Are Port Calculators Wrong

[kbreudi]

Ok im planning on building a ported box this weekend. But theres something thats bugging me that i need to have solved. Ok....how come, no matter what port calculator i use, once i enter a hight and width for my slot port, then tunning freq i get a lengh ok....BUT say i want a narower width on my port, so the port should now be longer to keep the same valume as with a wider port right? Worng, it says i need a shorter port...

Ex..

this is an example done with the same calc amatt uses, with same box dimensions and tunning

38hz-W=6 H=12 L=12

38hz W=3 H= 12 L =4

I dont get it, the first one has 864" cubed of port, the second has 144....how could the same tuning and the same box have a port 6 times as small but yet still be right?

I dont get it and this happend on all port calculators i use

Edited March 1, 2008 by kbreudi

[Decaf]

pm amatt then

i cant help unless i know what size ur dimensions are, and whats the desired size (cuft) and port surface area

[kbreudi]

pm amatt then

i cant help unless i know what size ur dimensions are, and whats the desired size (cuft) and port surface area

I will pm him, but either way its the SAME with EVERY calculator i used....ok the outside dimensions are 13.5 H x 36 W x 24 D

tunning is say 38 hz...basicaly what is says is i can use a port 12x6x20 or 12x3x4 and get the same tunning, when the second port is 6 times as small.

[Decaf]

this is as big as i could get the port and volume

4.5cuft@38hz w/57sqin port dim= 36w x 13.5h x 24d

http://www.subwoofertools.com/forum/ported...mp;Fs=&CE=0

and u can build it either way, i was trying to figure out if you wanted it to be a specific cuft

Edited March 1, 2008 by decafcappucino

[kbreudi]

what size subs, what cuft do you want the box to be after port displacement

im not having the problems u are, unless the problem is that ur trying to fit too big or too many drivers in too small of box so the programs go awire

Hmm well its one 15" RE MT...its just a temp box for a few weeks... When you say what cuft i want the box, i though you choose the box dimensions, then build the box and port and the box gets its cuft after the port displacment and sub displacment

[Decaf]

right but in ur case its a difference of .6cuft so....

this would work also

36w x 13.5h x 24d

3.9cuft@38hz w/72sqin port

http://www.subwoofertools.com/forum/ported...mp;Fs=&CE=0

but i dont know if its worth it to increase port surface area and sacrifice volume

Edited March 1, 2008 by decafcappucino

[EricM9104]

When you do a bigger port, the port is going to be longer than a smaller port that's tuned at the same frequency.

[Torres]

yeah there's a lot more that goes into tuning a port than just keeping the space the same. really technical. i just listen to the formulas

[Decaf]

When you do a bigger port, the port is going to be longer than a smaller port that's tuned at the same frequency.

x2

thats why i asked everything question when making a box

outside dimensions, desired volume, desired port surface area,

sub, size, spl/sql/sq:

each affects the box differently

ive never used an mt but if i remember correctly they like bigger boxes unless ur giving them uber power since they are so stiff and have such a strong motor

so is this box for music or to compete

[andym85]

Ok im planning on building a ported box this weekend. But theres something thats bugging me that i need to have solved. Ok....how come, no matter what port calculator i use, once i enter a hight and width for my slot port, then tunning freq i get a lengh ok....BUT say i want a narower width on my port, so the port should now be longer to keep the same valume as with a wider port right? Worng, it says i need a shorter port...

Ex..

this is an example done with the same calc amatt uses, with same box dimensions and tunning

38hz-W=6 H=12 L=12

38hz W=3 H= 12 L =4

I dont get it, the first one has 864" cubed of port, the second has 144....how could the same tuning and the same box have a port 6 times as small but yet still be right?

I dont get it and this happend on all port calculators i use

i didnt really go through and read all the other replies...but....

first off the first port has 72sq" of area (12 x 6), not 864...that would be the volume...same thing with the second port...it has 36sq" of port area

to keep the same tuning frequency....then a big port will have to be long and a small port will need to be shorter...thats just the way it is..