From the
lower Mid frequencies (from around 150Hz) up to approximately 35KHz, the system uses three
Manger
MSW (Manger Schallwandler).
The side Manger drivers are not for increased S.P.L. output but for pneumatic
assistance at low frequencies.
Since the cabinet is 30 cm wide, it is large for frequencies above +/- 600Hz and
small below this frequency.
around this frequency there would be a 6 db step in the frequency response which
is now canceled by the side speakers.
Note this behavior is not typical for the MSW but general and applies to any
speaker.
These are build in in a cabinet which uses constrained layer damping. Actually there is an inner cabinet made of 13 mm Phenolic Resin (called HPL High Pressure Laminate) The HPL is the same kind product Wilson Audio uses, The Phenolic Resin is a material which has a E-Modus of over 10.000 MPa. This is roughly half that of steal (which has 21.000 MPa) and four times as high as MDF. The density is 1.400 Kg/m3. this is approximately double that of MDF and more then four times lighter then steal. This material has only two disadvantages. It is very expensive and extremely hard to treat. I sometimes got the idea that although we had the luck to use the most elaborate equipment available (thanks to the collaboration of the major Belgium distributor in Wood Work Equipment Halwema) the the saw blades and mils where softer then the Phenolic Resin.
Although
the cabinet is extremely ridged from itself, we still braced it internally in
several places.
Also note the biscuits on the bottom plate. These fit in slits of the side
panels.
Actually the complete cabinet is put together using this technique.
The inner construction is not simply glued on but milled into the side panels.
All these treatments where executed on a High precision CNC machines.
Here you see one in action on a side panel and the just finished center reinforcement
Now the inner cabinet was completely covered with 4 mm Bituminous material
Then the
outer cabinet which was made of 22 mm MDF, was glued around the inner cabinet
and the space in between was completely filled with liquid bitumen.
There is no contact between the inner and outer cabinet. The inner cabinet floats
in the outer cabinet.
Now the finished top cabinet was put in the corpus press and dried under high pressure.
Finally
the filter was put in the rear compartment. Its a 6 DB / octave filter at 160
Hz.
The filter was calculated with Audiosoft Calsod, a
program for computer-aided loudspeaker system optimization and design.
The three white 33 uF Mundorf Mcaps perform
this function.
The small 3 mH Aronit inductor at the left front of the picture
together with the two parallel green 820 uF capacitors and the metal film
resistors form the impedance correction. The large 4 mH / AWG 10 foil coil (It
weights approximately 5 Kg) is put in series with the 2 side Manger transducers. Paralleled
with 12 ohm metal film resistors it reduces the output from the side mangers
with 6 Db from approximately 750 Hz. The filter is air wired and the components
are glued with elastic glue to a phenolic resin board.
The
finished filter board is then glued with silicone to the inner phenolic resin
cabinet.
Note that this compartment is completely isolated from the speaker
compartment.
Detail showing the multi-layer construction
We
did not want to keep the impulse response of the complete Speaker from you.
This is with the woofer cabinet in place and connected.
It was measured in the living room performed with a PC based Audio
measuring system DAAS-32 from ADM.
The peak at 5.2 ms is the first reflextion from the back wall.
