Almost 30 years were spent in systematically searching,
testing, researching and rejecting until the vision
of the natural resonance-free radiation principle became
an acoustic reality.
This has resulted not only in one of the most elegant
appearances in the loudspeaker market, but also in a
masterpiece of precision mechanics. The decisive factor
in the Manger® sound transducer was the logical
turning away from the more than 75 year-old transducer
principle used in conventional loudspeakers, therefore
doing without the piston-like movements with their faulty
reciprocal overshooting.
 |
Left
a
well-known typical 3-way speaker. Clearly to be
seen the time-displaced displacements and transient
errors of tweeter, mid-range and woofer.
This speaker has been designed exclusively for
a smooth frequency response. Explanations of the
meaning and interpretation of this measurement
can be found on our homepage at Measuring Engineering.
|
Instead, Josef W. Manger relied on the principle of
bending waves, which starting from the centre of a plate-like
diaphragm, travel to the outside, like waves after a
stone is thrown into the water. The rigidity of this
thin flexible panel increases from the centre to the
outside at an equal ratio, very similarly to the basilar
membrane in our ear. High frequencies quickly run out
in the inner area of the membrane, whereas long waves
(low frequencies) concentrically reach right to the
edge at the star-shaped damper. There they are absorbed
so that no reflections can come from the edge.
 |
Left
a
cross-section through the Manger sound transducer
with the complex and precisely tuned functional
elements.
The manufacturing process demands tolerances of
as close as an eight-thousandth of a millimetre
(0.008 mm).
Seen left the diaphragm is the stylized wave movement
of the diaphragm in the range between low and
high frequencies. |
 |
In
this way the Manger® sound transducer controls
the complete frequency range from 80 Hz to 35000
Hz on its surface and is at the same time close
to the ideal of the point sound source. The
conventional splitting into several ways (tweeter,
mid-range and woofer) for different frequency
ranges is therefore avoided.
The
active surface of the 19 cm diameter flexible
diaphragm becomes smaller as the frequency increases
so that the effective surface is always kept
small in comparison to the wavelength to be
radiated.
Left
The images made with laser Doppler vibrometrics
show the concentric wave movement of the bending
wave diaphragm at various frequencies. |
The Manger® sound transducer in spite of its large
frequency range of between 80 Hz and 35 kHz and its
sensitivity of 91 dB 1W/1m can achieve the tremendously
fast rise time of 13 µs is attributable to many
design finesses:
|
The Coil
In the woofer range large displacements are necessary,
which would lead to a long and therefore heavy
moving coil. These in turn would be much too slow
for fast movements with their mass.
The solution is both simple and clever, but nevertheless
producible only under the most difficult conditions:
Two voice coils, mounted mechanically in series
and switched electrically in parallel, using aluminium
wire on an aluminium backing and copper strip
leads, produce the solution of an overall long,
but nevertheless extremely light driving coil.
This is unique for a wide-band transducer in spite
of a possible displacement of ± 3,5 mm
and a total weight of only 0.4 grammes. A further
advantage of this design is the drastic reduction
in non-linearities, which are common with larger
displacements.
In addition this arrangement of a double voice
coil, for which Manger received a patent as far
back as 1969, considerably suppresses the natural
resonance. |
|
The
Drive
No less than 15 neodymium magnets concentrating
their extremely strong magnetic field of 1.32
Tesla on an air gap of only 0.95 mm width, in
which the lightweight 70 mm diameter coil moves,
supply the drive for the diaphragm and are responsible
for the fast rise time and the high sensitivity
of 91 dB, 1W/1m |
 |
The
Diaphragm
Not
rigid as in conventional piston speakers, this
flexible diaphragm represents a frequency-independent
impedance for the driving force.
Or to put it more simply, it behaves like an ohmic
resistance in a power circuit. Neither leading
nor lagging forces are stored, i.e. neither potential
energy (spring/capacity) nor kinetic energy (mass/inductance).
These stored forces also lead to the transient
errors or also transient noises described above
in the commonest piston loudspeakers (each electrodynamic
dome tweeter is, for example, such a piston loudspeaker).
The inventors of the electrodynamic piston loudspeaker,
Rice and Kellogg, described around 70 years ago
that "the membrane with ideal resistance
in contrast to the mass-spring type is the only
one where the exerted electrodynamic force is
directly proportional to the desired diaphragm
speed."
And this is exactly the type of diaphragm with
an ideal resistance used in the Manger sound transducer. |
When Prof. Dr. Manfred Heckl († 1998) was asked
around 25 years ago to examine the theory of the Manger
sound transducer, he was initially sceptical of this
new sound radiation principle using a flexible plate
as the diaphragm. Prof. Dr. Manfred Heckl was even during
his lifetime an internationally respected and eminent
authority in the field of acoustics/structure-borne
sound. His book "Structure Borne Sound" is
a standard text in physical acoustics known throughout
the world.
Prof. Dr. Heckl wrote in 1978:
"Dear Mr. Manger,
In order to ease my guilty conscience somewhat, I spent
last weekend looking at the theory of your loudspeakers.
To my surprise it turned out that the radiation principle
selected by you, at least in the idealization I investigated,
produces a radiation in line with the current at all
times; i.e. transient noises and similarly annoying
effects do not occur".
Click
icon to download
a PDF describing the Heckl Calculation - 54.5 KB
 |
The
Advantages
Since 1978 the MANGER sound transducer has been
the pinnacle in theory, poised to conquer the
world of high-end audio in a practical application
– loudspeakers. For anyone who enjoys listening
to music, the advantage is quite evident: a perfect
impulse behavior without any transient errors,
whatsoever! The incoming signal is converted directly
into sound. Initial transients from vocals and
instruments are reproduced with absolute dead-on
precision… an all-important prerequisite
for our sense of hearing to recognize and localize
the different musical sounds in a given space.
Left shows the step response of the Manger
sound transducer in a Zerobox 107. The extremely
short rise time and the lack of energy-storing
elements provides an almost ideal step response,
without transient errors and without transient
noises. |
And there’s more… due to the total
absence of transient noise, the MANGER sound transducer
cannot be heard nor localized, as can all conventional
loudspeaker drivers. Whether listening to music for
pure enjoyment or in a professional recording studio,
listen for hour after hour after hour – never
suffering from that dreaded side effect, "listening
fatigue."
The list of benefits and advantages continues…
toss out the notion of having to sit in the "sweet
spot” (center) in order to enjoy stereo imagining.
With the outstanding dispersion qualities of the MANGER
sound transducer, multiple listeners can enjoy listening
to music – at the same time – and, yet,
stereo imaging and balance remain in tack.
The
Future
And the future has also not been forgotten.
The Manger sound transducer, with its fast rise time
or even high cut-off frequency (these values can be
mathematically converted internally) of 35 kHz (-3 dB),
and 60 kHz (-20 dB) respectively, is excellently suited
for the future standards of DVD audio and SACD.
Manufacturing
Each Manger sound transducer is made under
extremely close tolerances by hand and using special
machines. A task that is more comparable to that of
a watchmaker than the mass production normally found
nowadays in loudspeaker manufacture. A test record ensures
that each transducer is exactly the same as the other
and also identical to the reference model. The otherwise
standard practice of choosing two as closely matched
speakers for a stereo pair is not necessary simply for
this reason. The complex production process, the exact
checking and the final autographing make each Manger
sound transducer an unmistakable and unique item. This
exclusivity does not only guarantee every customer a
life-long guarantee of spare parts and in the worst
case also competent repair by qualified specialists,
but also the fair service of the manufacturer.
|
THE
TECHNICAL FACTS |
| frequency
range |
80
Hz - 35 kHz |
| rise
time |
13
µs |
| sensitivity
|
1W/1m
91 dB |
| max.
SPL long/short term |
110
dB / 116 dB |
| recommended
amp. outp. power |
10 W - 400 W |
| nominal
impedance |
4
Ohm / 8 Ohm |
| DC
resistance |
4,2
Ohm / 7,1 Ohm |
| resonance
frequency |
88
Hz |
| induction
B |
1,32
T |
| voice-coil
inductance |
18 µH |
| air-gap
energy |
560 mWs |
| air-gap
volume |
1043
mm3 |
| air-gap
height |
5 mm |
| air-gap
width |
0,95
mm |
| voice-coil
diameter |
70 mm |
| max.
voice-coil amplitude |
±
3,5 mm |
| dimensions
|
d
210 mm x 22 mm |
Diagrams
and measured curves
|
