Ground Sound

Old drivers + old Coolbacks - New Active Loudspeakers

The system that I build in gallery 1 has been redesigned to fit a new purpose - Stereo setup. I decided to go for a rather high big loudspeaker yet still suitable for my living room. Given the fact that I had some old drivers
(2 pcs ScanSpeak D2905/9700, 4 pcs ScanSpeak 15W/8531K00 and 8 pcs ScanSpeak 21W/8555-00)
left over from the earlier system each loudspeaker could be built with 1 tweeter, 2 mid-range and 4 bass drivers. It was obvious that I should make a D’Appolito coupling with the tweeter in center at about 90cm and again the height was given 180cm. I really liked the box design/assembly used in the XT612 loudspeaker, so this was reused here. The box should be capable down to about 25Hz or below, which required a rather big internal volume about 150 liters. Below you can see the proto type build:

Cheap left over chip board/MDF was used for the proto type. The "old" Coolback was fitted with an extra amplifier module PA1CC - to better match the power capability in the bass range - two anti parallel PA3CC amplifier modules.
Assesing the capability of the design - "it was okay" considering the less fortunate stiffness of the proto type box.

Testing the fitting of the drivers in the proto type box.

With the experience from the proto type in mind the internal of the final boxes was designed much more complex for greater stiffness to yield more control and relaxed bass response.

Gluing the CNC milled front panels

Cutting holes for the vent ports, which is tuned for 25Hz.
The CD cover gives a illustration of how big the boxes are.

The updated Coolback with the extra PA1CC module above the digital crossover module DCN23

A tired man building loudspeakers late at night...Robert GS

Ohhh - they sound like a dream - much much better than I had hoped for - what timing, what precision in image, very upfront without getting aggressive and lots of bass when present in the program material !

What do I have to build next to outclass this setup ?
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Obviously better drivers would be a start....!
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Or maybe go for higher dynamics via PRO drivers.....
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What is your next project ?
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- besides it obviously must be active with Ground Sound technology !

active@groundsound.com