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Woofer size vs tuning

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  • Woofer size vs tuning

    I have some questions about tuning and bass output. Lets say we have a two-way design that uses a 7" woofer with the enclosures port(s) tuned to 30hz. Then lets say you have a different two-way design that uses an 8" woofer with the enclosures por(s) tuned to 30hz as well. Furthermore, lets say you have a 2.5-way design using two 6-1/2" woofers with the enclosures port(s) tuned to 30hz. Will the bass output (how loud and deep the bass) be the same for all three examples given? Keep in mind that the three scenarios I mentioned are NOT based on the same exact enclosures. Rather, each mentioned design utilizes its own box dimensions and port tuning to achieve the 30hz for that particular design.

  • #2
    Originally posted by NickA1976 View Post
    ... Will the bass output (how loud and deep the bass) be the same for all three examples given?...
    no

    "Not a Speaker Designer - Not even on the Internet"
    “Pride is your greatest enemy, humility is your greatest friend.”
    "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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    • #3
      Ok. Thanks

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      • #4
        The optimum box volume and tuning is dependent on each woofer (it's T/S parameters). Free modeling software at www.linearteam.org - WinISD Pro (Download the latest version).

        Is fairly intunitive but you'll have issues until you know a few "secrets". After that, it takes about 1 minute to model a woofer in a box.

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        • #5
          Drivers vary in sensitivity, how loud they are for a given power input.

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          • #6
            The cab tuning alters its response, but doesn't determine its response. In technical terms Fb does not equate F3. It can, but it usually doesn't.
            www.billfitzmaurice.com
            www.billfitzmaurice.info/forum

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            • #7
              I'm still confused. I was looking at the PE Solstice kit which uses two 6-1/2" woofers and i think is tunf to 30hz. I came across another design, Zaph Audio's ZRT two way ported design which uses a 7" woofer and is tuned to 30hz. From what you are all saying the bass output of these two designs will be completely different? I dont hang out in speaker forums every day so my knowledge about speaker design is limited. Im trying to learn. To me it makes no sense why the amount of bass would be different. An explanation of things in more layman's terms perhaps would be a little more useful to me. I do appreciate all of the responses though it helps me learn.

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              • #8
                Originally posted by NickA1976 View Post
                IFrom what you are all saying the bass output of these two designs will be completely different?.
                Probably. There are a number of factors that determine response, Fb is only one of them. The only one way to learn how it all works is to download a modeling program and work with it. Until you do you wouldn't know what we're referring to when trying to answer your questions, for instance terms like Fb.

                www.billfitzmaurice.com
                www.billfitzmaurice.info/forum

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                • #9
                  So in other words, my question is simply not technical enough. Again I respect everybody's responses. This must be a very advanced forum. I'm going to do some research about what FB means and all of the other parameters so I have a better understanding of what everybody is talking about.

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                  • #10
                    A good starting point: http://techtalk.parts-express.com/fo...building-bible
                    www.billfitzmaurice.com
                    www.billfitzmaurice.info/forum

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                    • #11
                      Builds - C-Killa - Speedsters - LithMTM - Talking Sticks - Pocket Rockets - Khanspires - Dayton RS Center - RS225/28A - Kairos - Adelphos - SEOS TD12X - Dayton 8 - Needles - 871S - eD6c - Overnight Sensations - Tritrix (ported) - Lineup F4 - Stentorians - The Cheapies - Tub Thumpers - Barbells - Tuba HT - Numerous subwoofers - probably missing a few...... :p

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                      • #12
                        Nutshell: 3 MAIN "T/S" (Thiele and Small (did I spell that right?) - 2 guys (from Australia?) who figured this stuff out - maybe in the '70s?) parameters are:
                        Qts (kind of a resonance "value" - with NO units), I think it's actually the resonance "Q"uality?
                        Fs (the "natural" resonant freq. of the driver (the cone, on its suspension) in "free air" (meaning - NO box) in Hz (used to be called "cps" for cycles per second),
                        and Vas (which is a cubic volume of air that's equivalent to the suspension's "softness" (like having softer or stiffer shock absorbers on your car)) commonly given in cubic feet (here in the good ol' U.S.A.) or in Liters (everywhere else in the world - which is where a LOT of our drivers come from)

                        How low a driver/box combo can go is its "F3" - meaning where the bass output (on the bottom end) has rolled off -3dB "down" from its nominal output. THAT is determined by a driver's Qts and its Fs (regardless of driver size).
                        How large a box you need (Vb for a vented or ported box - which is the net internal box volume required to achieve the F3 you're targeting, OR Cb for a closed (sealed) box) is determined by Qts (again) and Vas.

                        Fb is the freq. a vented box is tuned to, which you're picking as 30Hz.

                        Certain drivers will love a box tuned to 30Hz, AND if they've got a Qts very close to 0.40, and an Fs of 30Hz, most likely they'll have an F3 ALSO of 30Hz.
                        Some drivers (using a box tuned to 30Hz) will actually be able to play below 30Hz, even strongly. Others won't be able to even get close to 30 in a box tuned to 30. A 4" midrange with an Fs of 150Hz probably won't even hit 100Hz in almost any size box that's tuned to 30Hz. It all depends.

                        A GREAT book for learning all this stuff (and more - and also makes a good reference to keep around) is "SpeakerBuilding 201". (sc)
                        Last edited by Chris Roemer; 03-04-2018, 08:51 AM.

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                        • #13
                          Q is not the resonance quality. It is a measure of damping. Qms being mechanical damping, Qes being electrical damping, and Qts being the total damping derived from the other 2 specs.

                          Later,
                          Wolf
                          "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
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                          • #14
                            Originally posted by NickA1976 View Post
                            So in other words, my question is simply not technical enough. ...
                            The Tuning numbers you quoted reflect frequency NOT how loud ( SPL ), nor slope of bass falloff.

                            The Q factor is a dimensionless parameter that indicates the energy losses within a resonant element which could be anything from a mechanical pendulum, an element in a mechanical structure, or within electronic circuit such as a resonant circuit. In particular Q is often used in association with an inductor.
                            "Not a Speaker Designer - Not even on the Internet"
                            “Pride is your greatest enemy, humility is your greatest friend.”
                            "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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                            • #15
                              Originally posted by Wolf View Post
                              Q is not the resonance quality. It is a measure of damping.
                              While technically correct I wouldn't use the term damping when describing Q, as damping also refers to something else entirely. For the sake of not making a confusing subject even more so I prefer to use the term losses.

                              www.billfitzmaurice.com
                              www.billfitzmaurice.info/forum

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