David Love wrote: > While greater backscale length does seem to give greater flexibility in > terms of downbearing settings (for all the reasons previously mentioned) it > still may be that more downbearing isn't necessarily desirable, just > tolerable. I never said more bearing was desirable. I said RC&S is more tolerant of a broad range of bearing settings. >> The bottom line is that with an >> RC&S design I think one should rethink downbearing as well. It doesn't >> serve the same purpose and therefore may work at cross purposes. > >> Depending on the configuration. > > > Or our ability to perceive the differences. Or appreciate them. > I have to disagree here. I think that the RC&S assembly is demonstrably > stiffer. It depends on where, and when you look. The RC&S will likely be more flexible in the bass, and stiffer in the treble. That very control is one of the points. >By many of our own discussions the CC board cannot maintain > stiffness through compression for any reasonable length of time (generally). > Therefore, it is inevitable that the RC&S assembly is or will be stiffer. Over time, of course. Longevity is another of the points for RC&S. I was talking about "as built". > An analysis of the beam strength on each of these two boards makes that > pretty clear that once the stiffness in the panel due to compression starts > to diminish at all the RC&S board will be stiffer. Doesn't the prevalence > of the killer octave alone suggest that the RC&S board is stiffer? Over time, yes. That wasn't the point. > As for the second point about directional stiffness, once you load and RC&S > board with downbearing then the effectiveness of similar stiffness in both > directions is lost. No it isn't. RC&S boards don't "hit the floor" when the panel compression maxes out because of the low panel compression. CC boards have a very steep spring rate progression as they're loaded. RC&S boards have a nearly linear spring rate. > If you have crown whether by design in the rib radius > or by compression, downbearing will increase the stiffness and as the > panel(s) move down there will be a movement in the direction of more > stiffness and as they move up there will a move in the direction of > looseness or less stiffness. It's a matter of degree. The two systems are considerably different in panel compression levels. >But more to the point, the question is whether > you can tie the board down with too much downbearing. On a CC board since > you are achieving the requisite stiffness with downbearing there is less > (though not zero) risk of that. With an RC&S board since it is already at > the requisite stiffness before you set any downbearing then the addition of > downbearing can only push it in the direction of being less mobile. How much less mobile, and with how much bearing? Ron N
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