From: shaun.at.pukekohe@gmail.com   
      
   Somewhere on teh intarwebs Trevor wrote:   
   > "~misfit~"  wrote in message   
   > news:kvbqm7$lgh$1@dont-email.me...   
   >> Somewhere on teh intarwebs DecadentLinuxUserNumeroUno wrote:   
   >>> On Mon, 22 Jul 2013 00:26:27 +1200, "~misfit~"   
   >>>  wrote:   
   >>>> Alas, on getting them home I discovered that the 'rubber' surrounds   
   >>>> of the 12.5" woofers had gone hard   
   >>>   
   >>>  There is no such animal.   
   >>>   
   >>>  You measure the speaker size by measuring the bolt circle diameter,   
   >>> not the outside rim of the speaker.   
   >>   
   >> Oh, wait a minute. WTF do you mean by the "bolt circle diameter"? Do   
   >> you mean the mounting holes? Because, if you do I've just measured   
   >> these and they're *exactly* 12.5" from the centre of one bolt-hole   
   >> to the centre of the opposite one. I guess that could be referred to   
   >> as the "bolt circle diameter".   
   >>   
   >> (Although *why* anyone would want to use that measurement as a   
   >> driver size instead of the cone diameter is beyond me.   
   >   
   > It's just historical, and important if you want a drop in   
   > replacement, but your measurement does prove the lie to the claim   
   > "There is no such animal", and why it is difficult to obtain   
   > replacement surrounds.   
      
   Indeed.   
      
   >> It's asking for manufacturers to 'cheat' by having a really wide   
   >> flange and spacing the holes all the way to the edge.)   
   >   
   > For comparison and TS measurement purposes active cone area is used   
   > instead, so not a problem.   
      
   Yep, I've made a few boxes (and have the software to prove it - these days)   
   so know all about TS params. However, as I alluded to in my other post -   
   I've seen "10 inch" drivers (for instance) with cones that vary by around   
   two inches in diameter. As most speaker-buyers will never need to know what   
   size a replacement driver will need to be it could potentially be very   
   misleading.   
      
   I mean, if your average punter is looking to buy speakers and it's a toss-up   
   between two different brands, both 3-way with a "10 inch" woofer (which vary   
   by the afore-mentioned 2" or thereabouts) said punter might not know that in   
   fact one woofer has 30% more cone area than the other. After all they're   
   both 10" right?   
      
   Cheers,   
   --   
   /Shaun.   
      
   "Humans will have advanced a long, long, way when religious belief has a   
   cozy little classification in the DSM."   
   David Melville (in r.a.s.f1)   
   [Sent from my OrbitalT ocular implant interface.]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)