holy run on sentence
Ok, first things first. The easiest way to think about how much air the cone is moving is to imagine that the cone is planar. Parabolic cones and planar cones are nearly the same Sd, so thinking in terms of a flat circle is ideal. Next, the effective piston area includes PART of the surround, not the entire surround. The large surrounds that you see are for high excursion drivers that need specialized suspension systems to allow for full travel. You see this on alot of lower grade speakers because it is aesthecially pleasing to put a large foam surround on a speaker even when it doesn't need it. The size of the surround has absolutely ZERO bearing on how loud the speaker is, so don't base it on that. Take a DD 9512 and a JL 12w7 and put each in the lanes and the 9512 will walk all over it. The surround on the w7 is HUGE whereas the surround on the 9515 is truly not that large at all. So remember these points:
1. The EFFECTIVE cone area (which moves the air) includes only a PART of the surround.
2. Surround size has no bearing on how loud the speaker will be.
3. Keep asking questions
//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
-Dave
1. The EFFECTIVE cone area (which moves the air) includes only a PART of the surround.
2. Surround size has no bearing on how loud the speaker will be.
3. Keep asking questions
//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
-Dave
You are referring to effective radiating area....or "Sd" in the T/S parameters.
And you are correct, those large wide-roll surrounds do eat up cone area, decreasing the volume of air the subwoofer can displace (Vd, which is essentially Xmax * Sd), decreasing potential output. If you take two exact same drivers, one with a wide-roll surround (and hence less Sd), and the other has a "normal" surround....the one with the normal surround will have more potential output because of it's increase in effecitve radiating area.
Sd takes into account 1/3 (or 1/2 depending on the company) of the surround when calculating effective radiating area. The actual calculation for Sd is;
Sd = (3.1416 * D^2)/4
where D is the diameter of the cone plus 1/3 (or 1/2) of the surround at both ends of the measurement.
Not saying the 9512 couldn't "walk all over" a W7 in the lanes...but it's not really because of their surrounds. One thing you are forgetting is that the W7's surround overlaps the mounting ring, whereas most other subwoofer's surrounds do not. What's this mean? The surround is moved further outward, increasing cone area //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif Even though the W7 does have a wide surround, it isn't really at a cone area disadvantage to most other subs because of it's unique design. The 12W7 actually has slightly more cone area than the 12W6v2, which uses a comparatively smaller surround, but "typical" mounting system. Compared to other "supersubs" like the XXX, Brahma, MTX 9512 (which uses a "high roll" surround), IDMax (high roll surround), etc etc.....the W7 again comes out either on top or equal as far as Sd is concerned.
Though I couldn't find an actual Sd for the DD 9512, I'd venture to say the 12W7 does not have an Sd disadvantage to it.
Actually, twice in one thread //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif You replied before I was done pwning j00
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