MrSkippyJ 1904 Report post #91 Posted May 15, 2015 So SD is the way you determine which sub will be louder? good to know.. Share this post Link to post Share on other sites
firebirdude 150 Report post #92 Posted May 15, 2015 The title of the topic is cone area of a subwoofer. I didn't read 5 pages of people asking for someone to do their math, but nobody is asking simply "which will be louder". Share this post Link to post Share on other sites
MrSkippyJ 1904 Report post #93 Posted May 15, 2015 actually the post above yours did exactly that, which is what I thought you were answering. I see what you are saying now though. Share this post Link to post Share on other sites
firebirdude 150 Report post #94 Posted May 15, 2015 (edited) Ahhh true. Posting from my phone sometimes and don't read everything. This board displays weird.... Why is this stickied anyway??? A simple "look at the Sd spec and add them together" is all that needs to be said. Edited May 15, 2015 by firebirdude Share this post Link to post Share on other sites
MrSkippyJ 1904 Report post #95 Posted May 15, 2015 If I had to venture a guess it is because i think the some of the competitive organizations use the traditional area for a circle equation in their class breakouts. But that's just a guess. Share this post Link to post Share on other sites
tulowd 0 Report post #96 Posted December 14, 2017 On 5/15/2015 at 12:16 PM, MrSkippyJ said: If I had to venture a guess it is because i think the some of the competitive organizations use the traditional area for a circle equation in their class breakouts. But that's just a guess. My first post on a car audio board.......ever! Back in the day, it was to simplify categories. Technically speaking, the quoted cone area or piston diameter by the manufacturer usually includes some portion of the surround, as it technically does compress air. As previously mentioned, excursion plays a part when considering compression. A few things that are missing from this discussion are the dynamic specs when comparing speakers. Cones that flex or compress, long excursions that move the voice coil out of the gap and thus lose control, etc etc. Some of these specs at full tilt become fluid dynamics, since we are interested in maximum air pressure and thus surface area x distance. For comparison purposes, the (small) differences between overall dia and actual cone dia make for huge discrepancies.......because 1" dimensional delta on a 15" woofer is app 6.7%; on a 8" its 12.5%....and that's before you halve the new number, then square it and use multiple speakers with the largest discrepancy compared to fewer larger speakers with smaller discrepancies. 8" dia = 4" radius --> SA = pie r squared = 4x4x3.14 = 50.24 in squared 8' - 1" = 7" = 3.5" radius --> SA = pie r squared = 3.5x3.5x3.14 = 38.47 in squared actual Therefore: 50.24/38.47 = 1.31, so actual cone area is 31% smaller than using the overall size. If this reduction % was consistent between sizes, it would allow for accurate relative comparisons. But it's not, so it doesn't work. 10" dia = 5" radius --> SA = pie r squared = 5x5x3.14 = 78.5 in squared 10' - 1" = 9" = 4.5" radius --> SA = pie r squared = 4.5x4.5x3.14 = 63.6 in squared actual 78.5/63.6 = 23.4% cone area reduction 12" dia = 6" radius --> SA = pie r squared = 6x6x3.14 = 113 in squared 12' - 1" = 11" = 5.5" radius --> SA = pie r squared = 5.5x5.5x3.14 = 95 in squared actual 113/95 = 19% cone area reduction 15" dia = 7.5" radius --> SA = pie r squared = 7.5x7.5x3.14 = 176 in squared 15' - 1" = 14" = 7" radius --> SA = pie r squared = 7x7x3.14 = 154 in squared actual 176/154 = 14.3 % cone area reduction 18" dia = 9" radius --> SA = pie r squared = 9x9x3.14 = 254 in squared 18' - 1" = 17" = 8.5" radius --> SA = pie r squared = 8.5x8.5x3.14 = 227 in squared actual 254/227= 11.9 % cone area reduction Granted, many larger dia speakers have bigger surrounds, so the 1" reduction may turn into 2". This mistake shrinks as you get larger in diameter, and that's why the initial comparison doesn't serve any practical purpose. The concept is correct, just enter actual cone dimensions and all is well. Since most speakers use similar dimensions and construction methodology, measuring across the speaker cone and half the surround on each end should suffice for this discussion and should allow for 90+% of woofers to be compared. Granted, many larger dia speakers do have bigger surrounds, so the 1" reduction may turn into 2". Use a yardstick across opposed mounting holes to measure between half surround to half surround across the centre. Of course speaker efficiency, FS, enclosure size and style, amp capability at the chosen load, etc all affect the final performance and sound level, so this comparison is only part of the larger analysis and design criteria. Share this post Link to post Share on other sites
WalledSonic 1786 Report post #97 Posted December 14, 2017 2 minutes ago, tulowd said: My first post on a car audio board.......ever! Back in the day, it was to simplify categories. Technically speaking, the quoted cone area or piston diameter by the manufacturer usually includes some portion of the surround, as it technically does compress air. As previously mentioned, excursion plays a part when considering compression. A few things that are missing from this discussion are the dynamic specs when comparing speakers. Cones that flex or compress, long excursions that move the voice coil out of the gap and thus lose control, etc etc. Some of these specs at full tilt become fluid dynamics, since we are interested in maximum air pressure and thus surface area x distance. For comparison purposes, the (small) differences between overall dia and actual cone dia make for huge discrepancies.......because 1" dimensional delta on a 15" woofer is app 6.7%; on a 8" its 12.5%....and that's before you halve the new number, then square it and use multiple speakers with the largest discrepancy compared to fewer larger speakers with smaller discrepancies. 8" dia = 4" radius --> SA = pie r squared = 4x4x3.14 = 50.24 in squared 8' - 1" = 7" = 3.5" radius --> SA = pie r squared = 3.5x3.5x3.14 = 38.47 in squared actual Therefore: 50.24/38.47 = 1.31, so actual cone area is 31% smaller than using the overall size. If this reduction % was consistent between sizes, it would allow for accurate relative comparisons. But it's not, so it doesn't work. 10" dia = 5" radius --> SA = pie r squared = 5x5x3.14 = 78.5 in squared 10' - 1" = 9" = 4.5" radius --> SA = pie r squared = 4.5x4.5x3.14 = 63.6 in squared actual 78.5/63.6 = 23.4% cone area reduction 12" dia = 6" radius --> SA = pie r squared = 6x6x3.14 = 113 in squared 12' - 1" = 11" = 5.5" radius --> SA = pie r squared = 5.5x5.5x3.14 = 95 in squared actual 113/95 = 19% cone area reduction 15" dia = 7.5" radius --> SA = pie r squared = 7.5x7.5x3.14 = 176 in squared 15' - 1" = 14" = 7" radius --> SA = pie r squared = 7x7x3.14 = 154 in squared actual 176/154 = 14.3 % cone area reduction 18" dia = 9" radius --> SA = pie r squared = 9x9x3.14 = 254 in squared 18' - 1" = 17" = 8.5" radius --> SA = pie r squared = 8.5x8.5x3.14 = 227 in squared actual 254/227= 11.9 % cone area reduction Granted, many larger dia speakers have bigger surrounds, so the 1" reduction may turn into 2". This mistake shrinks as you get larger in diameter, and that's why the initial comparison doesn't serve any practical purpose. The concept is correct, just enter actual cone dimensions and all is well. Since most speakers use similar dimensions and construction methodology, measuring across the speaker cone and half the surround on each end should suffice for this discussion and should allow for 90+% of woofers to be compared. Granted, many larger dia speakers do have bigger surrounds, so the 1" reduction may turn into 2". Use a yardstick across opposed mounting holes to measure between half surround to half surround across the centre. Of course speaker efficiency, FS, enclosure size and style, amp capability at the chosen load, etc all affect the final performance and sound level, so this comparison is only part of the larger analysis and design criteria. Competitive orgs list their cone diameter assumptions to keep the playing field even. Most manufacturers list their own calculated cone area for TS parameters, and since many manufacturers have different area values, we can assume they make their own assumptions based on the surround they use. Share this post Link to post Share on other sites
youdoofus 0 Report post #98 Posted January 11 (edited) On 6/2/2007 at 10:59 AM, Derrick824 said: How to calculate cone area Cone area = pi x (r x r) pi = 3.14 r = radius of sub etc etc etc etc this is why paying attention in math class was important Edited January 11 by youdoofus Share this post Link to post Share on other sites
k58.cross 9 Report post #99 Posted Wednesday at 06:26 PM (edited) The shape is a conical frustum: http://mathworld.wolfram.com/ConicalFrustum.html Measure the open end radius and the dust cap to cone radius, and the vertical height from where dust cap meets cone to open end, then calculate as shown in the link. Multiply that by xmax to get the potential displaced volume, but don't mix metric and standard units. If you use xmax in mm, convert your surface area to mm^2, or convert both to desired unit. You'd have to do this on a sub by sub basis because of differences in surround design, dust cap design, and slope of the cone. Can't just go by 12, 15, 18, etc. You could approximate the dust cap as a hemisphere and include that surface area as well. Yeah I'm a nerd. Edited Wednesday at 07:40 PM by k58.cross Share this post Link to post Share on other sites