Ported Boxes... All new to me

[LoudCrownVic 5,000+ posts]

I'm building a ported box to replace my prefabbed one, which is undercubed and falling apart. I've got one all drawn up to build, but don't want to start until i get a few things clear...

My questions:

1. Is 2 1/3 inches from the bottom of the box enough for a 4" port tube to breathe if not, how much room does one need?

2. Does port volume take away from the cubes of the chamber?

3. How much bracing is suggested for a divided box made of 3/4"?

4. Will 4" PVC work for a port tube until I get port tubes or should i make slot ports (which i don't have the faintest idea how to do)?

If you have anything that will help , it would be greatly appreciated.

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[helotaxi 5,000+ posts]

1. Is 2 1/3 inches from the bottom of the box enough for a 4" port tube to breathe if not, how much room does one need?

Having less than the diameter of the port for clearance will affect tuning and performance. You should plan for at least 4", but more is better.

2. Does port volume take away from the cubes of the chamber?

If the port is inside the box, it displaces its volume from the effective volume of the box.

3. How much bracing is suggested for a divided box made of 3/4"?

It depends on the size of the box and the type of sub and amount of power you will be running. Bigger box needs more bracing. More powerful sub with more power needs more bracing. The divider between the chambers is a very good brace and adds a lot of strength to the box.

4. Will 4" PVC work for a port tube until I get port tubes or should i make slot ports (which i don't have the faintest idea how to do)?

It will work, assuming that 4" will be big enough to minimize port turbulence for the sub you are using. The larger the excursion of the sub, the more air has to move through the port. As you decrease the amount of area that the air has to travel through, the air starts to compress and cause turbulence and noise.

To build a slot port, figure the area of the round port that you planned for and make a rectangle with the same area. You can use the edge of the enclosure for one side of the port which makes the construction easier. Several websites have tutorials or diagrams that show you how it looks. That will make it easier to visualze, just adjust the dimensions to suit your application.

 

[Trixter 10+ year member]

If you are wanting to go with round ports look into precision ports at http://www.partsexpress.com. I have had very good experience with them.