Calculate subwoofer cone area from radius or find radius from cone area using inches, feet, centimeters, and meters for unit conversion.
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Subwoofer Cone Area Formula
The calculator finds circular projected area, not the sloped surface area of a cone. Choose area from radius, area from diameter, or radius from area, then enter the relevant dimension and output unit.
- A = subwoofer cone area
- r = cone radius
- π = pi, approximately 3.14159
If you enter radius, the calculator uses exact length conversion factors, finds circular projected area, then converts to your selected area unit.
If you enter cone area, the calculator converts the area to a consistent internal basis, solves for radius, then converts to your selected radius unit.
Common Cone Area Values and Unit Conversions
These values assume the cone is a perfect circle and the radius is half of the listed diameter. Actual subwoofer effective cone area can be different because of the surround and basket design.
| Nominal diameter | Radius | Cone area | Cone area |
|---|---|---|---|
| 8 in | 4 in | 50.27 sq in | 324.29 sq cm |
| 10 in | 5 in | 78.54 sq in | 506.71 sq cm |
| 12 in | 6 in | 113.10 sq in | 729.66 sq cm |
| 15 in | 7.5 in | 176.71 sq in | 1,140.09 sq cm |
| 18 in | 9 in | 254.47 sq in | 1,641.73 sq cm |
| Conversion | Approximate displayed conversion |
|---|---|
| 1 ft | 12 in |
| 1 cm | 0.393701 in |
| 1 m | 39.3701 in |
| 1 sq ft | 144 sq in |
| 1 sq cm | 0.155 sq in |
| 1 sq m | 1550 sq in |
Example Problems
Example 1: Find cone area from radius
You have a subwoofer cone radius of 6 in.
The cone area is about 113.0973 sq in.
Example 2: Find radius from cone area
You have a cone area of 78.54 sq in.
The radius is about 5 in.
FAQ
Is subwoofer cone area the same as speaker size?
No. Speaker size is usually the nominal outside diameter, such as 10 inches or 12 inches. Here, cone area means the circular projected area based on radius, not the sloped cone surface. The usable moving area, often called effective piston area or Sd, may be smaller than the nominal size suggests.
Should you use radius or diameter?
Choose the radius or diameter mode to match your measured dimension. A 12-inch projected diameter corresponds to a 6-inch radius; a nominal 12-inch speaker need not have that effective piston diameter.
Why does actual subwoofer cone area differ from the calculated area?
The calculation treats the cone as a perfect circle. Real subwoofers have surrounds, dust caps, mounting frames, and cone shapes that affect the true moving area. For box design and acoustic modeling, use the manufacturer’s listed Sd value when it is available.
