Realm of Excursion

Realm of Excursion (https://forum.realmofexcursion.com/)
-   Enclosures (https://forum.realmofexcursion.com/enclosures/)
-   -   How to: NET Enclosure Volume/ Slot Port (https://forum.realmofexcursion.com/enclosures/51063-how-net-enclosure-volume-slot-port.html)

ndstrctbl 05-13-2008 07:41 PM

How to: NET Enclosure Volume/ Slot Port
 
I have come to realize lately that a lot of people dont know how how to find the net volume of an enclosure in cubic feet. i thought this might help some people that are having a hard time.

I am using the example that Aroc gave me.

So now we have
14.5H X 32.5W X 12.5D=5890.625 cubic inches
5890.625 divided by 1728 = 3.4 cubic feet


now you take all the dimensions you have and minus 1.5"(if your using 3/4" MDF on each side of the enclosure)

so are new dimensions are:
13"x31"x11"=4433
divided by 1728=2.565 cubic feet.
now, if you were going to add a port to this, i would shoot for 32" of port area(width of the port x the height). a good rule of thumb is to have 12-16" of port area per cubic foot(this box will have a little more but its just an example).

to achieve this, you will have a slot port that is 2.5" wide and 13" tall(13" is the internal height of your box) this gives you 32.5", pretty close eh?

now lets just say the port is 25" long. to find out how much space this port takes up, you take the port width and add the thickness of your wood to it(that is the outside of the port). so now we have 3.25". times that by the height(13") and then by the depth(25"). lets put it into a formula.

3.25x 13 x 25=1056.25
divided by 1728=.611 cubic feet.

subtract this number by the internal volume of your box

2.565-.611=1.953 cubic feet internally.

now you have to subtract sub displacement. lets say we have a pretty beefy 10" woofer(hdc3 10" for example) and it has a displacement of oh maybe .2 cubes?

1.953-.2=1.753 cubic feet after all displacements.

i hope this helps you guys out. this box went from 3.4 to 1.753 cubes pretty quick didnt it? with some braces this example box would work great for a decently sized woofer like a hdc310. dont forget to subtract the displacement from braces if you using them.



oh and i thought i would add how to find the displacement of round ports:

use this formula, Pi x R^2 x D/1728 (3.14 x Radius x Radius x Depth of Port/1728)

i will use a 6" port that is 25" long as my example

3.14 x 3 x 3=28.26"

28.26" x 25"=706.5

706.5/1728= .408 Cubic Feet

just as you did with the slot port, minus this from the internal volume

BlackWaterOp 05-13-2008 07:54 PM

I actually just was looking this up yesterday. Good writeup.

ndstrctbl 05-13-2008 08:01 PM

Quote:

Originally Posted by BlackWaterOp (Post 638752)
I actually just was looking this up yesterday. Good writeup.

thanks i appreciate it.

ndstrctbl 05-13-2008 09:16 PM

EDIT: round port displacement added

Sticky maybe?

tymoto21 05-13-2008 09:46 PM

good descirption. this should help alot of people out there.

btw were is kaukauna? is that by greenbay?

tommyk90 05-13-2008 09:55 PM

The easy way that I calculate up a NET enclosure is like this.

1) Figure out what net volume you want
2) Figure out the port size and length needed to tune it to what you want
3) Figure out the port displacement
4) Add 1&3 together
5) Design a box that has that much gross airspace

:)

kun3racer 05-14-2008 01:04 AM

Quote:

Originally Posted by tommyk90 (Post 638888)
The easy way that I calculate up a NET enclosure is like this.

1) Figure out what net volume you want
2) Figure out the port size and length needed to tune it to what you want
3) Figure out the port displacement
4) Add 1&3 together
5) Design a box that has that much gross airspace

:)

dont forget sub displacement! but yeah this is the way i do it also.:D

ndstrctbl 05-14-2008 09:55 AM

Quote:

Originally Posted by tymoto21 (Post 638876)
good descirption. this should help alot of people out there.

btw were is kaukauna? is that by greenbay?

in between appleton and greenbay

tommyk90 05-14-2008 10:49 AM

Quote:

Originally Posted by kun3racer (Post 639010)
dont forget sub displacement! but yeah this is the way i do it also.:D

Yeah, forgot about that. :)

Usually sub displacement doesn't affect the volume/tuning too much unless it's a BIG sub or lots of them.

Fallen 05-14-2008 01:39 PM

Quote:

Originally Posted by tommyk90 (Post 639202)
Yeah, forgot about that. :)

Usually sub displacement doesn't affect the volume/tuning too much unless it's a BIG sub or lots of them.

Agreed...or its a small box. .1cuft into a 1cuft box is noticeable.

When I design boxes I usually make the a bit too big, then I use the space up with bracing.




ndstrctbl 05-14-2008 03:32 PM

well hey i posted this because i seriously can find some people who come here who cant do this, and i tried putting it into the simplest terms i could.

kun3racer 05-14-2008 06:33 PM

Quote:

Originally Posted by tommyk90 (Post 639202)
Yeah, forgot about that. :)

Usually sub displacement doesn't affect the volume/tuning too much unless it's a BIG sub or lots of them.


well like my setup im running 4 d6 12's with a common chamber so since each sub is .1 ft3, they add up to .4 which does affect the tuning.

kensaudio99 05-15-2008 09:46 AM

What about the woofer xman?? Does that affect the enclosure too? Also i didn't read the whole thing carefully but how to figure out the tuning frequency of ported box??

ndstrctbl 05-15-2008 10:04 AM

Quote:

Originally Posted by kensaudio99 (Post 639818)
What about the woofer xman?? Does that affect the enclosure too? Also i didn't read the whole thing carefully but how to figure out the tuning frequency of ported box??

thats not in there but i can get you the forumula.

ndstrctbl 05-15-2008 10:12 AM

Fb = 0.159*SQRT[(Av*(1.84*10^8)]/(Vb*1728*[Lv+(.823*SQRT(Av))])

LV is the length of the port

AV is your port area

VB is your boxes internal volume(every displacement accounted for)

Fb will be your tuning frequency once you work the formula through.

kensaudio99 05-15-2008 12:04 PM

Quote:

Originally Posted by ndstrctbl (Post 639828)
Fb = 0.159*SQRT[(Av*(1.84*10^8)]/(Vb*1728*[Lv+(.823*SQRT(Av))])

LV is the length of the port

AV is your port area

VB is your boxes internal volume(every displacement accounted for)

Fb will be your tuning frequency once you work the formula through.


Alright, i write that down and i will see if come up with anything that is right. Also, i want to know if the woofer xmas is important while tuning a box?? Anyone know??

Fallen 05-15-2008 05:06 PM

Quote:

Originally Posted by kensaudio99 (Post 639886)
xmas is important while tuning a box?? Anyone know??

I usually wait till Christmas to tune my boxes :lol:
Otherwise it will adversely affect its response.

haha

xmax :P

And xmax has little to do with port velocity. Motor strength has more to do with it.

Think about a pro audio sub...they have less than 10mm xmax...but they need large ports to keep the port velocity down.

Look at it this way: The driver moves the LEAST when the port is at tuning and is moving the MOST!




matt caudill 05-24-2008 03:20 PM

gust bought 2 AQhdc315 need to know what size port i need i want to tune it to 40 hz

stratusrt01 05-24-2008 03:43 PM

One thing I noticed is that you figured the port displacement by taking the entire length of the port. Don't forget, the 1st 3/4" is already accounted for by outside of the box, so you can subtract that from the length. Also, if the port turns, you have to take that into account, as it will not take up the entire length as you figured it out, you would end up tuned lower than expected.

I always do it the way TommyK suggested also.

stratusrt01 05-24-2008 03:44 PM

Quote:

Originally Posted by matt caudill (Post 648133)
gust bought 2 AQhdc315 need to know what size port i need i want to tune it to 40 hz


Port depends on the enclosure size, not the woofer.

kensaudio99 05-31-2008 02:58 PM

Quote:

Originally Posted by Fallen (Post 640113)
I usually wait till Christmas to tune my boxes :lol:
Otherwise it will adversely affect its response.

haha

xmax :P

And xmax has little to do with port velocity. Motor strength has more to do with it.

Think about a pro audio sub...they have less than 10mm xmax...but they need large ports to keep the port velocity down.

Look at it this way: The driver moves the LEAST when the port is at tuning and is moving the MOST!


uhmm, You saying that it has nothing to do with the volume enclosures? Let say an Re audio xmax is 22 so how big do you thing the port should be? Sorry I'm kinda new to with enclosures, but I'm here to learn.

ranmansnaple 05-31-2008 03:42 PM

about the round port so is that example port 6 inches tall by 6 inches wide and you figure it 3.14x3"x3". or is it really just a 3" pipe

ndstrctbl 05-31-2008 08:41 PM

Quote:

Originally Posted by ranmansnaple (Post 653304)
about the round port so is that example port 6 inches tall by 6 inches wide and you figure it 3.14x3"x3". or is it really just a 3" pipe

the formula to find the aera of a round port is (Pi times radius times radius). the diameter is 6", and half of that is the radius which is 3". so it looks like this:

3.14x3x3.

then to figure out the displacement you times it by the depth and divide by 1728.

so, no it is not a 3" pipe, it is infact a 6" pipe.

D3CIBEL 06-06-2008 04:43 AM

Spl
 
Explaination with diagram will be very appreciated, i'm still confused about where to start to measure the start of the port :mrgreen: :mrgreen: :mrgreen:

slowEF 07-20-2008 11:55 AM

Nice write up! Thank you.


All times are GMT -7. The time now is 09:46 AM.

Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Friendly URLs by vBSEO 3.6.0 ©2011, Crawlability, Inc.
ABMM Powered by Syrian Medical Society
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.