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Port Width through the port


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So I recently built a box for my 2 X-18's. It was a really rush build to just have something since I blew my old subs and something to just break them in. This is the first time building such a large port in a box, last several boxes all used aero's too. But with all of that, when it came to the port, there was a huge difference in width from the center of the bend and the actual width. I made a 45 to compensate the difference but it still made me curious. I know having a point through the port where the width is smaller than the planned width will choke it. If there is a portion however that is larger, how would that effect playback? Here are some pics to explain what I am talking about.

This is the width of the port by plan and on paper.

20170401_164039_zpsefpjg4ty.jpg

This is the width of the bend

20170401_164051_zpsdq3xbhhj.jpg

On 11/20/2012 at 8:54 PM, AMI CUSTOMS said:

Turned mine up today at a light, guy next to me his steering wheel started moving and he looked over at me like I was a magician lol.

On 5/9/2012 at 8:45 PM, skittlesRgood said:

fuck the plating. look at what the main metal used is. you could buy unicorn blood plated terminals but if its just covering up dog shit, whats the point

On 4/10/2013 at 12:26 PM, mrd6 said:

I'll admit, half way through sanding that fiberglass in the rain and cold while I was all itchy I was definitely starting to question why i was doing this haha

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1 minute ago, caraudionoob said:

Basically, you're asking if having 45's will do anything. This has been debated over and over again. Here are some of the threads that cover it

 

 

No I am not asking if 45's will do anything. I stated, "If there is a portion however that is larger, how would that effect playback?". I know having a portion of the port that is thinner will choke the port, but how will the inverse effect playpack, port noise, and other aspects of playback. 

On 11/20/2012 at 8:54 PM, AMI CUSTOMS said:

Turned mine up today at a light, guy next to me his steering wheel started moving and he looked over at me like I was a magician lol.

On 5/9/2012 at 8:45 PM, skittlesRgood said:

fuck the plating. look at what the main metal used is. you could buy unicorn blood plated terminals but if its just covering up dog shit, whats the point

On 4/10/2013 at 12:26 PM, mrd6 said:

I'll admit, half way through sanding that fiberglass in the rain and cold while I was all itchy I was definitely starting to question why i was doing this haha

  • Soon To Be
  • '04 Ford Escape
  • US Alternator 280A Hairpin
  • D4800 Under the Hood
  • (6) XP3000's in Rear
  • 1/0 SHCA & XS Power 4 runs to back
  • TORK2 kit from Tony @ CE Auto Supply
  • Pioneer DEH-80PRS
  • DD AW6.5 (2) per door
  • *Tweeter Unkown*
  • DD SS4a & C3d
  • (2) SCV4000 @ .5Ohm
  • (2) 15" Sundown Zv5
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As far as air flow would go, a decrease in cross section would cause the velocity to increase. An increase in cross section would cause the velocity to decrease. As far as sound waves go, I think it would effect the overall average size of the port. I have always wondered if having a tapered port where the cross section increases like a horn would help output.

Edit: further thinking about port velocity, a smaller section would choke the port because it would increase velocity at that point. A larger cross section would decrease velocity and lower velocity is not detrimental to port effeciency.

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I suspect the increase in port internal volume will lower the tuning frequency slightly due to a greater mass of air being inside the port.  I've never tested to see how much difference it makes but I bet its pretty small, definitely not something to worry about.  

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That is what I was looking for. Thanks guys. Half of me wanted to just go buy a design from someone reputable, the other half wanted to build 25 boxes, all being nearly identical just 1 variable difference to test for myself what does what and come to a final design myself.

On 11/20/2012 at 8:54 PM, AMI CUSTOMS said:

Turned mine up today at a light, guy next to me his steering wheel started moving and he looked over at me like I was a magician lol.

On 5/9/2012 at 8:45 PM, skittlesRgood said:

fuck the plating. look at what the main metal used is. you could buy unicorn blood plated terminals but if its just covering up dog shit, whats the point

On 4/10/2013 at 12:26 PM, mrd6 said:

I'll admit, half way through sanding that fiberglass in the rain and cold while I was all itchy I was definitely starting to question why i was doing this haha

  • Soon To Be
  • '04 Ford Escape
  • US Alternator 280A Hairpin
  • D4800 Under the Hood
  • (6) XP3000's in Rear
  • 1/0 SHCA & XS Power 4 runs to back
  • TORK2 kit from Tony @ CE Auto Supply
  • Pioneer DEH-80PRS
  • DD AW6.5 (2) per door
  • *Tweeter Unkown*
  • DD SS4a & C3d
  • (2) SCV4000 @ .5Ohm
  • (2) 15" Sundown Zv5
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It shouldn't effect it. A port with varying dimensions will function as the if it were the same throughout using the smallest opening. I.e. if your port has a section that is 15x5 and a section that is 15x8, it will function as if it were 15x5 the whole length. Changes in size may cause it to be slightly less efficient, or more efficient (i.e. a port that starts small and gets larger at a certain rate can make for a more efficient acoustic coupling.) In your case it shouldn't make a noticeable difference and as far as tuning, it should act the same as if the wider section was the same as the rest.

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