Thanks Brian
Forgive me if I'm getting too technical here for some, but if we're using such sophisticated drivers & especially electronics, we should do the best job on the enclosures . .
No problem at all. There is a saying to the effect that "if no one asks questions after a presentation, it is either too perfect, or nobody understands to ask questions."
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"the reactive force of SW12-16FR is already 20% smaller than a woofer with 100g Mms"?
So the force cancellation is based (only?) on cone weight (which is half Linkwitz' driver, the XLS12 inch) rather than cone excursions, which would be greater with the SW-12-16FR having 25% greater Xmax?
And does the servo's action also increase bottom end bass, therefore more reactive forces?
When we compare two systems, we assume they are under the same output condition. In this case, it means the same velocity and same excursion. Xmax is related to the maximum capability. The reactive force is the opposite of active force which is the force exerted by the voice coil to move the cone. What does this force move? A mass-spring system. For SW-12-16FR, not only the mass is lower, the spring is also more compliant (146L vs others?). The result is it takes less force to move to the same speed. For the same active force on the cone, there is an exact opposite sign force on the frame/magnet structure.
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"the frame needs to structured so that the force transfers at the shortest distance between them for the cancellation. If the force needs to propagate via the long panel dimension, it will cause vibration, and propagate and lose the effectiveness".
Not sure what you mean in practise ? make the depth as short as possible?
Actually I meant adding direct supporting links between the locations where those 2 drivers are mounted. Force does not magically transfer from one place to another. In needs the material/media to compress or bend. Once that happens, the energy is formed, on the loose and can propagate to all direction. Before that, it was just a force. If we install very sturdy links between drivers' mounting location, the force will propagate via the supporting links faster, cancel the reactive force as its earliest time, and reduce the net force remained to propagate to the entire panel.
BTW, you also bring up a good point of what impact it has if the depth is less. I think it will move the resonance higher. Maybe it is high enough where sound absorbing material is very effective. It is good for sub too if you roll it off fast enough.
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"Another thing to consider is the "structure" to cause resonance is still there. So one should not place any driver (other than subwoofer) *close to it".
For the 'mid-woofer' sitting above this sub, what is the minimum distance away that you'd recommend?
* To get to the core of it, esp where a more modest height helps with WAF, what OB 'enclosure' shape do you think gives the best result?
(And what size would you recommend)
(presumably then we wont need a notch filter?)
Thank you
I cannot answer the last part. Maybe other members can help me out here. I am not very artist to come up with a design both good to look at and also sound in engineering. My thought is that the cavity exposed to you is the most important. You can use sound absorbing material to control the cavity resonance. If you at the same time, applied sufficient attenuation slope, it can help further. For the midrange driver, if you can somehow block the path of energy from midrange driver to the front cavity of the W frame, it also helps. In addition, the sound energy is inversely proportional to distance squared, so ...
