This guy always beat his own path from way back then too:
Oskar Heil A.M.T.
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The
research behind the Oskar A.V.T. ( AMT)
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.[/FONT]
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Spurious
Diaphragm resonances:The design of the Oskar A.V.T. ( AMT) diaphragms makes
the use of dampening material with all of its detrimental effects, totally
unnecessary[/FONT][/TD]
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Non Uniformity
of Driving force: In the Oskar A.V.T. ( AMT), the driving force is applied
uniformly over the entire surface of a structurally rigid diaphragm by means of
the conductive aluminium foil strips.[/FONT][/TD]
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Ability to
move air efficiently: The A.V.T. ( AMT) diaphragm’s pleats propel air at a
speed of 5.3 times their own velocity.Oskar Heil AVT/AMT[/FONT][/TD]
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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[/FONT][/TD]
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-------airconditioner noise -
- - - desired information[/FONT]
[FONT=Arial, Helvetica, sans-serif]noise as discriminated by
the ear is always below the level of the desired
information.[/FONT]
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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 speechpattern produced by the changing
of the tension of his vocal cords.[/FONT][/TD]
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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 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.[/FONT][/TD]
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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 extremly 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[/FONT][/TD]
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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
charactristic, 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[/FONT][/TD]
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s[/FONT][FONT=Arial, Helvetica, sans-serif]
ingle point of energy: (
flaps)
dual point of energy ( reduces flapping)
energy
applied over the surface, (no flapping)[/FONT][/TD]
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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%[/FONT][/TD]
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[FONT=Arial, Helvetica, sans-serif]Large
diaphragms and differentiated driving force. Efforts have been made to
minimize unwanted diaphragm resonances by applying the driving force more evenly
over a large area of the diaphragm.
[/FONT][FONT=Arial, Helvetica, sans-serif]Electrostatic speakers distribute the
driving force over a large, flexible plastic panel suspended on a framework.
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[FONT=Arial, Helvetica, sans-serif]EMIT and
magnetostatic speakers utillize 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 uniformely
like a rigid piston, but will vibrate like a suspended flexible membrane and
produce a self resonance with a pitch. (singing saw effect)[/FONT]
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[FONT=Arial, Helvetica, sans-serif]electrostatic[/FONT]
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[FONT=Arial, Helvetica, sans-serif]Heil
A.M.T. actual membrane [/FONT]
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[FONT=Arial, Helvetica, sans-serif]the way
the membrane works[/FONT]
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[FONT=Arial, Helvetica, sans-serif]Large
diaphragms and differentiated driving force. Efforts have been made to
minimize unwanted diaphragm resonances by applying the driving force more evenly
over a large area of the diaphragm.[/FONT]
[FONT=Arial, Helvetica, sans-serif]Electrostatic
speakers distribute the driving force over a large, flexible plastic panel
suspended on a framework. [/FONT]
[FONT=Arial, Helvetica, sans-serif]EMIT and
magnetostatic speakers utillize a differentiated driving force applied to
different areas of the diaphragm[/FONT]
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[FONT=Arial, Helvetica, sans-serif]Spurious
Diaphragm resonances:The design of the Oskar A.V.T. ( AMT) diaphragms makes
the use of dampening material with all of its detrimental effects, totally
unnecessary.
Non Uniformity of Driving force: In the Oskar A.V.T. (
AMT), the driving force is applied uniformly over the entire surface of a
structurally rigid diaphragm by means of the conductive aluminium foil
strips.
Ability to move air efficiently: The A.V.T. ( AMT) diaphragm’s
pleats propel air at a speed of 5.3 times their own velocity.Oskar Heil
AVT/AMT
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[FONT=Arial, Helvetica, sans-serif]How the
OSKAR A.V.T. operates.[/FONT]
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The unique design
feature of the OSKAR A.V.T. which distinguishes it from all other speakers is an
extremely lightweight diaphragm, folded into a number of accordeon-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 under
pressure out of the pleats and sucking the air in on the other side, the
airmovement is 5 times bigger than the movement of the membrane, therefore also
the velocity must be 5 time bigger.The total moving mass is approx. 1 gram, we
have therefore an almost perfect transducer system. This principle can be
demonstrated very simply by taking a sheet of DIN A 4 paper with a surface of
616 cm2, folding it in the center lengthwise and bending the long edges together
to form an opening of 5 cm on the one side. We imagine, that the upper and lower
part of the structure is closed and move each side 2.5 cm together. With a
frontal surface of 140 cm2, we have now moved 770 ccm of air, compared with the
350 ccm of air moved by a flat diaphragm. Our transformation is now 1:2.2, by
making the triangle (top view) a square form, we doubled the transformation to
1:4.4 The selected transformation ratio with the Oskar A.V.T. is
1:5.3.
Unlike conventional speakers, whos diaphragms move air only in a
direct proportion to their own movement with the inherent inertia. The A.V.T.
multiplies (transforms) the Air Velocity by a factor of 5.3 (with a total mass
of less than 1 gramm) and is, therefore, appropriately called an “AIR VELOCITY
TRANSFORMER.[/FONT]”[/TD]
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[FONT=Arial, Helvetica, sans-serif]Precide
SA
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