making vented subwoofer enclosure?

I am looking into making my own subwoofer enclosure because generically most enclosure company's don't make a box with nearly enough air space and one that could fit my car. i understand that sealed enclosures are straight forward and just need enough air space for your subwoofer to act as it is designed to. but as i was looking around to make a vented box i much harder apparently? i don't understand why i cant just make the box a little bigger and put some ports in? i don't understand the tuning? how am i supposed to do that? like where will my vents be located? and how big do they have to be? also whats the difference that i have seen with some subwoofer boxes, where the back of the subwoofer is firing into the box, and then goes down what looks like a "chamber"╔. the chamber just leads to outside the box. what is the difference between just making ports and the chamber idea. thanks to who ever can help me, maybe a website would give me an understanding but i like peoples explanations better as i can understand them. thanks-Lanzar car audio

Your questions explain why a ported enclosure is harder to build/design then a sealed enclosure.A ported enclosure needs to be tuned speifically for the sub you are using and the sound you are looking for. You would use either manufacturer's recommendations or an enclosure design program such as WinISD to determine what tuning frequency to use.The tuning frequency depends on the internal volume of the enclosure (not including any displacement from the ports or subs), the length of the port, and the cross sectional area of the port. The trick is to design an enclosure with a big enough cross sectional area to not have any port noise (happens when your port cross sectional area is too small) while keeping your port relatively short. This can be hard sometimes but it usually is fairly straightforward. There are two basic types of ports, a round port and a slot port. I believe that the slot port is what you were referring to as a chamber. It is exactly the same as a round port for sound and calculations. There are benefits and disadvantages of each in certain situations.Hopefully that gives you some basic information. The link below may help you some...http://mobile.jlaudio.com/support_pages.php?page_id=141

i hvae been looking into building my own speaker box for quite some time but i can not find any where that says the ports placement. so if some one who knows any thing about building subwoofer boxes please help me. I need to know if it matters if its to the side of my subwoofer, to the back of it, on the sides of my box? thanks alot hope someone can help!Lanzar car audio

usually placing the port on the same plane as the subwoofer is the best way but ive seen boxes with the port on the side too. its really whatever fits your install best. personally i like slot ports over round ports because they are easy to calculate the port volume and if you need a longer port than your boxs' depth, you can make it wrap around the box like an L shape. if box size isn't an issue then round ports would definitely be easier to use for a beginner. try to look up the specs of your subwoofer from the manufactures web site they might have a recommended box design already so that way you could just try to build that box instead of trying to figure out the tuning and volume. if you dont like the sound of that box then try to play with the box dimensions or port length.

What subs are you planning on using? Some subs work better in sealed, some ported. Both have advantages and disadvantages. Tuning will depend on the speaker and what you are expecting from it. Tells us what you are wanting to do.

I am using Lanzar heritage 15" HRWDC15, i had them in a bandpass box, but it was just bought off ebay, before i knew about the whole tuning thing, and i was always wondering y there was so much noise from the ports as the air passed through them, and thats y i want to build my own to stop that noise but still give me the edge that a vent does. thanks for any one who can help me!=]Lanzar car audio

The owner's manual for that woofer says the following: 2.5ft per woofer. 4" diameter x 6" long port per woofer. Tunes to 38.8hz. A 1.5ft Sealed box is also an option.

building enclosures takes experience...trial and error...building and testing. Also I never go by "recommended" specs...those usually suckCustom Enclosure Design

so if I use the recommended specs as above, will my sub sound horrible? or will it just sound better if i go through all the math and trial and error? thanks-Lanzar car audio

some people like crappy sounding bassCustom Enclosure Design