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  • Sub enclosure calculation

    Working on a sub for my computer setup, I'm mounting a 4"sub inside a classical/studio size guitar and using an SA25 plate amp on the back. Trying to figure out the volume of this is past my knowledge. I can block off the top half where the gray line is if it would be better. I am also using 1/2" thick felt to line the back and sides. Any input would be greatly appreciated.

  • #2
    That guitar is probably going to be a pretty bad enclosure for your subwoofer.
    Brian Steele
    www.diysubwoofers.org

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    • #3
      I didn't ask if it was a good or bad enclosure. I'm trying to figure out the best way to implement the sub into it. The speaker is mounted inside the sound hole. The plate amp on the back which gives me some room to get inside and work if need be to box it in.

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      • #4
        Dawnut, not sure I'm understanding your question right. Here is my attempt...

        Print off (or just draw) a grid of 1" x 1" squares on a sheet of normal paper (may have to tape a few together). Trace the guitar and you can figure out a good estimate of the square inches, multiply times the height to get the cubic inches. Divide by 1,728 to get cubic feet and you can use google to convert cf to liters if you need to. That is your Gross volume. Figure out an estimate for the volume of the driver and plate amp (if it will be taking up space) to get your Net volume.

        Brian's point is probably pretty good...try to figure out a way to make the case more rigid - maybe glue some 1/4 inch MDF or 1/8 hardboard pieces to the inside walls (not sure if you can do that or not). Also, add some bracing, get a 1/2" dowel from Home Depot or somewhere and cut several to brace the front and back walls of the guitar.

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        • #5
          Thank you a4eaudio, I have some poster board I could use My thoughts were to port it. But maybe better to build an enclosure inside the guitar.. There are braces that run across the guitar top and back just above and below the sound hole so I could make a box inside the guitar to optimize the sealed specs of the driver just have to build it a piece at a time and with the depth I'm working with I'm not sure I can make the top any thicker.

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          • #6
            Don’t dismiss Brian’s advice, he’s just trying to be helpful. The thin tone wood of the guitar makes beautiful music, and about the worst speaker enclosure on earth. Not saying don’t do it, but beef it up inside and you will have better success. Cool idea!

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            • #7
              Thanks all for the input. I didn't mean to sound like I was dismissing what Brian said, I'm just a little sarcastic by nature. The reason I'm using the classical guitar is mostly to complement the decoration in my computer room. My two main computer speakers are two dreadnaught size acoustic guitars hanging from the ceiling with exciters mounted just under the bridge. They actually put out some really clean highs and mids but needs just a touch of help on the bass side of things. .

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              • #8
                Yeah, Brian wasn't commenting on the looks of the guitar, he was just letting you know how bad it will sound w/a subwoofer inside it. I'll be OK (if it's the correct internal volume - you can model your sub of choice in WinISD from linearteam.org ) as long as you can add another 5/8" of fairly rigid "stuff" to ALL wall surfaces (inside or out, it doesn't matter). The only alternative is to add (many) triangulated "dowel" braces (or equivalent) inside to stop the enclosure from resonating. Resonant box = : GREAT for guitar, dismally horrible for speaker enclosure.

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                • #9
                  You can fill the guitar with something like packing peanuts and then dump them out into a box and measure it to get a volume.

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                  • #10
                    Again I would like to thank all of you for your input. As I stated I was just trying to find the best way to implement putting this Sub into the classical guitar. After weighing the input from each of you and doing a little more head scratching here is what I have decided to do to get the best sound and yet keep the aesthetics of the guitar. I have taken the back off the guitar and will make the back out of 3/4" MDF salvaged from a discarded Ikea desk. I will build the sides (also with the MDF) of enclosure behind the sound hole integral with the back then glue to the top and back. Since depth restraints prohibit me from doing the baffle out of the MDF my plan is to make a decorative bezel from some 1/2" Aspen I have from another project that will go on the top. The SA25 will be mounted in the bottom area on the back. What is left of the interior of the guitar I will cover with some 1/2 felt. Will keep you posted but bear with me a couple days.

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