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  • Xmax in a horn?

    Question:
    When a driver, lets say for example an Alpha 6a, is placed in a sealed box, lets say .25 cu ft, it will reach Xmax at about 90 watts at 90 hz (which in this case is 3.5mm).
    If a horn of lets say 37 inches path way, is placed in front of that driver will that change the Xmax "modeling"?

    I know that the horn can potentially change the driver's ability to go lower (than a simple sealed chamber), and affects Fs also, but how much of a difference will that make in the X max modeling of a driver?
    Two very good sociological markers.
    The state of our public wash rooms.
    How we treat each other behind the safety of a monitor and key board.

  • #2
    Re: Xmax in a horn?

    Originally posted by Music is life View Post
    how much of a difference will that make in the X max modeling of a driver?
    Completely different. Horn modeling programs have excursion plots just like standard box modeling programs do.
    www.billfitzmaurice.com
    www.billfitzmaurice.info/forum

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    • #3
      Re: Xmax in a horn?

      Originally posted by billfitzmaurice View Post
      Completely different. Horn modeling programs have excursion plots just like standard box modeling programs do.
      So I'll have to learn a modeling program then! Was not wanting to hear that.
      Two very good sociological markers.
      The state of our public wash rooms.
      How we treat each other behind the safety of a monitor and key board.

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      • #4
        Re: Xmax in a horn?

        Originally posted by Music is life View Post
        So I'll have to learn a modeling program then!
        How were you planning on designing a horn without one?
        www.billfitzmaurice.com
        www.billfitzmaurice.info/forum

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        • #5
          Re: Xmax in a horn?

          Originally posted by Music is life View Post
          .. it will reach Xmax at about 90 watts at 90 hz ...
          The Alpha 6A will hit Xmax in that size box at half that power input at 90hz. 40-45W is about the limit there. Not sure why but your "sim" is off by a factor of 2X there.

          Adding a horn to the alpha 6A in that box, could buy upwards of 20dB maximum output down around 90hz, however, keep in mind that doing so will limit the useful bandwidth to about 2 octaves.
          Pro/Fi Cinema Speaker project: "From the Ashes"

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          • #6
            Re: Xmax in a horn?

            Originally posted by mdocod View Post
            keep in mind that doing so will limit the useful bandwidth to about 2 octaves.
            A well designed horn can run with a 90Hz to 2kHz useable bandwidth, though that level of engineering expertise is way beyond a newbie and for that matter most oldbies. But I wouldn't run an Alpha 6 that low anyway, 150Hz is the practical lower limit. It can take 100w without exceeding xmax when horn loaded, again with a well designed horn.
            www.billfitzmaurice.com
            www.billfitzmaurice.info/forum

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            • #7
              Re: Xmax in a horn?

              Hi Bill,

              Bandwidth, Efficiency, Size... Pick 2 right I was tinkering and came up with an example of the later 2.

              Regards,
              Eric
              Last edited by mdocod; 04-02-2012, 08:10 AM.
              Pro/Fi Cinema Speaker project: "From the Ashes"

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              • #8
                Re: Xmax in a horn?

                Here: http://www.eminence.com/pdf/Alphalite_6A_cab.pdf
                2nd one down. (almost identical to the alpha 6a).
                .25 cu ft. sealed.
                At 90 watts hits Xmax of 3.5mm at right about 92hz. Hits mechanical limit of 4mm at 58hz.

                This download:
                http://www.ajdesigner.com/speaker/index.php
                (sealed)
                Has almost the same results for the Alpha 6a when Qtc is set at .73 (.25 cu ft or 7liters) and diameter is set at 16cm. Power at 90hz, X max is achieved at 93 hz. But here mechanical limit is never quite touched with this input.

                I've built about 50 different mid range mid bass horns and styles of horns. Most of them are trash now.
                Two very good sociological markers.
                The state of our public wash rooms.
                How we treat each other behind the safety of a monitor and key board.

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                • #9
                  Re: Xmax in a horn?

                  Hi Music is Life,

                  I've run the numbers on 2 of their boxes there through 2 different pieces of simulation software. Hornresp is not apt to be wrong on this, and WinISD has always proven to be very reasonably accurate as well. Both programs are agreeing that the Eminence charts for displacement are wrong, or have been fudged.

                  Consider the possibility that the Eminence charts are simply wrong... Notice they suggest HPF set around 200hz for those sealed designs, it's possible they are fudging things a bit and assuming a HPF in place for some of the charts, or tried to present a manipulated chart that would more closely resemble the behaviour with a HPF in place.

                  Here's the Alpha 6A charted in 7L sealed @35W... Hornresp is predicting it hit's ~3.5mm at 90hz.

                  Regards,
                  Eric
                  Attached Files
                  Pro/Fi Cinema Speaker project: "From the Ashes"

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                  • #10
                    Re: Xmax in a horn?

                    Originally posted by mdocod View Post
                    Hi Music is Life,

                    I've run the numbers on 2 of their boxes there through 2 different pieces of simulation software. Hornresp is not apt to be wrong on this, and WinISD has always proven to be very reasonably accurate as well. Both programs are agreeing that the Eminence charts for displacement are wrong, or have been fudged.

                    Consider the possibility that the Eminence charts are simply wrong... Notice they suggest HPF set around 200hz for those sealed designs, it's possible they are fudging things a bit and assuming a HPF in place for some of the charts, or tried to present a manipulated chart that would more closely resemble the behaviour with a HPF in place.

                    Here's the Alpha 6A charted in 7L sealed @35W... Hornresp is predicting it hit's ~3.5mm at 90hz.

                    Regards,
                    Eric
                    I presume you got that set at 7 lit?
                    That's 4db down! That would be way off!

                    Will "horn response" model the exertion in a 32in horn?
                    If so that's what I have to learn.

                    Thanks for the info!
                    Two very good sociological markers.
                    The state of our public wash rooms.
                    How we treat each other behind the safety of a monitor and key board.

                    Comment


                    • #11
                      Re: Xmax in a horn?

                      Hi Music Is Life,

                      Hornresp can model about any box or horn your imagination can conger up. I'm just learning it myself over the last few weeks and must say, it is quite impressive.

                      Here's a simulation at 35W of an Alpha 6A in 7 liters sealed, horn "mounted" to a horn that is 32" long, and, has a 32" x 32" wide mouth at the front. I've only chosen this horn shape to illustrate that giving a single dimension to describe a horn is sort of silly, because I have no idea what a "32" " horn is looking like in someone else's head. (length? width? radius?)

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                      The power of horns is interesting. In 2pi space, the Alpha 6A in that 7 liter sealed box can do ~120dB flat from 30hz to 300hz in a large enough horn. (~12 foot diameter at the mouth, 32 foot long, exponential).

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                      Regards,
                      Eric
                      Pro/Fi Cinema Speaker project: "From the Ashes"

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                      • #12
                        Re: Xmax in a horn?

                        The power of horns is interesting. In 2pi space, the Alpha 6A in that 7 liter sealed box can do ~120dB flat from 30hz to 300hz in a large enough horn. (~12 foot diameter at the mouth, 32 foot long, exponential).
                        That's the one I'm building!

                        Going to go to 3 way. Cannot get "the smallest size possible" in a horn to work at this time. And the prototype that I'm using does not have the midrange dispersion that I want and it is already a few db down there. 3 way here we go.

                        Horn response here we come.
                        Thanks Eric.

                        BTW do you know a good place to get a tutorial for that program?
                        Two very good sociological markers.
                        The state of our public wash rooms.
                        How we treat each other behind the safety of a monitor and key board.

                        Comment


                        • #13
                          Re: Xmax in a horn?

                          Originally posted by Music is life View Post
                          BTW do you know a good place to get a tutorial for that program?
                          http://www.avsforum.com/avs-vb/showthread.php?t=1212465
                          "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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                          • #14
                            Re: Xmax in a horn?

                            This tutorial here was the only one I have found that really helped me make sense of how to use hornresp for all sorts of enclosures:

                            http://www.hometheatershack.com/foru...-everyone.html

                            The reason it's "so good" IMO, is that for each box type imaginable, there is a clear diagram of what input in hornresp correlates to what section of the box or horn or port or whatever it is you are creating. I tried reading some of the help files for hornresp, and the tutorial for tapped horns that Sydney Linked to, but neither seemed to hone in on what's "going on" with so much conciseness.

                            Those diagrams are worth about a hundred pages of words IMO.

                            Regards,
                            Eric
                            Pro/Fi Cinema Speaker project: "From the Ashes"

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                            • #15
                              Re: Xmax in a horn?

                              Originally posted by mdocod View Post
                              The reason it's "so good" IMO...

                              Regards,
                              Eric
                              IMO the reason it's "so good" is the guy that wrote it. Remember his name and search for more info posted by him. As far as I know, there's no one more knowledgeable about horns and willing to share as that guy.

                              He's got at least a couple of other insanely helpful tutorials, and you could educate yourself just by searching for posts authored by him in the various forums he's involved in.

                              His posts regarding proper horn folding are gold, it's especially illuminating when he points out that MOST people don't build what they simulate, as he shows by breaking complex horns down into 30+ segments to accurately simulate all aspects of the horn (like the expanding and contracting mess you get going around bends).

                              I wish he was around when I was learning about horns, it would have saved me so much time and frustration...
                              Don't even try
                              to sort out the lies
                              it's worse to try to understand.

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