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Two-way using Esoteric 7" Woofer & New Esoteric AMT, with First-Order XO?

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  • #31
    Originally posted by ernperkins View Post
    Noticed that you're not using any z-axis offset (mod delay in XSim). I don't know what it will be for these two drivers and maybe some one else has an estimate. The offset will change the phase response, especially at the crossover frequency. I wouldn't order any crossover components until you can measure and sim with the actual value.
    My understanding is that leaving XSim's mod delay set to zero for both drivers represents mounting both drivers flush with the baffle, and arranging the drivers on the baffle such that they are equidistant from the listener's ears. I know that in some designs that the tweeter must be moved further away to achieve time alignment, but the phase tracks better without any added delay in this simulation.

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    • #32
      Originally posted by dcibel View Post
      Looks like the datasheet data is being used for that AMT, it will be miles off. Real measurements always recommended for successful design, especially with decent drivers like these. Odd that you continued designing using manufacturer data after finding some guy on DIYA that measured the AMT and found it to have very sloped response, I'd trust his measurements . The Esoteric AMT response is similar to AMT3-4 but with a bit more extended response on both ends.
      Dcibel, I almost didn't get your joke! Did a double-take and realized they are your measurements! I just fed them through FPGraph Tracer, and I'm attaching the resulting files, as well as the far less compelling new XSim result (using derived phase). Sadly, the real world Esoteric AMT response rather ruins its prospects for easy integration with the 7" Esoteric woofer. Let us have the truth, though the heavens fall
      Attached Files

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      • #33
        Originally posted by stellarelephant View Post

        My understanding is that leaving XSim's mod delay set to zero for both drivers represents mounting both drivers flush with the baffle, and arranging the drivers on the baffle such that they are equidistant from the listener's ears. I know that in some designs that the tweeter must be moved further away to achieve time alignment, but the phase tracks better without any added delay in this simulation.
        It doesn't quite work that way in my experience - I don't think that's the intent either. The offset is to the acoustic center of the driver, not the front of the frame. It's not really something that you can measure with a ruler either - you either have to use measured data which includes time of flight/phase data, or you need to empirically discover the offset through a series of measurements and then derive minimum phase.

        You need to KNOW the delay before you can add it. Phase may track better in your simulation as it exists today - without the offset, but the sim isn't accurate without the correct offset. Basically, your sim won't match reality.

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        • stellarelephant
          stellarelephant commented
          Editing a comment
          Wow! I know that the acoustic center is always some distance behind the mounting plate, and I always assumed that this difference was accounted for in the phase data of PE's driver response files. If this is not the case, why doesn''t PE just tell us the distance between faceplate and acoustic center in the specs for each driver, to aid with modeling?

      • #34

        From your comment: Wow! I know that the acoustic center is always some distance behind the mounting plate, and I always assumed that this difference was accounted for in the phase data of PE's driver response files. If this is not the case, why doesn''t PE just tell us the distance between faceplate and acoustic center in the specs for each driver, to aid with modeling?

        The phase is dependent on the baffle (and crossover, but that's not relevant for this part of the discussion) via the frequency response, as speakers are minimum phase devices - meaning for each unique frequency response measurement, there is a single solution to the minimum phase of the driver. There's also an excess phase measurement, but that's specific to the particular situation and only has meaning in those specific situations - those that use excess phase files know how and when to use them, I'm just not one of them. Basically, the phase changes when you put the driver on a baffle that differs from that on which the manufacturer measured it.

        I've never seen any manufacturer publish acoustic centers (not saying it's never happened). It's not really best practice to design speakers without measurements. In the days before measurement equipment and software was readily available and somewhat affordable - a lot of speakers were designed by ear using the published manufacturers graphs. It's hard and you need a trained ear. There were a lot more bad designs. I created some of them.

        If you want to move forward (and you should, it's a great hobby), you should temper your expectations and perhaps give it a try with some cheap drivers to see if you like it and as a proof of concept that the single cap/coil XO with notches really has the benefits you think it does before you dive in with the Esoteric drivers as your second design. I'd hate to see you buy hundreds of dollars of drivers and not be satisfied and quit the hobby.

        You can build really, really, great speakers with humble drivers and thoughtful designs - take for example the Kii Three and its near-universal acclaim, which is reported to use a $70 Seas DXT tweeter and a few $30 peerless woofers (all of which could of course be modified versions of the retail ones) which has a list price of something crazy like $17,000/pair (which includes amplification) ...but still, the point should be made that expensive drivers are not required for world-class audio.

        There are many, many examples on this forum of excellent execution elevating humble drivers well beyond what they "should" be able to do. It'd be a dis-service to the many skilled members here to try to list them all, but designers such as Chris Roemer, Wolf, and the late Jeff Bagby all have excellent designs published.

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        • #35
          Where time align is concerned it's primarily an issue if the woofer and tweeter approach 180 degrees total phase shift within the crossover region. One way to minimize the potential for destructive interference is to use higher order filters, reducing the region of pass band overlap. From a real world practical standpoint having the tweeter acoustic center closer to the listener makes the speaker sound subjectively brighter, while having it further from the listener than the woofer makes the speaker sound subjectively duller. In extreme cases, usually when the HF is horn loaded, the horn is long and the crossover is in the lower midrange, more aggressive methods of time align are required. That situation is seldom seen today, but an example from the past where this was done was the Altec A-7. Between the length of the HF horn and the 500Hz crossover time align issues would have been severe, but they were addressed by horn loading of the woofer. It's widely assumed that the intent of the woofer horn was to increase sensitivity, but the actual reason was to place the woofer and HF driver acoustic centers on the same plane. There was even a procedure to acoustically measure the offset and physically move the HF horn back and forth to realize perfect alignment. Today one uses DSP to correct serious time align offset.
          www.billfitzmaurice.com
          www.billfitzmaurice.info/forum

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          • #36
            Adam and Bill,
            Thanks for the reality check. Sounds like my best bet as a beginner is to stick with proven designs or else experiment with cheaper drivers, ideally with the help of measurement gear and/or DSP, although I would aim for a passive XO for the permanent speaker, since I have built a DAC that I like.

            Coming from listening to full-range speakers for a while, I am hung up on the coherence factor. Here are a couple DIY designs that aim to achieve phase coherence with simple XOs. One flips the tweeter to the bottom to introduce delay, while the other uses a waveguide. I have also seen Troels Gravesen's website, which is full of stepped baffles. If anybody has any specific recommendations for other DIY speakers in this vein, please share.

            https://www.diyaudio.com/forums/full...f-monitor.html
            https://www.diyaudio.com/forums/mult...waveguide.html

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            • #37
              Originally posted by stellarelephant View Post
              ...my best bet as a beginner is to stick with proven designs or else experiment with cheaper drivers, ideally with the help of measurement gear and/or DSP, although I would aim for a passive XO for the permanent speaker, since I have built a DAC that I like.
              I would suggest starting with a nice proven design with a passive crossover. Except, build each loudspeaker with its drivers wired to separate external terminations (with reference designations clearly marked/labeled), and with its crossover in a separate external enclosure (likewise with reference designations clearly marked/labeled).

              Then you can experiment.

              Keep the original crossovers as baseline for future use and comparisons. You could try connecting it as an active loudspeaker with various DSP filters. And/or, build a second set of passive crossovers of your own design. Compare. Tweak. Refine. Maybe you circle back to the original, or maybe you find something better, but you will also learn much in the journey.
              "Our Nation’s interests are best served by fostering a peaceful global system comprised
              of interdependent networks of trade, finance, information, law, people and governance."
              - from the October 2007 U.S. Naval capstone doctrine
              A Cooperative Strategy for 21st Century Seapower
              (a lofty notion since removed in the March 2015 revision)

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              • #38
                I would check out Jeff Bagby's Kairos. The is a 23 page write-up and kit available on one of the other sites. It's right up your alley.

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