Box Time

[terra 0]

OK im building my box at 12 cu ft tuned to 31 hz. 41x20x30 roughly 192 sq in of port area...port back subs up. port going along the bottom width 39 inches wide and 5 inches tall with a kerfed port. i get a port length of 14.54 inches. correct or i done screwed up?

Edited August 11, 2007 by MagnoliaBass

[terra 0]

anyone?

[mrogowski 6]

Hang in there... I'll check it out tomorrow for you.

[Mike P. 0]

If the port is 39 x 5 then my math shows the port needs to be 33 inches long to tune 12 cubic feet to 31 hz. The port area is 195 sq in, not 192. 14.54 long would tune the box to 41hz.

[terra 0]

ya definitly messed up a dimension there....heres what i got. 14.3 cu ft before displacement. 12.3 net...tuned to 31 hz resulted in a port length of 13.68 in and 39.5x5

[terra 0]

so im at 12.3 net cu ft..with a port 39.5x5x13.68 in....correct?

[Mike P. 0]

so im at 12.3 net cu ft..with a port 39.5x5x13.68 in....correct?

If the port is 39.5 x 5 inches, then 13.68 inches long will tune a 12.3 net cu. ft. box to 41 hz. 33 inches long will tune the box to 31 hz. I'm using WinISD for box modelling. What program are you using?

[terra 0]

so im at 12.3 net cu ft..with a port 39.5x5x13.68 in....correct?

If the port is 39.5 x 5 inches, then 13.68 inches long will tune a 12.3 net cu. ft. box to 41 hz. 33 inches long will tune the box to 31 hz. I'm using WinISD for box modelling. What program are you using?

im using carstereo.com and their port length calculator

[terra 0]

i cant get winisd on this computer so i cant look this up. but how long does the port have to be if 39x5 and 12.3 net tuned to 33hz?

[Mike P. 0]

WinISD says 27 inches long will tune to 33 hz. I used the one at carstereo.com and it says 25.5 inches long. I'm not sure where you're going wrong with the calculations. You must be entering something wrong somewhere.

[terra 0]

my port is now 39x8 in...carstereo gives me a port length of 28.69 inches. for a 12.3 net cu ft box tuned to 33 hz with 1 slot port. what does winISD say?

[Mike P. 0]

my port is now 39x8 in...carstereo gives me a port length of 28.69 inches. for a 12.3 net cu ft box tuned to 33 hz with 1 slot port. what does winISD say?

This calculator says 44 inches http://www.carstereo.com/help/Articles.cfm?id=31

WinISD says 48 inches.

[mrogowski 6]

WinISD, even with the flaws it has, is quite accurate with vent lengths and tuning. I have found that 1/2" of port length equates to about 1Hz.

Best,

Mark

[Exploder 0]

http://www.reaudio.com/speaker_box/LPort_Box_Calc.html

I like to use this

[terra 0]

ok right now i have 2 options. 1 port opening of 39x8 or the other port opening of 39x5. my box is only 31 inches deep so im trying to keep port length under that if possible. if i have to turn the port and go up the back wall..will i run into problems of having the subs basically playing into the port? this is subs up port back. trying for 32-34 hz. and what would be the length for each? my mac and winISD dont get along so sorry for making you guys do the work thanks.

[Mike P. 0]

39 x 8

32hz = 54.25"

33hz = 50.25"

34hz = 46.50"

39 x 5

32hz = 31.75"

33hz = 29.50"

34hz = 27.25"

All assuming 12.3 cubic feet net.

[terra 0]

well that pretty much figured everything out for me...but if the port has to climb the back wall and the subs facing up, will i see any negative effects from the subs playing into the port?

[terra 0]

hey mike would u mind doing those 3 frequncies again but for a port height of 6.25 inches? lol dont ask how that happened because i honestly dont know. and im starting at 14.c cu ft so is it reasonable that after port, sub and brace displacement id be at 12.3? or would net be lower?

[Mike P. 0]

39 x 6.25

32hz = 41.00"

33hz = 38.00"

34hz = 35.00"

Edited August 16, 2007 by Mike P.

[terra 0]

wait so for 32hz..a port 6.25 tall is longer than one 5 in high and one thats 8 inches high? how does that work out?

[Mike P. 0]

wait so for 32hz..a port 6.25 tall is longer than one 5 in high and one thats 8 inches high? how does that work out?

My bad. I had the wrong cubic feet entered. I edited the post to the correct lengths.

[terra 0]

thanks for the help..wish i could get winISD on here but no luck. ill be finishing it up tomorrow and ill have pics