how to calculate box volume .........?????

[bigchiefpatterson5]

I know how to find cubic feet and such , only question is when porting a box is the port included in total volume or is it just the chamber in where the sub is set ? I have ported boxes before just never really got down to the science of tuning . planning on a 5.8 cubic foot box, 5.5 after sub displacement and if I port it will I only get whats in the chamber ?

[reedal]

subtract the amount of volume the port uses to calculate net volume of box after sub displacement. Same thing with bracing.

[bigchiefpatterson5]

so when a recommendation for the sub is a five foot enclosure are they talking about 5 foot net or 5 foot total volume enclosure?

[reedal]

Net

Edit: but you should try a design software. Even one that doesn't account for cabin gain. Just to get a model of the roll off in the enclosure before building it, to get a better feel of how you want it to sound and how efficient it will be. I use WinISD, or if you want to buy one you can. I think term lab sells one that can account for cabin gain. Not sure though. Having it modeled out to get a rough idea of how the box will perform is better than just going with manufacturers specs and it not sounding the way you want after you already put the time and effort into building it.

[bigchiefpatterson5]

Thanks

[bigchiefpatterson5]

That box is for a single fi 18 bl and i meant say 5.5 after displacement and bracing

[reedal]

Do you have a particular design already? like how much port area and what tuning frequency and everything you want? I can try to plug it in on my computer and see what I come up with. Not sure what all info I'll need, haven't used WinISD in a while. I know I'll need tuning frequency and power supplied. But WinISD is free so you can do it yourself if you want. It's fairly easy to figure out once you start clicking around, and there might even be a tutorial thread on here (not sure though). If not on here, I have no doubt there's one on YouTube. I'm working on my door pods right now but once I'm done with that If you haven't already done it yourself I might plug all your specs in. Need to know tuning frequency desired, how much power you're feeding the sub, and your gross box net before displacements as well. Maybe dimensions too. Aero port or slot port? Any kind of info you have for your box and amplifier will be helpful

[bigchiefpatterson5]

I'm gonna try and download it I've found out on Google, I really appreciate all the info and help

[Jessica]

for a reference point, this picture might help. Blue is the net box volume (internal dimensions), Green is the port volume (internal dimensions)

When figuring net volume with a port make sure you remember where your port wall are.

If you arent using sketchup you can draw it out on paper but the port wall does consume some of your net volume, so a 4" wide port like in this pic is actually 4.75" wide.

If you use sketchup you can just mark off the port entrance and right click and get the area of a space and multiply that times the height to make it easy

[Jessica]

also, some people prefer this method, its basically half the port width into the box counts as port.