Help with box design

[Sweety]

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

[Joe X]

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.

[Sweety]

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

[Joe X]

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:

 

 

 

[Sweety]

Many thanks Joe X for your help as it has helped me a great deal & gives me 2 different options. Now I have to find somewhere to mount my as it's just been screwed to the back of my temporary box 

[Sweety]

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 

[Sweety]

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 ?

[ckeeler11]

If the port goes top to bottom along 1 side then it should be 3 common walls. Top, Bottom, and Side.

[Sweety]

Thanks for that port will have to be in an L shape to fit in the box so that would make it 4 common walls then ? I better change things then &will put up the changes to see if it works out right

[ckeeler11]

No still 3 after it makes the turn it is Top, Bottom, Back.