how to build a sub box pt1

[1koerner]

here is a good rule of thumb for building a sub enclosure both ported/sealed for those on this site who may not quite understand the peticulars on box fabrication for those that do know please feel free to comment or add anything i may have missed thanks

A strong box is essential in a high output system. Your box should be free from air leaks and braced internally if the volume exceeds 2 cuft. Internal cross bracing is far more effective in making a rigid box than doubling the wood thickness. Doubling the wood thickness adds a great deal of weight to your vehicle, and the added wall stiffness is less than stiffness added by cross bracing. Try to cross the braces at the same point so that they add strength to each other.

The inside seams of the enclosure can be a source of air leaks and potential weakness if the joints are not cut perfectly. One way to strengthen these joints is to use gluing cleats on the inside seams


How To Figure Box Volume
Cubic feet is measured by multiplying the height X width X depth of the inside dimensions of the box, and dividing that total by the number of cubic inches in a cubic foot (a cubic foot is 12 X 12 X 12= 1728).

For example, a box with outside measurements of 16 inches high, by 34 inches wide, by 14 inches deep would be figured as so; first we subtract the wood thickness. This is usually ¾” thick, times the thickness of both sides of the box= 1 ½ inches. We subtract this from the outside dimensions.

So now we have
14.5H X 32.5W X 12.5D=5890.625.

5890.625 divided by 1728 = 3.4 cubic feet.

You can keep changing dimensions and refiguring the box volume, until you come up with the ideal box size and shape for your application.

5890.625 divided by 1728 = 3.4 cubic feet

Calculating Net Volume:

The volume occupied by the woofer and port is approximately 18% of the box. We need to deduct this volume from the gross volume of the box to find the net volume. The port will be calculated on the net volume.

Now, take your 3.4 cubic feet and multiply by .82 (3.4*.82=2.788) so your Net Volume is 2.788 cubic feet.

Calculating Port Area:

Our port formula uses 16 square inches of port area per cubic foot of box volume. Now, take your 2.788 cubic feet and multiply it by 16 so get your Total Port Area 2.788*16 = 44.608 sq” of port area.

Calculating Rectangular Port Dimension:

Port area needs height and width. For a rectangular box with known dimensions, we already have a height, we just need to find the width of the port.

Now, take your 44.608 and divide it by the height of your box, so this example we would divide 44.608/16= 2.788 (this is width of your port opening) Round it to the nearest .25”.

The “Average” recommended length of the port is 18”, tuning around 40hz. The longer you make the length of the port, the lower the tuning. Those that listen to nothing but hip/hop, rap and chopped & screwed, you can make your port length 22-24” long.

 

[1koerner]

no input anyone???

 

[oblivion]

This will go over the heads of most people and alot of it is great for designing a enclosure but only 2 paragraphs on building the actual enclosure. High output is a relative term. To some 2000w is high output...Double wall thickness and on an everyday consumer enclosure is not necessary at all. 3/4" at minimum sure. Gluing seams, caulking seams or fiberglassing seams.... Nails or screws or both? Jigsaw or router for the sub openings? Net volume of the enclosure with or with out the volume of the subs them selves? Clearance for vented pole pieces..... Rounding corners on ports...... distance from the driver to the port and location.....

Not harping but theres alot more to go here.

 

[1koerner]

I hear ya oblivion that's y its building a enclosure pt1 lol

 

[Lightnig]

While good information there sir, thank you

But too me, from a design point of view it seems a bit backward to me.

I always started off by determining what sub(s) I wanted to run, as each sub has it's own 'ideal' enclosure volume and then began designing the enclosure from there.

The next decision was style of enclosure; ported, sealed, band pass. The decision here also greatly affects enclosure volume.


I have worked backwards though; I have a given volume that I can build a box to fit, then work backwards to fit a sub that will work well in that size. That can be a tough way to go though, as subs that work in a given volume may not provide the characteristics one wants and it will really limit choices.

And as far as calculating volume is concerned, a person should also be calculating actual port size to fit the frequency desired, which will give a proper displacement volume, plus most sub manufacturers publish specs about volume their speakers consume. It is far better to use actual numbers than an estimate...