winIsd port question - Home Theater Forum and Systems - HomeTheaterShack.com

Old 08-12-12, 09:20 AM Thread Starter
Senior Shackster
mikey

Join Date: Apr 2008
Location: Chula Vista, CA
Posts: 124
winIsd port question

Hi all,

I'm using winIsd and I put in 3 2.5" ports. It gives me a length of 30" vs around 12" for one 2.5" port. Is it 3 diveded into the 30" and use that number for each of the 3 ports or is it 3 30" ports. I'm modeling a Dayton designer 12 in 2 ft3.

Thanks

Mike
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Old 08-13-12, 11:19 AM
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Kick logic 2 da curb

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Location: Calgary
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Re: winIsd port question

A port is a mass of air whose acoustic impedance interacts with the inside and outside of the box.

One 2.5" x 12" port might give you a specific tuning, but doubling/tripling the surface area changes the pressure relationship with the box/air.

To keep the tuning the same, EACH of the three port will need to be 30" long.

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Old 09-11-12, 07:14 PM
Shackster

Join Date: Feb 2012
Location: Long Island, NY
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Re: winIsd port question

To put it simple, the more port area you have, the more port volume you need for the same tuning.
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Old 09-12-12, 09:45 PM
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Russ

Join Date: May 2007
Location: The Inland NW, USA
Posts: 1,788
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Re: winIsd port question

As mentioned, yes the 30" length would be for each of the three ports.

In case you didn't already know: To determine if you need one vs. three, you'd refer to the port velocity graph in WinISD. For ports of that size you wouldn't want more than 16-17m/s of maximum port velocity.

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Old 11-16-12, 12:13 AM
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paulspencer

Join Date: May 2007
Location: Melbourne Australia
Posts: 167
Re: winIsd port question

I suggest you also look at Collo's "flareit.exe" which is a little free app for determining the max velocity before chuffing. Very useful.

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