Art & Acoustique Appliquée
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Référence
R120
The doublets
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300 (first version)
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300 (second version)
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395
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Allégro Disco
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Alto
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Allégro HP 120
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Alto HP 60
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Alto HP 70
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Alto HP 75
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Pro 150
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Pro 300
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Alto iX 100
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Arioso iX 150
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Reference 2008
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Master Reference 2008
The slaved
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Andante Electronic 40
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Andante Electronic 60
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Andante Electronic Type 64
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Andante Linéaire
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Andante Linéaire de contrôle (first version)
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Andante Linéaire de contrôle (second version)
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Andante Master Control
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Andante Master Control Type 64
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Andante Master Control Type 680
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Andante Prélude
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Andante Studio
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Andante Ultra Linéaire
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Référence 1000
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Référence 2000
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Référence R100
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Référence R120
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Triphonic TR500
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Triphonic TR800
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Triphonic TR1000
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Triphonic TR1200
The Infinites
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390 (first version)
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390 (second version)
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Adagio Infinie (first version)
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Adagio Infinie (second version)
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Adagio Infinie (third version)
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Digitale Adagio 390 D
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Studio Infinie
The laminar
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340
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370
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380
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385
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390 (third version)
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420
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450
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Alphase (first version)
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Alphase (second version)
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Apogée Monitor Type 290
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Apogée Monitor (first version)
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Apogée Monitor (second version)
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Auditorat
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Auditorat Phase Plus
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Digitale Auditorat 380 D
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Triphonic Atom 2 (first version)
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Triphonic Atom 2 (second version)
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Triphonic Atom 3 (first version)
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Triphonic Atom 3 (second version)
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Digitale Allégro 750
The Triphonic
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Triphonic TR500
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Triphonic TR800
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Triphonic TR1000
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Triphonic TR1200
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Triphonic SB80
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Triphonic TR60
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Triphonic TR100
The Equiphases
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Référence 2000
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Référence 2001
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Référence 2002
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Référence 2008
The Push-pull
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M5 (first version)
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M5 (génération II)
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Triphonic SB80
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Triphonic TR60
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Triphonic TR100
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Divine
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Integrale
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Suprema
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Aura M5
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Baccarat
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Cristal
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Doublet
1972
3A patent filed June 7, 1972 n° 72 20 413
72 20 413 - Doublet (french)
Synthesis
This system is to associate two speakers in series or in parallel depending on the impedances, and load them differently by two resonators of Helmotz.
The two speakers must have different resonant frequency and the two resonators are aligned on those frequencies.
Simultaneous operation of these speakers by a serie connection of their coil provides exceptional bass reproduction.
This system has the advantage of delivering a high serie level and easily reach 91 dB of sound level for 1 W at 1 m with conventional sensitivity speakers (88-90 dB).
Acoustic pressure feedback
1972
3A patent filed November 30, 1972 n° :
• 72 42 542 for France
• 209 390 for Canada
• 468 868 for USA
• 53 787/74 for Japan
72 42 542 - Asservissement de pression (french)
Synthesis
The acoustic pressure feedback (APF)
The speaker is a mechanical system which generates a sound while moving. This displacement is nonlinear (speaker's shape, suspension, non-uniform magnetic field) and the sound is distorted. So a speaker can reproduce low notes only if it's shut in a large enough « box »... In 1950,
C.A. Briggs
advised a brick enclosure of one cubic meter to reproduce a 16 feet organ pedal (32 Hz) !
To reduce these fantastic dimensions, engineers only found palliative (cavities, resonators, closed depreciation), but with these systems the mechanical movement of the boomer is not controlled, it is corrected. There are manufacturing of basses and not reproduction.
M.
Brette
and
Perrin
, french acousticians from the Ecole Supérieure d'Electricité (E.S.E.), were the first in 1961 to propose an acoustic pressure feedback loudspeaker, technique that was then aerospace technology. Later the company
PHILIPS
proposed the « Motional Feedback » (or M.F.B.) loudspeaker, based on a piezoelectric accelerometer. In 1971, Mister
Daniel Dehay
, Chairman of the company
3A
, engineer E.S.E., succeeded to the industrial development of the acoustic pressure feedback loudspeakers.
This discovery not only removes the speaker deformations but also allow to reduces the size of the cabinets to the minimum. All mechanical movements of the driver are electronically controlled (slaved), as in the car with power brakes, power steering, in industry with machine tools programmed by computer or in aeronautics where rudders and flaps of the aircrafts are assisted.
So the basic idea was to remove the sound boxes and replace them with an amplifier that controls the movement of the driver. For that an electronic sensor records the movements of the membrane and instructs to the amplifier in the speaker to correct deformations related to the movement of the speaker. This process achieves incredible performance in miniature boxes : Linear bandwidth from 30 to 40 000 Hz in 20 dm³.
The amplifiers powering the slaved 3A loudspeakers are industrial design. All components used meet professional military standards (electrolytic or tantalum capacitors, layer resistances, integrated circuits). The circuit boards are epoxy glass, the oversized transformers are impregnated.
Each amplifier is tested at the vibrating table to test welds and avoid manufacturing defects. Finally, the electronics are made reliable by 100 hours of high power operation (60 watts), allowing debugging of components according to semiconductor technology for the space industry.
The electronics failure probability is then almost zero.
The APF system
1) - Speed bridge
The speed is detected by a Maxwell bridge system, known method for measuring the speaker characteristics.
2) - Analog calculator of slaving
This amplifier at transfer function Zm (speaker radiation impedance) was obtained experimentally by comparing the actual sound pressure in front of the speaker to the coil speed.
The vectorial composition of these two quantities allows to determine the module and phase function. A feedback electronic circuit on an amplifier with very high gain gives a very accurate picture of Zm.
The speed voltage is applied to this circuit and the output voltage is a perfect simulation of the sound pressure.
3) - The results
The amplifier necessary for the linear reproduction of 30 Hz is 125 watts. The speaker's membrane at this frequency moves about 2 cm for an electric attack power of 5 watts, corresponding nevertheless to a musical program of 100 watts.
Thus, the APF system provides to obtain from a miniature loudspeaker the same return in the bass and sub-bass than with a 15 to 20 times larger loudspeaker. Distortion is extremely low, since difficult to measure from 60 Hz. At 40 Hz, it remains below 2%. In the same volume without feedback control, a speaker would give 8% distortion.
1 watt
30 Hz
40 Hz
50 Hz
80 Hz
100 Hz
250 Hz
Normal loudspeaker
18 %
7.8 %
5 %
3 %
1.9 %
2 %
Same volume's slaved loudspeaker
3 %
1.8 %
1.2 %
0.9 %
0.5 %
0.6 %
Infinite acoustic line
1975
3A patent filed décembre 1, 1975 n° 75 36 678
75 36 678 - Ligne acoustique Infinie (french)
Synthesis
This system combines the results got with a closed enclosure and those obtained with a labyrinth and folded pavilion.
It is indeed recognized that a closed chamber has many advantages for the damping of the speaker, so its transient response, provided you have a very flexible speaker and strong magnetic field. However, the resonance frequency of the speaker in an enclosed cabinet (of reasonable size) significantly increases and the acoustic performance below that frequency decreases very rapidly to 6 dB per octave. On the other hand, the back wave is lost. The efficiency of such a speaker is in any case 6 dB lower than a system that recovers the rear wave.
The Infinite acoustic line system is to use the rear wave. It is "forced" in a labyrinth tapered whose length is at least equal to 1.50 m
The labyrinth is folded so as to collect the back wave in phase* with the front wave to enhance performance in the bass and sub-bass...
Then The originality of the system resides in an internal acoustic filter which acts as a "low-pass" for the rear wave and "high-pass" for the front wave, the assembly acting as two loudspeakers coupled without delay (unlike the passive-active system).
The speaker A (front wave) sees its sound pressure decreases by 6 dB per octave from the resonance frequency of the speaker in the enclosure (70 Hz to 100 Hz depending on the speakers) and the speaker B (rear wave) sees his sound pressure almost constant of 30 Hz to 70 Hz or 100 Hz to decrease above 100 Hz.
The combination of the two waves in phase gives a perfectly linear reproduction from 30 Hz.
(*) Rigorous phasing is obtained by a progressive damping of the rear wave through increasing density absorbent.
The careful calculation of absorbent densities allows to artificially lengthen the path of the rear wave up to 3 times the geometrical length of a constant section pipe.
Peripheral laminar decompression
1976
3A patent filed November 25, 1976 n° 76 35 488
76 35 488 - Décompression périphérique laminaire (french)
Synthesis
Derived from the granted resonator system of Helmholtz type and the RJ decompression system, the peripheral laminar decompression system constitutes an exceptional load of the driver in the very low frequencies improving speaker's braking, so transient rendering.
This system is similar in operation to the bass-reflex by the presence of two resonances framing an anti-resonance adjusted to the resonant frequency of the speaker in open air.
However the enormous progress made on the bass-reflex system is the coloring abscence (barrel's sonority) from 80 Hz to 300 Hz, by :
• Total acoustic filling of the enclosure increasing its apparant volume and avoiding all standing wave (coloring).
• The rear wave quickly exit the enclosure in phase with the front wave rolled through the cavity located immediately behind the speaker, this cavity acting as a low pass filter with very sharp cut (80 Hz to 30 dB per octave).
• The distortion obtained is extremely low compared to that obtained with a closed box.
• The cavity and its second baffle allows the rigorous phase of the tweeter with the boomer by spacial shifting from 3 to 5 cm (depending cutoff frequency).
1- Vent
2- Speaker
Triphonic
1977
3A patent filed April 13, 1977 n° 77 11 085
77 11 085 - Triphonic (french)
Synthesis
Given the small stereo perception below 150 Hz, the 3A Triphonic system proposes to mix the left and right channels in one cabinet. Of course the mid-high ways are not mixed, the separation of ways remaining identical to the traditional stereo system.
The advantage here again is to reduce the volume of the speaker. The « Satellite » in such a system no longer having to reproduce low frequencies, it may be of reasonable size.
Thus 3A invented the « subwoofer », principle widespread today.
To combine helpful with pleasure, this subwoofer will naturally take the form of a coffee table, equipped according to the models with 2 to 4 slaved 27 cm speakers (see Acoustic pressure feedback). This is the « Sub Bass » Triphonic table (30 Hz to 3 dB). This table can be incorporated into any existing stereo systems, however it comes with two types of stallites developed for the occasion, the Atom 2 (2 ways) and Atom 3 (3 ways).
Ten years later, 3A offers the « Stele Sub Bass » (SSB), of reduced dimensions, and once again innovative with the principle of « Push-pull » in symmetrical load (see Push-pull). This new Triphonic integrates two incredibly small satellites (see TR60 & TR100)...
Midrange speaker plane Equiphase
1980
3A patent filed March 6, 1980 n° 80 05 030
80 05 030 - Haut-parleur médium plan Équiphase (french)
Synthesis
The Planar Equiphase
Electrodynamic plane loudspeaker with rectilinear magnets and linear suspension with constant phase. Total linearity of the magnetic field, very low distortion. Uses a printed aluminum film on Kapton. The membrane is stiffened by composite materials. Honeycomb sandwich Nomex / Kevlar.
This speaker reproduces a medium of 200 to 12,000 Hz almost perfect. Can be close to the quality of the electrostatic midranges, without having the drawbacks (impedance transformers, THT power supply, saturation). The induction is constant in plan of loudspeaker, the vibratory movement free of distortion.
The narrow geometry of the Planar allows the reproduction of high frequencies with an extraordinary spatial distribution. This is the perfect theoretical speaker.
Membrane printed flexible circuit
After forming membrane
Exploded view of the speaker plane Equiphase
final membrane
Push-pull
1988
3A patent filed January 13, 1988 n° 88 00 317
88 00 317 - Push-pull (french)
Synthesis
This is a symmetric (or asymmetric) load wherein are mounted two speakers facing each other. The back side of the upper speaker looks at a fully enclosed load damped by some absorbent material while that of the lower speaker looks a bass-reflex load where the vent is located at the base of the enclosure. Each of the two speakers respectively receives the modulation from the right channel and the left channel. They are connected in parallel with crossed phases, so when one ahead the other back, and vice versa (push-pull) ... Thus they accept twice the power of a unique speaker with full compensation of non linearities.
This push-pull mount with shifted coupling allows to smooth the parasitic resonances and to down very low in frequency with excellent linearity for a reduced volume. By this principle of load, the cut is made acoustically and so there is no need of a lowpass filter, hence a better impulse response and a damping factor close to ideal.
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