"The best loudspeaker is the one you don't
hear." |
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
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."
 |
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.
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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
STEP RESPONSE
 |
IMPULSE RESPONSE
 |
FREQUENCY
RESPONSE
|
PHASE RESPONSE
 |
IMPEDANCE
MAGNITUDE
 |
CUMULATIVE SPECTRAL
DECAY
| |
| |
