jmmlc lecture on horns

5/19/2018 JMMLC Lecture on Horns

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wavegu esJean-Michel Le Clach

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,

toutes illustrations droits rservs sauf spcifi


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etymology: Greek : karnon,

Latin : cornu.the horn of an animal

a "wind instrument

(originally made from animal horns)

reference to car horns is first recorded in1901.

cornucopia

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Neolithic carving

Laussel cave, France


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(in French)

Pavillon de loreille = part of the external ear which looks like a butterfly=

3

,

An automatic translation may also lead to surprising results like "small house" or "flag"...


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a horn is a tube whose cross-section increases from throat to mouth in order

to increase the overall efficiency of the driving element = the diaphragm. Thehorn itself is a passive component and does not amplify the sound from thedriving element as such, but rather improves the coupling efficiency betweenthe speaker driver and the air. The horn can be thought of as an "acoustictransformer" that provides impedance matching between the relatively dense

.

This is important because the difference in densities and motional.

the horn next to the speaker cone "driver" is called the "throat" and the largepart farthest away from the speaker cone is called the "mouth.

4


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Historical milestones

1876 ____________ Bells Telephone

1877 ____________ Edisons Phonograph

1906 ____________ Lee de Forests triode

1920_____________first commercial radio broadcast

_____________

1926 ____________ First commercial talking movie

1953 ____________ Transistor commercialization

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Oliphant

Shofar hornbelarussia

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Shell from Nepalwith the Godess

Mandala.

Tahitian Pu-Toka

7Turbinella PyrumIndia


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megaphones

Echo Lake megaphoneFisherman using amegaphone

Giant megaphone in BrusselsAnd now she beats her heart, whereat it groans,That all the neighbour caves, as seeming troubled,Make verbal repetition of her moans;

Ay me, she cries, and twenty times, Woe, woe,And twenty echoes twenty times cry so.

Venus and Adonis , Shakespeare

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horns as musicinstruments

First horns China

Oxus

Egypt Greece

Alphorns and thibetan horns

Strings instruments with horns

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4000

BC

in

China

3000 BC inOxus(AfghanistanRussiafrontier)

Oxuscivilization

300 BCin Greece

300

BC

in

America

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Peru


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ancientGreece

Tutankhamuns

trumpets

"tuuut.....!"

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ancientEgypt


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Thibetan

Alphorn

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from the 19th

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127dB!

vuvuzela

14brass horn used to load aloudspeaker by SusumuSakuma


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violophone

hornviolin

When strings meet horns

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vioara cu goarnastrohcello


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Non musical

purposes architectural acoustics

og orns

firemen sirens

car horns and Klaxon m ary megap ones

acoustic locatorsPropagation Horns

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(Kempten 1673)


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Architectural ur oses

the princelistening to thecourtiers speaking

outside the

Athanasius Kircherinvented the megaphone

(1608 Germany - 1680 Italy)

Horns used in ancient architecture

Today in Mexico

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JohnTyndall1820-93

Circa 1873

18foghorns designed by Lord Rayleigh

Trevose Head Lighthouse, Cornwall (1913)


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Firemen siren

sirens andKlaxons

a siren playing trumpet

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victim of pollution

Kopenhagen siren


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military

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before radar:

acoustic

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Hearing aids

Athanasius KIRCHER

(1673)

, ,O would thou hadst not, or I had no hearing.Thy mermaids voice hath done me double wrong;I had my load before, now pressed with bearing;Melodious discord, heavenly tune harsh sounding,

22

, .

Shakespeare


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Recording and

reproducing soundsThe very first recording of sound was made by Edouard Lon

,

probably 1854 as written in his writting Fixation graphique de lavoix (1857) . He didnt know how to reproduce those sounds

First successful recording followed by its reproducing (1877) is

due to Thomas Alva Edison with his phonograph .

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Phonautograph1860-Scott-Au-Clair-de-la-Lune_2.mp3

a simplistic horn

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In December of 1877, Edisons machinistpresented him with the completed prototype.

Edison leaned toward the recording horn ands ou e ou e wor s ary a a e am ,it's fleece was white as snow, and everywherethat Mary went, the lamb was sure to go.

It was hardly a moving speech, but thennobodynot even Edisonexpected the

.

To his great surprise, a highly distorted but

out of the machine when the tinfoil was crankedunder the needle once again.

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mary_jas_a_little_lamb.mp3


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at the French Academy

Phonograph

Edison Thomas.mp3

,

recording of a piano on a cylinder recording at Smithsonian

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Dickson first

Experimental soundfilm (1894)

for recording through the horn,

the head was replaced by a"recording head"


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Cylinder version

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The E.M.G.Mark Xa

gramophone

28see: Horn theory and the gramophone Percy Wilson in JAES 1974

Trapezoidal Horn Fitted to an "Expert" GramophoneBalmain Gramophone with 5ft. StraightHorn


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The world's first commercial electrical recording

The setup for Guest and Merriman's pioneering

electrical recording of the Burial of the UnknownSoldier in Westminster Abbey on 11 November 1920.

On February 25, 1925, Art Gillham recorded"You May Be Lonesome, a song written by Art

.

It was the first master recordedto be released using Western Electric's

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e ectr ca recor ng system.


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times

1920In Pittsburgh, Westinghouseradio station KDKA schedules the

The first radio

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first commercial radiobroadcastthe Harding-Coxpresidential election results.

microphone


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a question of conversion efficiency of the energy

between air and

water.Im edance match

o move e oa sfar more efficient to

the water than in the

air.

Impedance mismatch

characteristic impedance of air is about 420 Pa s/m

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.

(nearly 3600 times higher)


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- to progressively adapt the acoustical impedance

from the throat to the mouth

- to control the dis ersion of the waves out oin

32from the horn


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The specific acoustic impedance z of an acoustic component

n s mis the ratio of sound pressure p to particle velocity v at its

Where:

is the sound ressure N/m or Pav is the particle velocity (m/s), andI is the sound intensity (W/m)

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Sound power:

no oss ns e t e orn:

Sound intensit :it is the sound power per

unit area

It = Pt / At

=

Thus:

For a given sound intensity

It / Im = Am/ At

proportionnal to the ratio ofthe mouth area on the throat

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area


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the horn creates a higher acoustic impedance for the transducer to work

into thus allowin more ower to be transferred to the air.

- increase of efficiency (up to 50% )

use of low ower am lifiersuse of low ower am lifierslower distortion due to smaller displacement of the membranelower distortion due to smaller displacement of the membrane

- acoustical gain (10dB and more)

- depends on the need of a narrow or a wide spread of

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the sound in the room


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Webster's e uationWebster's e uationWebster's equation for a constant bulk modulus:

where :

The only assumption which has been made is that the.

isophase surfaces. Plane waves, spherical waves, orother wavefront shapes can be assumed within the

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framework of Webster's equation.


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1) pressure p depends only on a single coordinate

2) only longitudinal waves propagates from throat to

mouth

Theor tells us:

only 3 shapes for the wavefront and for theinfinitesimal sound duct obey to the 1P hypothesis:

wavefront shape: duct shape:

spherical cap conical hornc linder toroidal horn

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isophase surfaces are parallel

iso hase surfaces are er endicular to horn wall

38 isobare (= isopressure) surfaces are parallel to isophase

William Hall (1932)


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William Hall (1932)

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For horns for which p depends on 2 or 3

coordinates we have to take in accounthi h order modes HOM .

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Isobare curves inside a horn

to take in account the

not sufficient to relysimulation to measurement

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The quest for efficiency,the quest for loading

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R.P.G. Denman, "In Search of Quality", Wireless World, Vol. 25 pp97-101 (July 31, 1929)


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Mr. Kei Ikedas listening room

In 1926, the

Vita hone s stem

Julien Sullerots

uses the famousdriver WE 555-Wcoupled to the

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of an Onken Wenclosure

WE15A horn

(100Hz to 5kHz)


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Acoustic studies using theWE15A .See on right Wente's planar waves

tube he used to measure the powerresponse of the WE555 driver

development of theStereophonic system

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1933)

H ll d f d


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Holl wood oes for sound David FisherMajors' fi lm releases in 1928 Majors' fi lm releases in 1929

In1928thesevenHollywoodmajorsreleased220 In1929thebalancehadshiftedradically.

,

only synchronisedmusicandsoundeffects,23

were parttalkieandonly10,allfromWarner

Bros,were alltalkie.UniversalandParamountin

,

parttalkieand36withonly musicandeffects.

Silentreleaseshaddwindledtoonly38outofa

totalof290.

productions.

silent films synchronized music part talkie all talkieand sound effects

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1926 "Don Juan" first talking movie, 1927 "The Jazz Singer"


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1929 - 1935

47Sid Graumans Chinese theater in Hollywood inaugurated in 1927


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VOT A2

48VOT A7


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1960s

60080 X JBL375

+

acous cwattsGenerator

vibrationanalysis

multiple

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diffractor couplers (Karlson coupler)

reflectors

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JBL "potatoe crusher"


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Acoustic

lenses

51Klanfilm horn with acoustic lens at mouth JBL acoustic lens


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JBL

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JBL

JBL


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Karlson coupler

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Elliptical reflectors = acoustic shells


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Elliptical reflectors acoustic shells1673

doctor andpatient

oca ors

Elipson loudspeakers

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old folded horns


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old folded horns

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WE 13A horn

571929 - 1935

WE the Tub , circa 1938


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58WE collector in Japan


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59Fletcher system (1933-1940)

modern folded horns


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YL folded horns (Japan)

Technics folded horns


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Yoshimura Laboratory, Ale and Goto horns

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Yamamura fullrange

Churchill and Dionisio 32Nelson Passs fullrange Kleinhorn

First folded bass horns


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WE TA7396, 1936 -1937The Shearersys em rece ve atechnicalachievement

award at the 1936Academy of MotionPicture Arts andSciences

62RCA

ceremony.


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Early exponential straight horns


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e ore

my home made crystal radio with a Vitavox E190 horn

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Horn tweeters


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Klangfilm20 hz Tractrix horn

Germany, 1951

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Strai ht bass horns


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Bjorn Kolbreks long throw bass horns

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Vincent Brients 30Hz basshorns (France)

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Klaus Speth, full horns with Goto drivers (Germany)

Quasi cylindrical waves bass horns in France


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Jean-Paul

Marcel Roggero

Frdric Lebas

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Salmon family (exponential, hypex, etc.)

Tractrix, Kugelwellen and Spherical

oblate spheroidal Le Clac'h

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hyperbolical Le Clac'h

+ Kugelwellen

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resistive art

from catenoidal (T = 0)

< 1)reactive part

of theacousticalimpedance

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Western Electric exponential horn

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Normal rangeof T valuebetween


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0 and 1 For T>>1 the profile becomes progressively conical

rofiles of h erbolic famil horns with T value variation between 0 and 128

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the Tractrix hornthe Tractrix horn


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Paul G.A.H. Voigt

the mathematical pseudosphere

-

principle

a square tractrix horn built by

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son e n ng an

"The onl wa that he could fi ure out to makehis driver sound good was to horn load it, but he


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his driver sound good was to horn load it, but he

couldn't understand the mathematics behind theexponential, so he said, "Well, the exponentialtheor redicts that the wave form oin downthe horn is plane or flat, but if you look at thephysics of the situation, the wave front has todrag along the horn walls. So naturally it's going

to be curved. What if I eometricall desi ned ahorn that has curved wave fronts all the waythrough the horn and see what happens?"

So he did a geometrical construction of a horn that would give him.

done and said, "Oh, that's a Tractrix curve." The Tractrix curve comesabout because if you have one airplane chasing another on a different

,other plane, and it turns out that's a Tractrix curve."

Bruce Ed ar on Voi t's tractrix

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expansion law of the Tractrix horn A = 2 R h = 2 R [1-cos( )]


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KugelwellenKugelwellenRsch ( KLANGFILM laboratories )


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Rsch ( KLANGFILM laboratories )

radius is the double of the radius used in the tractrix horn

78see also : H.Schmidt: "ber eine neue Lautsprecherkombination" Funk und Ton N5, 1950, p.226-232

Ku elwellen


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re ne v ew oa Kugelwellen horn

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radiation diagram of the Kugelwellen horn

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" ' "


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Le Clachs method to calculate the profile of an horn knowing therelation between the area of the wavefront and its distance to throat


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Wireline 3D view of

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Current driven

Current driven

Voltage driven

Voltage driven

84analysis by Jacek Zagaja


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J321 (Fc = 320Hz)

rec v y pa ern o ewLe Clac'h horns

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J871 (Fc = 870Hz)

compared profiles of exponential, spherical, Le Clac'h,, ,


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Note how the profiles of the Kugelwellen

and Le Clach horns are ver similar

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waveguidesThe benefits of the directivity of a waveguide

levels within the included angle of thewave uide within the o eratin fre uencband of the waveguide.

In addition, sidewall and floor bouncereflections are reduced by the controlled

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conical hornconical horn


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Oblate spheroidal waveguideOblate spheroidal waveguide


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Earl Geddes

"The concept of a waveguide asa rec so u on o e waveequation was shown to becapable of exact solution, free

of Webster'equation. "

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oblate spheroidal

system of coordinates


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90

While the summed power responsedi t d b th OS id i f ll


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radiated by the OS waveguide in fulls ace is ver smooth the fre uencresponse curve at any given anglefrom the axis is never smooth

See measurements of Earl

Geddes loudspeaker on.

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and simulation

of horns

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above: the first models used atank filled of water.

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on right : later finite elementsmethods were used


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one of the first ublication on FEM results of the simulation of soundfields

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in horns

easuremen s

performed


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performed

an exponential horn by JohnSheerin

Anal sis usin Caraperformed my MichaelGertsgrasser

wavetank analysis in

95David McBeans Hornresp

software.

Radiation from a

differentfrequencies


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Pressure map

Polar graph witha 3D

presentation

Various simulations of theradiation of a iston and of

a horn.

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conical horn Le Clac'h horn

FEM simulations performed by John Sheerin

Note the distortion of the shape of the wavefronts Note the very smooth wavefronts

97(Half horn represented only)


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s mu a ons o an wavegu e a eren requenc es

Note the wavy isobare curves over 2000Hz

98

Copyright John Sheerin


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Note the smoothness and the linarity of the

isolevel contours.

polars obtained by FEA of a 275Hz tractrix

'

99FEM simulations performed by John Sheerin


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simulation by

John Sheerin

my

e achorn

the J321 horn

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backreflected waves,

g r er o es (HOMs)

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from mouth tothroat inside a


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from mouth tothroat inside ahorn.

Single reflection

Double reflection

Triple reflection

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When the pathlength between the direct wave ande re ec e wave s equa o a mu p e o e

wavelength at the considered frequency, we

observe a summation of their pressure.

Wh th thl th b t th di t d


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When the pathlength between the direct wave andthe reflected wave is equal to a odd multiple of thehalf wavelength at the considered frequency, weobserve a subtraction of their pressure.

easy demonstration of backre ec e waves w aloudspeaker, a magazineforming a cone and a towel

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large diffraction low diffraction


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large reflection low reflection

- on left, high reflectance

- on ri ht ver low reflectance

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measuremen s

performed at ETF2010

HOMs absorptionHOMs?

Effect of the


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wavelets graph of the oblate subtraction of the

sp ero a wavegu e

OSWGD without its foamplug and with its foam HOMs have non axial

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rave ns e e orn

HOMs ? HOMs ?


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Jmmlc OSWgd econowave

the wavelets graph may be used in order to show the

107existence of sub-millisecond delayed energy (HOMs?)


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optimization with the goal

o a ow re ectance

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horns having a lower reflectance at mouth havesmoother frequency response curves


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increasedopening angle at

110optimized profile for the lowest reflectance at 27 frequencies

In search of a more constant

radiation angle


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radiation angle

Multicellular horns

Constant directivityorns

Wave uidesQuadratic throat waveguideOblate spheroidal waveguide

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mu ce u ar orns


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with curved dividers

the idea is to split the wavefront near the throat of the hornthrough several ducts before the wavefront at HF begins to

separate from the walls of the horn.

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multicellular horns with

curved thin dividers


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The dividers follow flow lines .Different shapes of cell coexist.

WE 24A,1936 - 1967

Flat mouth

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multicellularhornswithidenticalcells

Altec


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Onken 255 wood and Onken 455

114Onken 255wood Altec LansingH1804B

bass reflex enclosure


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eta othe assembly

of cells

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t i l h h li ( i l )


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sectorial horns have linear ( conical )expansion in one plane and

exponential expansion in the other.

Dividers can be flat (e.g. Altec 511 and. .

JBL2397)

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n en


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e

117


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The TAD

TH4001 hornhas a Smith horndesign at throat

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A300horn


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Altec

the Mantara horn

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from diffraction horns to biradial horns


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JBL

Electro Voice

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its goal:

to obtain a more constantfrequency response over a

chosen solid an le

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Oblate spheroidal

waveguide

Note the rather constant


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directivity over 1kHz andthe wavy contours

horn calculated by the

"Le Clac'h" methodNote the directivity regularlyincreasing with frequencyand the smooth contours

simulations using

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ornresp

2 ways enclosure


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See also:

Acoustic waveguide for controlled

sound radiation

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United States Patent 7068805

mode 00


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mode 00

mode 00 mode 01

mode 01

mode 10 mode 11

only modes 00, 0i, j0

124exist with round horns

each High Order Mode has its own cut-off

frequency


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Michael Gerstgrasser'minphase horn is a good

Le Clac'h horn and the

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profile of the

mouth of an OSwave uide iscurved at a


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nearer distancefrom the throat

3 4

simulations

MichaelGerstgrasserusing AxiDriver

126from 1 to 4, note the more evenly distributed pressure field

frequency response from 0 on axis to 90off axis by 5 steps


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without e ualization with e ualization

Le Clac'h horn Min-Phase horn

The Min-Phase horn provides a better directivity control than the Le Clac'hhorn while kee in the smoothness of the fre uenc res onse curves on and

127off axis.


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128

(France), 1903

a new Le Clac'h horn (2007)

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