Loudspeaker Cone Area Myths

by Eddie Runner (NU5K)

Double Power = 3dB

I have heard installers say doubling the power gets us 3dB
and doubling the cone area gets us another 3dB.

Electrons flow through the wires to our speakers.
The electrons are changed to electromagnetic energy.
The electromagnetic energy works with permanent magnet energy
to make a speaker cone move. which produces acoustic energy in the air.

The movement vibrates air and we have sound..

Its common to hear, doubling the power to the speaker will get us only 3dB.
This is important to remember because this is a big jump on the power end
and a very small jump in the acoustic end (sound in the air)..
Big jump in electrical, small jump in acoustical.

But, the speaker is not guaranteed 3dB if we double the power!
That's up to individual speaker, and the speaker obviously can not
contiunue producing another 3dB forever, the speaker has its limits.

So that being said, doubling power into the speaker motor
may give us an extra 3dB in the air, but it may not...

So, to say doubling the power will always get you 3dB from a loudspeaker is just a guess at best!
Defiantly not a law of physics! Definitely not always true.

But unfortunately, it is a story commonly told.

Now, Cone area!

Cone area is not talked about as much as it used to be, but it is
still heard, and printed on the internet in various places that
doubling the cone are will get you 3dB

It is true that if we have an 8 inch speaker producing 90dB and
turn on another 8 inch speaker also producing the same
sound at 90dB, that will likely measure a 3dB increase in the air.

but, it is also true if we have an 8 inch speaker producing 90dB
and we add a small 4 inch speaker producing the same sound also at 90dB
then we will also have a 3dB increase in the air.

OR, the second speaker can be a 15 inch playing the same sound at 90dB,
or the second could be virtually anything that can produce the same
sound at 90dB.. It doesnt even have to be a loudspeaker.. It can be
the fat lady from the opera singing the same sound at 90dB. Then we will
still likely have the 3dB increase in the air.

So you see, the POWER MYTH and the CONE AREA MYTH although based in facts are often misused in the car audio world and are easily proven to be untrue..

The truth to the physics of sound is actually very simple!

1. Adding one sound to another sound of the same amplitude (volume) will gain you 3dB.

2. Adding one sound to another sound of the same amplitude and correlated will gain you 6dB.

(correlated means exactly the same phase, and likely to occur with the long wavelength of bass notes in our cars)

And let us not forget one of my favorite things.. The inverse square law.
if you 1/2 the distance from your tester (dB meter or ear) to a point source of sound,
then you will get 3dB increase. or if you double the distance from the point source, you will loose 3dB.