The Manger Head

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" which nowadays has stopped buissines) 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


When I added the Accuton ceramic head I completely rework the MSW filter
This is the latest incarnation the electric cutoff is 500 Hz at 12dB/oct


This is the in room (50cm on axis) response and distortion of the filtered Manger
It's a bit bumpy and second order distortion reaches around 1% at around 750Hz and 1.7Ghz
but the rest and the higher order distortions are around 0.1%

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.


This is schematic of the Manger cabinet.