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View Full Version : Ehh how do I find subwoofer displacment ?? And measure port ??



dedwardk
01-26-2013, 08:39 PM
So ive done some builds in the past (been a while) and Im very rusty on calculations. I know they have internet calculators (which Ive been using) but it comes down to a few tricky things for me.

Kicker manual says this for max enclosure ...which is what id like to aim for


Box Volume, ft³ (L) + port = 5 (142)
Port Opening Size, in x in (cm x cm) = 3X15.5 (7.6X39.4)
Port Length, in (cm) = 22 (55.9)
Power Handling, RMS = 900


according to the specs I would want to figure out what the actual port displacement is and subtract that from 5 to get the actual box cubic feet spec ?

And how do I know what the above is tuned at ???

Random1010
01-26-2013, 08:45 PM
Port displacement is simply the volume occupied by the port including wood. Your simple 4th grade math should do the trick.

dappa5
01-26-2013, 10:17 PM
it is 5 ft^3 plus the port and driver .... but that is the max ...depending on how much power you are running could be fine either way...
what sub?power and what are your max dims ...and sub/port orientation?

dedwardk
01-26-2013, 11:05 PM
Port displacement is simply the volume occupied by the port including wood. Your simple 4th grade math should do the trick.

wow your a big help thanks for your 2 cents worth ...

kushy_dreams
01-26-2013, 11:08 PM
So ive done some builds in the past (been a while) and Im very rusty on calculations. I know they have internet calculators (which Ive been using) but it comes down to a few tricky things for me.

Kicker manual says this for max enclosure ...which is what id like to aim for


Box Volume, ft³ (L) + port = 5 (142)
Port Opening Size, in x in (cm x cm) = 3X15.5 (7.6X39.4)
Port Length, in (cm) = 22 (55.9)
Power Handling, RMS = 900


according to the specs I would want to figure out what the actual port displacement is and subtract that from 5 to get the actual box cubic feet spec ?

And how do I know what the above is tuned at ???

use this to figure out what your box is tuned at: Subwoofer Enclosure Calculators, Fraction to Decimal, Parallel, Series, Port Length and Volume Calculators (http://www.the12volt.com/caraudio/boxcalcs.asp)

box is tuned around 30hz assuming 5 cu/ft is AFTER sub and port displacement. If its 5cu/ft BEFORE sub and port disp, tuning will be higher

what sub is this?

jnewnam88
01-26-2013, 11:10 PM
wow you're a big help thanks for your 2 cents worth ...

You're welcome!!

jnewnam88
01-26-2013, 11:11 PM
Sounds to me like L7 15" with those measurements

dedwardk
01-26-2013, 11:26 PM
it is 5 ft^3 plus the port and driver .... but that is the max ...depending on how much power you are running could be fine either way...
what sub?power and what are your max dims ...and sub/port orientation?

Hey thanks for the help... I was confused on the spec sheet.... says Box + port = 5

Two 15" Kicker CVX
1 Alpine Mono D 1000 rms @ 2
Box = 48" Wide ---- 19"-22" Depth ----- 30"-35" Height


I want to build a slot port with shared port and shared box space ..


here is another question about box.

Obviously if I use both of my subs they wont be getting 1000rms .. so is it pointless to build a box that is for that power ?? would it effect loudness if I shrank the box down to a box that has a max recommended of 500 per sub ??

My gut says stick with large box for loudness and quality ...

dedwardk
01-26-2013, 11:29 PM
You're welcome!!

who called the grammar police ?? I dont care enough to properly word my internet post .. you still knew what I meant :D Im here to build a box not spell properly .. I passed all my English classes already .. when I transfer for my bachelors I be on my tippy toes again

jnewnam88
01-26-2013, 11:31 PM
who called the grammar police ?? I dont care enough to properly word my internet post .. you still knew what I meant :D Im here to build a box not spell properly .. I passed all my English classes already .. when I transfer for my bachelors I be on my tippy toes again

Haha Im here for you man!!

dedwardk
01-26-2013, 11:32 PM
Sounds to me like L7 15" with those measurements

hey see we both made mistakes ... not a L7 .. its a 15"cvx ... and my post wasnt in audio so it couldnt have sounded like an L7 .. unless you read it out loud .. but then you'd still be wrong :suicide:

hey you should quote me and tell me I left out a couple of apostrophes

kushy_dreams
01-26-2013, 11:33 PM
Hey thanks for the help... I was confused on the spec sheet.... says Box + port = 5

Two 15" Kicker CVX
1 Alpine Mono D 1000 rms @ 2
Box = 48" Wide ---- 19"-22" Depth ----- 30"-35" Height


I want to build a slot port with shared port and shared box space ..


here is another question about box.

Obviously if I use both of my subs they wont be getting 1000rms .. so is it pointless to build a box that is for that power ?? would it effect loudness if I shrank the box down to a box that has a max recommended of 500 per sub ??

My gut says stick with large box for loudness and quality ...

When running on low power, its best to go with the absolute biggest box you can fit in because larger boxes are more efficient

dedwardk
01-26-2013, 11:35 PM
use this to figure out what your box is tuned at: Subwoofer Enclosure Calculators, Fraction to Decimal, Parallel, Series, Port Length and Volume Calculators (http://www.the12volt.com/caraudio/boxcalcs.asp)

box is tuned around 30hz assuming 5 cu/ft is AFTER sub and port displacement. If its 5cu/ft BEFORE sub and port disp, tuning will be higher

what sub is this?

thanks for the reply !! I was already using that exact site .. Problem is it doesnt hint on the calculator page whether you should add to the box for port space .. or just keep same specs and put port inside what you got already .. thats where I was drawing a weird face :confused:

thanks though

dedwardk
01-26-2013, 11:38 PM
When running on low power, its best to go with the absolute biggest box you can fit in because larger boxes are more efficient

also that would help with port noise theoretically ?? cause when you use smaller box and crank it up it may give a whistle ??

or is that what you meant by efficient :D

sorry guys .. told u im rusty

jnewnam88
01-26-2013, 11:42 PM
hey see we both made mistakes ... not a L7 .. its a 15"cvx ... and my post wasnt in audio so it couldnt have sounded like an L7 .. unless you read it out loud .. but then you'd still be wrong :suicide:

hey you should quote me and tell me I left out a couple of apostrophes

Missed more than a couple of apostrophes! When I read Kicker I instantly think L7 I forget about the "CVX"

kushy_dreams
01-26-2013, 11:47 PM
also that would help with port noise theoretically ?? cause when you use smaller box and crank it up it may give a whistle ??

or is that what you meant by efficient :D

sorry guys .. told u im rusty

port noise has to do with the size of the port or obstructions in the airflow through the port.

I'm no expert by any means but from what I understand, efficiency of large boxes come from allowing the woofer to reach xmax sooner than in a small box, given the same amount of power. I also think that large boxes rise less through the impedance curve, but there are others that say that smaller boxes have less impedance rise, I don't have the equipment.... yet, to test that theory.

dedwardk
01-27-2013, 12:29 AM
Well thanks for your help and time !!