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air space??

This is a discussion on air space?? within the Stereo and Electronics forums, part of the General Help category; how do you figure cubic air space i have a jl w7 10 needing 1.5 cubes ported...

  1. #1
    Junior Member stormkarma's Avatar
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    air space??

    how do you figure cubic air space
    i have a jl w7 10 needing 1.5 cubes ported

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    HEHEHEHEHE Dabom75's Avatar
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    What size port you need?

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    Junior Member stormkarma's Avatar
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    no idea this sub needs 1.5 cube ported how big would that make the port

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    length x width x height of box would give you the cubic area .. is that what you're looking for? or am I not getting you? so I'm just gonna elaborate...lol

    That being done, ported means having a port? can't you buy those and just make a hole and bolt them on to the final box?

    lol ... here's a page on it ... http://www.diysubwoofers.org/misc/portcal.htm

    here's port tubes ... http://www.crutchfield.com/g_745/Port-Tubes.html?tp=814 maybe you can calculate the dia and length to achieve 1.5cuft?
    Last edited by Mean Green Z28; 02-26-2010 at 11:04 PM.

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    Member Blue28's Avatar
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    You need to know the frequency (in hertz) you want/need the port tuned to first.

    Also that 1.5cu.ft. enclosure, does not include the air space that the Sub, and port occupies. So the actually enclosure air space will be larger than 1.5cu.ft. before the port, and Sub is installed.
    Last edited by Blue28; 02-27-2010 at 12:39 AM.

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    Make sure you utilize the inside dimensions of the box and not outside as that will greatly affect your calculation. My understanding is that the cubic foot recommendations do not require subtraction of the speaker volume, but it has been so many years since I have played with high end audio that I may be off on this.

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    Electrical Engineer KMdef9's Avatar
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    Quote Originally Posted by pajeff02 View Post
    Make sure you utilize the inside dimensions of the box and not outside as that will greatly affect your calculation. My understanding is that the cubic foot recommendations do not require subtraction of the speaker volume, but it has been so many years since I have played with high end audio that I may be off on this.
    Your right on, even terminals can be neglected.

    Each subwoofer requires/recommends a specific amount cubic ft, so if yours is 1.5ft cubed, for dimensions (as mentioned before) are Length x Width x Height. It doesn't have to be a prefect cube, since bass has to do with the movement of air and a specific amount of it for optimal use. Each sub also should have 2 different volumes for ported and non-ported, so make sure you know which one is which.

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    Junior Member stormkarma's Avatar
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    thanx for the input i went ahead and put it in a sealed box the the specs sent from jl and its outrageous cant wait to get a custom ported box
    if anybody is looking to piss off the dead and want to do so with 1 sub this is it
    jl 500 1 running 10 inch jl w7 with jl amp kit just gotta work on the mids and highs now wanna run mb qs as there was no monsoon amp in my car when i got her gonna run a 4 channel jl amp to these later

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    Member bberretta's Avatar
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    I just checked the JL Audio site- the 1.5cuft ported and 1.25cuft sealed does not include the displacement of the sub or ports. Add an additional .09 cuft for driver displacement plus whatever you use for the port. Recomended port tuning is 32hz in a slot style rather than the plastic tube ones. The W7 is a killer sub and is HUGE! I used to install JL all the time and by far the 7-series is one of their most impressive.

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    Junior Member Archaelas's Avatar
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    For what it's worth, I usually find it easier to calculate the dimensions in inches rather than feet and then convert over once done.

    You'd use length x width x depth (this is for a square or rectangular box) in inches. The number you arrive at should be relatively huge (in the thousands). Divide that by 1728 (12 x 12 x 12) to get cubic feet.

    Example: A box 28" x 14" x 12"
    28 x 14 x 12 = 4704cu"
    4704/1728 = 2.72cu ft

    You *can* reverse the process as well. Knowing that you need a 1.5 cuft area, plus .09 for the sub and we'll guesstimate .04 for the port (probably WAY off) that gives you a needed volume of 1.63 cuft. 1.63 x 1728 = 2816.64 rounded up to 2817.

    I don't know where you're putting the box but I'm going to assume center of the trunk. In my '98 T/A, the bottom of the trunk measures 12" from front to back. The outside of the box should be no more than about 11.5" to allow you to easily set it in there and most boxes are made of 3/4in MDF so we'll subtract 1.5in (2 sides x .75) to get an internal depth of 10".

    So, 2817/10 = 281.7.

    I will also assume that you don't want the box to be taller than it is wide so we'll assume a height of, say, 14".

    281.7/14 = 20.12

    That would make your measurements 10" (front to back) x 14" (tall) x 20.12" (1/8 is .125 so we'll call that 20 1/8)

    Remember, those are INTERNAL measurements.

    Sorry for the length of the post but I've been working on my own custom box and all this info is fresh in my mind

    Edit-- This also assumes that you are going with a straight up rectangular box. If you want an angled top, it gets a little more complicated but it's still not bad. You just have to calculate two different volumes (one based on the shorter of the two vertical sides and the other based on the remainder of the longer side - the shorter side. The second volume, you divide by 2 to account for it being a triangle instead of a rectangle).
    Last edited by Archaelas; 03-01-2010 at 06:53 AM.

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    HEHEHEHEHE Dabom75's Avatar
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    Excellent post Arch.

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    Junior Member Archaelas's Avatar
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    Thanks

    Just installed my subs during my lunch (pissed off a few coworkers who sit close to the window). Two Jensen XS1010s on a Pyle 600W 2-channel. Amp still needs a little tuning since it doesn't seem to hit as hard as I remember but it's in .

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    Junior Member stormkarma's Avatar
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    arch

    you were right on thanks

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    Junior Member stormkarma's Avatar
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    Quote Originally Posted by bberretta View Post
    I just checked the JL Audio site- the 1.5cuft ported and 1.25cuft sealed does not include the displacement of the sub or ports. Add an additional .09 cuft for driver displacement plus whatever you use for the port. Recomended port tuning is 32hz in a slot style rather than the plastic tube ones. The W7 is a killer sub and is HUGE! I used to install JL all the time and by far the 7-series is one of their most impressive.


    thanx, still had not figured the port out
    how long does the break in process take and anything special i should do

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    Member bberretta's Avatar
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    Quote Originally Posted by stormkarma View Post
    thanx, still had not figured the port out
    how long does the break in process take and anything special i should do
    not really sure with JL- they've always sounded great out of the box. Break in on a sub usually refers to the loosening of the suspension over time resulting in a better throw on the sub. Sealed boxes especially will always have a tighter, more solid hit because you're dealing less with the movement of air whereas a ported box may have a more hollow, airy sound to it. As for anything special you need to do- tune it well. Start everything at base 0 and go up from there tuning it little by little. Don't go overboard with the gain because if you put too much gain without first tring to see if you get better sound from the eq, then the subs will sound like crap- and you've got too nice a sub for it to sound bad!

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    Junior Member stormkarma's Avatar
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    Bberreta

    come to dallas and throw me double din in

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    Member bberretta's Avatar
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    Quote Originally Posted by stormkarma View Post
    Bberreta

    come to dallas and throw me double din in
    I'd say it was one of the easiest radio installs I've done but it was one of the more time consuming ones!

    Dude, you get a nice radio and install that JL right and you'll have the foundation for a killer system. Just keep this link handy when you get ready to wire your subs so you can get the most out of your amp and subs.

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