As shown in „Basics
– Reflections“, we have to avoid
as much as possible bad influences caused by reflections and edge
Best case: such disturbing areas arenīt
there. But because some assemblies are neccessary for a functionable
driver, we collected a whole bunch of methods and some of them we
want to present::
It sounds paradoxical, but
in a coaxial system, the woofer ist he greatest enemy
of the tweeter. This is because a low-frequency cone
has its own requirements on geometry and stability.
These usually do not meet the ideals of an infinitely
large, plan or spherical surface.
Conventional – even highest
quality coaxial (and coincident) drivers use a traditional,
inward-pointing Cone. That is because it has been always
like this and you can use tried and tested technologies,
which means you can minimize development effort and
costs. Often you can take already existing components,
which again means: saving costs.
With the driver from Audio
Consequence everything is different:
A conventional cone is not
the best surrounding for a tweeter. First we had to
think about everything known and we thought about how
to join the requests of the tweeter to his surrounding
with the requests of the woofer to stabilization and
resonance poverty. In the basic idea the result was
so simple but very difficult to translate in practise.
Assuming that asphere builds
an excellent suitable environment for a tweeter, an
inverted cone, which thought peak shows outside, not
inside, was the best solution. The tweeter is situated
in this thought peak, free off the usual swinging funnel,
and there it can make its work mostly undisturbed: the
natural reproduction of the frequency area. The points
that initiate the power of the voice coil in the dome/cone
of the tweeter and the woofer are nevertheless in one
level – for perfect coherence of the sound creating
In contrast to the flat " cone" –
also a possibility to give the tweeter a fitting surrounding – with
this solution the benefits for the tweeter will not buy at a disadvantage
for the woofer. Stability and poverty response are as safe with
a traditional cone – a reason why this has proven itself over decades.
Keeping proved ideas if it makes sense
and inveting new technologies if necessary was the base of the construction.
Because many relationships had to be inverted
with this new construction, we had to create each component of the
driver to its task, which means not only a lot of work, but also
the additional advantage to re-think all long-standing and to optimize
An insignificant component
in the first view, that carries a not insignificant
influence on the behaviour of the tweeter: The tweeter
flange is the front cover of the tweeter, and it docks
it with its direct neighbours, the woofer cone.
Many models were created, hundreds
of measurements were made until we had the optimal shape
identities in the end. A short horn intent was kept
off: This narrows the angle of the tweeter and makes
him so sensitive to his surroundings, but it is precisely
this restriction that prevents a balanced development
of the high acoustic sounds in the room. No alternative
for a uncompromising driver.
At the same time usually used
diffusers or lenses were eliminated by tests and measures,
because they can improve the radiation at a certain
angle, but this means also disadvantages at other angles.
double wave surround:
A surrounds first task is to
center the woofer cone and to separate the front and
the rear side of the drivers airtight.
Belonging to the interpretation
of the system it also has to damp the membrane resonance,
and care for planned displacement of the cone without
changing its spring action.
It also has to be long-living
in stability, which means a foam surround is no alternative.
A multiwave-rubber surround
can attend these requirements without any problems,
but in case of a coax-construction it also has to take
another task, to which it is predestined, because
it has another characteristic: It is very flat in relation
to it's possible stroke.
Even in multiway-systems with
tweeter and woofer close together, you can see that
the surround forms a barrier in the directly neighbourhood
of the tweeter and that results in clear response interferences.
Thatīs why it is very important in a coaxial system,
where it is situated all round the tweeter.
basket edge design:
The design of the edges of
Usually woofer-drivers have
a more or less thick and flat basket-edge. Even if it
is good enough for pure low-to mid, it causes problems
in a coaxial-system, which we can reduce by beveled
design. Cone angle, bead and edge of the basket are
forming a homogeneous line for a minimal influence on
The fact that the mounting
screw holes of the filligree, but still very rigid and
resonance-free aluminium die-cast basket are sunk acoustically
invisible (stealth ), is a matter of course.
Another advantage for DIY:
You donīt have to care about the extensive shaping of
the basket in the baffle.
basket brace design:
Also behind the cone, there
is something going on: Basically, here is generated
the same sound pressure as on the cone front.
This sound is normally largely absorbed by damping material
in the speaker housing. But what about the early reflections,
those who donīt reach the damping material?
The sound can be reflected
by the motor and the braces of the basket and rejected
to the cone. Because normally it is no good acoustic
isolator, these reflections add up –with time delay
- to the sound emitted just from the cone -- distortions
and interferences are the result.
The braces of the basket of
the Audio Consequence coaxial driver are elliptical
in shape and offer only a minimal attack surface for
maximum stability in the level of vibration. Although
other manufacturers have recognized the problem, however,
if at all, they mostly round off only the clearly visible
back side of the braces, while the much more important
front side remains flat.
Also the inner flange for the
motor has been carefully rounded at the top for the
The support surface of the
spider can not be accousticly defused by rounding.
Therefore it is made as thin as possible and at least
its backside is rounded to minimize the sound refraction
at the edges.
When we look at the rear
sound reflections, a conventionally constructed motor
with a ferrite magnet is a disaster.
For long time, we only had
few alternatives and thatīs why these reflective " monsters"
With the currently available
advanced magnetic materials, it is now possible to construct
motors so slim that they find their place in the woofers
voice coil and donīt offer a significant reflection
surface, if there is no dustcap
Wich other advantages
you can reach with a cleverly studied and constructed
Neodymium motor, we tell you in the chapter “Technology
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