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whoooaaaaaa.....I just got a thought. (Read 10788 times)
fordpwnzchevy
Ex Member



Re: whoooaaaaaa.....I just got a thought.
Reply #30 - 10/03/06 at 19:11:38
 
A flat piston driver such as the older ed's, earthquake magmas maybe, and a couple others wouldnt have these phase issues.  Obviously, since both sides of the cone share the exact same shape, the front a back wave will be in phase.  I bet if you used a flat coned woofer this would work out awesomely and be more than just a 1 note wonder.
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musgofasa
Ex Member



Re: whoooaaaaaa.....I just got a thought.
Reply #31 - 10/03/06 at 19:29:05
 
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
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fordpwnzchevy
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Re: whoooaaaaaa.....I just got a thought.
Reply #32 - 10/03/06 at 19:36:09
 
To tell you the truth i have no justification except pictures in my mind and what alot of people have told me about flat piston woofers.  Not to sound ignorant (although it thoroughly does haha), but the people that i've heard this from i've usually taken their word as law for audio purposes and never thought otherwise.  Hopefully someone else can come along and prove it right or wrong.
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musgofasa
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Re: whoooaaaaaa.....I just got a thought.
Reply #33 - 10/03/06 at 20:23:27
 
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
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J_Rock
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Re: whoooaaaaaa.....I just got a thought.
Reply #34 - 10/03/06 at 21:15:27
 
No matter the shape of the cone, the rear wave is always 180 out of phase from the front wave.  Which is why a woofer sitting on the floor will have little if any of the output it will have in an enclosure.  

Just picture a sine wave.  A perfect up and down wave.  This picture represents the position of the speaker at any given time. No matter what the cone looks like, everypoint on the cone moves like that.

As a matter of fact, thats the whole original point of enclosures, to contain the rear wave of the speaker.  Then they were adapted to turn the rear wave into useful output and control the movement of the driver better.


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fordpwnzchevy
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Re: whoooaaaaaa.....I just got a thought.
Reply #35 - 10/04/06 at 01:42:05
 
Glad thats cleared up haha, thnx. Cry
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J_Rock
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Re: whoooaaaaaa.....I just got a thought.
Reply #36 - 10/04/06 at 01:50:28
 
Sorry if I sounded condescending, its these major theorys that need to be correct for you to do your own thing in audio.  I just wanted to make sure you knew- because that is a pretty big mistake to make and would hinder you from now on when attempting to go big and loud.
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fordpwnzchevy
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Re: whoooaaaaaa.....I just got a thought.
Reply #37 - 10/11/06 at 08:05:42
 
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.
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fordpwnzchevy
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Re: whoooaaaaaa.....I just got a thought.
Reply #38 - 10/11/06 at 09:30:22
 
One other thing i was thinking about was the sine wave thing you mentioned.  It would seem to me the only way the negative part of the wave would cancel out the positive is if they were playing at the same time.  Ex.  2 subs wired 180 degrees out of phase.  One sub plays the positively and the other plays negatively, both at the same time.  Equal but opposite.  I cant describe the full thought i have at the moment which more than likely means i'm ignorant (not being able to explain something means you yourself dont understand it hahaha).  But i think you would at least understand why i had the incorrect idea in my head about phase cancellation.

*edit*- srry for ranting and threadjacking again, i'm really interested in this topic.:(
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« Last Edit: 10/11/06 at 09:31:03 by fordpwnzchevy »  
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J_Rock
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Re: whoooaaaaaa.....I just got a thought.
Reply #39 - 10/11/06 at 13:27:27
 
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.
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ST33M
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Posts: 7
Re: whoooaaaaaa.....I just got a thought.
Reply #40 - 06/08/07 at 19:56:51
 
What if you were to port the sealed section into the front next to the sub before the horn, only one octave over ?

Say you know your peak is 40hz and port it to 80hz. Would this in turn help in spl or would this hurt ? Just throwing something out there to ponder on.
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