tuned boxes??

[sound giant 10+ year member]

pardon the newbie q but what does it mean when i hear people say that u have to tune a box to like say 30hz etc? does it have anything to do with gain? and what is the difference between say a low tuned box (20 lets say) and a higher tuned box (40hz)????

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[ShakinSupra 10+ year member]

They're talking about the tuning frequency of a ported box. The size of the box and port effect the tuning frequency, a lower tuning around (40) will result in a louder setup. If you play a note to a sub in a ported box that is below tuning frequency, it's like the sub isn't in a box at all, so people use subsonic filters to filter out those notes.

 

[DFW40 10+ year member]

Be aware that a box tuned to 45hz will be louder at 45hz but will not play well or loud very far below that 45hz. So if you want a box that is very loud at a low freq like 30 hz then tune it to 30hz. Most ported set-ups get loud it just depends on whether you want a wide range of freq. to get loud or a smaller range.

 

[sound giant 10+ year member]

i see... how do u measure this?

 

[DFW40 10+ year member]

It has to do with port length/diameter/box size. For a given box size the longer the port ie pvc pipe etc the lower the tuning. If you had a 3 inch diameter port that is 12 inches long in a 1 cubic ft box it would be tuned to 36 0r 37 hz, to get that same box tuned to 26 hz it would have to be 26 inches long. The longer the port the lowet the tuning, but if the port is 4 inches in diameter then it would have to be even longer. I've attached a page that has a port length calculator and box dimensions etc. Play with it and do some searching on the web.

http://www.the12volt.com/caraudio/boxcalcs.asp#par

 

[sound giant 10+ year member]

thanks alot fellahs

 

[Underage Driver 10+ year member]

how would you measure a square port?

 

[JimJ 5,000+ posts]

same way...but you need to calculate the width of the box for an "end correction factor"...but slot ports work the same way.

 

[sound giant 10+ year member]

what about if i had the box tuned at 30hz, does that mean a not at 45hz would not be as loud as a note at 30? or does that rule only apply to frequencies below the box value???

 

[DFW40 10+ year member]

This is a great question, I thought that the Freq response is realtively flat from tuning of lets say 30hz on up. Would a 30hz tone be louder than a 40hz tone if the box was tuned to 30hz? All things being equal.