# Surface not a good predictor of volume

Discussion in 'Amps and Cabs [BG]' started by tmu, May 12, 2004.

1. ### tmu

Mar 14, 2004
Surface area is often used on this website as a sort of predictor of volume. However, I don't know if this is valid. Because larger speakers are deeper, the actually surface area of a larger speaker is likely significantly larger than the calculated surface area, as compared to a smaller speaker.

Any thoughts?

2. ### Transverzbeliever of the Low End Theory

May 3, 2004
Los Angeles, CA
hmm...

please explain difference between "calculated surface area" and "actual surface area"

sorry, probably dumb newb question, but I'm interested...

-T

3. ### tmu

Mar 14, 2004
No, not a dumb questions. Because speakers have cones (that is, they are not two dimensional and plate-like), the actual surface area (SA) is the area of the cone. However, most people calculate SA using the diameter of the speaker, which gives a calculated SA for the plate-like structure.

4. ### Happy MurphDay

Mar 9, 2004
around
true, speakers arent flat, there deep and shallow, but i think that the depth would be such a small amount that it wouldnt significantly alter the equation of speaker surface area, jmo,
but i would love to hear what others will say

5. ### Rickenbackerman

Apr 17, 2001
Laurel MD
You only look at the *projected* area of the cone (the area you see when looking directly at it). Think about this: if the cone angle got smaller and smaller until it was a hollow cylinder, would the speaker make any sound?

6. ### tmu

Mar 14, 2004
Sure, if the cone approaches a cylinder, there is no speaker projection. However this is not the case for speakers. The angle is perhaps 45 degrees from the horizontal for a large part of the cone. I still maintain that a 15" driver has more effective surface area that a few smaller drivers with equal calculated surface area.

7. ### inazone

Apr 20, 2003
This is with all things being equal though. A 210 in not always a 210 when comparing brand to brand.

8. ### Saetia

Mar 27, 2003
Wisconsin
True the surface we talk of is of a 2 dimensional circle not a cone, but comparatively the surface area would be slightly larger, but exponentially the same between say a 10" speaker and a 12" speaker, but the variable being the depth of the cone and voice coil size. I don't see it as being any different in judging the speaker, because it will be relative to the calculations that we judge from now. I believe that judging the volume that a cab can produce is a combination of its cone area as well as taking into account its efficiency. More cone area means it can push more air; its efficiency is how efficiently it can push that air. Hope that wasn't wordy or ununderstandable.

Peace
-Ben

9. ### Petebass

Dec 22, 2002
QLD Australia
And I agree. To me this is the most widely accepted piece of marketing propaganda ever. Sure ther are 4x10's nowdays that can go as deep as a 15, but that has nothing whatsoever to do with speaker area, rather the relationship between size, efficiency, and frequency response. (Loud, Low, Small - pick any 2). You can't argue with the laws of physics........ but you will anyway Let the party begin.......

10. ### BassIan

Apr 27, 2003
Cupertino, California
Due to the nature of a speaker, the projected area is what's neccessary to make such a conclusion. The speaker cone is essentially a piston, moving in a linear fashion. It is only along this line that the speaker will push air, and thus only with the frontal area (not the SURFACE AREA OF THE CONE, but the simple circular area of the cone) does the speaker move the air. In other words, assuming such a thing could be done, if two speakers, identical but for the cone angle were compared, they should displace the same amount of air. That said, dispersion characteristics for higher frequencies may differ, but this is generally not what we are referring to when we speak of speaker area.

All that said, I do agree that there is way more to "volume" than the cone area of a speaker cabinet. In the end, sit down and stop looking at numbers/specs/paint/logos, and LISTEN.