Oskar Heil Speakers
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Art by Oskar Heil done in 1921

Heil's can be wife friendly!
Fit in with any decor!
Heil Kithara and a real 1960 Epiphone Grandana!
Is it live or is it the Kithara?
The Kithara $6,000
Read the all new review of the Oskar Heil Kitharas
by the legendary Wayne Donnelly
at enjoythemusic.com under the
"Superior Audio" section of the site.
Here's a link
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"The Kitharas recreate the performing space — especially on naturally mic'ed recordings — extremely well. Specific vocal and instrumental images are stably located within a nicely dimensional sound field, but without the laser-beam imaging precision and hyper-detail retrieval that are characteristic of imaging “champs” such as the Wilson WATT/Puppy and ambitious minimonitors. As someone who attends dozens of live concerts every year, I can testify that listening to the Kitharas is much closer to what I hear in the concert hall than with most audio systems, even those with much more expensive loudspeaker systems"
"The Kitharas are real right brain loudspeakers — as emotionally seductive as any loudspeaker I have heard. And in that sense they are, as declared in the title of this article, greater than the sum of their parts."

How the devil does this thing make such beautiful sound!
The Heil AMT driver!

Click here for a review!

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 B. Kotmel Konzertmeister
Czech Philharmonic Orchestra...
There are four reasons why I have chosen Heil A.M.T. speaker boxes:
As far as I can judge, the performance of string instruments timbres is exceptionally faithful, which is very important for me as a violinist. The spatial performance feeling of both small and big ensembles creates the original atmosphere.There is virtually no loss on sound character change during quiet listening.
The superbly looking outside design creates the atmosphere of recording studios of the 60´s. Since I don´t support any kind of outside extravagance I give many thanks to the manufacturer for the design given to these speakers. While listening to my favourite music, I need peace in my soul and Heil A.M.T. - Kithara speakers always give my soul that kind of rest.

The Kithara
Only $6000
Speaker elements: 1 A.M.T. mid range - tweeter 700 - 23000 Hz , 1 25 cm bass unit 28-700 Hz.
Total Frequency response: 28-23000 Hz +- 5 dB Sensitivity: 94 dB 1 W 1 meter
Sensitivity: 94 dB 1 W, 1 Meter
Amplification Requirements: 50 - 200 W
System Type: Bass reflex
Impedance: 4 ohm minimum
Cabinet finish: Oiled walnut, cherry, or black, maple wood veneer
Dimension W/D/H: 40 x 40 x 110 cm including A.M.T.
Weight: 35 Kg.

The Heil tweeter used on this speaker, designed many years ago by Dr. Oskar Heil, uses a totally different method of reproducing the highs.  The usual dome or cone is replaced by a large corrugated membrane, driven from its edge, so that its folds move the air. It doesn't require a huge coil, and it can be built so that its resonant frequency is outside the frequency band it needs to reproduce.

The tweeter operating down to an astonishing 700 Hz! It is inherently bidirectional, and so it sits atop the enclosure rather than in it. It is complemented by a 25 cm woofer which points straight up. The reflex port is on the bottom, and so the wooden feet supplied are not an option. We wish the Kithara came with spikes, as most high end speakers do, but we should add that the woofer, because of its vertical position, will tend to move the speaker up and down rather than forward and back.
The tweeter itself looks hand-made, and in fact it is. The Kithara looks much better with its two cloth grilles on, and the woodwork is strikingly handsome.
The Kitharas, with their 94 dB rating, needed only a fraction of power. Sensitivity figures are notoriously optimistic, but comparisons to speakers of known efficiency seemed to bear this one out.
Dr. Oskar Heil, noted physisist and inventor of the Field Effect Transistor, began his research into loudspeaker design, not with abstract theory of how a loudspeaker should work, but with a study of the peculiarities of the human listening aparatus. The result of this intensive year-long research program led to his discovery of the principle on which the Oskar Air Velocity Transformer is based. By applying this principle to the design of a loudspeaker diaphragm, he was able to achieve a revolutionary breakthrough in solving the fundamental problems of diaphragm mass, inertia and self resonance. In the following, we describe the results of Dr. Heils research and how it led to the development of the Heil Air Motion Transformer speaker.
The research behind the Oskar A.V.T. As a physicist, Dr. Heil concentrated his study on how nature designed and constructed the human ears. Then his studies concentrated on animals of a small proportion, which can produce a loud sound, especially compared to their size. These studies led to Dr. Heil's formulation of his basic diaphragm design theory and the subsequent development of the Oskar A.V.T. (AMT) Air Velocity Transformer.

How the A.V.T. (AMT) operates: The unique design feature of the OSKAR A.V.T. (AMT) which distinguishes it from all other speakers is an extremely lightweight diaphragm, folded into a number of accordion-like pleats to which aluminium foil strips are bonded. The Diaphragm is mounted in an intense magnetic field and a music signal is applied to the aluminum strips. This causes the pleats to alternately expand and contract in a bellows-like manner in conformance with the music signal forcing air out of the pleats and sucking in on the other side, the air movement is 5 times bigger than the movement of the membrane, therefore also the velocity must be 5 times bigger.The total moving mass is approx. 1 gram, we have therefore an almost perfect transducer system. The A.V.T. (AMT) multiplies (transforms) the air motion by a factor of 5.3 (with a total mass of less than 1 gram) and is, therefore, appropriately called an "AIR VELOCITY TRANSFORMER".
Ability to differentiate sounds: A principal function of the ear is to identify voices and for this it has developed an extraordinary ability to differentiate sounds. Single sound sources, such as a distant voice can be separated from other sounds by concentrating our hearing apparatus upon the voice and ignore noise or other voices which we do not want to hear.
Volume (Intensity) variations: The ear has little sensitivity to sound level "jumps" or to the relative loudness of different sound's which are audible at the same time. For a loudspeaker, sound output levels (amplitude) over a range of frequencies are valid criteria, but are of less importance for our ears. Our ears are protected from damage by a construction which makes them relatively insensitive to amplitude changes. The difference in amplitude between a whisper and normal volume speech is not just 1:2 or 1:4, but 1:100'000.The relative loudness of different sounds, within certain limits, is therefore not too important to us, since the ear has the ability to adjust to different levels. This explains why street noises do not necessarily disturb conversation level. It also explains why we can hear an opera singer even though the sound level of the orchestra is many times that of the voice itself.
Frequency variations: In contrast to its relative insensitivity to amplitude variations, the ear is extremely sensitive to minute fluctuations in the frequency of sounds, especially in the mid. frequency range. a half-tone in the musical scale represents a frequency change of 6% while the frequency shift in the vibrato of a violin is approximately 0.5%. In the critical midrange of 250 - 6000 Hz, we can differentiate between two tones even when the frequency difference is as little as 0.06%.
It is this sensitivity to frequency variations that enable us to identify different voices. When we speak, we do not produce constant tones, but tones which are constantly varying. We can usually recognize a familiar voice immediately even over the telephone and can often tell the mood of the other party by the differences in speech pattern produced by the changing of the tension of his vocal cords.
Frequency variations verses amplitude variations: It is commonly accepted that the smallest change in amplitude that the ear can detect is 1 dB, which is a power difference of 26%. Compared to the ear's sensitivity to frequency variations of 0.06%. Contrasting to this relative insensitivity to amplitude changes with the ear's extreme sensitivity to frequency variations, it is difficult to understand the loudspeaker industry's obsession with the minor loudness variations of 1 or 2 dB in the frequency response of a loudspeaker, while completely ignoring the audible shifting or fluttering or high frequencies which can result from changes in membrane stiffness as a sound wave spreads transversely across a diaphragm.
Phase Differences: The Ability to Localize Sounds A listener's ability to localize sounds is made possible by phase differences ( time delays) resulting from the difference in path lengths from a sound source to each ear. This ability is frequency dependent and is more pronounced in the critical range of 500 - 3000 Hz. than at lower and higher frequencies. This is why the speed of response of a loudspeaker diaphragm is extremely important to the faithful and realistic reproduction of music. If the loudspeakers diaphragm cannot respond fast enough to enable it to reproduce these transients, or if it distorts them, the listener's ability to recognize and localize the sound source is greatly diminished and the realism of music reproduction and the pleasure of listening is seriously reduced.
Problems of loudspeaker design
Spurious diaphragm resonances: Any solid material which is made to vibrate by striking it or otherwise setting it in motion will produce a unique pattern of resonances characteristic of that particular material. If made to vibrate at a specific frequency by an external driving force it will, in addition to this frequency introduce its own resonances. In music, the pattern of these resonances or harmonics is peculiar to each instrument and enables us to distinguish between the sound of a saxophone (metal), for example, and an oboe (wood) even though both instruments are playing the same fundamental note. This characteristic, useful in recognizing musical instruments, constitute a major problem for the loudspeaker designer, since spurious resonances generated by a diaphragm will distort and mask the musical signal. In order to move a large amount of air with minimum loss and provide fast response to the transients, the diaphragm must be extremely lightweight. However, if the diaphragm material is too thin and light, it will not be sufficiently rigid to prevent it from flexing and producing its own resonances. If the deformation occurs between the center area and the edges, that portion will vibrate independently of the music signal and produce standing waves or bell shaped vibrations which are clearly audible as distortion. In addition, the diaphragm will store the resonant energy and, when the music signal stops, it will continue to move in order to dissipate this energy. The continued vibration of the diaphragm will dampen (absorb) the sharp rising transients of the following music and seriously affect the quality of the music reproduction.
Efforts to Eliminate Unwanted resonances: Attempts by designers to minimize diaphragm resonances usually consists of coating the diaphragm with silicon rubber or other substances (this is called dampening) to increase its rigidity and prevent it from flexing. There is a trade-off, however, while the damping material may help to reduce resonances, it adds to the weight of the diaphragm increasing its inertia and resulting in a slower speed of response to the transients of complex musical wave forms. The ability of the diaphragm to move air efficiently is also reduced on many loudspeakers to a mere 0.25%.
Large diaphragms and differentiated driving force. Efforts have been made to minimize unwanted diaphragm resonance by applying the driving force more evenly over a large area of the diaphragm. Electrostatic speakers distribute the driving force over a large, flexible plastic panel suspended on a framework. EMIT and magnetostatic speakers utilize a differentiated driving force applied to different areas of the diaphragm to compensate for the varying flexibility of its surface. However, when a flat or conical diaphragm supported at its edges is caused to vibrate only part of the diaphragm oscillates in a direction perpendicular to its surface. At the outer edges, where it is suspended, it cannot oscillate in the same manner since the surface of one side will stretch with each + sinus oscillation, while the reverse side will be compressed or "crunched" and vice versa. Thus the entire diaphragm will not move uniformly like a rigid piston, but will vibrate like a suspended flexible membrane and produce a self resonance with a pitch. (singing saw effect)
The OSKAR A.V.T. Kithara

Custom Granite slab for the Kithara $600
Your choice of color!

The Heil driver below, what the devil is that thing?
When you hear these speakers you won't care what they look like!
This thing produces the mids and highs from 700 up to 23000hz.
A close up view.

The Syrinx

This was an interesying system the Syrinx on top and the Aulos on bottom for a
huge wall of sound! The only reason this works is that all Heil speakers are perfectly in phase.
This system for Syrinx $4200 and Aulos $3000 will compete at $10,000 speaker price level.
The sound was huge tall and typically wide as Heil speakrers ar famous for, WOW!
It was like having two 13" woofers and 40 - 1" tweeters!  

The Syrinx

The Heil A.M.T.® Syrinx is based on the experiences made with the Heil A.M.T.® Kithara and Aulos, which are successfully on the market for over 10 Years. The extensive studies of wood combinations and other acoustical factors have delayed the launching of this speaker for more than one Year. Its modern exterior design comes from TELOS of Berlin, whereas the acoustical refinements to match the sound impressions of the other two models have been made by Precide SA, with the great help of Mieko Dürrenmatt, (my wife) As the other speakers, the Syrinx uses the Heil A.M.T. Made by Precide, which covers the important frequency range from 1000 Hz on up to 23 KHz. The bass driver is a paper cone unit with an inverted dust cap and is working as a bass reflex. The alignment between the bass and the Heil is very phase coherent, as a matter of fact; one could say that it is a point source speaker. The Bass unit faces app. 45° upwards and the Heil driver is located in such a way, that the two units match perfectly. The X over is completely electrically separated, so that bi-wire or bi-amplification does not present any problem at all. The unit comes with pin points and specially made plates, so that the floor will not be damaged. The available wood veneers are: Cherry, Maple and back ash. Warranty is 5 Years and instructions are in four languages, English, German, Italian and French.

1 A.M.T. mid range tweeter 1000 - 23000 Hz
1 15 cm bass unit 40 - 1000 Hz
Frequency response:
40 - 23000 Hz
90 dB 1 W 1 meter
4 ohm minimum
Cabinet finish:
black maple and cherry
including grill:
W x D x H 270 front 105 back x 270 x 910 mm
14 Kg.

The Aulos Loudspeakers
Click here for;
UHF  Magazine Aulos Review

The Aulos Loudspeakers

Speaker Elements: 1 A.M.T. mid range tweeter 1500 - 23000 Hz 1 15 cm bass unit 40 - 1500 Hz
Total Frequency Response: 40 - 23000 Hz
Sensitivity: 89 dB 1 W 1 meter
Amplification Requirements: 50 - 200 W
System Type: Bass reflex
Impedance: 4 ohm minimum
Cabinet finish: Oiled walnut, cherry or black maple veneer
Dimension including grill W/D/H: 23 x 30 x 50 cm
Weight: 8.7 Kg.

Review by
by Neil Walker
Review Summary
Sound  "No question these are musical speakers -- easy to listen to, capable and charming as they bring out the beauty and emotion I seek from music."
Features  Heil AMT driver along with a 6" woofer; unique styling and cabinet with real-wood veneer.
Use  Ditch the grilles for serious listening as they degrade the sound noticeably.
Many speakers these days look downright odd. The average consumer wants to see a 10" chromium or clear polypropylene woofer surrounded by an array of metallic-cone midranges and tweeters. But a speaker that resembles a hooded monk at prayer or Darth Vader with metal pipes for legs is not going to fulfill the average listener’s fantasy of high-tech gizmos. However, now that I am growing accustomed to the unusual and the arcane in speaker design, I was beginning to think that I had seen it all.

Just in time to reassure me that I had not seen everything in the area of unusual design, along comes the Oskar Heil Aulos. With its grille in place, it looks fairly ordinary. But once the grille is off, it really stands out.

Technical description

When you remove the speaker's grille, you have to defy the laws of physics; that is, you have to allow it to bend so that you can wiggle out the little plastic pegs that hold it in place. Imagine an L attached at both ends. There is no way you can install or remove such a structure without breaking the L or snapping one of the pegs (which had already happened to one of the speakers I received for review).

Once you have the grilles off, leave them off except for shipping or for repelling the inquisitive hands of curious two-year-olds. The Aulos's grille definitely degrades the sound. Once you have it off, you can appreciate what makes this speaker so unusual. The tweeter, also known in this configuration as an Air Motion Transformer (AMT) or Air Velocity Transformer (AVT), appears to be little more than a small rectangular plate filled with what appear to be horizontal ventilation slots, each attached vertically to the speaker enclosure just above the upward-pointing woofer. It covers the range from 1500-23000Hz. The woofer is set at a 45-degree angle to maintain correct phasing. This 6" driver is claimed to respond within +/- 3dB from 40Hz to the crossover point of 1500Hz.

This tweeter is the product of genius. It is the design of Dr. Oskar Heil, a physicist who invented the field-effect transistor. We learn from Précide S.A., the Swiss manufacturer of the driver, that Dr. Heil began his research into loudspeaker design by studying "…how nature designed and constructed the human ear. Then his studies concentrated on animals of a small proportion, which can produce a loud sound, especially compared to their size. These studies led to Dr. Heil’s formulation of his basic diaphragm design theory and the subsequent development of the Oskar AVT (AMT) Air Velocity Transformer."

The unique design feature of the OSKAR AVT, which distinguishes it from all other speakers, is an extremely lightweight diaphragm, folded into a number of accordion-like pleats to which aluminum foil strips are bonded. The diaphragm is mounted in an intense magnetic field and a music signal is applied to the aluminum strips. This causes the pleats to alternately expand and contract in a bellows-like manner in conformance with the music signal, forcing air out of the pleats and sucking in on the other side. The air movement is five times greater than the movement of the membrane; therefore the velocity must also be five times greater. The total moving mass is approximately 1 gram, and we have therefore an almost perfect transducer system. The AVT multiplies (transforms) the air motion by a factor of 5.3 (with a total mass of less than 1 gram) and is, therefore, appropriately called an Air Velocity Transformer.

The cabinet of the speaker is constructed of MDF, and a high-quality wood veneer covers it on all sides. While the wood veneer is attractive and quite conventional, the bass ports (yes, ports, as in two of them) on the front of the speaker are unique. Instead of the usual big hole, there are two round ports 1" in diameter.

This moderately sensitive speaker earns a manufacturer’s claim of 89dB/W/m sensitivity. Its impedance of 4 ohms and sensitivity presented no problems whatsoever for the Audiomat Arpège integrated amplifier’s push-pull EL34s at 30Wpc. At all volume levels, the sound remained clear and undistorted, and at low volume it still presented a reasonable soundstage and low-frequency response.

At 19 pounds, with dimensions of 9"W by 11.8 "D x 20"H, this speaker, as odd as it may look to some, is easy to place, attractive with its real-wood finish (oiled walnut, cherry or black maple veneer are the choices) and is family-room friendly.

Gertrude (Oskar Heil's daughter) far left and the guys from Heil USA

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