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  • #76
    Re: Third Order Transient Perfect Passive Crossover

    Originally posted by DDF View Post
    "Determining a time and distance of echo location" is just a fancy shmancy way of measuring minimum audible angle. Many many studies have done that. But that is completely different phenomenon than the perceived impact of group delay distortion.

    The GD distortion studies of real interest are the ones that show how it affects perceived tonality (and how that varies with SPL) since these apply directly to stereophony.
    Unless you are defining the fundamental and the harmonic as two different groups then I don't really see how group delay is of any significant interest. In which case it seems like simply saying don't put your woofer further away than your tweeter.

    I am confused by the phrase "minimum audible angle". I don't think there really is such a thing except at specific frequency and volume. Using this phrase implies a complex series of charts to when a simple formula would suffice.

    Originally posted by Pete Basel View Post
    Linkwitz's 1978 paper discusses compensation, or actually using what we call today a Linkwitz transform to realign the tweeter's highpass to form one section of a 4th order transfer function, see part 3 pages 14-16. Clearly at least Linkwitz knew about this issue back in 1978:
    http://www.linkwitzlab.com/Removed%2...x-sb80-3wy.htm

    This is off track, sorry Jeff not trying to take away from your new design here. Much of the last few pages should probably be split off into a new thread.
    Yes, I was wondering if Jeff is doing a variation on Linkwitz. The right half of my brain wants to say yes but the left half is confused by how his green phase line tracks every little squiggle of his SPL. He mentions "just the right driver" which would seem to suggest a linkwitz type approach.

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    • #77
      Re: Third Order Transient Perfect Passive Crossover

      Originally posted by moron#99 View Post
      Unless you are defining the fundamental and the harmonic as two different groups then I don't really see how group delay is of any significant interest. In which case it seems like simply saying don't put your woofer further away than your tweeter.

      I am confused by the phrase "minimum audible angle". I don't think there really is such a thing except at specific frequency and volume. Using this phrase implies a complex series of charts to when a simple formula would suffice.



      Yes, I was wondering if Jeff is doing a variation on Linkwitz. The right half of my brain wants to say yes but the left half is confused by how his green phase line tracks every little squiggle of his SPL. He mentions "just the right driver" which would seem to suggest a linkwitz type approach.
      In min-phase systems, phase is a direct result of frequency response, the rate of change. That's why the squiggles follow.
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      • #78
        Re: mildy OT, with a shoutout to Mr K

        Originally posted by moron#99 View Post
        Leach was generally clue less about loudspeakers. He conducted one of the most bone-headed experiments ever performed with regards to phase distortion. He could grind out formulas but lacked the intuitive ability to discern their meaning.
        My first "real" TM was the Leach Vifa 2 way in 2002. Never sounded right to me or my wife. I finally found a crossover by JohnK that fixed it good.

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        • #79
          Re: Third Order Transient Perfect Passive Crossover

          I think you guys are making way too much of this. It is just a crossover. Once you know the required transfer functions it is no different that any other crossover with regard to designing the passive filter. It happens to be close to TP. You construct a topoloigy that allows you to match the drivers' responses to the acoustic targets defined by the theory. Then adjust the offset.

          My old quasi-second order stuff can be found here. where you can still download the write up.
          John k.... Music and Design NaO dsp Dipole Loudspeakers.

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          • #80
            Re: Third Order Transient Perfect Passive Crossover

            Originally posted by DDF View Post
            Tilted baffles help lock this in much more easily. They also allow an easier attainment of smooth off axis response, along with smooth on axis.
            Absolutely, I am using a tilted baffle. The exact angle was determined through measurements.
            Click here for Jeff Bagby's Loudspeaker Design Software

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            • #81
              Re: Third Order Transient Perfect Passive Crossover

              Originally posted by johnk... View Post
              I think you guys are making way too much of this. It is just a crossover. Once you know the required transfer functions it is no different that any other crossover with regard to designing the passive filter. It happens to be close to TP. You construct a topoloigy that allows you to match the drivers' responses to the acoustic targets defined by the theory. Then adjust the offset.

              My old quasi-second order stuff can be found here. where you can still download the write up.
              Right, it's the same as designing any other crossover type to a target. You just have to have the target defined first.
              Click here for Jeff Bagby's Loudspeaker Design Software

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              • #82
                Re: Third Order Transient Perfect Passive Crossover

                In min-phase systems, phase is a direct result of frequency response, the rate of change. That's why the squiggles follow.
                Elementary, my dear Watson. That's as basic, where phase is concerned, as it gets. :rolleyes:
                Click here for Jeff Bagby's Loudspeaker Design Software

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                • #83
                  Re: Third Order Transient Perfect Passive Crossover

                  Originally posted by johnk... View Post
                  I think you guys are making way too much of this. It is just a crossover. .
                  C'mon John, that's just a low blow. I've seen you generously post page after page on web sites to describe TP crossovers with truly small incremental audible benefits (FWIW I've studied and heard and built TP xovers and they do make a difference IMO, but a very small one). The technique here certainly deserves a few squiggles on a board without being minimized as inconsequential.

                  It sounds like Jeff locked onto a crossover target I know I locked into myself a long time ago (and as did George Short at North Creek) as the best compromise for most system designs, and one I've tried to socialize over the years:
                  - sloped baffle
                  - soft knee thirds with staggered xover frequencies and mini-ripple response through xover

                  Benefits:
                  - flat response on axis through xover, but one easily tuned if a slight dip or bump is desired
                  - high out of band attenuation
                  - low complexity and parts count
                  - soft knees reduce tweeter "flare" off axis and provide better driver integration
                  - sloped baffle allows the power response to more closely mimic the on axis through xover
                  - low GD variation over frequency
                  - it sounds bloody good!

                  If anything, we should be making more a big deal about it to the point that others try it and report back.

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                  • #84
                    Re: Third Order Transient Perfect Passive Crossover

                    Originally posted by johnk... View Post
                    I think you guys are making way too much of this. It is just a crossover. Once you know the required transfer functions it is no different that any other crossover with regard to designing the passive filter. It happens to be close to TP. You construct a topoloigy that allows you to match the drivers' responses to the acoustic targets defined by the theory. Then adjust the offset.

                    My old quasi-second order stuff can be found here. where you can still download the write up.

                    And from that paper:

                    "In closing I would like to make a few comments about why I believe that transient perfect crossovers are superior to standard crossovers, be they the even ordered LR type of odd order Butterworth. The common argument is that we can not hear phase differences in musical tones. While this continues to be an area of argument between audiophiles and theorists, it remains an unresolved issue. However, perhaps a more relevant issue, and one that may be easier to grasp is that associated with the over shoot and ringing of the impulse response as shown in Figures 8, 9 and 10. For example, ignoring the observation that the tweeter is firing in the wrong direction in Figure 8, clearly there is still the issue of overshoot. The initial response to the impulse is significantly greater than the signal. In the real case there would be some limitation on this due to the limited band width of the tweeter, but never the less, this over shoot would result in excessive SPL levels for the initial rise to a sharp musical tone. This may be perceived as coloration to the sound of such instruments as a piano or other percussion instruments. Ultimately this may be perceived as unnatural or even fatiguing. Obviously, this depends on the sensitivity of the listener to such effects, but I believe that the issue goes beyond simply arguments on the audibility of phase shifts. From my personal experience I have found that among speakers that are relatively equal on all other factors, those with superior transient response prove to sound more natural in the long term when listened to on their design axis."

                    Now I am really confused:rolleyes:

                    I guess the bottom line that we need to worry about phase response and not just a flat frequency response or don't we? If it was easy it wouldn't be any fun.

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                    • #85
                      Re: Third Order Transient Perfect Passive Crossover

                      My point, and I think Jeff understands it, is that Jeff did all the hard work and from there it is not different than implimenting any crossover. I'm not at all minimizing what Jeff has done; take it for what it is and run with it if you like, once Jeff releases the details.

                      I mean, going off on Leach and all that really doesn't, in my opinion, add anything to the discussion. That's where I was coming from.
                      John k.... Music and Design NaO dsp Dipole Loudspeakers.

                      Comment


                      • #86
                        Re: Third Order Transient Perfect Passive Crossover

                        Originally posted by fdieck View Post
                        And from that paper:

                        "In closing I would like to make a few comments about why I believe that transient perfect crossovers are superior to standard crossovers, be they the even ordered LR type of odd order Butterworth. The common argument is that we can not hear phase differences in musical tones. While this continues to be an area of argument between audiophiles and theorists, it remains an unresolved issue. However, perhaps a more relevant issue, and one that may be easier to grasp is that associated with the over shoot and ringing of the impulse response as shown in Figures 8, 9 and 10. For example, ignoring the observation that the tweeter is firing in the wrong direction in Figure 8, clearly there is still the issue of overshoot. The initial response to the impulse is significantly greater than the signal. In the real case there would be some limitation on this due to the limited band width of the tweeter, but never the less, this over shoot would result in excessive SPL levels for the initial rise to a sharp musical tone. This may be perceived as coloration to the sound of such instruments as a piano or other percussion instruments. Ultimately this may be perceived as unnatural or even fatiguing. Obviously, this depends on the sensitivity of the listener to such effects, but I believe that the issue goes beyond simply arguments on the audibility of phase shifts. From my personal experience I have found that among speakers that are relatively equal on all other factors, those with superior transient response prove to sound more natural in the long term when listened to on their design axis."

                        Now I am really confused:rolleyes:

                        I guess the bottom line that we need to worry about phase response and not just a flat frequency response or don't we? If it was easy it wouldn't be any fun.
                        That was his old thinking, this is the latest:

                        Originally posted by johnk... View Post
                        Hi Jeff,

                        As you well know I used to be a very strong advocate of TP design. I could swear I could hear differences with could only be attributable to TP design. The problem today is that with codes like the Phase Arbitrator and the Bodzio UE I can correct any system to be linear phase while leaving everything else un altered (axial response, vertical and horizontal polar, power response...). And I can rapidly switch back and fourth between linear and nonlinear phase. The results I have found in doing so are that only on very limited material and under very limited conditions can I detect a difference between TP and nonTP systems. I am forced to conclude that ultimately the differences I used to hear had more to do with differing power or polar response than TP vs non TP.
                        His latest view agrees with findings in the literature from 1982:
                        http://techtalk.parts-express.com/sh...5&postcount=15

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                        • #87
                          Re: Third Order Transient Perfect Passive Crossover

                          Remember that I wrote that paper 11 years ago. In the past few years I have had the tools to look at this in cases where the speakers are not relatively equal on all other factors but identical on all other factors. And under those conditions I don't find such a significant difference.

                          The comments in the paper are accurate, but my opinion as to their importance has changed. Back then I was a strong proponent of TP crossovers. Today, not so much. I also listen much more casually now. I find that I enjoy listening much more if I'm not constantly trying to evaluate what is right or wrong with the reproduction.
                          John k.... Music and Design NaO dsp Dipole Loudspeakers.

                          Comment


                          • #88
                            Re: Third Order Transient Perfect Passive Crossover

                            Originally posted by johnk... View Post
                            ....
                            .... I also listen much more casually now. I find that I enjoy listening much more if I'm not constantly trying to evaluate what is right or wrong with the reproduction.

                            +1

                            I'm also of the opinion that if we spend too much energy listening to the sound of the music rather than music ITSELF, we are depriving ourselves of much of the emotional involvement with what the artist was conveying, and that is a diservice to the artist.
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                            • #89
                              Re: Third Order Transient Perfect Passive Crossover

                              Originally posted by johnk... View Post
                              Remember that I wrote that paper 11 years ago. In the past few years I have had the tools to look at this in cases where the speakers are not relatively equal on all other factors but identical on all other factors. And under those conditions I don't find such a significant difference.

                              The comments in the paper are accurate, but my opinion as to their importance has changed. Back then I was a strong proponent of TP crossovers. Today, not so much. I also listen much more casually now. I find that I enjoy listening much more if I'm not constantly trying to evaluate what is right or wrong with the reproduction.
                              did you do so while monitoring the output? I think if you wanted to perform a conclusive test with your DSP then you would need to measure the output and verify that there is no ringing.

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                              • #90
                                Re: Third Order Transient Perfect Passive Crossover

                                Originally posted by Pete Basel View Post
                                Cone breakup modes are complex.
                                Yes indeedie . . . and while they are commonly "modeled" as simple resonances (and thus "minimum phase") there just may be a little more to it than that . . .:rolleyes:
                                "It suggests that there is something that is happening in the real system that is not quite captured in the models."

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