Can you do that? Instead of 80sqin x 20" can you do 40sqin x 40" or does the port need to be large enough so that theres more air being pushed at one time? If the port is 40" x 1"-2" wide will that make for a weak port if it needs to be around 5-6?

 

The length of the port in addition to the volume of the box will change the tuning frequency of the enclosure. Most subwoofers require around 12-16 square inches of port area per cubic foot of volume. So, want a box that is 1 cubic ft, the you would want a port that is 2" X 8" or 1" X 16". From there you will have to adjust the length of the port to adjust the tuning frequency. Here is a link to a box building calculator from RE that you can play around with to get a better idea.

 

I'd really like to know who came up with this port volume vs. box volume rule of thumb. It's moronic. No, sorry, that is insulting to morons.. Did some manufacturer put this in their manuals or on thier website or something???


To answer the question, NO you cannot make up for area by adding depth. As the area of a port gets smaller, so does the length, and vice-versa. It is not a total volume thing.

Also, a slot port should ideally not be more than to 6:1 in length vs. width and definitely never more than 12:1

 

Most manufactures websites that give enclosure advice that I have seen suggest using 12-16 sq inches per cubic foot. What would you recommend to us morons?


The numbers 2X8 and 1X16 were purely examples, thank you for clarifying.

 

I'm trying to foreward fire a box!

 

I never called you a moron - I called whoever thought up that bullshit rule of thumb a moron. It is easy to find a 6, 8, 10, and even a 12 that will all work in 1cuft vented. They all need the same port area? Hardly.. THAT is moronic.

Show me these sites.

 

I was being facetious when I said us morons. I just wanted to know why you thought it was a dumb rule of thumb. Here are a few links to manufactures sites that I was referring too. I think we can agree these are reputable companies all recommending 16 sqaure inches of port per cubic foot.

http://www.ddaudio.com/dd/caraudio/e...Size_hiEff.asp

https://ssl.perfora.net/www.ficaraudio.com/sess/utn;jsessionid=154a18920421b91/shopdata/0070_Tech/0070_Speakers/0020_Tech.BL/product_overview.shopscript

http://www.audioque.com/aq/portSize.htm

Obviously not all drivers have the same T/S and have different requirements, but at least it is a place to start, seeing how he hasn't posted any other information. To the original poster: what do you meant forward firing? Do you want the port on a different side of the box than the subs?

 

I want to flip the rear seat down and see woofers and a port and have the trunk closed off.

 

Thanks for the links. If you study the DD page, you can see that their arrival at ~16sqin/cuft comes from testing their woofers in their boxes. Where they made the error was in assuming, and then promoting, that this is a good rule of thumb that works across a broad range of drivers and a broad range of tuning. The other two pages I believe just copied DDs information. They all offer the same type of woofers so it's not surprising.

Further to that, DD is after a certain performance from their drivers and their box chart there allows Joe Consumer to build something that works with a DD speaker. Move to a different brand of speaker though and it's a guess on how well it will work.

Proper speakerbox design should consider the driver you are using and what you want it to do. People would laugh openly if one said that every 10" driver should go into a 0.75cuft box. At the same time, it is laughable to believe every 0.75cuft box should have a 12sqin vent in it.

Anyway - again thanks for the links. I knew someone had to have posted that bad info somewhere.