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Help with box design


Sweety

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I'm planing on building a new box & was hoping someone could check over my plans to see if I have calculated it correctly. It's going to be a wedge shape so it fits up against the back seat so I get as much room in the trunk as possible the aim is for 1.9ft^3 & tuned to 35Hz
Width 35"
Height 15"
Top panel 8" depth
Base Panel 11.5" depth
Port internal size (made from 3/4" MDF) 4" x 4" & 15" long
Sub being used is an old JBL GT3 12" getting powered from a 220wRMS JBL amp

I know this is probably simple maths to most of you but I suffered from meningitis 22 years ago & it wiped out some of my memory & am still relearning things

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Your calculations check out (almost) assuming your square port has no common walls with the box,  also I assume your port is firing sideways, if your port has common walls with the box then your tuning would be down to about 33Hz.

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Thanks Joe X, yes the port wouldn't be part of any of the walls but would need a 90' bend in it as it would have to be rear facing with the sub due to truck space, my other option which will be a more costly one as pvc pipe isn't cheap here in the UK would be to use a 4" pipe which I think for a 35Hz tuning point would need to be 12.5-13" long with a 90' bend in it but if I got this way i'm not sure what the volume of the enclosure would be but guessing it would be close to 2ft^3

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In the case of a 4" round port it would be close to 11" and yes net volume would be 2 cubic feet net, anyways here's a simple way to do a slot port firing back with only two pieces of wood, this would be 1.94 net @ 35 Hz with a 4x4 port:

 

image.jpg

 

 

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Think i'm going to have to change my plans as a square port isn't going to do it for me when it comes to looks & 4" pvc pipe here in the UK isn't that cheap & all I can find is thick wall pipe? ideally I would like a wedge shaped enclosure 14" high, around 35" wide (can't go wider) & with a difference of 3" between the top panel & base so it would fit nicely against the back seat with a 2" wide port but i'm struggling badly to work it out. I have tried to work out a rectangular enclosure but think i've got the maths wrong 34" wide, 14" high, 11.25" with a 2" port 24.8" long would give a 35Hz tuning & a net volume of 1.9ft^3 ? net volume can be dropped to 1.8ft^3 if needed

Sorry for being such a pain with all of the questions & asking for so much help 

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I've just downloaded the torres calculator & wondered if I put the right info in & also wondered about the wedge shaped enclosure details mainly for the port length as the port would go along one side & along the back of the box & is thereenough port area ?

enclosure2.jpg

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