Ports, rectaungular or round?

Just wondering if there is a difference between using rectangular port VS. Round ports......    I am going for high SPL but would like to maintain sound clairty as much as I can with a ported box.....I have the figures for round ports but I dont have the figures for rectangular?   There must be a figure somewhere.........any suggestions please help...

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2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place

I suggest the rectangular port because there is less ( if any ) port noise in comparison to a round port. Check this site out ( AWESOME !! ) https://www.eatel.net/~amptech/syndicate/spboxnew2syndicate.htm

• If you want to use square ports, use a port who's height multiplied by its width equals the 'port area' on the calculator. The port length will be the same as the round port.

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Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA

It would occur to me, that if you have a round port, say 4"ID, 8" long, that you could calculate the *volume" of this as a cylinder instead of surface area as a circle.
Then calculate a fixed width and heighthfor the square port, based on box dimentions (making a slot at the bottom of the box, if you will) and make the depth your variable, so that you equate the volume of the new port as a rectangular box, equal to the volume of the previous cylinder.
This way both a round, or rectangular-slot port would have equal volume with which to move air.

Would that make sense?


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-GlassWolf
Pioneer Stage-4, Orion, DynAudio, Fi

Here's an additional query I have.
I've got a pair of 12" subs. designed to be ported.
I'm thinking of doing a new Isobarik clam-shell box for them, using a slotted vent. The subs will be face-to-face, out of phase in a push-pull configuration.
Now, how do I calculate enclosure volume? Is is based solely on the internal speaker's specs? or on both drivers somehow, since they are both integrally moving the same mass of air between the two cones?
heheh Thanks




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-GlassWolf
Pioneer Stage-4, Orion, DynAudio, Fi

This may help you out..... https://www.colomar.com/Shavano/4thorder_info.html

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Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA

Check this out for info on isobarik loading: https://www.jlaudio.com/tutorials/isobarik/index.html

As to calculating ports - unfortunately, working out volumes doesn't quite work like that. Ports aren't just about volume - they have to do with surface area and length. I wish I could explain it better to you, but I'm still trying to grasp all of the concepts. Maybe someone here can explain it better for me and you?

Go here: https://www.wssh.net/~wattsup/audio/

And get winISD. It's an awesoem design program. Also, check out the Java port calculator.

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/NyxBass

well    everyone wants to jump around on my post ....damn you stinking apes...

but im looking for some help....ive been a little sick and not thinking logically   hoping someone can help.....velocity....ahhem    if you wouldnt mind....

here is what I am fooling with

I am running 3 --10inch subs.....  going for SPL...building a ported box....   using slots instead of round ports....

here is the deminsions I am using for each chamber of the box....this is including 3/4 MDF    

12 width----18 depth...16.5 height.....

My width and Height are the max room I have to use all 3 ....and still have room for the other 3 subs I plan to place in a box diplicat to this one...

i do have some rome to tinker with the depth but dont want to go extream as I only have about 35 inches from the rear seats to the trunk lid......

when I plug everything in I come out to 1.504 Cu Ft..3    which is ample for the subs I am using.....1.81 is optimum.....   but when I go to figure the port diameter    it spits me this   3.142 area    10.878 length.....I would like to run a slot along the whole bottom of the chamber is this feesible?   or should I re caculate the box size?    re comfigure the port

Any one really wondering....I am at home trying to build and conspire my new SPL car while suffering from Mono......no not a bridged amp    but mono the sickness.....   hey time off real work to play I guess....thanks for the support

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2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place

That figure is right. You will have to make the slot of the port along the long side of the entire bottom of the box. That's the way you make square ports .... along the bottom or the side of the box. What is your total trunk dimensions that you have to work with ? From what you have above I think you have a total area of 36 ( W ) x 18 ( D ) x 16.5 ( H ) and this is the outside measurements for the box. Am I correct in assuming this ?? You have quite a bit to play around with from the dimensions that you have compared to the optimum for the subwoofer. I would use this gap and shrink your box down otherwise you will notice that your design will drop the frequency sooner than if it were optimum volume casuing the subs to sound flat and also bottoming out at lower frequencies.

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Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA

well I am still fiddling with it in concept...those deminsions were for all 3 subs       I am fooling with anywhere from 1.5 cu ft to 2.cu ft.....   my subs will handle anywhere from 1 to 2 cu ft ina vented or ported box.....im looking to go toward the higher without bottoming them out as you said.....so I have been fooling more with 1.5 today......figuring as to how I will be running the ports along the bottom front face of each chamber how far back should I make them......I am still a little confused witht he demensions     if it gives me...

3 x 10    is this 3 inch ports by 10 inch depth    or can I make a 10 x 1 inch rectangular port going 3 inches deep into the box?    hope I can get this solved soon and get to work   thanks

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2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place