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1/4 wave theory

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Old Oct 19, 2010 | 02:41 PM
  #11  
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If the subs were pointed rear-ward, the port would be facing into the cab, and there would an unobstructed view from the port in the cab to the sub motors at the rear. If there was about 10" for the subs to load at the rear, would it act like a leaky 4th order?
Old Oct 19, 2010 | 02:56 PM
  #12  
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Originally Posted by Livin Louder
Generally the wave should be longer if the woofers are pointing to the rear and not forward, as the sound has to travel further and reflect off a surface before going forward to your cab.
So if you turn a speaker around outside so the sound has nothing to reflect off of and stand right behind it, you won't hear it?

A speaker (and speaker box) radiates sound in a sphere around it unless there is a boundary (like the ground or floor or a wall)

The reason most sedans have better bass with the woofers pointing backwards is because of where the woofer is in the trunk, not because of the direction it points. Decreasing the distance from the radiator (woofer/vent) to the back of the trunk increases the null point usually out of the bass range. A trunk is small enough that you do get into boundary loading as well but most of it is because you moved the standing wave frequency.

Last edited by Dukk; Oct 19, 2010 at 03:04 PM.
Old Oct 19, 2010 | 03:01 PM
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Originally Posted by BigRedGuy
Which begs 2, nope make it 3 questions....

1: Did you try figuring out what frequencies were being canceled? I'm curious if the math supports what you were hearing.....

2: Did you try facing the box forwards and to the rear while moving it front to back? I would assume the frequencies affected would be lower when facing the rear but I've never had the chance to test for it.

3: Does this mean you're working on the hearse again....that seems to have slipped onto the back burner for a while.....
1) Nope. Didn't care. Bad sound is bad sound. If I do it again though, I'll check now that I have a handy pocket RTA

2) Nope. Theoretically if the location of the baffle is the same, it does not matter what side of it the box is on (front/back). Again, the radiation is a half sphere if it is sitting against a surface like the floor.

3) This was when I first got it before I put in the wall. The first thing I have to do is rip that back out of there before I do anything else audio wise. It's gonna be shitty so I have been avoiding doing it..
Old Oct 19, 2010 | 03:03 PM
  #14  
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Originally Posted by Lord Huggington
If the subs were pointed rear-ward, the port would be facing into the cab, and there would an unobstructed view from the port in the cab to the sub motors at the rear. If there was about 10" for the subs to load at the rear, would it act like a leaky 4th order?
Not really. You might get some boundary loading from the woofers being close to the rear wall though.

Be careful with the vents on the opposite side of the baffle. That is usually bad news.

And sorry for the thread detour up there - at least it was semi-content related
Old Oct 19, 2010 | 03:15 PM
  #15  
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Originally Posted by Dukk
Not really. You might get some boundary loading from the woofers being close to the rear wall though.

Be careful with the vents on the opposite side of the baffle. That is usually bad news.

And sorry for the thread detour up there - at least it was semi-content related
Would a 4th order keep them loaded?
Old Oct 19, 2010 | 09:53 PM
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Originally Posted by Dukk
1) Nope. Didn't care. Bad sound is bad sound. If I do it again though, I'll check now that I have a handy pocket RTA

2) Nope. Theoretically if the location of the baffle is the same, it does not matter what side of it the box is on (front/back). Again, the radiation is a half sphere if it is sitting against a surface like the floor.

3) This was when I first got it before I put in the wall. The first thing I have to do is rip that back out of there before I do anything else audio wise. It's gonna be shitty so I have been avoiding doing it..
1: That sounds like a very cool little tool to have.....I love toys like that.....

2: I might be trying to split a hair too fine here.....

3: So the 6 15"s is last years idea?.....hmmm...got a new plan for it yet?

You are going to keep those cute little red and white seats tho right?....
Old Oct 20, 2010 | 07:23 AM
  #17  
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[QUOTE=Dukk;618947]So if you turn a speaker around outside so the sound has nothing to reflect off of and stand right behind it, you won't hear it?



Ha, ok i understand. Defiantly you will hear it! But if you were to put a loading surface in front of it, it will change the wave reflection, the standing frequencies, and the length of the 1/4 wave from the moving mass of the driver. (The wave should be longer facing the woofers backwards in a sedan than facing forward?)

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Old Oct 20, 2010 | 07:28 AM
  #18  
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Originally Posted by Lord Huggington
If the subs were pointed rear-ward, the port would be facing into the cab, and there would an unobstructed view from the port in the cab to the sub motors at the rear. If there was about 10" for the subs to load at the rear, would it act like a leaky 4th order?


Oh and like Dukk said... Be careful if your going to have the port on the opposing side of the woofers as it forces al the back pressure straight out of the enclosure and can lose woofer control very easily with and without proper tunings and loading. Although It being loaded off the rear might help to control the woofers though... hmm.
Old Oct 20, 2010 | 10:07 AM
  #19  
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A 4th order would keep them loaded, it would be like a sealed box.

If an SPL oriented sub rolls off at 70hz in a sealed box, what happends to it in a 4th order?
Old Oct 20, 2010 | 02:06 PM
  #20  
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You're probably already familiar with wave theory. Wave theory simply states that certain things behave in a wave-like manner, meaning that they oscillate (go "up" and "down" periodically and in a predictable manner).



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