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  • MLTL question for Paul K, others

    I have some SS 18w/8545K woofers, and I'd like to try an experiment or two or three with them.

    First off, lots of people seem to say they sound good in a good ol' 15L vented box, so I may try that first. The F3 is simmed somewhere around 45 Hz, but it varies depending on what software you ask. Knowing Scan Speak, although that's not "wall-shaking" extension, I imagine the bass is still very excellent nonetheless.

    But I was browsing Troels' website and came across a suggestion of using a similar SS woofer in a transmission line. This dropped the F3 about 15 Hz!

    I'll be the first to admit I know very little about Transmission Lines. But I've heard enough of Paul's designs (and looked at the CAD drawings) to know that the sound of a Mass-Loaded transmission line does have a very musical, natural quality, and they also don't seem like much extra work to construct, compared to just a regular vented box.

    So Paul, since you are pretty much the only one I know of who can work that crazy math cad software, is it possible to get a MLTL design using this woofer? Can you help me out?

    Thanks very much!
    Isn't it about time we started answering rhetorical questions?

    Paul Carmody's DIY Audio Projects
    Twitter: @undefinition1

  • #2
    Re: What T/S values do you want me to use?

    I'd be happy to model an ML-TL for you and these drivers. I need to know what T/S values you want me to use; those from SS, ones from your actual measurements or ones from someone else's measurements (Zaph?). Also, I need to know what your cabinet size and shape restrictions are. I can't promise miracles, like a 15-Hz F3, and results, in my experience, are almost always not very good with low-Qts drivers. The 8545's Qts is spec'd at 0.27 and with some series resistance, like from an inductor, it will be a bit higher and might work out satisfactorily but not great, I suspect.
    Paul

    Originally posted by undefinition View Post
    I have some SS 18w/8545K woofers, and I'd like to try an experiment or two or three with them.

    First off, lots of people seem to say they sound good in a good ol' 15L vented box, so I may try that first. The F3 is simmed somewhere around 45 Hz, but it varies depending on what software you ask. Knowing Scan Speak, although that's not "wall-shaking" extension, I imagine the bass is still very excellent nonetheless.

    But I was browsing Troels' website and came across a suggestion of using a similar SS woofer in a transmission line. This dropped the F3 about 15 Hz!

    I'll be the first to admit I know very little about Transmission Lines. But I've heard enough of Paul's designs (and looked at the CAD drawings) to know that the sound of a Mass-Loaded transmission line does have a very musical, natural quality, and they also don't seem like much extra work to construct, compared to just a regular vented box.

    So Paul, since you are pretty much the only one I know of who can work that crazy math cad software, is it possible to get a MLTL design using this woofer? Can you help me out?

    Thanks very much!

    Comment


    • #3
      Re: MLTL question for Paul K, others

      Originally posted by undefinition View Post
      I have some SS 18w/8545K woofers, and I'd like to try an experiment or two or three with them.

      First off, lots of people seem to say they sound good in a good ol' 15L vented box, so I may try that first. The F3 is simmed somewhere around 45 Hz, but it varies depending on what software you ask. Knowing Scan Speak, although that's not "wall-shaking" extension, I imagine the bass is still very excellent nonetheless.

      But I was browsing Troels' website and came across a suggestion of using a similar SS woofer in a transmission line. This dropped the F3 about 15 Hz!

      I'll be the first to admit I know very little about Transmission Lines. But I've heard enough of Paul's designs (and looked at the CAD drawings) to know that the sound of a Mass-Loaded transmission line does have a very musical, natural quality, and they also don't seem like much extra work to construct, compared to just a regular vented box.

      So Paul, since you are pretty much the only one I know of who can work that crazy math cad software, is it possible to get a MLTL design using this woofer? Can you help me out?

      Thanks very much!
      I think you are trying to get something the woofer does not want to do. I raised its qts by adding a 50 watt 2 ohm resistor and a high ohm inductor. yeah I know don't ever add a resistor right to the positive lead on a woofer. this brought the new qts to .366 in a sealed box that gives an f3 of 54 hz in a 14.5 liter box with a qtc of .73 just a simple 6db low pass crossover a 50 watt resistor and a .9mh inductor pe part 255-046 is the inductor low passes at 1860hz. with out the resistor system the qts is .27 and a sealed box of 11 liters gets you a f3 of 75 and a qtc of .6. trust me it sounds pretty good with the resistor and the inductor in a sealed box of 15 liters. If you mix and active crossover on top of it it will sound really good. a have a rane 23 i run a scanspeak 23w from 30hz to 60hz the 18w from 60hz to 1860hz and a scanspeak 2905 tweeter from 1860hz and up. that woofer can sound really good from 60hz and up sealed you can try it in a tl but it won't sound right below 45hz or so.

      Comment


      • #4
        Re: Why are my 18w/8545K meas so different than Scan Speak?

        Originally posted by Paul K. View Post
        I'd be happy to model an ML-TL for you and these drivers. I need to know what T/S values you want me to use; those from SS, ones from your actual measurements or ones from someone else's measurements (Zaph?). Also, I need to know what your cabinet size and shape restrictions are. I can't promise miracles, like a 15-Hz F3, and results, in my experience, are almost always not very good with low-Qts drivers. The 8545's Qts is spec'd at 0.27 and with some series resistance, like from an inductor, it will be a bit higher and might work out satisfactorily but not great, I suspect.
        Hmm. Now this is weird. I've had these for a while, but hadn't bothered measuring them. What I'm getting is this:
        Fs: 41 Hz
        Re: 5.6 Ohm
        Qms: 4.73
        Qes: .57
        Vas: 21.5 L
        Le: .27

        which is markedly different than the mfr specs:
        http://www.madisound.com/catalog/PDF...w_8545k00e.pdf

        Maybe I'm measuring wrong. I don't do T/S measurements too often, but my measurements usually come out pretty close to mfr specs.

        Anyway, whatever happens, I'm trying for a baffle width of about 9".
        Isn't it about time we started answering rhetorical questions?

        Paul Carmody's DIY Audio Projects
        Twitter: @undefinition1

        Comment


        • #5
          Re: MLTL question for Paul K, others

          Are there any Excel sheets with the calculations floating around on the net for this configuration? Like something similar to Unibox for example.

          Comment


          • #6
            Re: MLTL question for Paul K, others

            Originally posted by Jed K. View Post
            Are there any Excel sheets with the calculations floating around on the net for this configuration? Like something similar to Unibox for example.
            You have to order the MathCad spreadsheets from Martin J. King, our utmost authority on TL-modeling. AFAIK, there is not any other spreadsheet that does what these can do. IIRC, they are $25 for a yearly subscription.
            Later,
            Wolf
            "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
            "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
            "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
            "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

            *InDIYana event website*

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            http://techtalk.parts-express.com/blog.php?u=4102

            Comment


            • #7
              Re: Undefinition, YGM

              The modeling was very successful, IMO. I sent you an email at your AOL address that contains several graphs and a description of the required cabinet build. I hope it meets your wants and you like it. Let me know if you need anything further.
              Paul

              Comment

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