is this box calc accurate?

[panda714 10+ year member]

Red is the speaker baffle. Black is the back. Teal/violet are the inner walls of the port. Yellow and green are the sides of the box.

Can I use the top of the box as the speaker baffle? Would it effect the sound? Sorry for my ignorance i'm a total noobie.

 

[Raven 10+ year member]

It would be better to keep the ports and the woofer facing the same direction. Just lie to the program when you give it the width and height.

 

[panda714 10+ year member]

What do mean by lying to the program? I have 30 inches for the width and 18 inches for the height for the box i'm gonna build. Well i read on the forums that it would be better to have the port facing the rear of the cabin, and have the sub facing upwards to the window in a hatchback.

 

[Logikalliquid 10+ year member]

As long as the depth is enough for your speaker placement you don't need to "lie" to the calculator.

 

[panda714 10+ year member]

The depth is 24". So am i good to go?!?!?!

 

[Logikalliquid 10+ year member]

unless you have a 25inch woofer your good.

 

[panda714 10+ year member]

unless you have a 25inch woofer your good.

lol //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif Thanks.

 

[beerman 10+ year member]

I thought about adding a "port position" selector box.

Options would be "side", "bottom" and "CRX".

Side is "standard" while "bottom" and "CRX" would have to work around the woofer basket. Difficult since the ports are enormous with those designs.

9:1 ratio with a 40" wide box would yield a 38.5x4.25" port, or nearly 164 square inches. Not really a problem with high-excursion woofers, since the port is going to be that big anyways, but many people wouldn't want that for two or three "entry level" woofers.

 

[bimma85 5,000+ posts]

I thought about adding a "port position" selector box.
Options would be "side", "bottom" and "CRX".

Side is "standard" while "bottom" and "CRX" would have to work around the woofer basket. Difficult since the ports are enormous with those designs.

9:1 ratio with a 40" wide box would yield a 38.5x4.25" port, or nearly 164 square inches. Not really a problem with high-excursion woofers, since the port is going to be that big anyways, but many people wouldn't want that for two or three "entry level" woofers.

//content.invisioncic.com/y282845/emoticons/yumyum.gif.0556df42231b304b9c995aefd13928a8.gif You are the man.

 

[Goldtaz1 10+ year member]

You're thinking about it backwards.
Since the outer wall of the box is the outer wall of the port, it tends to lengthen the port beyond the inner port wall. To correct, you remove half a port width from the inner port.

http://www.jlaudio.com/tutorials/ports/index.html

One has to remove that length from the inner port wall.

Ok Beerman, I guess I'm still not understanding you here. I went to JL's site and it states "Calculating end factor may sound like it would be more trouble than it's worth, but it's actually quite simple. To calculate end correction factor, simply add one-half of h to the physical length you calculated above (L1 + L2)." Just above this statement it gives a pretty little picture to try to explain. Please help me understand why they say add and you say subtract?

 

[beerman 10+ year member]

Please help me understand why they say add and you say subtract?

Simple: the JL tutorial helps you determine the tuning of a box that's already built. Note the formula is "solved" for "Fb" and not "Lv". "Lv" is one of the factors that determines "Fb". Determining the "real Lv" in this case requires you to add to the "physical Lv".

Designing a box from scratch requires one to solve for "Lv" (given "Vb" and "Fb") , and then remove the ECF from the "real Lv" to determine "physical Lv".

A word of advice: real gangsta azz fritters don't flex nutz, cuz real gangsta azz fritters know they got em. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[Goldtaz1 10+ year member]

Simple: the JL tutorial helps you determine the tuning of a box that's already built. Note the formula is "solved" for "Fb" and not "Lv". "Lv" is one of the factors that determines "Fb". Determining the "real Lv" in this case requires you to add to the "physical Lv".
Designing a box from scratch requires one to solve for "Lv" (given "Vb" and "Fb") , and then remove the ECF from the "real Lv" to determine "physical Lv".

A word of advice: real gangsta azz fritters don't flex nutz, cuz real gangsta azz fritters know they got em. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

BWUAHAHAHAHA!!

I really appreciate you helping me understand this because this was the only thing that my spreadsheet had gotten wrong so far.