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Genèse :
The LEEDH E2 is the worthy successor of the LEEDH C and LEEDH E: while retaining exactly the architecture of the LEEDH E, it capitalizes 3 years of experience return and optimization. All of the improvements made to this ultimate version competed in the universality of its use regarding the dimension of the listening room, the sound level obtainable and the power of the amplififers usable.
Thus, even if the LEEDH E2 is now able to reproduce most of the instruments to their actual sound level in domestic listening, she excels to respect the integrity of the musical message with a 50 watt amplifiers.
The C and E versions are upradable into E2 version.
Vocation :
As mentioned in the Profession of faith, the LEEDH E2 loudspeaker vocation is to offer music fans of live music the same type of emotions they can experience in concert.
While aging techniques from traditional speakers do not allow to reach this ultimate fidelity, it was necessary, to get close to it, to cross, by a technological leap, the lastest milestone.
Further more, the best traditional speakers, despite their luxurious finish, remains heavy and bulky and many music lovers walk away from them, judging their domestic constraints unacceptable.
In this area too, new technologies implemented in the E2 LEEDH allowed them to take a decisive step towards domestic integration, dematerialization, mobility... and the consensus at home.
Taking value from those two directions, the LEEDH E2 represent for the sound the same quantum leap than the High Definition flat screen for the image. As a real technological breaking point, changing habits, the LEEDH E2 deserves the effort of his discovery, to live with every musics differently.
General architecture :
'The function creates the body' applies perfectly to the LEEDH E2 whose architecture flows naturally from the feature. Its specific functions are to present an anti-vibration structure and radiation directivity controlled.
The Acoustical Beauty loudspeaker (HPAB) is the basic element of this architecture. Its breaking point technology allowing it to operate with a very small volume of acoustic load (0, 3 litre), he composes with his bowl/cabinet an ultra-compact, independent acoustic module. The spatial association of five of these identical modules composed the specific architecture of the LEEDH E2 and frees it of the large and heavy box of traditional speakers.
The very low frequencies (from 20 Hz to 100 Hz) are reproduced by two identical modules on part of the base of the speaker.
To reproduce the low frequencies (from 20 Hz to 1 kHz), two other modules are joined back to back, at ear height, and radiate also orthogonally to the axis of listening. The reproduction of low and medium frequencies (20 Hz to 7 kHz) is entrusted to the third module, attached to a fourth speaker, says 'dumb', intended to cancel its bowl/cabinet vibrations.
A high frequencies module (from 7 kHz to 20 kHz) oversees these three sets.
The three emissive sets, located at ear height, are mechanically connected between them and to the base of the speaker through composite carbon/epoxy tubes. Radiation controlled directivity function assuming a minimum bafflage of sound sources, the design of the LEEDH E2 is naturally minimalist and organic.
This "dematerialization" contributes to its domestic integration. Base materials presented in their natural form, the quality of finish is produced economically, without ostentatious luxury.
Thus, the maximum of the budget focuses on the acoustic features.
HPAB (loud speaker Acoustical Beauty) :
The HPAB enjoys two breaking point technologies, owns by AB: the iron free motor and the Ferrofluid suspension joint.
The direct contribution of these technologies, compared with the prior art, is the drastic reduction of harmonic distortion (artificialization of the timbres of the instruments, saturation and audio aggression), to reach a level comparable to that of the best amplifiers (above 500 Hz).
Their collateral contribution is the removal of the parasitic resonance modes of the membrane, the bowl and air box/bowl (tonal balance coloration, loss of informations and dynamics). To associate these two technologies within a same loudspeaker, it was necessary to develop a specific, completely original architecture:
- The membrane, kind of piston like of 54mm in diameter, consists of a tube closed at one end by a dome.
- To move its resonance modes to the highest possible frequency and free, thus, the widest range of frequencies without any coloration, its rigidity must be maximum and minimum weight.
- The solutions involved to use materials with very high specific modulus (carbon/epoxy composite Ultra high modulus for space applications) and to optimize its structure (by vibro-acoustics simulation software) using adequate reinforcements.
- In particular, the short rectangular coil, carried out as a composite aluminum/epoxy, is his main reinforcement.
- The membrane’s first mode of torsion is postponed to 1, 5 kHz and its primary mode of bending to 14KHz. In his useful frequency range (20 Hz - 7 kHz), there are only 5 modes.
- By comparison, on a boomer membrane with traditional medium cone, the first modes appear from 60 Hz and there are about 100 of them in its useful bandwidth. Each mode with colorations (artificial reverb) and distortions, the sound message is rendered 'confused' on all of its spectrum.
- The dome of the HPAB is concave to limit its bandwidth beyond the useful frequencies and, thus, further reduce its residual distortion.
- The iron free motor consists of an external to the coil structure and an internal structure.
- These structures are obtained by assembling of magnetically oriented magnets radially (sectors) and axially (rings).
- Thus, each HPAB engine consists of 18 magnets (magnetise and of three different dimensions).
- With 660 g of rare earth magnets (NdFeB) by loudspeaker, the total mass of magnets used in a pair of speaker LEEDH E2 reaches 8 Kg (silent speakers and tweeters included). This engine allows the coil of the membrane to move in a constant magnetic field (± 5%) on an excursion of ± 7mm, thus with very low distortion.
- With a maximum, mechanically possible, excursion up to ± 12mm, the field that sees the coil vanishes for an excursion of ± 10mm, and then becomes negative beyond. This unique feature allows to "curb" the membrane when the excursion reached its limits. It behaves like an electromagnetic Compressor/Limiter that reduces distortion at loud sound level and play the role of protection in case of overload.
- In fact, the iron free motor allows membrane excursions two times larger than a traditional engine, with a far better control of his movement.
- So, for the same sound level, the iron free motor allow to reduce by half the membrane surface, it is, therefore, the key to the miniaturization of the HPAB.
- The suspension using a Ferrofluid joint is the only solution to guide a membrane dome of only 54 mm, on a trip that may reach ± 12mm.
- Any traditional suspension would have led to a geometry of edge source of unacceptable distortions. The Ferrofluid is an oil charged with ferromagnetic micro-particles.
This material, marketed since the 1960s, has been constantly improved, it is commonly used in the joints of ultra-high vacuum pumps for its faculty to not evaporate. Its use is even envisaged to achieve liquid Lunar telescope mirrors, in an absolute vacuum. In the application to the speaker (1970s), it replaces the air in the air gap of the engine to better exhaust the heat from the coil. Misused in too small quantities with a bad choice of grade (there are about a hundred), it could have given rise, in its first applications, to effects of "tarring" due to the evaporation of the solvent.
- Scientific and technological collaborations between FERROTEC (one of the two main suppliers of Ferrofluid) company and AB have been developed to optimize the choice of the grade of the HPAB Ferrofluid, based on many criteria revealed by this new application.
- The ring in which moves the membrane tube by sliding on the Ferrofluid seal is, in fact, the external structure of the iron free motor. The Ferrofluid take all the volume between the cylindrical interior of the external structure of the engine and the outside of the tube of the membrane.
- This volume is a magnetic gap, the Ferrofluid is held in place by the magnetic field.
- The Ferrofluid suspension joint exercing, by principle, no callback force on the membrane, it is maintained in its position of balance through the shape of his tube diabolo.
- In this position the coil, located in the center of symmetry of the membrane, is also at the center of symmetry of the iron free motor. This dual symmetry was chosen to minimize pairs harmonics distortion. The Ferrofluid plays full its historical role of heat transfer, by discharging the calories from the coil to the external structure of the engine, through the tube of the membrane (excellent heat conductor) used as a radiator.
- All of this architecture allows to associate the two breaking point technologies implemented in the HPAB.
- The box/basket of the HPAB has its name from its double function of acoustic load volume and home structure of the engine and the electrical connection. Cabinet air (0, 3 litre), compressed by the membrane, plays the role of air suspension (close load) and determines the frequency resonance of the HPAB at 90 Hz (without load volume, the resonance frequency is zero).
- The choice of this frequency, due to the very high magnetic damping, leads to a cut slope very progressive of 3dB/oct (100 Hz) at 12dB/oct below 40 Hz (a slope of 12dB/oct cut-off allows to keep the membrane a constant excursion, to constant close support voltage).
- This damping allows to suppress any form of dragging and enjoy the proximity of the walls, the floor and the ceiling of the listening room amplification, without exciting parasite redundancy. Four times greater volume load would have lead to a resonance frequency of 50 Hz with an identical frequency response, except below 40 Hz where the 6dB/oct cut-off would cause an overload of the diaphragm displacement.
- As the membrane, the box/basket of the HPAB is excited by parasites vibrations modes. These modes are caused by acoustic excitation of the load volume.
- In a traditional enclosure, the speaker is acoustically loaded by the volume of its box. Large, so very difficult to stiffen, it radiates from a hundred hertz, caracteristics colorations and dragging phenomenon. As such, electrostatic or Ribbon-electrodynamic acoustic panels, devoid of cabinet-type systems, are rightly appreciated for not be full of this type of flaws.
- The box/Bowl HPAB, tiny dimension (Ø 10 cm x H 10 cm), ultra-stiff and amortized (mineral filler resin thick-walled), begins to radiate only over 1, 5 kHz.
- The air contained in the load volume is, itself, the seat of parasitic vibrational modes (standing waves, as in a listening room).
-These modes radiate through the membrane thrue colorations and slowing phenomenon, that interfere with its useful acoustic signal.
- In a traditional enclosure, around 30 litres, they start at about 150 Hz. In the HPAB internal volume of 0, 3litres, this phenomenon appears above 1 kHz and at these frequencies, it is much easier to amortize these spurious modes with absorbent materials that fill this volume.
- Thus, in comparison with a traditional acoustic system, the membrane modes of vibrations, cabinet or the volume of air by the HPAB radiate from a ten times higher frequency, are fewer and of lower amplitude.
- So, specifically, the HPAB undergoes no vibratory disturbance below 1, 5 kHz, while the traditional speaker, together with its enclosure, generates colorations and dragging since the very first octaves of the musical spectrum. The emitting part of the membrane (end of the tube connected to the concave dome) exceeds 16 mm outside the box/basket. This provision, which is very close to theoretical Omni-directional sound radiation (4π), allows to get rid of all colorations by diffraction (megaphone effect) of the traditional speaker cabinets. It contributes primarily to the fidelity of reproduction of the sound recording space.
In conclusion, the HPAB, freeing the speaker of his large cabinet, gave birth to a new generation of speakers, created by association of acoustic modules.
This new architecture, of which the LEEDH C, E and now E2 are the first incarnation, allows a great freedom of design, both in terme of the control of the sound space, as of the 'sound objects' design to invent.
Sound source directivity controlled :
LEEDH E2 is intended to be used in a living room of about 10 m² to more than 50 m² and positioned from 30 cm to 1 m of the back and side walls, to allows freedom of movement at home.
The strengthening of low frequencies (below 200 Hz) produced by the proximity of the walls allows to limit to five the number of HPAB used by speaker.
Unlike a traditional speaker, the cost of the HPAB units constitute the main part of the total cost of the LEEDH E2. As so it was very important to maximize the number of unit. At low frequencies (where the wavelength is greater than the distance of the speaker with walls) the proximity of the walls is an advantage (acoustic reinforcement).
On the other hand, at middle and high frequencies (when the wavelength is less than the distance of the speaker with walls), this proximity becomes a disadvantage (excitation of colourings, resonances and parasitic reverberations of the room).
So, is it necessary to make progressive directivity of a speaker heard in a room and not in an anechoic chamber.
The directivity of a traditional speaker, imposed by the geometry of its front enclosure, is little controllable and insufficiently progressive.
Conversely, the freedom of spatial positioning that allows the HPAB (two very low frequency modules back to back at the base plus two modules low frequencies also back to back, radiating at right angles to the modules mid and high frequency) allows the LEEDH E2 to be omnidirectional up to 200 Hz, and then gradually increase its directionality depending on the frequency, reaching in a solid angle of 90 ° (±45 ° around the axis of listening) a constant frequency response of about 400 Hz to 20 kHz, with a progressive fading depending on the listening angle (-3dB ± 30 ° and - 5 dB at ±45 °).
This feature, combined with a perfect impulse response, allows, when listening shifted to the axis or with multiple listeners, to maintain a natural reproduction of the tones and a total stability of the sound space.
Further more, on a floorstanding speaker, which the units are classically arranged at ear height (about 1 m), there is a 'comb effect' between 100 Hz and 1 kHz. This effect, which is the result of the superimposition of the direct wave and the wave reflected by the ground, creates, in contrast of phase cancellation of certain frequencies and thus 'holes' in the bandwidth.
On the LEEDH E2, the module located close to the ground, that can not create ' comb effect', are cleverly filling much of the 'holes' of the bandwidth due to the superior speakers, thanks to their progressive filtering between 100 Hz and 1 kHz. The reduction of this parasitic effect improves the realism of the materialization of the sound image and can reproduce tones with their density, their original 'signature’.
Anti-vibration structure :
Traditional speakers are the seat of important parasitic vibrations.
On one hand, their cabinet undergoes internal pressure variations due to the back wave of the woofer. Secondly, any displacement of the woofer membrane causes mechanical stress, in turn, on its bowl, which is transmitted to the enclosure.
It is possible to reduce this effect by elastically decoupling the boomer bowl of the speaker enclosure, but at the price of a clear loss of dynamic. Despite the thickness of their walls and their many reinforcements, given their large size, these cabinets vibrate and re-emit spurious audio signals (it is to be convinced that to touch them when they are working).
On quality speakers, the compromise of always heavier, stiffer and more expensive has been selected, due to lack of radical solution to the root of the problems.
In the same way that for HPAB, several devices have been implemented to minimize any vibrations in the structure of the LEEDH E2:
- On one hand, cabinet vibrations due to its internal pressure variations has been radically decreased through the rigidity that it is easy to get over a box of very small dimensions, made with thick walls and extensive internal bracing, in a high Young's modulus ceramic composite material (report of the first modes above 1, 5 kHz).
- On the other hand, the vibration communicated by the mouvement of each HPAB membrane to its supporting structure has been auto cancelled by the mounting of the two very low frequencies modules and two low frequencies modules back to back ( push-push configuration) and the mechanical association of the low and medium frequencies module with a silent speaker.
- This module radiating into the listening axis, it was not possible to associate an identical module which would have radiated towards the rear of the speaker with an inadequate directivity.
- The solution was chosen to create a non-emissive speaker, with an annular membrane of very small surface, with the same mobile mass than the HPAB, radiating into two cavities (to absorb the front wave and the back wave) tuned in volume for the same resonance frequency of as the HPAB and operating on the same principle (free iron motor and Ferrofluid suspension joint) who plays the role of an electrodynamic actuator.
- The silent speaker (taking into account its characteristics) and the low and medium frequencies module, to which it is physically associated with exactly the same mechanical reactions, they auto-cancel their reaction on the support structure.
- Each sound module is rendered mechanically inert by these devices, the supporting structure (all four tubes, two flanges binding and a base) only ensure the function of spatial positioning of the modules and so can be light and minimalist.
Therefore (QED), by gently touching the LEEDH E2 during operation at high level, on a heavily loaded program with low frequencies, you will only feel that tiny vibrations, although its weight does not exceed 15 Kg.
In addition to the vibrations suppression of the supporting structure, these devices simulate for each sound module an infinite mass (as they can no longer be set in motion), they guarantee as well as all of the energy consumed by their engine will be used only to move the membrane (full restitution of the dynamics).
Use :
As mentioned earlier, LEEDH E2 is intended to be used in a living room of about 10 m² to more than 50 m² and positioned from 30 cm to 1 m from the rear wall and the side walls. Optimization has been transposed to operate in these conditions, its response in low frequencies (amplified by the proximity of the walls) is then linear up to about 50 Hz (-3dB) and fall below this frequency (- 8dB to 20 Hz).
The spectrum’s first octave (20 Hz - 40 Hz) is therefore rendered with a decrease, but with great readability and without dragging, taking into account the very low distortion and low phase rotation (close load).
In comparison, the traditional speakers that works with a bass-reflex load, in their vast majority, are settled (by simulation anechoic chamber) to fall down linearly as low as possible, up to the tuned frequency of their bass-reflex, then below this frequency fall brutally to-24dB/oct. The consequences of this type of load are the following:
- Excessive level of low frequencies in a typical listening room (amplified by the proximity of the walls)
- Acoustic coupling between the bass-reflex system and the resonances of the room (boomy effect)
- Brutal phase rotation at the bass-reflex tuning frequency (dragging, lack of readability, spectral monotony)
- virtual absence of sub-bass (crossover at 24dB/oct.) Absence of holding control of the boomer by the load, below the tuning frequency (membrane large deflection with spectrum of distortion associatedwith).
To the ear, the choice of this type of load, if implemented with talent, can be very spectacular and impressive. On electronic music its "special effects" will be perceived as "physiological", in the same way as during listening to a rock concert or sound nightclub.
In particular, on the first octave of the register, the strong attenuation of the fundamental notes restitution associated with the creation of harmonics distortion reinforces the 'impact' of percussion. The emotion is musical in nature, the speaker system behaving with its special effects as a coming instrument still "strengthening" the nature of the recording.
The reproduction of acoustic music gives rise to the creation of artifacts that can give the flattering impression that the musician plays on your own musical instrument. The good loudspeaker maker find therefore the best compromise between a pleasant and plausible play back of acoustic music, and a spectacular and physiological restitution of electronic music.
Conversely, the reproduction process of low frequencies by the LEEDH E2 favours the elimination of all forms of special effects, taking the assumption that they are incompatible with the reproduction of acoustic music and the restitution of the original emotion of the recording.
Is this to say that the LEEDH E2 is not intended for the play back of electronic music?
The correct answer belongs naturally to each person, basing his opinion on his own listening. But already, the feedback showed the great interest for electronic music lovers to discover the richness of the real information from the disk, without having it be "scrambled" by special effects complacent and repetitive. In particular, in terms of dynamics on high level listening (as in concert) where the absence of distortion is an unquestionable advantage.
It is not less than the LEEDH E2 with its five small speakers of 54mm in diameter, even if their excursion is double, is only able to provide the SPL of a traditional loudspeaker of 210mm, although with much less distortion and a greater ability to "redeem", in a inaudible way, the overloads of power, but it does not transgress the laws of physics.
Thus, in the recommended conditions of use, the acoustic power available at low frequencies is perfectly dimensioned. In the case of listening in rooms of more than 50 m² or big volume (mezzanine) with the speakers very removed from the walls, on electronic music programs, where you want to have for personal taste an extra power reserve, the use of a subwoofer may be judicious.
The market offer some very efficient ones, some of them of small volume, with an exceptional quality/price ratio that can also be used in stereo (a partner to each speaker), as the ATOHM Rafale V38S.
With regard to the sensibility of the LEEDH E2, low surface radiation of its diaphragmes physically requires it to be low as well (81 dB/W / 1 m).
On the other hand, the nature of its perfectly omnidirectional radiation on first octaves and its 4 ohms nominal impedance confer, compared to a traditional speaker, an apparent efficiency of about 86 db.
Thus, his association with a limited (from 50 W) power amplifier is possible.
Indeed, the lightness of the membranes of the loudspeakers units of the LEEDH E2 combine with the very strong stenght from their engines allows to not to disturb the operation of the amplifier by a parasitic back electromotive current (as is on the traditional speakers equipped with woofers of large dimensions with heavy membranes, that require to use disproportionate power amplifiers relative to their sensitivity).
Thus, the amplifier can be used at 100% of its capacity, retaining all its qualities (if he manifests his overload by sporadic clipping on a forte, just simply decrease the volume level to delete it).
In addition, thanks to its very linear impedance curve, LEEDH E2 is little greedy to the amplifier, especially in terms of load stability, and intrinsic power. So it is easy to marry her with a well balanced and musical integrated amplifier, but not necessarily very expensive, allowing to compose systems with an excellent quality/price ratio. It is an opportunity that is far from being a no-brainer, with the high-end speakers often tributaries of exclusive facilities.
Features :
Dimensions (ground)) : 39cm x 108cm x 41 cm
Weight : 15 kg
Impedance : 4 ohms
Minimum impedance : 3,5 ohms à 300 Hz
Power Handling : 500 watts
Regularity bandwidth : +/-1,5 dB de 100 Hz à 20 kHz
Low frequency response (Bessel 2nd order): - 3 dB à 50 Hz /- 6 dB à 25 Hz /- 8 dB à 20 Hz
Phase Response : +/- 15° de 500 Hz à 20 kHz
Directivity from 500 Hz to 20 kHz : - 3 dB at 30° / - 6 dB to 45°
Sensitivity : 83 dB / 1 m / 2,83 v
Price :
Retail price generally observed (France) :
LEEDH E2 :
16.000 €/pair
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