I need to build a 1.75 cu.ft. box for my sub.
Does the 1.75 cu.ft. include the port itself or exclude it?

The box design I'd like to go with is very simple. Only one baffle, slot port. I've built a couple boxes before. One sealed and another with a tube port. The tube port sounded odd but I used it for a few years now and figured it's time for a slot port.

 

Add for the vent and the woofer displacement.

 

If you don't ad displacements your tune will move up a bit, normally (if you are not to high) you wont notice this...so I will go like that.

 

Actuall design of enclosure volume does not include port or driver volume. So if you use a program such as ISDPRO to calculate box size you need to add port and driver volume. Having said that, most spec sheets that include a box and port size would normally have the port and driver volume calcualted in that. For a practical matter, the driver and port volume in a 1.75cf box may be quite small and have minimal effect compared to other variables such as accurace of the TS parameters and other production variances. I would say your car interiour would have a far larger effect on sound quality than accounting for port and driver volume.

In theory a round or slot port should make no difference to sound. It is purely a construcion option (easier to make big slot port that huge sound port)
Make sure you lookup lots of speaker designs sites before designing your own box. The end correction for slot ports is different than for round ports depending on where it is located. If you do not know what end correction is you have not read up enough!
WinIsdPro (alpha version) is available for free download at
http://www.linearteam.dk/

It also covers end correction and other thigns such as maximam driver excursion, max power handling etc. Read the help/manual section first.

This is not rocked science guys. If you want to design your own boxes you MUST use a box design tool.

Have fun

 

thanks guys.
looks like i have some research to do.

 

IMO, I wouldn't say a box design tool is a MUST....helpful at times, yes. I haven't tried the big fancy programs, but any of the freebies I've used I found lacking for designing BP enclosures. They're pretty good for sealed and ported enclosures. As long as you like math you can always plot the formulas on paper.

I would take pencil and paper and good old fashioned experience over WinISD, etc. any day.