#### BlueWizard

##### Distinguished Member

I've touched on this before, but I thought it might be nice to have this information all in one spot, and since I addressed this in another forum, I thought it would be worthwhile to cut and paste it here.

The question was asked, more or less, how many 4" speakers does it take to equal an 8" speaker-

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Find the Piston area of the speakers using the area of a circle. If you do this, you will get a chart that looks something like this -

4.5" - 1

5.0 - 1.3

6.5 - 2.6

8.0 - 4.3

10 - 6.8

12 - 9.9

15 - 16.0

This was actually given to me when I asked a similar question in another forum.

Area of a Circle equals PI times the Radius Squared.

A = (PI) R²

So, let's work this out.

A = (pi) R² = (3.14159) x 2² = 3.14159 x 4 = 12.566 square inches

A = (pi) R² = (3.14159) x 4² = 3.14159 x 16 = 50.265 square inches

So, if we divide the two 50.265 / 12.566 = 4.00

So, one 8" speakers equal FOUR 4" speakers.

Here is another chart that I calculated myself -

4.00" = 12.57 sq.in. = 1.00

5.00" = 19.64 sq.in. = 1.56

5.25" = 21.65 sq.in. = 1.72

6.00" = 28.27 sq.in. = 2.49

6.50" = 33.18 sq.in. = 2.64

7.00" = 38.49 sq.in. = 3.06

8.00" = 50.27 sq.in. = 3.999 = 4.0

10.0" = 78.54 sq.in. = 6.25

12.0" = 113.1 sq.in. = 8.997 = 9.0

15.0" = 176.7 sq.in. = 14.06

Using this chart, we divide 4 (for an 8" speaker) by 1 (for a 4" speaker) and we get the same result; FOUR 4" speakers equals ONE 8" speaker.

Also notice that a 6.5" speaker using this last chart, is 70% larger than a 5" speaker. (2.64/1.56 = 1.70)

A 12" speaker is 125% larger than a 8" speaker. (9/4 =2.25)

And so on...

Steve/bluewizard

The question was asked, more or less, how many 4" speakers does it take to equal an 8" speaker-

- - - - - - - - - - - - - - - - - - - - - - - -

Find the Piston area of the speakers using the area of a circle. If you do this, you will get a chart that looks something like this -

4.5" - 1

5.0 - 1.3

6.5 - 2.6

8.0 - 4.3

10 - 6.8

12 - 9.9

15 - 16.0

This was actually given to me when I asked a similar question in another forum.

Area of a Circle equals PI times the Radius Squared.

A = (PI) R²

So, let's work this out.

A = (pi) R² = (3.14159) x 2² = 3.14159 x 4 = 12.566 square inches

*(4" driver)*A = (pi) R² = (3.14159) x 4² = 3.14159 x 16 = 50.265 square inches

*(8" driver)*So, if we divide the two 50.265 / 12.566 = 4.00

So, one 8" speakers equal FOUR 4" speakers.

Here is another chart that I calculated myself -

4.00" = 12.57 sq.in. = 1.00

5.00" = 19.64 sq.in. = 1.56

5.25" = 21.65 sq.in. = 1.72

6.00" = 28.27 sq.in. = 2.49

6.50" = 33.18 sq.in. = 2.64

7.00" = 38.49 sq.in. = 3.06

8.00" = 50.27 sq.in. = 3.999 = 4.0

10.0" = 78.54 sq.in. = 6.25

12.0" = 113.1 sq.in. = 8.997 = 9.0

15.0" = 176.7 sq.in. = 14.06

Using this chart, we divide 4 (for an 8" speaker) by 1 (for a 4" speaker) and we get the same result; FOUR 4" speakers equals ONE 8" speaker.

Also notice that a 6.5" speaker using this last chart, is 70% larger than a 5" speaker. (2.64/1.56 = 1.70)

A 12" speaker is 125% larger than a 8" speaker. (9/4 =2.25)

And so on...

Steve/bluewizard

Last edited: Aug 18, 2014