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  • #16
    Re: Vas vs Box Volume

    Thanks for all of the help and responses... I think I'll go with 2.75 cu ft..... this should be a good trade-off in freq resp and power handling?

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    • #17
      Re: Vas vs Box Volume

      Originally posted by hotrod View Post
      Thanks for all of the help and responses... I think I'll go with 2.75 cu ft..... this should be a good trade-off in freq resp and power handling?
      Let us know how it works out. I purchased a pair of the 10" buyouts to add a couple of subs to my 2 way rig. I'm not looking for pounding bass, just something to fill in and smooth out the bottom end. I think I'm going to build a pair of 4 ft^3 boxes, so if I don't like these drivers I can upgrade to some of the LAB12's ported by just switching the front baffles.

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      • #18
        Re: Vas vs Box Volume

        I ordered the Dayton $78 300-802 -100 W @ 8 Ohms SA 100 sub amp and the Dayton $14 299-106- 10" sub.... While waiting on the order to arrive, I built the above mentioned 2.75 Cu Ft box and planned on using it as a sealed application..... When the order arrived, there was only an amp in the box.... The invoice said that the sub was "out of stock and discontinued"..... I called and reordered a Dayton $20 295-485- 10" sub..... this sub required a smaller box than the sub I originally ordered so I used a Port Size Calculator I found on the net I installed a 3" X 5.5" port.... supposedly tuned to 33 Hz.... Sounds really good, especially for less than $100.....

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        • #19
          Re: Vas vs Box Volume

          Originally posted by hotrod View Post
          I ordered the Dayton $78 300-802 -100 W @ 8 Ohms SA 100 sub amp and the Dayton $14 299-106- 10" sub.... While waiting on the order to arrive, I built the above mentioned 2.75 Cu Ft box and planned on using it as a sealed application..... When the order arrived, there was only an amp in the box.... The invoice said that the sub was "out of stock and discontinued"..... I called and reordered a Dayton $20 295-485- 10" sub..... this sub required a smaller box than the sub I originally ordered so I used a Port Size Calculator I found on the net I installed a 3" X 5.5" port.... supposedly tuned to 33 Hz.... Sounds really good, especially for less than $100.....

          Actually, a 3"d x 5.5" long vent tunes a 2.75 cf box to 30 Hz, which is almost exactly perfect for your situation.

          That SD sub series was a good one. While I never tried the 10", I DID use the 8" in about 1.5 cf with the 70w amp, and the 12" in 3 cf with your 100w amp.

          Have fun.

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          • #20
            Re: Vas vs Box Volume

            If you tune a little lower I think you will find 25 to 27 Hz tuning will give you a little better excursion , mind, if you already built it I would,nt bother.

            Never try to teach a pig to sing.
            Its a complete waste of time, and it just annoys the pig !.

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            • #21
              Re: Vas vs Box Volume

              Originally posted by hotrod View Post
              Thanks for the quick responses..... I tried downloading those programs.... the fisr one didn't seem to respond to the specs I entered.... there was a certain driver already in the graph and when I entered my driver's specs, the box volume info didn't change?? The second program was more confusing for me and I got constant error message as I entered my driver's specs.... If there is a simple (generel rule of thumb so to speak) formula for Vas to Vb formula, that would probably work.... it's just for a sub to go in my garage.... I was looking at this particular sub because PE has it on asle for $14.... thanks...
              Try Unibox. You can input the speaker parameters, enter the box design, and get a response simulation, ignoring things like room gain and baffle step. If you provide a desired Qtc, it will optimize the box size for you. It will simulate sealed, vented, passive radiator, and bandpass enclosures.

              Regards,

              Rob

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              • #22
                Hello!

                My question pertains to power handling that is limited by driver excursion around Fs when mounted in a large sealed box, say Vb = 4*Vas.

                Regarding - https://www.parts-express.com/grs-8p...oofer--292-408

                I want to keep the sealed box Qtc as low as possible, for which WinISD says a minimum 68 litres box would be necessary. I can accommodate this size which is not a concern.

                The concern though is how many watts it will take until it reaches it Xmax of 3mm in such a lightly loaded environment. WinISD shows 4 watts! Is it a reliable figure? In fact, i simulated a range of enclosure sizes, and until I go as small as 12 litres (Qtc > 1.5!) the excursion limited power handling around box resonance remains below 20 watts!

                A very similar case emerges with the Goldwood 8" driver, with the minimum box size being 51 litres for the desired Qtc, and the excursion limited power handling still being a measly 4 watts.

                * I don't understand the point in having its long term thermal power handling at 100 watts but really useable being not more than 8-10 watts in a real life situation. It seems frustrating.

                Could you please help me with these findings through your views or guidance, about the excursion limited power handling in a sealed box with Vb=68 litres for a Qtc < 1.1?

                Thanks in anticipation,
                Sujat (an enthusiastic student looking for guidance)

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                • #23
                  If Xmax is that small, your best choice is probably ported to reduce excursion. It's often the situation that Xmax is the limit on low frequency output.
                  Francis

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                  • #24
                    Yeah. If you want to keep "Q" as low as possible, don't start out w/a driver w/a raw Q of 0.93. In a closed box, Q can never be forced lower, it can only go up.
                    In 2.4cf (sealed and stuffed), that driver only extends down to around 50Hz. At 50Hz, it'll breach Xmax at 6 watts.

                    A good book to help you learn about all this stuff (in an organized manner) is "Speakerbuilding 201" by Ray Alden (sorry Craig).

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