and in particular about
40.degree.. The acute angle .alpha. may be about 15.degree. to
about 25.degree., and in particular about 20.degree..
Alternatively, the slot 43 may expand in a curved line to provide a
smooth transition or expansion from the back portion to the front
portion.
[0038] FIGS. 9 and 10 illustrate alternative slots that may be
formed within the RBI 50. That is, the number of slots and
configuration of the slots may vary in size and shape to achieve
the desired result of having the surface of the contour RBI 50
being substantially acoustically solid to high frequency sound. For
example, FIG. 9 shows a smaller circular slot 100 filled with foam
within a larger circular slot also filled with foam. FIG. 10
illustrates six slots 104, 106, 108, 110, 112, and 114 within the
RBI 50, where each of the slots 104, 106, 108, 110, 112 and 114 has
a smaller width than the slots 43. The RBI 50 may also be
configured to have one continuous slot such as a slot forming an
"O," "S" or "Z" shape.
[0039] In general, the size of the slots may be optimized if the
area of the slot or slots is too large or if there are too many
slots. Thus, the foam inserts may not be adequate to form a
substantially solid acoustic surface for the high frequency sound
waves. If the area of the slots is too small, or if there are not
enough slots, then there may not be enough slots for the
mid-frequency sound to pass through the slots.
[0040] FIG. 11 illustrates the RBI 50 used in a line array speaker
configuration 70 masking midrange sound sources. This way, the
invention may also be able to direct sound radiation to a
predetermined area. That is, listeners seated within a
predetermined area would receive substantially the same quality of
sound as other listeners at other locations within the same area.
This feature is particularly advantageous when used in large area
performance environments, such as auditoriums where there are many
listeners.
[0041] FIG. 12 illustrates, the RBI 50 used in a line array speaker
configuration 70 arranged vertically. This example implementation
may be referred to as a line array speaker system because these
speakers can be stacked one on top of another, creating an array.
These speakers typically are suspended from overhead, forming
vertical lines of transducer arrays within their original
bandwidths bass, mid-range and treble. By forming those individual
lines and curving these speaker arrays, improved dispersion
uniformity and better control of the radiated sound may be
realized. The sound radiating from the array of loudspeakers may be
further improved by improved integration of the sound radiation
from the mid-range and high frequency elements by providing a
substantially solid boundary for the high frequencies while
allowing the mid-frequency sound to be emitted through that solid
boundary by way of slots in front of the mid-frequency speakers.
This arrangement may also act as a volume displacement device to
improve loading and efficiency of the mid-range frequency
elements.
[0042] While various embodiments of the application have been
described, it will be apparent to those of ordinary skill in the
art that many more embodiments and implementations are possible
within the scope of this invention. Accordingly, the invention is
not to be restricted except in light of the attached claims and
their equivalents.
* * * * *