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View Full Version : 2.4ft^3 @ 34hz, two 8's, are my plans right?



Supergumby5000
05-13-2007, 08:59 PM
Whelp, this is box design number 2. still learning, so im looking for someone to see if i did this right.

external dimensions: 26Lx12Hx17.5D
port: 3"x10.5" = 31.5" port area
port length: 26"

Its supposed to be 2.4 cu ft tuned to 34hz.

So, if one of you guru's out there could double check this for me and see if im right, that would be great. Im open to suggestions as well! this will be for two 8" kicker compVR's off of around 300RMS.

http://img170.imageshack.us/img170/1111/2434singleportts5.jpg

Blove1991
05-13-2007, 09:06 PM
With 3/4 MDF and if those are external dimensions I got 2.38ft^3 WITHOUT the subwoofer displacement and the port displacement........


EDIT: I got .59ft^3 for port displacement,, Then you got take sub(s) displacement away.

Supergumby5000
05-13-2007, 09:09 PM
the sub displacement is teeny according to the specs on the kicker website, so rounding may have changed that abit heh. how about tuning? thats what im really concerned about hehe

billy18bm
05-13-2007, 09:12 PM
just make sure u measure ur port from the middle of it... so go in 1.5 on each side..... then u also need to extrude it 1.5 inches from the end of the middle and angle it to the back of the box.. like this...
http://home.comcast.net/~tshot39/done.jpg

thats the "Port length" and u dont have any dimensions on your box...
so its hard to tell but if ur port lenght is measured from the middle and its 26"inchs i came up w/
Total volume before port and driver displacement...
26-1.5=24.5
17.5-1.5=16
12-1.5=10.5
24.5*16*10.5 = 4116/1728 = 2.3819444444444444444444444444444
port displacment = 31.5*26 = 819
drive displacement = SHOULD BE LISTED ON YOUR SUB SPEC SHEET
net volume = 4116-819 = 3297/1728 = 1.90798611 cuft........
so ur box is 1.90798611 minus ur driver displacement.....
tuned @ 34.10hz........

1.9079861106666666666666666666667

take the top off and and add dimensions.... and use google sketch its easier and free.......

Supergumby5000
05-13-2007, 09:17 PM
k i'll get some dimensioned images for ya, and yes, the port is 26" down th emiddle of the port

Supergumby5000
05-13-2007, 09:28 PM
http://img96.imageshack.us/img96/4177/244singleportdimensionsuk8.jpg

port length, from the middle of the port is 26"

oh and i forgot height, internal height is 10.5", external 12"

billy18bm
05-13-2007, 09:32 PM
you have to calc the port like my box... so in your eyes make the port 24.5"............
u have to calculate and extra.....1.5 inchs...... from the middle like this pic
http://home.comcast.net/~tshot39/done.jpg

Supergumby5000
05-13-2007, 09:37 PM
so, i have to shorten my port by 1.5", then it will come out around 2 cubes at 34hz? i am happy with that i guess thats close to what i wanted heh. is there an explanation for why i need to minus the 1.5" from the port length?

billy18bm
05-13-2007, 09:49 PM
yea ur port goes along the back wall when it goes that that u have to include... half of your ports width out from the middle so in actuallyity your ports lenght was 27.5 before.. if you measure it correctly

Supergumby5000
05-13-2007, 10:03 PM
yea ur port goes along the back wall when it goes that that u have to include... half of your ports width out from the middle so in actuallyity your ports lenght was 27.5 before.. if you measure it correctly

hmm im confusd now. i understand your logic, but if i dont change the port wall (leave it without subtracting 1.5" length), the total length of the port, going along the middle o fthe port, is 26"

Blove1991
05-13-2007, 10:09 PM
just make sure u measure ur port from the middle of it... so go in 1.5 on each side..... then u also need to extrude it 1.5 inches from the end of the middle and angle it to the back of the box.. like this...
http://home.comcast.net/~tshot39/done.jpg

thats the "Port length" and u dont have any dimensions on your box...
so its hard to tell but if ur port lenght is measured from the middle and its 26"inchs i came up w/
Total volume before port and driver displacement...
26-1.5=24.5
17.5-1.5=16
12-1.5=10.5
24.5*16*10.5 = 4116/1728 = 2.3819444444444444444444444444444
port displacment = 31.5*26 = 819
drive displacement = SHOULD BE LISTED ON YOUR SUB SPEC SHEET
net volume = 4116-819 = 3297/1728 = 1.90798611 cuft........
so ur box is 1.90798611 minus ur driver displacement.....
tuned @ 34.10hz........

1.9079861106666666666666666666667

take the top off and and add dimensions.... and use google sketch its easier and free.......

You didnt add the .75 to the port width considering the port wall :fyi:

Supergumby5000
05-13-2007, 10:15 PM
*sigh* lol. could someone just run the numbers and see what my box is actually designed to? ill make changes from there hehe.

billy18bm
05-13-2007, 10:50 PM
i tried u wont listen look at my box do you see how i went out 1.5"......half the port width.... uve measured.. 26" right from the middle so if you add 1.5" which ur supposed to u get 27.5

so u need to make it 24.5".........then u add ur 1.5... u get 26" does that make sense

its just a rule of thumb
u add half the port width when u use the back wall of a box....
its really simply... and i did calculate ur numbers...you know what you doing..