mustang guy Posted December 14, 2014 Share Posted December 14, 2014 (edited) This is something that came to mind when I realized they are dependent on a couple of factors. The first factor is the stiffness of the suspension, or the spider and surround material/shape and size, and perhaps to a lesser extent the vacuum in the former or the dustcap porosity.. The other factor is the manufacturing tolerances, which according to wiki are 20-30%. A new speaker will definitely be more stiff than a broken in one. To me, that means both the CMS and the VAS are changing with use. Does it occur to others here that measuring a broken in driver would be a smart thing to do after break in, so the enclosures can be modified with such things as polyfill, port dimension changes, or even enclosure volume enlargement or reduction? Edited December 14, 2014 by mustang guy Quote Link to comment Share on other sites More sharing options...
Ski Bum Posted December 15, 2014 Share Posted December 15, 2014 Gotta test your drivers once you have possession of them rather than relying on specs. If you're DIY competency is up for that, re-checking when the speakers have more mileage on them is no problem. IME getting perfectly matching pairs of drivers is the bigger problem. Quote Link to comment Share on other sites More sharing options...
mustang guy Posted December 18, 2014 Author Share Posted December 18, 2014 I have a tendency to think the VAS and CMS specs from manufacturers are from fully broken in drivers. Does anybody know if this is true? Quote Link to comment Share on other sites More sharing options...
Jay L Posted December 18, 2014 Share Posted December 18, 2014 I have a tendency to think the VAS and CMS specs from manufacturers are from fully broken in drivers. Does anybody know if this is true? This is the way we use T/S parameters to design with. All drivers go through a break-in procedure. I am pretty sure this is common in the industry. Quote Link to comment Share on other sites More sharing options...
mustang guy Posted December 18, 2014 Author Share Posted December 18, 2014 (edited) That makes better sense. I don't know why it didn't occur to me before I created this thread. Has anybody tested a vintage driver to see how an extremely broken in driver has changed? Some of the Heritage speakers in use today probably have tens or hundreds of thousands of hours on them. Edited December 18, 2014 by mustang guy Quote Link to comment Share on other sites More sharing options...
djk Posted December 18, 2014 Share Posted December 18, 2014 Drivers with different T/S parameters may be evaluated by this method: Fs divided by Qts = as close as possible. Qts squared times Vas = as close as possible. Quote Link to comment Share on other sites More sharing options...
mustang guy Posted December 18, 2014 Author Share Posted December 18, 2014 You bring up a very good point. If the CMS and VAS parameters change with break in, so do the Q and the FS. Quote Link to comment Share on other sites More sharing options...
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