Announcement

Collapse
No announcement yet.

Isobaric loading

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    Originally posted by Paul K. View Post
    I have no knowledge of what the kaboominator is or was, but in any isobaric mounting configuration for a pair of drivers, there cannot be any increase in output SPL since only one driver is exposed to the room. While the thermal handling will be doubled simply due to there being two driven drivers, power requirements are also doubled without any increase in SPL for a specific input voltage compared to a single driver. While distortion may be reduced with the drivers facing each other, the only real advantage is cutting Vas and, therefore, Vb in half.
    Paul


    Always good to look at a link when you don't know what someone's referring to. 4 drivers, two clamshells in the kaboominator.

    Comment


    • #17
      Originally posted by johnk... View Post
      May I suggest to read my analysis and look at the calculated examples here: http://www.musicanddesign.com/Isobaric.html
      Thanks, I had not seen that before.
      John H

      Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

      Comment


      • #18
        +1!

        Comment


        • #19
          Originally posted by jhollander View Post
          Dan Neubecker's Scimitars are push pull in a vented cabinet.
          Same thing I did with my 442's. You get the cancellation of mechanical noises due to the orientation of the woofers, but this is not an isobaric configuration.
          A mains
          The Ventures
          Open Invit8tions
          RSR
          Sound Troopers
          Acorns
          442
          DGBG's
          The Monuments

          Comment


          • #20
            Well, excuuuuse me for making a mistake. My main point are the alleged benefits of isobaric drivers, other than the reduction in Vas and Vb, and you are perpetuating a misleading benefit when stating the kaboominator has 4 times the thermal handling compared to single driver. That actually means 4 times the input power is required with half of it wasted on the 2 drivers not radiating into the room and not generating any SPL. I, too, used an isobaric configuration pair of woofers in each of a pair of 3-way speakers specifically to reduce the required cabinet size, but that was a long time ago.
            Paul

            Originally posted by badman View Post


            Always good to look at a link when you don't know what someone's referring to. 4 drivers, two clamshells in the kaboominator.

            Comment


            • #21
              Originally posted by Paul K. View Post
              Well, excuuuuse me for making a mistake. My main point are the alleged benefits of isobaric drivers, other than the reduction in Vas and Vb, and you are perpetuating a misleading benefit when stating the kaboominator has 4 times the thermal handling compared to single driver. That actually means 4 times the input power is required with half of it wasted on the 2 drivers not radiating into the room and not generating any SPL. I, too, used an isobaric configuration pair of woofers in each of a pair of 3-way speakers specifically to reduce the required cabinet size, but that was a long time ago.
              Paul


              You're being rude, while also being wrong. If you'd read what I'm saying, it's that the 4 drivers in a dual clamshell, in a given box size, are as efficient as the same single driver in the same box, but with higher output, distortion and force cancellation, and more coil to dissipate the heat. Four times the power is required is nonsense. It's the exact same efficiency and sensitivity as a single unit of the same driver in the same box volume. There's a slight adjustment to be made for displaced volume from a second driver in the box, but that's a 1" dimensional change in 1 dimension, in most boxes.

              Comment


              • #22
                Originally posted by johnk... View Post
                May I suggest to read my analysis and look at the calculated examples here: http://www.musicanddesign.com/Isobaric.html

                John
                Interesting discussion of these mounting methods and results.
                Couple of questions. How are you seeing the order of the distortion on the graphs you published in this article? Is it a separate vertical line for each order of distortion? Also, how would two drivers conventionally mounted on the same box look in terms of these comparisons?

                Comment


                • #23
                  And, you don't think what you said wasn't rude or at least sarcastic:" Always good to look at a link when you don't know what someone's referring to."

                  Two drivers in an isobaric configuration and wired in parallel, use twice the power as a single driver to generate the same SPL because there's only one driver facing outward. It would seem to follow, then, that two pairs of two parallel-wired isobaric-configured drivers use 4 times the power to generate twice the SPL of a single driver for the same reason.


                  Originally posted by badman View Post
                  You're being rude, while also being wrong. If you'd read what I'm saying, it's that the 4 drivers in a dual clamshell, in a given box size, are as efficient as the same single driver in the same box, but with higher output, distortion and force cancellation, and more coil to dissipate the heat. Four times the power is required is nonsense. It's the exact same efficiency and sensitivity as a single unit of the same driver in the same box volume. There's a slight adjustment to be made for displaced volume from a second driver in the box, but that's a 1" dimensional change in 1 dimension, in most boxes.

                  Comment


                  • #24
                    Originally posted by Paul K. View Post
                    And, you don't think what you said wasn't rude or at least sarcastic:" Always good to look at a link when you don't know what someone's referring to."

                    Two drivers in an isobaric configuration and wired in parallel, use twice the power as a single driver to generate the same SPL because there's only one driver facing outward. It would seem to follow, then, that two pairs of two parallel-wired isobaric-configured drivers use 4 times the power to generate twice the SPL of a single driver for the same reason.
                    Isobaric creates a 1/2 VAS compound driver, leading to half box size and half efficiency. From there, you can simply consider it a normal driver, and when you add a second one, as with any woofer, you have to double the box size back to the same size required by a single non-compound driver, doubling efficiency back to nominal single-driver specs along with it. There's also the ability to customize the load with your series/parallel wiring configuration to maximize power input which is a nice benefit. To achieve the double output, it takes double the power, not quadruple, and the efficiency is consistent with a single driver in the same box size. Efficiency for a given alignment in normal subs is always tied to box size as you know.

                    To have it be 1/4 as efficient, you'd have to be creating some sort of doubly-compounded 4 driver composite with 1/4 the VAS and according box size, one could "string" the drivers I suppose with 4 drivers operating on the same airmass, but that'd be a pretty silly thing do do unless you'd gotten a crazy deal on some super-high vas drivers and could figure out an efficient way to mount them so that the internal space taken by drivers and coupling spaces was minimized. I mentioned a number of times that the benefits were for a given box size, which would preclude describing some sort of 4 driver isobaric.

                    The benefits described lead to a higher performance sub within a given box size, which is a key limiting factor for the vast majority of systems. My own ~12 cu ft. 4x12" dual Push-Pull manifold setup is not domestically acceptable for the vast majority of users, but if they wanted the same output, they could achieve it in 6 cu ft. by doubling the number of drivers from 4 to 8, while retaining the force cancellation (but losing some, but not all, of the distortion cancellation. It would be half as efficient. If they had 12 cubic feet to work with, and could swing the cost, 16 drivers would allow them to double the output in the same box size I'm currently using, quadruple power handling, and while distortion cancellation would be less, overall cone displacement would be reduced 50% so distortion would generally be lower overall.

                    Comment


                    • #25
                      Originally posted by skatz View Post


                      John
                      Interesting discussion of these mounting methods and results.
                      Couple of questions. How are you seeing the order of the distortion on the graphs you published in this article? Is it a separate vertical line for each order of distortion? Also, how would two drivers conventionally mounted on the same box look in terms of these comparisons?
                      The plots show the distortion magnitude at 2, 3, 4, ... up to 10 times the fundamental, thus 2nd, 3rd, 4th..... 1oth order harmonics, left to right. Two INENTICAL drives in the same box would be similar to the first three figures left, right, down one, left . It would not make a difference theoretically if each driver is in a separate box or both drives in a single box of twice the size.
                      John k.... Music and Design NaO dsp Dipole Loudspeakers.

                      Comment


                      • #26
                        So two drivers would not show lower distortion figures than a single driver at the same level?

                        Comment


                        • #27
                          Originally posted by skatz View Post
                          So two drivers would not show lower distortion figures than a single driver at the same level?
                          Oh. No. The plots are based on the same excursion so for the same SPL level you would expect lower distortion.The idea of my discussion is not about how distortion varies with SPL but in showing how distortion varies with configuration. How a push pull dual woofer system can reduce even order distortion but the push pull isobaric doesn't have the same cancelation properties.
                          John k.... Music and Design NaO dsp Dipole Loudspeakers.

                          Comment


                          • #28
                            You said the following, badman, and after I worked through the math more carefully, I determined you are correct:

                            "Isobaric creates a 1/2 VAS compound driver, leading to half box size and half efficiency. From there, you can simply consider it a normal driver, and when you add a second one, as with any woofer, you have to double the box size back to the same size required by a single non-compound driver, doubling efficiency back to nominal single-driver specs along with it. There's also the ability to customize the load with your series/parallel wiring configuration to maximize power input which is a nice benefit. To achieve the double output, it takes double the power, not quadruple, and the efficiency is consistent with a single driver in the same box size."

                            If box size is all important, an isobaric configuration, whether one uses a single pair of drivers or two pairs, is certainly the way to go as long as driver quality, and therefore performance, aren't unnecessarily sacrificed to get the smaller box. While I can't independently prove it one way or another, claims of reduced distortion appear to be questionable, however.

                            Paul

                            Comment


                            • #29
                              The distortion reduction from clamshell mounting is not the most effective way- push pull alignments are better. That, however, is offset for a given cab size (again- reasonably well matched drivers within budget is a factor) by allowing twice the SPL for a given amount of cone deflection in the same cab size, which as we all know will substantially reduce distortion for a given SPL. Turning your 12" sub into an effective 18" with force cancellation, even if clamshells were completely ineffective for distortion (which hasn't been my experience though I don't have measurement to back it up) is a pretty big benefit.

                              Comment

                              Working...
                              X