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View Full Version : make sure i got all this $#!t right



nismboy6986
02-24-2005, 03:27 PM
1. can you go over that nine to 1 ratio jl talked about on thier tutorial. my port would be 2"x20" would that be good?
2. to find find the physical length of a port you would just make a imaginary line that goes through the center of the port and stays going through the center of the port and measure it.
3. to factor in end correction i would just take half the width of the port, in my case 1" and add that to length of said imaginary line when figuring out the length of the wood that would make that wall. so i would make that piece of wood that makes the port 1" inch longer than it would be if i just went by that imaginary line when i compensate for end correction. and since i rather "grasp" info that just go with it what exactly does end correction account for? the bends in the port and the fact that the air isn't going to turn around exactly at the inside wall of the port in a bend or what?

req
02-24-2005, 03:33 PM
correction is like a 'buffer' because the air on the walls of the port has friction to deal with and all kinds of gay things. your tuning wont be EXACTLY 3.124hz or whatever. but it will be close.



the bends in the port and the fact that the air isn't going to turn around exactly at the inside wall of the port in a bend or what?

yea. basically the flaws of making it with wood... and not - lets say. completly uber smooth space age material with flared ends and rounded edges and perfect cuts and what not... :)
dont imagine the line. take a pencil, and draw the **** thing.

get a big piece of paper, and physically draw the entire box down. draw the 'imaginary line' and measure it. now, port correction is a 'dead zone'. its not part of the port, and its not part of the box. its an area- pretend its just space that the port cant use and the box cant use. but it still displaces that small 1"x2"x20" section. so you need to figure that when calculating internal volume.

i use autocad to sketch my box designs and get close to my tuning.

and yes, the ratio is a 'rule of thumb' if you have little wattage, a smaller port wont matter, the 1:8 ratio is only for port noise (that annoying sound like when a box is not sealed completly) otherwise, use as small of a port as you want (after a point, the SPL will drop however - there are so many ****ing factors :p:)

theres lots to know.

www.r3q.net/port.html
www.r3q.net/req_files/portcalc.zip

nismboy6986
02-24-2005, 03:43 PM
i actually was talking about drawing the thing. i have a notebook full of drawings. so am i right on what i think is how you compensate for the end correction. the jl tutorial completely confused me because i'm not sure of what part of the port or what view of the port are they talking about when they explained end correction