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Vented box WinISD issue
Vented box WinISD issue
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Old 18th January 2019, 12:45 PM   #1
trojantrow is offline trojantrow  United Kingdom
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Join Date: Jun 2015
Location: Doncaster
Default Vented box WinISD issue

Hi all. Please donít hammer me for not searching for this. I canít seem to find something answering my specific question.

Iím trying to model a ported enclosure with WinISD. The problem is the port velocity and first resonance usual issue

Question is when I tell WinISD that the port will have 2 flared ends, nothing changes. Velocity and length stay the same

I donít know how long to male my ports due to the flared ends. I know this alters the length needed.

And more
Importantly what port velocity can I go up to and how much does the flared ends help.?

And do I need a specific flare size?

Plans are as follows

Alpine swr1542D
140litre box (solid rosewood tv cabinet) with added 18mm mdf on all sides)
Tune to 19 or 18 hz
External port in order to achieve adequate port length

Any other pointers I should consider?

Thanks in advance
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Old 18th January 2019, 04:15 PM   #2
The Lord Flashheart is offline The Lord Flashheart  United Kingdom
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I've also searched this and come up blank, I was trying to model a T shaped slot port and was given the end correction to use.

I couldn't get WinISD to accept it or even calculate for flanged ends as you have found.
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Old 18th January 2019, 06:33 PM   #3
trojantrow is offline trojantrow  United Kingdom
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Join Date: Jun 2015
Location: Doncaster
Yeah and Iím now left
Iím a position where I need to make sure that the port velocity it not too high.

If someone could just come and say ďwell I had a calculated 30ms in WinISD and I used flared ends and I canít hear itĒ then that would be great.

Or even better ď you can go up to 35ms at 20hz with flared ends no problem at allĒ

Thatís all Iím looking for
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Old 18th January 2019, 07:25 PM   #4
chris661 is offline chris661  United Kingdom
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Location: Sheffield
With a Faital Pro 15HP1060, I was getting 2dB of port compression when dropping a kilowatt of sine tones in there, with a port cross-sectional area that got to a smidge over 300cm^2, but was larger at each end.

At domestic levels, you'll be fine - remember that the simulated port velocity will only occur when there's a full-power sine tone at that frequency.


Last edited by chris661; 18th January 2019 at 07:31 PM.
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Old 20th January 2019, 07:45 PM   #5
GM is offline GM  United States
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Location: Chamblee, Ga.
Maybe this will help: Port Flares

Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
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Old 23rd January 2019, 06:11 PM   #6
Crashpc is offline Crashpc  Czech Republic
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Join Date: Nov 2008
Best way is to tune in real life. WinIsd is not accurate at all.
Port size and allowed velocity greatly depends on box volume, tuning frequency, speaker excursion and motor strength, content you play, allowance for port noise and more. For 15“ and PA usage, good shot would be between 35% and 50% of the cone area. The more, the better.
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