Port Length?

[Fi_all_d_way]

hi guys i need some insight in the slot port length in an enclosure. I am using BassBox pro 6 to design my enclosure but before i start, i would like to understand the port length. for example if i design a box and the program says a port of 3 inch wide x 25 inch in length, do i measure 25 inches in length along the center of the port and then add 1.5 inches (half of 3inch width) at the end for END CORRECTION??? im asking this because bassbox pro don't say anything about end correction. what is the value of end correction? please use the diagram bellow to help understand...

another thing is if the slot port isnt that long do i still need end correction???

eg 3inches width x 8 inches long...use the diagram below to understand

so my questions are:

1) if bassbox pro says a port length of 25" x 3" wide eg diagram #1 do i measure the 25" along the centre and add 1.5" for end correction???

2) if bassbox pro says a port length of 8" x 3" wide eg diagram #2 do i add end correction after the 8"???

i would like meade and thumper to add to this post....thanks in advance guys

Do bassbox pro take end correction into consideration and i just hav 2 measure along the centre of the port???

[Decaf]

1) when u use one of the sides of the enclosure the sub "sees" or "thinks" the port is longer since one side extends beyond the other port wall. this lowers ur tune frequency slightly. so if it says 3wide x 25l, the actual length the sub sees is around 26.5, so you dont need to add onto the 25, you just need to understand that the end correction with a slot port slightly lowers the tune freq. if you want 35hz, and it says on bassbox to make it 25, then you could theoretically make ur port 23.5 and it would be tuned to 35hz actually, instead of the length of 25 which might yield 1-1.5 hz lower tuning

2) same answer, the end correction factor lets you know what the "actual" port length so you can change accordingly whether u need to tune higher or lower

and because diagrahm 2 has such a short port, the sub might even think the port is even longer then the 1.5 correction and might "think" part of the right angle is the port wall. this is why sometimes you just gotta build boxes until they sound right to the ear and on paper

[Decaf]

o and if you use a 3/4" roundover bit on both ends of the port you negate the end correction (.75x2=1.5")

so the port length is the actual length in the center of the port

[Fi_all_d_way]

o and if you use a 3/4" roundover bit on both ends of the port you negate the end correction (.75x2=1.5")

so the port length is the actual length in the center of the port

thanks alot bro but can u tell me is bassbox pro take this into consideration?? because its not a free software and its a professional software....so im wondering if bassbox pro minus the end correction or not so u just have to cut the mdf 2 the size it gives you????

[Fi_all_d_way]

[Decaf]

hmm shoot me ur dimensions, subs, amp, desired cuft and tuning and i could figure that out too

[Fi_all_d_way]

hmm shoot me ur dimensions, subs, amp, desired cuft and tuning and i could figure that out too

SUB = Two Rockford fosgate P312D4.....

AMP = 1200RMS Digital Design amp....

Space = height (15) x width (28) x depth (30)

[Decaf]

this will be good

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

[Decaf]

ur going to have to mount one on top and the front or some configuration cause the front piece is only 24 1/4" for 2 12" subs that have an outerdiameter wider than 12"