Boomin Boy
my box i have planned is 9.2 cubic feet after brace and port displacement. Im looking to tune it to 44 hz as my truck peaks at 48-49hz.

How much port area do you recommend for an all out SPL application?

My current design (not yet built) is a 35.5X7 port which is 248.5 sq inches of port. Is this too much for 1 18 inch sub (254 sq inches of cone)

thanks
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maxxology
its hard to believe a 18 has 254 sq inches of cone area but if thats what its got. then i wouldnt think 248.5 would be too much you might want to make it so you can put some plug into it just to see what happens when you lower the sq inches. also with the phat surround of the hc 18 wouldnt that make it almost down to 16 inches across from the edge of the surrounds, but then again the cone is concaved and has a rather large dust cap right? so that could add some more cone area. anyways it sounds like it should work good.
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caraudiophile
it doesn't have 254. if it has a 1 inch surround its closer to 200.
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Boomin Boy
yea you guys are right i wass going by the iasca cone chart no the individual drivers specs.

so exactly how much is this port going to hurt my box then?
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dwood127
i think ive heard some guys say that you shouldnt go above 75% of sd(cone area).

also, the physical contours of the cone(concavity, dustcap size) dont effect cone area. when you measure the cone area, you the effective piston area. measure from the center of the cone to the edge, square that, then multiply by Pi. thats your cone area. it doesnt matter if the cone is flat, curved, ect.
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caraudiophile
150 inches of port should be kosher
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Boomin Boy
yea ill make a plug to bring it down to 150.5 and test it out.

thanks
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DrLowfreq
Quote:
Originally posted by dwood127:
i think ive heard some guys say that you shouldnt go above 75% of sd(cone area).

also, the physical contours of the cone(concavity, dustcap size) dont effect cone area. when you measure the cone area, you the effective piston area. measure from the center of the cone to the edge, square that, then multiply by Pi. thats your cone area. it doesnt matter if the cone is flat, curved, ect.
I would think a cone would have more surface area than a circle would. pi*r^2 vs pi*r^2 + pi*r*L(length of side of cone). anyways. i had a stroker 18 in a 17.5 cub box with 650 sq in of port...worked out well. This was about 2x SD on the stroker, if i remember right(was about 3 yrs ago). Also if you make a plug to decrease the port area, be careful of the tuning frequency changing. It would be easy to conclude that reducing port area increase/decrease because of the changed frequency vs resonant frequency of car and impedence with amplifiers. isnt it fun change one variable, and a million others change, hehe. thats why its always a challenge and what works for one person, wont necessarily work for another. let us know how your system comes out.
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Boomin Boy
yea my tuning frequency is going to drop down to 39hz with the new port....so hopefully it will peak at around 45-46 hz.

still better than 36 hz peak i suppose
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Boomin Boy
well you guys were right...150.5 sq inches of port was a whole lot louder (to the ear)

ill test it on the meter tomorrow
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