enclosure understanding

[jacka 10+ year member]

I'm trying to get an understanding of enclosures since my shop obviously doesn't know sh!t about the subject. Totally messed up the tuning Hz for my vented W3s. Well anyway. First off, I'm looking at recommendations and many say, for example, X.xx net cu ft. Now, if I wanted that exact about, I would have to add the driver displacement correct? and the MDF board doesn't play a role in that measurement, correct?

Now on to vented boxes.. i'm lookin at soundsplinter recommendations and for the rl-p 12, they are saying 1.5 cu ft with 20 sq inch of vent area. i'm guessing that 20 sq in. means the visible port area from a 2D perspective, so a port of 1.6 inch wide and 12 inches will suffice for the requirement, am i correct? (my shop totally messed up on that part, and it shouldnt be that hard for them). Now tuning to certain frequencies is a bit hard to understand, how do I know how long to make the port?

I guess that's all the questions I have right now. I'm looking to buy RL-p's next week and I don't really trust my shop to do me any good. I don't even know if they will make a sealed box to my preference. But yeah.. I'm just lookin for some info, I know a few people make boxes out there if you could quote me prices that'd be awesome. I don't really have the tools/room to build a box. Thanks.

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[itzme218 10+ year member]

whats up, you're from the bay too, cool. Just take a look at the sticky plans by moelester. Its a great tool, lots to chose from and I believe sub displacement is already somewhat considered in thoes plans

I have 1 RL-p 12 D2 in the 1.75^3 32hz box

 

[Trixter 10+ year member]

when you talking about box volume, it should be the net volume, that is the internal volume (not counting the mdf the box is made of) subtract sub and port displacement. the area of a port is it's opening. you should keep a 9:1 ( some say 8:1) width to heigth ratio. once you have your area, you can then find your length to tune it to the desired freq. once you have your correct length then you need to find the total volume of the port, including the mdf that it is made of. if it shares a common wall with the box you don't need to count that since you already did when getting you initial volume, same goes with the length. ( the 3/4" at the front of the box/port) once you have the port's volume displacement you subtract that from your box's volume to get the net volume. now that you have a new box volume, you'll need to refigure you port's length, using your new net volume, to get an acurate port length. hope i didn;t confuse you more:crazy:

 

[jacka 10+ year member]

it helped a bit, though a bit unclear at first. the port explanation was sorta confusing but it worked. so if they want a net volume of 1.15 for a driver. I just make a box with an internal volume of 1.15 and not worry about driver displacement? or do I add the displacement of my driver and then make number the internal volume?

 

[Trixter 10+ year member]

use the internal volume with the sub displacement. figure out port length using that number. now that you have the length, you can find out the port displacement. subtract this number from the net volume + sub dispalcement and refigure the port length.

i'm not sure if your using an online port calculator of pencil and paper. if your using a calculator, you may wnat to find out if refiguring is necessary. some calculators account for port displacement on the first try. (use the old skool method myself.)