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  • subwoofer interior volume

    All,

    I'm in the process of building a subwoofer for my garage sound system using two 8-inch subs I have lying around. If I add a 10-inch passive radiator to the box, what's an ideal interior volume?

  • #2
    As a general rule, you would use at bare minimum the Thiele-Small parameters of Qts, Fs, and Vas to generate a rough estimate for enclosure volume of a bass-reflex enclosure, for a standard alignment. Do you have those parameters available?

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    • #3
      +1 on Thiele-Small parameters and some modeling. Self linking here, but I make no money off this site anyway so... Start here for some super basics about woofer design.
      Electronics engineer, woofer enthusiast, and musician.
      Wogg Music

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      • #4
        I don't have those parameters on hand. I was thinking a box with an internal volume of .63 - .7 would work for the two 8-inch subs alone. I know the PR would call for a bit more internal volume, I just don't know how much more.

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        • #5
          I think guessing will get this nowhere, unless by sheer coincidence it turns out to need that much volume. Why not look up the subs on this new thing called the internet? Or you could just build it and hope for the best if you wanna go with your gut feeling. I personally think it would be a waste of time based on mystery 8" subs whose parameters are a huge wildcard. But that's just me.

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          • #6
            Slatfour, where are you located? A lot of the people on the forum have the tools to measure the TS parameters. If you are close to someone they would likely help, it literally takes about 1 minute.

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            • #7
              See my signature related to PR to help a bit once you know more about the woofers you have.
              Feel free to rip my assumptions apart when wrong, or fix if close.

              Passive Radiators:
              All PR(s) Vd must at-least double all woofer(s) Vd. Calc = Sd x Xmax to get Vd for all PR(s) and all woofer(s). If all PR(s) Vd at-least double all woofer(s) Vd they'll work.
              For woofer(s) with large Xmax vs Sd, all PR(s) with Xmax at-least double all woofer(s) Xmax will work.
              A PR max weight is said to be its Mms x3

              PR Systems - tight focus with key parameters.
              PR Speaker Design - thorough coverage.

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              • #8
                About the only thing that I can think of that's worse than just throwing 2 "random" 8" drivers into a random box would be to throw 2 random 8" drivers into a random box along with a random (10") PR. Yeow!

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                • #9
                  The speakers are Rockford Fosgate (Clarion). They are the subs I took out of two Nissan's that I've owned in the past. If I could simply go to a manufacturer's website and get parameters I would do that...too easy, but I can't. I can crunch the numbers if I had them. Again, this is going to be added to a garage sound system, so it doesn't have to be perfect. I will search the web...

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                  • #10
                    Can you give us the subwoofer model numbers (say off the magnet??) We will try and help find the T/S parameters, maybe one of us could get Google to cooperate more???>>
                    Paul

                    The "SB's" build page
                    http://techtalk.parts-express.com/sh...-4-(pic-heavy)

                    Comment


                    • #11
                      Originally posted by bullittstang View Post
                      Can you give us the subwoofer model numbers (say off the magnet??) We will try and help find the T/S parameters, maybe one of us could get Google to cooperate more???>>
                      And take and post some pictures of the things too. Is there a name of any kind anywhere on it? Just need some kind of breadcrumbs to follow.

                      With more info of some kind it may be possible to locate the OEM or a set / single that used to be for sale somewhere.

                      There's very likely a PDF hiding out in the wild somewhere with manufacturer TS and other parameters for it. That's all these guys need to start putting useful information together.
                      Originally posted by Chris Roemer View Post
                      About the only thing that I can think of that's worse than just throwing 2 "random" 8" drivers into a random box would be to throw 2 random 8" drivers into a random box along with a random (10") PR. Yeow!



                      Yeah it would be one horrendous POS for sure. Hoping he can provide something giving a clue WTH the things are. Since it sounds like he has them free hand, so perhaps pictures will be enough, unless it's super generic and has absolutely nothing on it anywhere externally.

                      But if that were the case they're probably not worth using anything for at all except seeing how far away he can be when tossing them into a trashcan.
                      Feel free to rip my assumptions apart when wrong, or fix if close.

                      Passive Radiators:
                      All PR(s) Vd must at-least double all woofer(s) Vd. Calc = Sd x Xmax to get Vd for all PR(s) and all woofer(s). If all PR(s) Vd at-least double all woofer(s) Vd they'll work.
                      For woofer(s) with large Xmax vs Sd, all PR(s) with Xmax at-least double all woofer(s) Xmax will work.
                      A PR max weight is said to be its Mms x3

                      PR Systems - tight focus with key parameters.
                      PR Speaker Design - thorough coverage.

                      Comment


                      • #12
                        Originally posted by slatfour View Post
                        The speakers are Rockford Fosgate (Clarion). They are the subs I took out of two Nissan's thatsu I've owned in the past. If I could simply go to a manufacturer's website and get parameters I would do that...too easy, but I can't. I can crunch the numbers if I had them. Again, this is going to be added to a garage sound system, so it doesn't have to be perfect. I will search the web...
                        Are they subs that are originally mounted on a baffle that separates the cabin from the trunk airspace by any chance? If not, where on the vehicle were they actually installed?

                        Comment


                        • #13
                          Originally posted by slatfour View Post
                          The speakers are Rockford Fosgate (Clarion). They are the subs I took out of two Nissan's that I've owned in the past. If I could simply go to a manufacturer's website and get parameters I would do that...too easy, but I can't. I can crunch the numbers if I had them. Again, this is going to be added to a garage sound system, so it doesn't have to be perfect. I will search the web...
                          Follow the link.

                          This modest contribution is for newcomers to this great hobby who have done kits, but wish to go deep (football pun intended) and design their own. We often read
                          "Our Nation’s interests are best served by fostering a peaceful global system comprised
                          of interdependent networks of trade, finance, information, law, people and governance."
                          - from the October 2007 U.S. Naval capstone doctrine
                          A Cooperative Strategy for 21st Century Seapower
                          (a lofty notion since removed in the March 2015 revision)

                          Comment


                          • #14
                            And... Follow the link.


                            "Our Nation’s interests are best served by fostering a peaceful global system comprised
                            of interdependent networks of trade, finance, information, law, people and governance."
                            - from the October 2007 U.S. Naval capstone doctrine
                            A Cooperative Strategy for 21st Century Seapower
                            (a lofty notion since removed in the March 2015 revision)

                            Comment


                            • #15
                              In this newbie thread it should be mentioned that the enclosed net volume starts with calculating gross volume from internal box dimensions. From that subtract the volume occupied by bracing, drivers, passive radiator or port tube, crossover or amplifier, etc., to find the enclosed net volume, and use that in your models.
                              "Our Nation’s interests are best served by fostering a peaceful global system comprised
                              of interdependent networks of trade, finance, information, law, people and governance."
                              - from the October 2007 U.S. Naval capstone doctrine
                              A Cooperative Strategy for 21st Century Seapower
                              (a lofty notion since removed in the March 2015 revision)

                              Comment

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