The Subwoofer Enclosure Tuning Thread

[sumone 10+ year member]

and why do people buy plans again? it's that easy??? lol.

lol, don't I feel stupid! I spoke too soon //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

I think I'm thinking too hard...

 

[Zeph 10+ year member]

ah, good, now i can figure out without using a calculator!! //content.invisioncic.com/y282845/emoticons/thumbsup.gif.3287b36ca96645a13a43aff531f37f02.gif

thanks guys, man , im retarded to when it comes to math, but i figured this stuff out! good post

 

[jp101]

thanks guys for the great formula, I'm calculating the port for my box. it will have 1 S12L5 in it and I only have one question, how do you get the AV? I'll be putting a slot port in it. this will be my first time to build an enclosure and I really want to get it right on papers first. thanks!

 

[sumone 10+ year member]

Av is your port area.

from a post above,

...I'll assume that the box needs about 50 square inches of port (this is suitable for a single 15" or a pair of 10's or 12's in most cases) and about 4 cubic feet after all displacements

Now, I didn't know you could assume how much port area a sub needs. Maybe Donn or Jmac can answer that.

But if you already have a set dimensions of the port, it'd just be port_width * that_other_dimension. Like in my case, my box's max height was 16.5, therefore 15 inches internal. Then I just chose a port_width of 1.75 arbitrarily because just from analyzing the equation of Lv (as related to Av, Fb, and Fb), the more port area, the longer the port; which makes sense, cause the bigger the area of the port, the less resistance therefore the length of the port has to make up for that resistance. I'm just guessing though, again, more experienced people like Donn or Jmac would know the real answer/reason.

 

[jp101]

will it be ok if I tune it 40Hz? I listen to rap and rock. I just want to make sure that I wont damage the speakers. any suggestions?

 

[sumone 10+ year member]

It's not like it's wrong to tune to 40hz. As far as I understand it, mid-high 20s gives you the best SQ, 40 and above, SPL, and 30s a mixture of both. So it depends on whether you just wanna be "loud" or you wanna actually "enjoy" your music (not that they're mutually exclusive though)

 

[LoneRanger 10+ year member]

Av is your port area.
from a post above,

Now, I didn't know you could assume how much port area a sub needs. Maybe Donn or Jmac can answer that.

But if you already have a set dimensions of the port, it'd just be port_width * that_other_dimension. Like in my case, my box's max height was 16.5, therefore 15 inches internal. Then I just chose a port_width of 1.75 arbitrarily because just from analyzing the equation of Lv (as related to Av, Fb, and Fb), the more port area, the longer the port; which makes sense, cause the bigger the area of the port, the less resistance therefore the length of the port has to make up for that resistance. I'm just guessing though, again, more experienced people like Donn or Jmac would know the real answer/reason.

You can't just assume how much it will need. I said "assume" because i was creating a hypothetical situation. The area of the port in relation to the driver's sd is just as realevent to output (read as SPL) as the tuning frequency. More port area = more output.

The more surface area the port has, the longer it will have to be to achieve a given tuning frequency as compared to a port with less surface area.

It's pretty much a given that a box with a larger port will allow the woofer to reach XMAX with less effort because there's not as much resistance. If you're designing an SPL system and your only goal is efficiency and output, go for a big port. If you're trying to maintain tonal accuracy, go smaller. Just remember, this port has to actually fit inside your box so if you're trying to tune the port to 25hz and you want 80 square inches of port, the port is probably going to be bigger than the woofer chamber.

 

[#1AlpineFan 10+ year member]

So in order for me to understand how all these calculations work, I am using the recommend ported box for my 13w7 and trying to work the math and come up with the answer (because i know the answer).

If someone wil help here's the stuff. There is a pdf of the box diagram at this link

I want to solve for the equation JMAC posted

Lv = Av*1.84*10^8/[Vb*1728*(Fb/0.159)^2] - 0.823*sqrt(Av)

Lv = Port Length in inches

Av = Port Area in square inches

Vb = Net Internal Volume in cubic feet

Fb = Desired Tuning Frequency

As stated before AV=(W+T)*H*D. I think this is where i'm having problems.

Vb=2.375 cu ft

Fb=30 hz

Slot opening(not including the board)=2 inches

Front baffle = 1 inch

Rest of box = 3/4 inch

Slot height = 15.75 in

So with AV=(W+T)*H*D

(2+.75)*15.75*????

If i'm trying to solve the lenght of the port how can i know what D is? Do i just guess or throw a number in? I know 15.75 is the height because the box can't be any higher than 17.25in.

The answer is Slot length LV = 25.375. But i don't get that of course.

 

[carguy83 10+ year member]

Very informative thread! I learned a few things already just by reading this. But I have a quick question since this is on the subject of subwoofer enclosure tuning. I know bass is non-directional, so does that principle apply to where a port(s) is pointing? Will there be any audible differences if the ported is say, for example, pointed to the rear of the car versus a port aiming straight up?

 

[maniackilla 10+ year member]

jmac .... the reason they pay you ... is b/c the money is worth not dealing with the stress of that and knowing if its right

and ... your sig ... is interesting, atleast it counts by the pwoer of 2, making it representative of binary. choose a 1 or a 0, 1 means stay on drugs, 0 means get off them ..... thats also a binary based decision. as for statistics and probability ... the 1 choice of making the decision which has 2 outcomes give you a probable 1/2 chance of choosing one over the other. if it were me ... my probability of staying on drugs, even though i have a theoretical perfect chance of 1/2, would be is a 100% success rate of being a 1 ...... i just got of work ... excuse my post

/me puts down powder contaminated dollar bill, resinated rolling paper, nutritous 8oz bottle of max strength tussin with the only active ingredient of DXM, salvia pipe, and fungus filled home-made biodome .... those icons sure would come in handy about now ...

edit: edited to add some ... //content.invisioncic.com/y282845/emoticons/silly.gif.3549b64aaa5b6729eb8e865319a3234f.gif//content.invisioncic.com/y282845/emoticons/smash.gif.499e08a4a35ffaf54f4c8194fb8fe8ed.gif//content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif//content.invisioncic.com/y282845/emoticons/thumbsup.gif.3287b36ca96645a13a43aff531f37f02.gif//content.invisioncic.com/y282845/emoticons/spank.gif.0d78e34d42ea8780359e903aeb6697d6.gif

 

[Jimmyd_442 10+ year member]

Jmac will ur formula work with round ports to