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BDIDDY

05-21-2003, 12:47 PM

My friend abcdefg got me these port dimensions ( and I am not questioning his abilities) but was wondering if these were right. The box is 7 cubic ft and the port is 18.5x6 and I want it to be tuned to 50hz. he got depth as 11.84. Just wondering if that was right.

fantomas

05-21-2003, 11:47 PM

Originally posted by BDIDDY

My friend abcdefg got me these port dimensions ( and I am not questioning his abilities) but was wondering if these were right. The box is 7 cubic ft and the port is 18.5x6 and I want it to be tuned to 50hz. he got depth as 11.84. Just wondering if that was right.

well...using WinISD 0.50a6 i got the length of the port to be....8.32".

paikiah

05-21-2003, 11:49 PM

Originally posted by fantomas

well...using WinISD 0.50a6 i got the length of the port to be....8.32".

Jmac enlightened me about 10 mins ago that WinISD pro isn't so accurate in port calculations. Seems it's about 5% off.

fantomas

05-21-2003, 11:53 PM

so then what would be an accurate tool? im about to build a ported enclosure with leftover mdf just for the hell of it....and i want it to be pretty accurate.

paikiah

05-21-2003, 11:54 PM

Originally posted by fantomas

so then what would be an accurate tool? im about to build a ported enclosure with leftover mdf just for the hell of it....and i want it to be pretty accurate.

I guess manual calculations would be best... refer to Jmac for proper formula..:) but seeing that it give 5% longer ports, I thoguth it'd be alright to shave just a tad off. :)

fantomas

05-21-2003, 11:56 PM

actually, it was 3.52" shorter than the original calculation

paikiah

05-21-2003, 11:58 PM

I'm as boggled as you are about this matter...

all this time I put my trust in winISD pro, thinking that it was accurate, but alas, it proves the statement: if you want something done, do it yourself.

fantomas

05-22-2003, 12:02 AM

im curious as to what the formula is. its probably some big extensive formula....and if you're making a program to calculate the port, why would you use the wrong formula? i think that once i find the correct formula ill program something in VB...

paikiah

05-22-2003, 12:10 AM

Originally posted by fantomas

im curious as to what the formula is. its probably some big extensive formula....and if you're making a program to calculate the port, why would you use the wrong formula? i think that once i find the correct formula ill program something in VB...

I don't remember the exact formula, but it wasn't that long...

VB, excel whatever it is, if you can make a more reliable box program than winISD pro, lemme know :D

fantomas

05-22-2003, 12:13 AM

well, if you can get me the exact formula, then it shouldnt be too hard to whip up a simple program...

paikiah

05-22-2003, 12:34 AM

Originally posted by fantomas

well, if you can get me the exact formula, then it shouldnt be too hard to whip up a simple program...

Paging Dr. Jmac....

fantomas

05-22-2003, 12:36 AM

i just did a search and found a few formulas...now im reinstalling vb6..

BDIDDY

05-22-2003, 03:03 PM

so is that 8.32 right???

fantomas

05-22-2003, 06:18 PM

what about for a slot port?

Randy Savage

05-22-2003, 06:24 PM

You can also use this formula:

Fb= tuning freq., Av= cross sectional area of port (in in^2), Lv=length of port (in in.), Vb=enclosures net volume (in in.^3)

fantomas

05-22-2003, 06:29 PM

i'd rather have it solve for the length of the port instead of the frequency

Randy Savage

05-22-2003, 06:36 PM

Originally posted by fantomas

i'd rather have it solve for the length of the port instead of the frequency

so, find a way to solve for the length of the port...it shouldn't take too long, assuming you have some math skills...

P.S.- WinISD is pretty good when it comes to port lengths, I used WinISD to find a port length for a frequency of 33 hz, then used the formula to calculate the frequency, and came out with about 33.15...so it's pretty accurate...

fantomas

05-23-2003, 01:03 AM

well...i just tried it with the beta 0.44...and it gave me a length of 7.79" which is 1.03" shorter than the alpha version of the same program.....