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Absolute minimum cabinet coloration

   The cabinets do have sound coloration due to vibration and the edge diffraction. The edge works as secondary sound source. His influence depends on frequency, distance to the edge and how sharp the edge is. Diffraction changes speakers impulse response quite a lot if the design is bad. Vibration can also have big impact if there is a lot of surface area to vibrate. If the panels are completely rigid they will not resonate but still radiate. In example take box speaker of size for easy calculation 1 m x 0.25 m x 0.25 m. Lets say its weight is 20 kg and woofers moving mass is 20 g. Force equals reaction so the box will move 20 g/20 kg=0.001 one thousand of the driver diaphragm movement. So 1000 times means 60 dB less sound coming from the box surface than from the driver (assuming the cone area equals panels area). We can cut this by half approximately, because only half of the walls are opposite to the driver and are working. So we have 66dB. But half of the box walls have the surface area of (1 m x 0.25 m)x2=0.5 m2. The speaker cone area Sd lets say 250 cm2=0.0250 m2. So the box has radiating area more than cone by 0.5 m2/0.0250 m2=20 times or 26 dB. So the sound coming from cabinet walls will be 66 dB-26 dB=40 dB below compared to what is coming from the cone. Is it a lot or not? Better not to have them. Better to have all sound coming from the place where it is designed to come from and have full control over it.

   So speakers having no big baffle is a benefit. And having it dipole is another benefit. Because equalising after edge diffraction issues on axis  the of axis equalises also. For bigger baffle which works above first dipole peak equalisation is possible only for on axis.

   On top of that baffles speakers are decoupled from the ground with sorbothane feet (Pic1). Sorbothane is a special visco-elastic polymer with very high damping coefficient. Loudspeakers upper part is decoupled from subwoofer part also with sorbothane (Pic 2.) so if any vibration would occur  in subwoofer part, they will not be transferred upwards. But actually vibrations are incredibly low in subwoofer part that i can't feel with the hand. It is very impressive to press my ear against the subwoofer side wall when it is operating close to its Xmax + - 12.5 mm and feel almost nothing. There are two reasons for that:

  •    First one is that subwoofer part is solid piece of hardware of 30.4 kg 

  •    The second one and most important that two subwoofer drivers are mounted in W frame baffle configuration. And drivers are mounted together by the metal rods between them instead of mounting them directly and only to the frame. The woofer cones moves in opposite directions and the forces cancels completely (Pic.3) through these rods.  



Baffless speakers decoupled from the floor with sorbothane feet

Pic.1  Speaker bottom decoupling

Baffless speakers upper part decoupled from sub

Pic. 2 Speaker upper part decoupling

Subwoofer force canceliation mounting technique

Pic. 3 Subwoofer mounting with metal rods

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