Mark Zarella wrote:

Not sure what you're getting at here. Are you suggesting that the
(theoretical) 3dB increase occurs only when the total system power is
doubled, but not when the cone area is doubled?

NEITHER!!!

You get the 3db for the simple reason that two like sounds combine.
it has nothing to do with doubling the power or doubling the cone area!
(other than the power or cone area make the sound in the first place.)

This is the same thing though.

No its not.... you cant double the cone area without doubling the motor
and the cone mass and a whole bunch of other variables.... You cant magicly
double the cone area and even if you did it would not guarantee a 3db
increase.... SO its NOT the same thing... Doubling the cone area MIGHT
give you 3db... doubling the sounds WILL give you 3db increase!! (correlated
gives you 6db)..

See the difference??
your way is MIGHT
my way is WILL
!!!!!!!!!!!!!!!!!!!!!

Not the same thing at all..

Two like sounds combining is the same thing
as doubling the cone area (note: all else being equal, which as you pointed
out before, is a difficult proposition in the real world).

all of what being equal???
Equal voice coil, equal magnets, equal suspension, equal cone weight???
???? Equal power??? How do you know its equal???

And what if it is NOT EQUAL???
What if one speaker is an 8 inch and one speaker is a 15 inch???
it could still be a 3db increase if they combine sounds!!
Then again it might not be!!

The common myth that doubling the cone area gets you 3db is
all full of holes!!

On the other hand 2 equal sounds however is not all full of holes...
it WILL get you 3db or 6db if correlated...

Oftentimes,
modeling loudspeaker output consists of treating the cone as an infinite
amount of point sources. Whether you double cone area or double the number
of cones, you're doubling the number of "point sources". In effect, you've
got the same thing going on. So to say it has nothing to do with doubling
the power or cone area is not correct. It has everything to do with it.

NO!
Its not the fact that the cone area doubles.
Its the fact that the sound doubles!!

MAYBE (and maye not) when you double cone area you get 3db!
But ALWAYS when the sound doubles you get 3db!

Not sure what you mean here. Doubling the power or cone area WILL ALWAYS
yield a 3dB increase, assuming everything else is held the same.

Everything else??
Your statement is missleading and flawed!
doubling the INPUT power to the speaker is likely to not give you
a 3db increase, you just said it as well....

Cone area IS NOT WHY the sound is louder!!
We could do it with a smaller cone or a larger cone or NO CONE AT ALL!

Blaming it on CONE AREA or POWER or BOTH is a flawed
way of looking at something thats very simple....

IF! and I stress IF!
your second speaker is the same size and IF it puts out the
same dB as the first one which is already playing then you
would get 3db, and you would be doubling your cone area.

BUT, and I stress BUT!
you could also get the same3dB without doubling your cone
area! You could get it if a smaller or larger speaker was
playing the same sound or you could get 3dB if a fat lady
was singing the same song at the same level... See, it has
nothing to do with cone area!!!

You COULD!
You MIGHT!
But it wont always!!
read this http://www.installer.com/tech/conearea.html

Eddie Runner