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Thread: Box size for .85 Cubic Feet?

  1. #1
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    Box size for .85 Cubic Feet?

    I have two of the three dimensions I need.

    Width = 12 Inches
    Hight = 12 Inches

    What I need to know is the Depth measurement to get .85 Cubic feet. Thanks in advance.

    EDIT: My calculations show 11 Inches would be close enough. Can any one confirm this?

  2. #2
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    IMHO, If you can hear the difference between .85 and .9 cubic feet you are amazing. Take it from an installer who has built hundreds of custom subwoofer enclosures..... Get it close and it will work fine. If you were really picky you would need to subtract the volume of the driver from the internal box volume. The volume of the port should be subtracted from ported enclosures also. With sealed boxes you have a good 10-20% tolerance larger or smaller and still get good performance. I usually use a larger enclosure then the manufacturers recommend. I like to build a box for a Q of about .8-.9 for a car where some manfucturers go with a Q of 1.0-1.3 The smaller, higher Q enclosures give an f3 that is too high and the sub sounds too punchy with no bottom end. 3/4" mdf and internal bracing makes for a nice box. I found some stuff called ultralight mdf that is just as dense as regular mdf but weighs 1/2 as much. It's great for high performance vehicles. To figure box volume the formula is: LxWxH/1728 (in inches, and those are internal measurements)

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    Thanks for the info. This is going in my 78 camaro trunk (not alot of room) so I would also like to keep the weight down. Where do you get that ultralight mdf from and how is it priced compared to the regular?

    From you formula 12x12x11 would yield .92 (rounded up). I'm mostly looking to keep the size down as the trunk is small. Looks like 12x12x10.5 (inside mesurments) would be about right.

    I'm building this box for an IDQ12 D4 V2.0 sub and they listed three different sizes and this is the middle one.

    Just curious but what thickness do you usualy use to make your boxes. The ones I have made before I made out of 1/2 inch. Never used any bracing on them eather. I never saw any flex in the boxes even in the one I made for my 15" Solobaric L7.

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    Great sub. I have the IDQ10 v.2 D4. I had it in a .5^3 ft sealed box, and it sounded amazing, then I built a 1^3 ft. ported tuned to 28 hz and it is one of the best sounding setups I've heard in my area. Gets pretty loud too.

  5. #5
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    Yeah, the larger enclosure will usually give you better sounding and low frequency extended sub bass. A small box will give you higher power handling and spl. I found that ultralight mdf at a good lumber yard near Montclair, CA. He said it was hard to find but talk to your local supplier and see if he knows where you can get it. It only cost slightly more then the standard stuff at Home Depot. Around $26 for a 4x8 sheet. I would use 3/4" for most subwoofer enclosures. 1" is even better but it's just not practical for most applications. 1/2" will work ok but put some bracing inside. People who consider themselves audiofiles might argue this but their opinion is rarely backed up with any real science or personal experience

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    I'v heard it is the other way around. Sealed enclosures are suposed to be for SQ and ported is for SPL. I'm going for SQ because of the fact that a 12 inch driver in a 78 camaro is going to be more than loud enough. I'm planing on pushing it with an mtx amp that dose 280 watt rms. I'm trying to keep the power down in this car as I was drawing way to much current with my last set up.

  7. #7
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    Quote Originally Posted by hcker2000
    I have two of the three dimensions I need.

    Width = 12 Inches
    Hight = 12 Inches

    What I need to know is the Depth measurement to get .85 Cubic feet. Thanks in advance.

    EDIT: My calculations show 11 Inches would be close enough. Can any one confirm this?
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    I wonder if Lows has the light weight MDF. If not there is another lumber yard around here I can check.

    Jstarko0329: How many watt you runing to your 10"?

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    hcker2000, you are right about ported boxes giving higher spl but the cost is power handling. The ported enclosure will be 3db louder then the sealed box but the ported box will have to be larger and it would need a subsonic filter to give the same power handling as the sealed box. Under the tuned frequency of the ported box, the woofer is basically unloaded and can bottom out the voice coil easily. Most newer car audio woofers are designed with a small sealed box in mind. They have longer voice coils, bumped polepieces, stiffer spiders, bigger rolled surrounds, and stronger cones. These features are needed for small sealed enclosures. The sealed sq thing is because ported enclosures have inherant port noise. If the box is designed properly, the port noise can be kept to a minimum. The port length should not be more then twice the width if possible. You can round the inside and outside edges to cut down on port noise also. I like isobaric bandpass enclosures. I used to experiment a lot with those. You can get as much as 10db of gain out of the enclosure over a narrow bandpass frequency. I built one a long time back that had 10db of gain and a f3 of 22hz! It made 30hz bass levels that would make you sick! It was only about 1.5 cu/ft and had two 12" subs. Freeair woffers have the specs needed to perform well in that type of enclosure: high qts, low fs, medium vas and long excursion.

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    I'v had a band pass before. Of corse that was when I had a caddy with a huge trunk. I'm not sure why that box was so big it just had a single 12" generic sub as I remember.

    If I have enough room on the left side of the trunk the sub will be mounted facing the right side of the trunk with the box built behind it. If it works out like I think its going to there will just be a carpeted wall on the left that the sub will be siting in.

    I thought about going with a fiberglass box but I'v never worked with fiberglass and it seems like it would cost more.

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