Breakthrough innovations require to become aware of all the dominant ideas, to realize that we are focused on a single way in order to be able to put aside all these fixations and to be able to explore elsewhere, "out of the box" ... Number of creators do not even realize that they all offer the same ideas or solutions, and that they are locked in an intuitive behavior related to previous ideas or stereotypes ... "
Researcher in cognitive psychology
"Few people have new ideas,
and the ones who have some
don't have always the good ones."
Inventor of the Internet
|Key advances over the AIRLINES
Form and architecture
The cylinder, Form Follows Function
The shape of the AIRLINE is the first noticeable aspect of the design. The cylinder enclosure comes directly from its basic function : Form Follows Function. The rectangular box with parallel sides, is the worst container for a speaker to be placed in. The inside parallel walls of the box coincide with wavelengths of musical frequencies, creating standing waves and resonances like the skin of a drum. Their assembly joints create multiple reflection of these vibrations reducing the possibility for them to get damped efficiently. Flatness and parallelism of the surfaces promotes stray reflections known under the names of "edge effect", "baffle step" and "standing waves".All this is just a disaster.
Seeking for the ideal form devoid of flat or parrallel surfaces, without assembly joints and having higher stiffness and pressure resistance, cylindrical shape appeared among the most interesting.
A non baffled mid-woofer
When we finaly adopted the horizontal position of the main driver, the cylinder naturally imposed itself. There is no more reflecting front face neither flat nor curved.In this arrangement, the disastrous effect of baffling that destroys even sound spreading, makes impossible the creation of the sound stage and creates poor tonal balance becomes just non-existent.
A perfectly rigid and inert enclosure
As a consequence, as the most adverse vibration generator, the woofer, is in the vertical axis with the ground as reference for its movements and given the weigth and the extreme rigidity of our cylinder, no more enclosure intermodutlation is allowed. Unlike conventional speakers, vibration are spread in the direction of the longest dimension of the cabinet. Thus, vibrations can flow freely over the 92cm tall cabinet.Throughout this trip, the energy is absorbed by the cuved 19mm thick (rigid as a 30mm flat panel) continuous structure consisting of self-damping pine and fir wood fiber with zero intrinsic resonance.
A total absence of "box-sound"
In the unlikely event where a remaining part of this energy would be reflected at the base of the enclosure and go back up to upset driver's frame, it is a journey of 184 cm that the signal will make while still weakening gradually. In a conventional loudspeaker, this energy emitted horizontally in a vertical column only travels around the circumference of the enclosure in an endless round, upsetting sound emission with intermodulation, blur and resonances contribuing to the so-called "box sound".
By design, AIRLINE is completely free of this effect.
Are standard measurements meaningful ?
Traditional speaker design require the listener to face the drive units. So naturally conventional studies, measurements, analysis and controls are processed by facing a microphone 1 meter away to the tweeter. Frequency response of loudspeakers describe their behavior with great precision but only in the volume of a tennis ball one meter in front of them. Two loudspeakers with almost identical curves made in this way may sound entirely different in terms of whether they are bright or dull, smooth or rough. On-axis curve just forget to show that elswhere, lower, higher, on the right or the left or further away the response can be radically different showing dramatic cancellations over entire ranges of the audio spectrum ...
Measurements made at these other angles where it is hopelessly observed that the non-linearities can be moved but never canceled, are experienced with fatalism, despair and frustration by speaker designers.
"Classic design is simply obsolete"
Are drive units imperfect or improperly used ?
Cone drive units are the most reliable and durable but they are not perfect. The most neglected area of their design is how their response is impacted by sound pressure changes. Mecanical distortions appear with increasing the sound level at the rhythm the mecanical limits of their components, assemblies and materials occurs.
These mechanical distortions are added to the electrical signal delivered from the amplifier and nothing can prevent them or erase them any more.
The main drawback that cone drivers offer is their greater instability under varying sound pressure 30 degrees on the emitting axis. It is also where the largest response changes at high frequencies can be observed. Torsional and bending modes appear from 40Hz and there are 80 whithin the useful bandwidth. Each mode has its own coloration and induces aggressive and confused sounds.Shape and cone material choice and surface treatment can reduce some of the bending modes but could never achieve to cancel 80 different ones!
These are the defects that prevent the brain from forgetting the presence of loudspeakers because it recognizes their signature and lets you know it unconsciously without having to think further.
"It has taken a lot of hard work to forget previous knowhow and theory and create new concepts out of the box".
New questions, new solutions
We built our first prototype from this observation asking us with this new question :
Why not use the cone drive units in the domain where they are more stable in frequency response and have less harmonic distortion ?
This question can also be rephrased as follows :
Why should we always use and focus on the frontal emitting beam where drivers exhibit the most unstable response and the busiest mechanical harmonic distortion and project all this garbage toward the face of the listener ?
"They didn't know it was impossible, so they did it." - Mark Twain
Vertical firing mid-woofer
Thus, we placed our mid-woofer horizontally at the top of our cylindrical enclosure. In this configuration, unstable signals, non-linear frequencies and most polluted materials are sent vertically and never toward listener's face. The result is a dramatic reduction in the perception of cone artifacts, errors, non-linear distortions caused by the bending modes of the diaphragm. This deals with a uniquely free and clean signal.Experiencing this, one can easely understand that the non-linear mechanical distortions are the origin of hardness and "projected sound" of conventional loudspeakers.
The horizontal position of the main driver has many other critical consequences :
1) A true linear response all round
Whatever the angular position of the listener, the response level remains the same. This is never the case with normal speakers that beam the sound frontaly like the headlights of a car.
2) No baffle around the woofer
Thus the sound balance remains linear all round never affected by reflexions and the cancellations due to the front face.
Actually the baffle surface is limited to a 1cm ring surrounding the woofer that has no effect on the emited frequencies.
3) Vibration reduction by anchorage to the ground
There is no better static reference than the floor for a vertical movement, even more so when combinated with our inherently inert enclosure.Micro musical details, usually lost in MDF cabinets, are then revealed with the simple beauty of their infinite complexity.
4) Vertical firing mid-woofer cancels Doppler effect
In normal front firing speakers the large movement of the cone when bass are reproduced accelerates and slows smaller medium vibrations at the rythm of the cone movement.
This causes the Doppler effect that can also be understood as "in air" intermodulation on 3 and 4 ways speakers or "in cone" intermodulation on 2 and 1 way speakers.
This obscure but serious distortion is rarely mentionned by audio engineers because "we can do nothing against it". Meanwhile it produces a very audible and severe discomfort up to giving a robot accent to a natural voice. Doppler is clearly audible with cone movements from 1mm !
As a matter of fact Doppler can not be measured like harmonic distortions are, even if its impact on the sound quality may actually be much greater. AIRLINE's vertical emission cancels most of the Doppler effect. Acceleration and deceleration are transformed in a tiny undetectable vertical movement.
5) Measured harmonic distortion reduced
Most of measured distortions of a loudspeaker come from unwanted and uncontroled cone vibrations. They are harmonics, that means multiplications of the original frequency and they are emitted on the drive unit axis. The AIRLINES emit these frequencies vertically over them, where nobody actually stands to listen to music. Thus they are not thrown toward the face of the auditor. Distortion measurements in the listening area show level reduced by 10dB.
This is a major step forward in loudspeaker design.
6) Minimum crossover for the mid-low driver
Because higher frequencies, as well as mechanical distortions, are issued exclusively vertically, their contribution to the useful spectrum is tiny and filtering can be reconsidered. As a result, the woofer is connected directly to the output of the amplifier through one component only.
7) Orthogonal mid-woofer and tweeter firing cancels inter-modulation
The high frequencies are reproduced by the tweeter. Like any other drive-unit its reponse becomes more directive with increasing frequencies. To keep the whidest possible trebles extention, its axis remains classic, almost horizontal . As a result, woofer and tweeter are acting orthogonally and the most disruptive unit, the woofer acting vertically never upsets (by inter-modulation) the most sensitive one, the tweeter on its horizontal axis.
The importance of this point is particularly striking when the scale of the movement of a tweeter membrana is measured.If at maximum power the tweeter's dome moves less than a tenth of a millimeter, the majority of its job lies in movements of the thousandth (60db dynamic) or a ten-thousandth (80dB dynamic) that is then the 1/100 th of a micron ! Therefore to ensure proper dynamics the stability of the tweeter's body on the horizontal axis must be guarantied at this scale. Because the movements of woofer and tweeter are in the same axis this condition is difficult to fulfill in conventional front firing loudspeakers. Orthogonal emission can, if well implemented, ensure the stability of the tweeter's motor on its axis. This unique feature allows AIRLINES to deliver an unknown clarity and subtlety.
A non-baffled infra-cardioid tweeter
What generates the most dramatic accidents in the response of a tweeter is the flat or even curved cabinet front face panel on which it sits, or even just, in an already alarming way, its own front fixing plate! Our tweeter has no mounting plate and is not fixed to any panel. Its magnet and its body are smaller than its membrana. This membrana is maintained on 1 millimeter at its periphery and its frontal dome goes 3 mm beyond its support. Thus like a pulsing half sphere it radiates with an outstanding reflexion free dispersion pattern.
This performance is just out of the thinking with tweeters fixed to a loudspeaker, loaded with a horn, simply surrounded by a mounting plate or with ribbon tweeters where the ribbon is recessed in a cavity inbetween two big magnets.
An ultra-linear frequency response
Working on the linearity of the AIRLINE's response curve was facilitated by the absence of a baffle and reflective cabinet. As a result AIRLINE display a frequency response of a straightness worthy of the most recognized professional monitor speakers. Alas these allow neither to move away or deviate more than 15 degrees out of their axis of emission under penalty of severe unbalance of their restitution.
A point source for an all around coherent phase
The virtually coincident emitting of the two drive-units maintains a linear phase and spectrum throughout the all listening room. From the lower frequencies the tweeter has a natural infra-cardioid radiation pattern. The mid/woofer acquires the same infra-cardioid pattern. As the two patterns are the same no cancellation, no black hole, no coloration, no suckout is possible any more.
At all points of measurement, from the floor to the ceiling and 140 degrees horizontally, there is no accident in the response that would be due to signals canceled or reflected by one or the other drive unit.
This performance of spatial and spectral dispersion is rare or unique in the history of loudspeakers. It is the Holy Grail, confessed or not confessed as it seems so inaccessible, any speaker designer.
No more unique sweet spot
These are the features allowing to build an holographic soundstage either wide , smooth and accurate even though if the listener may stay outside of the space between the two speakers. From a distance of one meter, the speaker's response shows a remarkable linearity and allows the formation of this spectaculary holographic image significant anywhere in the listening room, even from the left of the left speaker !
The utopia of focusing a theoretically ideal sound on a single point suddenly appears totally obsolete and very unambitious.
There is no more privileged listening "sweet spot" as all past and existing stereo and multichannel setups impose.
AIRLINE pushes the boundaries of room acoustics
Because AIRLINES spread their energy equally in all directions room acoustics defects are no longer exited by the high pressures imposed by classical beaming loudspeakers. It is then possible to play louder.At very high level, it is surprising to find the same sounds, the same tonal balance and clarity than at a very low level: Room limits are pushed forward.
AIRLINES in the listening room
Thanks to their consistently wider dispersion, the reverberant damping of the room will be less significant. AIRLINES emit energy into a spherical pattern reducing the adverse effect of room reflection that destroy focus and coherent imaging. They load all wall surface evenly and have 60% less energy hitting the walls than conventional beaming speakers. Wall returned energy is reduced by the same amount, facilitating emergence of more nuances and more details all round.
From 10 watts ...
The Airlines don't have the excuse for being difficult to drive. A 10 watts amplifier can already allow a realistic sound level. However, one thing is certain, only the best currently available amplifiers and sources and a rigorous implementation of the whole setup will allow to reveal the true emotional potential they are capable of.Then, in return, AIRLINE will reveal the true potential of a true state of the art setup that other speakers will limit and will always hide.
An invisible connection
To reduce the visual impact of the speaker cable (some good ones are thin or even flat), the terminals are placed in the base under the speaker. Thus no speaker cable will hang behind the cabinet.
Funilly "wireless speakers" will always proudly exhibit a mains lead that requires to be plugged into mains outlets and installed not too far from them ! as elegant as promised ?
3 points for a perfect stability
Contact with the floor is provided through 3 small tangent cylinders, allowing infinitely small tangent contact withoutthe drawback of spikes that will always destroy your floor. This give the drive units an incredibly stable platform to work from, and with 3 points, no set up is required.
AIRLINE are ported cabinets. As a bass reflex port connects the inside of the cabinet to the listening area, having the port opening in the direction of the auditor or even on the back face of the speaker would have been a dramatic design mistake. From the port opening of a prestigious brand reference speaker we measured medium frequencies as loud as minus 12dB only under the driver level. Is this seriously acceptable in the high end industry? Definitely not for a Lecontoure speaker.
The port opening of the AIRLINE faces the floor and this deals with a reduction by a factor of 30 of the unwanted sounds it actually may radiate over 360 degrees instead of 10 for frontal ports. The gain is a blur free reproduction without the distracting and masking airflow noise and the background box escapted notes.
Airtight diaphragm for a silent woofer
The mid-woofer driver have a sealed center cap. This cap eliminates internal pressurised turbulent air noise leaking through the ring opening arount the center when a phase plug is used. This removes the unceasing airflow noise and hissing modulated by the sound pressure of said high end drive units having a phase plug. Conventional spectrum analysis fail to detect such a very audible non linear distortion, but good ears can !
A rock steady crossover
Vibrations and magnetic fields have a desastrous effect on analog and digital electronic circuits and signal pass.
We located the tweeter high pass crossover in the basement. Then it like on its own put directly on the floor free of any vibration.
Trebles adjustment switch
Once the AIRLINE loudspeakers are correctly positioned, some tuning of the sound may benefit the performance.The high-frequency output level of the AIRLINE 200 may be adjusted using the toggle switch near the binding post under the enclosure. The default setting (0 dB) provides a flat response. The + position gives more output, which may be required, for example, in larger rooms or if the acoustic of the room is dull, if circumstances dictate that the speakers have to be placed more off line than recommended, or if the speaker is placed behind or near curtains.
à suivre ...