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Derrick824

Cone Area Of A Subwoofer

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So SD is the way you determine which sub will be louder? good to know..


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actually the post above yours did exactly that, which is what I thought you were answering.

I see what you are saying now though.


F-150, Sundown Audio & Rockford Fosgate build
My someone what uniterrupted build log (xD UBL)
My xD build in it's current form. (SOLD)
My old builds!
My YouTube channel
My Garage link

Current Equipment:
Pioneer App Radio 3

RF T1652-s components

(2) Sundown Audio SA-8v2

RF 3sixty.2

RF T400.4

RF T1500.1 bdcp

Sky High Car Audio power, ground, and speaker wiring

 

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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 by firebirdude

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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.


F-150, Sundown Audio & Rockford Fosgate build
My someone what uniterrupted build log (xD UBL)
My xD build in it's current form. (SOLD)
My old builds!
My YouTube channel
My Garage link

Current Equipment:
Pioneer App Radio 3

RF T1652-s components

(2) Sundown Audio SA-8v2

RF 3sixty.2

RF T400.4

RF T1500.1 bdcp

Sky High Car Audio power, ground, and speaker wiring

 

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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.

 

 

 

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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.


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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 by youdoofus

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