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Copper - Posts: 81
Copper spacespace
Joined: October 29, 2007
Location: Texas, United States
Posted: December 07, 2007 at 3:09 PM / IP Logged  

jl.w7 wrote:
I actually find that circular ports produce more thump in a hatchback, i dunno maybe Im just hearing things.......

i was talking to a buddy of mine and he was trying to explain wavelength maturity or something like that....i didnt really get the way he was explaining it , but the point is i have the exact same setup as him..same box, same sub, same head unit, same settings in an f150. he has his in a 93 civic hatchback and its freaking violent in his car but is so so in my truck. so the theory behind it sounding the way it does is because i am too close to the sub to actually hear more than just the the sub noise. In the hatch you have it hit the glass at about a foot then bounce back and you have that extra 4 ft of wavelength that I obviously dont have in my f150 and according to him thats the difference in why the same setup sounds better in his car. I honestly dont know if this is true or not but this is just how i understood this "theory".

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Gold - Posts: 2,600
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Joined: May 01, 2006
Location: United States
Posted: December 07, 2007 at 5:00 PM / IP Logged this
jfinks...port shape DOES matter.
a port that is 10" x "10 is more efficient and effective than a port that is 1" x 100"
laminar flow
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Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: December 07, 2007 at 5:13 PM / IP Logged  
As long as the port area is the same, and the speed of the air within the port is kept to an acceptably low speed, laminar flow won't come into play.
When desiring laminar flow, you will really only need it at faster port speeds, to keep noise (wind noise) to a minumim. In a perfectly smooth tube, you can go significantly smaller on overall port area, as the noise will not be a factor - there isn't enough.
100 square inches will be just as effective as any OTHER 100 square inches, as long as the speed of the air is kept low enough. If your speed gets higher, then yes, I'd recommend a more square port, as opposed to a tall, narrow one.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Copper - Posts: 76
Copper spacespace
Joined: May 31, 2007
Location: United States
Posted: December 07, 2007 at 5:39 PM / IP Logged  

There are a couple of things going on between the two cars.

One: the the sound wave formation. Without going into a lot of theory simply put for use to preceive a frequency our ears need to receive 1/4 of the sound wave. the lower the frequency the longer the wave. So if the full wave is 60 feet long we need 15 feet. Not many cars have 15 feet of interior space with out folding it once or twice. This is why in smaller cars the bass sometimes sound louder stand just outside the car. And to complicate things we have not talked about nodes and what causes then and their effects.

Two: Coupling is an effect of the air all moving in unison. ever look at a trumpet? the tube gets gradually bigger untill the end where it spreeds out at the end. The hatch back area sorta forms the same kind of megaphone therefore increasing the Volumn of sound. Which leads us into

Three: resonance frequency. This effect is where a mass (in this case the air inside the car) moves in unison with incredible effency. All of the particals of the mass are moving in the same direction at the same time. Kids in a bath tub learn this one intuitively. If you sit in a tub of water and move back and forth in unisonwith the water, the wave gets bigger and bigger with very little movement...same thing. The interior of each car has a resonance (actually it can have many) frequency. If the sound of the woofers couples with the "Horn" of the hatchback at a resonance frequency of the interior everything will litterally shake and buzz and as you said get freaking violent.

Theese are simplifacations of what is going on. In one car its all working and in the other not so well.

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