software for port

[busterno1]

could someone tell the name of software to change a round port to a slot or a web site that will do it . I have a port 76mm X 503mm in a 60 ltr box . its a tight fit







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[jbateman]

This question was asked over at Madisound recently, and AndyG gave this answer:
"just calculate the area of the port using
Area = pi x radius squared. Now you can make he slot any opening dimensions that give that area.
Leave the length of the port the same."

[kelticwizard]

Buster:

You mean you hve a port that is 76mm diameter and 503mm long? That's 3 inch diameter by 20 inches long, by the way.

If you change the port to a slot with the same area, you will have the same length-unless you put the slot along the bottom or one of the inside walls. My understanding is that makes the tuning lower. There have been threads here that cover this. I'll do a search if you want.

Anyway, a 76 mm, (3 inch) diameter port is the area equivalent of the following. the vent length will remain the same: 503mm, (20.2 in).

A) 67.3 mm square port
B) 100 mm, (4 in), times 45.3mm slot
C) 125 mm, (5 in), by 36.25 mm
D) 150, (6 in), mm by 30.2 mm

Freeware WinISD will give you similar results, by the way.

www.linearteam.dk

Incidentally, these will tune your 60 liter box to 19.5 Hz, approximately. They will also yield some vent noise.

Don't forget-a slot that uses the bottom or side walls as part of the slot is supposed to give lower tuning. WinISD will not calculate this for you. There has been some discussion on this on this forum, including a formula, I believe.

[busterno1]

thanks for the answers .

i have also told that I can do it by having the same volume as the round port which is 2.28 ltrs . I got a port of 27mm H X 38 d X 225 mm long which is 2.30 ltrs ? so are both answers right

[kelticwizard]

To be honest, Buster, I have heard about the volume of the port idea before, but I never tried it out.

Let me run your port on WinISD and see what we get. Hold on.

[kelticwizard]

Buster:

Doesn't look like it. Win ISD says that port that is 27 mm high by 38 mm wide would need to be 107 mm long to tune a 60 liter box to 19.6 Hz. That is what your 76mm by 503 mm port tunes abox to.

The dimensions you give- 27mm by 38mm by 220 mm will yield a box tuned to 14.3 Hz.

A little hard to imagine a 60 liter box needing tuning that low, but whatever.

[busterno1]

I should have said Its a isobarik sub

[busterno1]

thanks for the help I will try to get the round pipe to fit by adding a bend it might fit

[kelticwizard]

Isobaric or not, it makes no difference.

If it is an isobaric setup that has two woofers inside the box, you might have to deduct some volume for the "one-behind-the-other" isobaric setup.

[busterno1]

so that woudl work out to be a area of 45.3 cm with a lenght of 503 mm . is that right