US2646851A - Loud-speaker baffle with elongated aperture for the egress of sound - Google Patents

Loud-speaker baffle with elongated aperture for the egress of sound Download PDF

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Publication number
US2646851A
US2646851A US47824A US4782448A US2646851A US 2646851 A US2646851 A US 2646851A US 47824 A US47824 A US 47824A US 4782448 A US4782448 A US 4782448A US 2646851 A US2646851 A US 2646851A
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Prior art keywords
slot
loudspeaker
sound
diffusion
width
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Expired - Lifetime
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US47824A
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English (en)
Inventor
Chapman Roger
Trier Robert Henry
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International Standard Electric Corp
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International Standard Electric Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/32—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only
    • H04R1/34—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by using a single transducer with sound reflecting, diffracting, directing or guiding means
    • H04R1/36—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by using a single transducer with sound reflecting, diffracting, directing or guiding means by using a single aperture of dimensions not greater than the shortest operating wavelength

Definitions

  • An object of the invention is to provide a loudspeaker batfle which effectively diffuses the radiation of sound waves emitted by a loudspeaker diaphragm.
  • Another object of the invention is to broaden the radiation pattern of the output of a loudspeaker.
  • Fig. 1 shows a loudspeaker in a box baiiie with an aperture in the form of a single slot extending the full width of the speaker diaphragm.
  • Fig. 2 shows a loudspeaker in a box baffle with an aperture in the form of a single slot less in length than the diameter of the speaker diaphragm.
  • Fig. 3 shows a loudspeaker in a box baffle with a round aperture of smaller diameter than the diameter of the speaker diaphragm.
  • Fig. l shows a radio set having the loudspeaker mounted behind a bafiie having two adjacent parallel slots divided by a decorative rib.
  • Fig. 5 shows a loudspeaker in a box barate having two parallel slots divided by a vane.
  • Fig. 6 shows a loudspeaker in a box having a number of holes in lieu of slots.
  • the invention consists of a device for coupling a loudspeaker to the atmosphere for the output of sound comprising a member adapted to be placed over one side of the loudspeaker having an aperture or apertures for the egress of sound, at least one dimension of which, if there is only one aperture, or where there are more than one aperture the aggregate dimensions of all of them in at least one direction, including the width of the space or spaces between apertures, is between 1 and 3% inches and is never more than half of the diameter of the effective radiating portions of the diaphragm of the loudspeaker at 500 C. P. S.
  • the invention consists of a battle for a loudspeaker with an aperture for the egress of sound, in the form of a virtual slot of the order of 3 to 4 inches in length and of the order of 1 /2 inches in width.
  • the invention consists of a baflfle for a loudspeaker with an aperture for the egress of sound in the form of a virtual slot of the order of 5 to 8 inch-es in length and 1% to 2 /2 inches in width.
  • the invention consists of a bafile for a loudspeaker with an aperture for the egress of sound in the form of a virtual slot of the order of 10 inches upwards in length and 1 /2 inches to 3 /2 inches in width.
  • the invention consists of a baffle for a loudspeaker having an aperture for the egress of sound, in the form of a virtual slot having dimensions of the order of l to 3% inches in directions at right angles.
  • the invention consists of a baffle for a loudspeaker having an aperture for the egress of sound in the form of a virtual slot of the order of 5 inches up to 18 inches in one direction and of the order of 1 /2 to 3 /2 inches in the direction normal to the first direction.
  • the invention consists of a baflle for a loudspeaker having an aperture or apertures for the egress of sound from one side of the loudspeaker in the form of a slot or slots the width of which, if only one, or the aggregate width of which if more than one including the width of the space, or spaces between the slots, is not greater than 2 inches.
  • a loudspeaker of the so-called direct radiator type is usually mounted in a device of some kind (hereinafter referred to as a coupling device), designed to separate sound waves generated on one side of the diaphragm from sound waves generated on the other side of the diaphragm.
  • a coupling device designed to separate sound waves generated on one side of the diaphragm from sound waves generated on the other side of the diaphragm.
  • Coupling devices of this type take various forms such as the familiar bafile, which may be a fiat board or an open-backed box such as a domestic broadcast receiver cabinet.
  • various forms of enclosure or semienclosures of one side of the loudspeaker may be used, these alternative devices having a number of objects: for instance, the phase shifting of the sounds originating on one side of the loundspeaker so that at certain frequencies, they reinforce, instead of cancel, the sounds originating on the other side; or the modification of'the acoustic impedance of the loudspeaker system as a whole, generally with a view to improvement of bass response and the damping of bass resonances.
  • bafiie As these alternative devices also separate the radiation from the two sides of the loudspeaker over substantial parts of the range of frequencies reproduced they are to this extent similar to a baffle, and the word bafiie is to be understood to include such devices where it is used hereinafter in this specification.
  • the sound intensity along the axis of the loudspeaker is greater than that at an angle to the axis, for frequencies whose wavelength is comparable with or less than the dimensions of the diaphragm. This phenomenon is commonly called focussing and it becomes more marked the higher the frequency.
  • the said aperture takes the form of a slot which may be substantially as long as the width of the diaphragm in one direction and smaller than that width in the other direction. Diffusion takes place in the direction of the narrow dimension, 1. e., if the slot has its longitudinal axis vertical, the diffusion is in a horizontal plane, which is the most useful arrangement in the case of a domestic broadcast receiver for instance.
  • the slot acts as a line source radiator of sounds whose wavelength is equal to or greater than the width of the slot, the diffusion falling oif at frequencies whose wavelength is less than the slot width.
  • the longer dimension of the slot can be reduced so that it is less than the width of the diaphragm, and if this is done there is some diffusion in the direction of this longer dimension also but the frequency band over which this diffusion is effective is limited at the upper end of the frequency spectrum, by the length of the slot.
  • the shortening of the slot can be carried to the extent of making both dimensions of the aperture equal (e. g. a round or square hole) and this produces hemispherical diffusion.
  • Apertures with more than one of their dimensions less than the width of the loudspeaker diaphragm have their uses where diffusion is required in more than one plane but the need to keep the loss of output within reasonable limits and the consequent necessity of maintaining a reasonable total area of aperture restricts the upper limit of sound frequency for which effective diffusion can be obtained and the usefulness of such arrangements will be limited to specialised applications such as speech reinforcement installations.
  • a slot extending substantially the full width of the diaphragm is used with a width of the order of the wavelength of the highest frequency for which the maximum diffusion is required.
  • this width is 1.92 inches, and 1.32 inches up to the 10 kc./s.
  • a width of slot which is equal to the wavelength of the highest frequency sound to be reproduced and with the normal radio set, a top limit of reproduced frequency of say 8 kc., may be adequate.
  • a slot of 1.65 inches, or, say, 1% inches wide will give maximum diffusion up to 8 kc.
  • the slot might be 2" wide with a falling off of the diffusion efiect from and above a frequency of somewhat below '7 kc./s.
  • a slot width of 2 inches is equal to the wavelength of sounds at 5280 cycles per second, above Which the diffusion effect would diminish, but would still be noticeable up to frequencies of the order of 7500 cycles per second.
  • the performance of the plurality of slots will generally be somewhat inferior to that of the equivalent single slot, however, since the obstructed space between the slots, while not materially affecting the diffusion effect, nevertheless reduces the total aperture area and causes some loss of sensitivity.
  • a row or rows of holes can be used in lieu of a continuous slot or slots with results approximately the same as those obtained with a single slot of the same width as the holes, or the same as the distance between the outer margins-of the holes of the row or of the outer rows where there 1 are more than two rows.
  • a box baffle I has a slot 2 in its front panel 3 behind which a loudspeaker is mounted, the lines 4 showing the position of the diaphragm mounting ring, the speech coil 5 being shown partly by dotted lines, and the cone diaphragm 6 being shown by shading lines.
  • the slot 2 extends across the width of the diaphragm '5 of the speaker and with this arrangement the diffusion attributable to the slot covers a space of half cylindrical form, the axis of the cylinder running down the slot vertically and the axial length of the cylinder bein co-extensive with the length of the slot.
  • vFig. 2 is similar to Fig. 1 except that the slot does not extend the full width of the speaker diaphragm.
  • the diffusion attributable to the slot is in substantially cylindrical form but the cylinder may be considered as being terminated by planes normal to its axis at the intersection of such planes with the plane of the baffle front and at an angle to the bafiie front being tilted upwards at the top of the cylinder and downwards at the bottom of the cylinder. There will be considerable loss of output with this arrangement.
  • Fig. 4 shows a table model broadcast receiver in 'whichtwo slots 2 :are used which'extend across the full width of the diaphragm of the speaker.
  • the distance between the outer margins of the two slots is equal to that of a single slot of comparable performance the division between them being a rib I which may .be added for decorative or structural reasons.
  • Two similar ribs '8, at the outer margins of the slots may be added as a further decorativeor structural feature.
  • a grille is shown covering the slot 2. This figure is an example of the use of a plurality of parallel slots .and, :of course, more than two slots, or more than one dividing member in a single slot, could be used.
  • Fig. 5 illustrates the arrangement where two parallel adjacent slots are separated by a vane.
  • the two slots 9 and I U have between them a vane 11 parallel to the length of the slots and normal to the battlefront 3.
  • the slots radiate into quarter-cylindrical zones each similar to the half-cylindrical diffusion zone in the case of Figure 1, and the two zones are separated by a vane H, so that each slot can be as wide as the wavelength of the highest frequency sound for which maximum diffusion is required.
  • the air loading of the diaphragm is halved, enabling the diffusion to be maintained to a higher frequency for a given .loss of output in the middle and bass register as compared with the single slot of Figure '1.
  • the same diffusion characteristic can be maintained and the loss of output in the middle and bass register can be reduced.
  • Figure 6 shows a bafile with a number of holes 12 in lieu of a slot or slots which may be resorted to for decorative or structural reasons though generally speaking the results will be inferior to those obtained with plain slots, and there will be irregularities in the radiation pattern due to the spaces between the holes.
  • the loudspeaker was first mounted in a plane battle with a round hole substantially the same size as the effective diaphragm radiating area and measurements of output at various frequencies were taken, at different angles to the speaker axis. Pronounced focussing became apparent at about 3 kc/s. being of the order of 8-10 db fall in output between measurements along the speaker axis and measurements at points 30 off-axis, and of 18 to 20 db at 45 off-axis. The focussing effect increased with rising frequency until at about 7 kc./s., the fall in output, as compared to the output measured along the axis,
  • the invention would be useful if at least one dimension of the aperture was small compared with the effective loudspeaker diameter (e. g. 1 inches or less).
  • the slot width will tend to be made wider than theoretical diffusion considerations would dictate, in order to avoid loss of power in the middle of the frequency range.
  • design for an upper frequency limit of say 8000 C. P. S. would call for a slot about 1 inches wide, the slot may actually be made between-sayl and 2 inches wide.
  • cones of this size will have a poor frequency response in any event at the latter frequency they will only be used alone where such an upper frequency limit is adequate, for instance in speech reinforcement systems, or where other measures, such as a separate high note loudspeaker, are adopted to handle the upper end of the frequency range.
  • the slot length may also vary from the effective cone diameter down a length equal to the designated slot width resulting, in the extreme cases, in a square, circular or polygonal aperture.
  • virtual slot used in the specification and the claims applies to any single aperture or slot of the type described, whether or not the same is obstructed or intersected by fabric, deco rative member or members or the like, and to a plurality of apertures used in lieu of a single slot.
  • References to a dimension of a virtual slot mean the gross dimension ignoring any such obstruction or intersections, and including the spaces between a plurality of apertures, in the line of measurements; and where the dimension in a given direction is not constant for all parallel lines of measurement in that direction the largest dimension in that direction is meant.
  • a loudspeaker comprising a diaphragm, a baffle plate arranged in front of said diaphragm and substantially perpendicular to the axis of the speaker, an elongated aperture in said baffle plate, one dimension of said aperture extending substantially the full width of said diaphragm and the other dimension of said aperture being substantially uniform and of the order of the wavelength of the highest frequency for which maximum diffusion is required.
  • a loudspeaker comprising a diaphragm, a bafile plate arranged in front of said diaphragm and substantially perpendicular to the axis of the speaker, a virtual elongated slot in said baffle, the width of said slot being substantially uniform and of the order of the wavelength of the highest frequency for which maximum difiusion is required.
  • a baffie plate for a loudspeaker arranged substantially perpendicular to the axis of the speaker comprising a plurality of apertures in the form of an elongated virtual slot, the width of said slot being substantially uniform and of the order of the wavelength of the highest frequency for which maximum diffusion is required.

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  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)
  • Diaphragms For Electromechanical Transducers (AREA)
US47824A 1947-09-10 1948-09-04 Loud-speaker baffle with elongated aperture for the egress of sound Expired - Lifetime US2646851A (en)

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Application Number Priority Date Filing Date Title
GB283814X 1947-09-10

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US2646851A true US2646851A (en) 1953-07-28

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Country Status (7)

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US (1) US2646851A (fr)
BE (2) BE522721A (fr)
CH (1) CH283814A (fr)
DE (1) DE944860C (fr)
FR (1) FR971128A (fr)
GB (1) GB659063A (fr)
NL (1) NL77682C (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2787332A (en) * 1952-09-06 1957-04-02 Norman C Fulmer Loud-speaker system
US3146848A (en) * 1958-08-25 1964-09-01 John O Fundingsland Hi-fidelity speaker
US4207963A (en) * 1978-12-11 1980-06-17 Integrated Sound Systems Inc. Loudspeaker system
US4870691A (en) * 1987-01-14 1989-09-26 Mindel Gerard S Load and dispersion cell for sound
US20080302595A1 (en) * 2007-06-08 2008-12-11 Moore Dana A Horizontally folded reflex-ported bass horn enclosure
US20090065293A1 (en) * 2007-09-12 2009-03-12 Moore Dana A Convertible folded horn enclosure with improved compactness
US20090277713A1 (en) * 2005-04-21 2009-11-12 Ambrose Thopson Acoustic Loading Device for Loudspeakers

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2694462A (en) * 1951-09-19 1954-11-16 Robbins Frank Acoustic system for loud-speakers
US2694463A (en) * 1952-04-07 1954-11-16 Robbins Frank Acoustic system for loud-speakers
DE1130472B (de) * 1957-11-22 1962-05-30 Philco Corp Lautsprechermembran
GB1557879A (en) * 1976-12-03 1979-12-12 Rank Organisation Ltd Electro acoustic transducers
DE3407980A1 (de) * 1983-04-20 1984-10-25 Tadashi Tokio/Tokyo Sawafuji Kristallschallerzeuger
FR2649572B1 (fr) * 1989-07-07 1991-09-20 Thomson Consumer Electronics Dispositif de reproduction sonore pour televiseurs

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US272866A (en) * 1883-02-27 Speaking-trumpet for receiving-telephones
US1616474A (en) * 1925-03-05 1927-02-08 Charles F Stehlin Tone-developing loud speaker
US1865735A (en) * 1929-04-01 1932-07-05 Rca Corp Sound reproducer
GB404937A (en) * 1932-07-14 1934-01-15 William Robertson Millar Improvements in sound-modifying devices for loud speakers or the like
US2214393A (en) * 1938-09-10 1940-09-10 Ingraham E Co Acoustical equalizer
US2373692A (en) * 1942-10-03 1945-04-17 Ray L Smith Loud-speaker

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR791142A (fr) * 1934-09-06 1935-12-04 Dispositif protecteur et amplificateur de son pour hauts-parleurs de t. s. f.

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US272866A (en) * 1883-02-27 Speaking-trumpet for receiving-telephones
US1616474A (en) * 1925-03-05 1927-02-08 Charles F Stehlin Tone-developing loud speaker
US1865735A (en) * 1929-04-01 1932-07-05 Rca Corp Sound reproducer
GB404937A (en) * 1932-07-14 1934-01-15 William Robertson Millar Improvements in sound-modifying devices for loud speakers or the like
US2214393A (en) * 1938-09-10 1940-09-10 Ingraham E Co Acoustical equalizer
US2373692A (en) * 1942-10-03 1945-04-17 Ray L Smith Loud-speaker

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2787332A (en) * 1952-09-06 1957-04-02 Norman C Fulmer Loud-speaker system
US3146848A (en) * 1958-08-25 1964-09-01 John O Fundingsland Hi-fidelity speaker
US4207963A (en) * 1978-12-11 1980-06-17 Integrated Sound Systems Inc. Loudspeaker system
US4870691A (en) * 1987-01-14 1989-09-26 Mindel Gerard S Load and dispersion cell for sound
US20090277713A1 (en) * 2005-04-21 2009-11-12 Ambrose Thopson Acoustic Loading Device for Loudspeakers
US8191674B2 (en) * 2005-04-21 2012-06-05 Martin Audio Limited Acoustic loading device for loudspeakers
US20080302595A1 (en) * 2007-06-08 2008-12-11 Moore Dana A Horizontally folded reflex-ported bass horn enclosure
US7520368B2 (en) * 2007-06-08 2009-04-21 Moore Dana A Horizontally folded reflex-ported bass horn enclosure
US20090065293A1 (en) * 2007-09-12 2009-03-12 Moore Dana A Convertible folded horn enclosure with improved compactness
US7513332B2 (en) * 2007-09-12 2009-04-07 Moore Dana A Convertible folded horn enclosure with improved compactness

Also Published As

Publication number Publication date
CH283814A (fr) 1952-06-30
BE522721A (fr)
NL77682C (fr)
DE944860C (de) 1956-06-28
FR971128A (fr) 1951-01-12
BE484735A (fr)
GB659063A (en) 1951-10-17

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