Port Volume vs Size question.

[Fastr 10+ year member]

Quick question for the box building gurus. Is the volume of the port the only important spec of the port? ie I have a 4ohm DVC Alpine Type-R. Alpine's optimum recomendation is 1.7 ft/3 enclosure with port size of 12" h x 1.25" w x 21" length.

I want to make the internal height of my box 14" high.. so can I just shorten the port length to get the same volume without hurting sound?

Recommend size: 12x1.25x21 = 315 cu. inches

Alternate size ok?: 14x1.25x18 = 315 cu. inches.

(Also, would anyone know how to calculate the tuned freq. of this box if I build to these specs?)

Thanks in advance for your help!

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[Hintzyboy 5,000+ posts]

Actually, the larger the port area, the longer the port needs to be to achieve the same tuning. Also, you need to figure out what you want for tuning first. That will indicate how long the port needs to be for a certain area. Check out ngsm13's sticky about ported enclosure design. Also, you can check out Moe Lester's sticky here. It has tons of ported box designs for 12" woofers. There are a bunch of different volumes and tunings, so you should be able to find something to fit your application.

 

[AAckley1 10+ year member]

alpine suggest an almost 1:10 port ratio? weird.

 

[Fastr 10+ year member]

Well, I looked at all those box plans that are posted, that is nice! I think I will try the 1.75 @ 32hz box (which will be almost exaclty 1.7 with the driver installed)

Something fun to do this weekend //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[jake760 10+ year member]

before you build that, my type r was really getting held back in 2 cubes with a 24" of port area, now its in 2.75 with 42" of port and its hitting alot harder. R's like alot more port and a little bigger box than recommended.

 

[Trixter 10+ year member]

before you build that, my type r was really getting held back in 2 cubes with a 24" of port area, now its in 2.75 with 42" of port and its hitting alot harder. R's like alot more port and a little bigger box than recommended.

it would also depend on the power your giving it.

 

[PatFitz9 10+ year member]

generally the recommended specs are conservative. and if you do some searching, there are many people with type R's and many different box plans around.