# How important is Air Velocity???



## matdotcom2000 (Aug 16, 2005)

This is my first REAL attempt at a ported enclosure and after playing with winISD I must say there is a real art to this that I am getting hooked on. I would like to find an answer to the question above??? And what does it really mean in the real world application and what differences in the reproduction of sound would it make???

My current box 1.55 box tuned to 25hz (port is 3in round X 17in long) and sub P1020DII same as P1020D found in winISD. The recommended is 1.75 cub. ft box tuned to 25 hz (port 3in round X 12in long). When I plug in both boxes into winISD the air velocity is something crazy but if i add another port it comes down dramatically. What is do I gain when adding another port and how bad would it mess with my displacement. BTW I have the sub wired at 4 ohms with 750 watts. its also stuffed with pollyfill.


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## Oliver (Jun 25, 2007)

By watching the impedance vs. frequency response of a ported box it is easy to understand why a properly sized and ported enclosure will offer increased power handling at the frequency of that port.

If the port does not make a chuffing sound at the max limit or it is not noticeable , you're good to go.

A 2nd port would need to be the same [ identically ] as the first.

In some box building programs the number will appear green = acceptable.

Red = possible chuffing when sub is turned up loud.
*
Rounding over the opening will help somewhat!*


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## matdotcom2000 (Aug 16, 2005)

Thanks for the advise!!!! I will be rounding it over soon and I do not get any shuffling so I must be good to go.!!!!! I think I am going to remove some pollyfill because it does not get as loud as I would like it to.


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## matdotcom2000 (Aug 16, 2005)

I added an additional port and it make a difference... LOVING these Ported ENCLOSURES


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## Oliver (Jun 25, 2007)

Very Nice !


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## Brian10962001 (Jul 11, 2009)

25hz tuning in a vehicle, that is LOOOOOW. I would raise the tuning up if it's not to much hassle. If you want to be brave, try 40hz, 35hz or so would be a nice compromise


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## ihartred (Jun 1, 2009)

I completely expected some VBA comment by now:laugh:


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