I have been in this a long time and I have never heard that the shape of the cone would affect the phase of the sound wave???????
I am not usually a smart alek and I will try not to sound like one here, but how would the shape of the cone affect the fact that the wave created by the direction of movement is opposite?
If this is true, it throws a whole lot of the theories I use out the window in one fell swoop.

Like I said, not trying to be smart, but I would like to hear this explanation. I used a bunch of the old PPI woofers back in the day with the flat pistons. I didn't notice that they were any different personally.

clarification??

Thanks,
Robert

OK
so the way I see phase is pretty simple:
Driver moves one direction sound moves away from driver in that direction.
Driver moves other direction, sound moves in the other direction
IE out of phase to first direction by 180 degrees.

There are other types of phase shift and lags that are common to frequency shift and other electronic factors, but mechanically speaking that should be about it.
Case in point. Take two speakers (left and right) play music through them. Run balance to one side and then the other. If the speakers produce more bass when both are playing, they are in phase. If the bass goes away when both are playing, then one is firing in the opposite direction to the other and needs to be reversed.

Now if we can apply that simple philosophy to the length of time it takes the sound from the back side of the driver to reach the same point that it is leaving the front side, we could increase efficiency at the frequency that it happens. Unfortunately it would have the nasty result of throwing all other frequencies out of phase (correct me if I am wrong) 180 degrees per octave?

That is what causes most SPL cars to have that classic "Wet fart" sound
(Sorry EZ, couldn't resist)

Robert

Glad thats cleared up haha, thnx.

One thing just came to mind.  I dont know if it is right or wrong.  The Adire Parthenon.  It uses a flat piece of mdf as the cone surface and is for use in free air, no enclosure, from what i understand.  I dont mean to bring up dead threads, or questions that've been answered.  And dont want to seem pestering or anything.  But i seem to have a slightly questioning nature.  I was wondering if someone could explain this driver to me.  Also, sorry for threadjacking.

Well, its a matter of partial vs full cancelation.  A driver playing free air with no baffle will make noise- this is because some of the sound energy is canceled out, but some is not.  

Even playing two subs out of phase next to each other would result in some output.  Simply because- yes the wave are out of phase, but the distance seperating the source causes a lag so the waves may sum in in different places.

The Parthenon was made with a square cone simply because it was a structural solution.  It was tested without an enclosure and I bet was used without one.  This is probably due to the size of the baffle allow it to be used OB- open baffle.  Theres a huge thread in the speakers builder forum on this site that goes into OB.