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  • MLTL help request for 831735 driver

    I'm toying with a project for next year that would have 2 Peerless 831735 6.5" drivers wired in parallel at the bottom. In a bass reflex enclosure I was thinking of tuning 40L to 38Hz. I also wanted to try to model the speaker as a folded MLTL just to see what going down that path would look like.

    What I'm wondering is if someone could model the enclosure and snag screen shots of how to correctly enter the data into the MLTL Quarter Wave worksheet. When I gave it a shot at home I'm assuming I failed to enter a value(s) somewhere since it was rolling off much earlier than I'd expected and the speakers curve looked somewhat choppy.

    I'm trying to get the mathcad demo installed to give an example of what I was looking at on my laptop. The driver parameters and the idea for the enclosure is in the attached .jpg file.

    Take it easy
    Jay

    I attached what I'm inputting and what the response looks like to see if I'm using the sheet right. What I don't see is how to define what area is stuffed vs not stuffed etc. I figured out 1 mistake my tuning was previously too high I was using the default radius of 2 not thinking about the fact it would be 4" diameter.
    Attached Files
    Last edited by Brewski; 07-22-2011, 04:14 PM. Reason: Got Mathcad running
    "I like Brewski's threads, they always end up being hybrid beer/speaker threads based on the name of his newest creation." - Greywarden

    Breakfast Stout - HiVi RT2 II/Aurasound NS6
    Imperial Russian Stout - Vifa DX25/Fountek FW146/(2) Fountek FW168s - Built by Fastbike
    Ruination 2.5 way - Vifa DX25/Fountek FW168
    Levitation TM
    - Vifa BC25SG15/Fountek FW168

  • #2
    Re: MLTL help request for 831735 driver

    As far as I can tell you haven't made any data entry errors, but you simply need more volume in the line to get a lower F3. I modeled what you show and got the same results, and it appears a 40-Hz system tuning frequency is about right and what I saw in the modeling. Unless you just have to, I'd locate the port's center a little further away from that end of the line, like 3-4 inches. The TL design center, the midpoint between the two woofers, isn't ideal. It ought to be closer to 10" but you have no choice. Oh, those angled corner reflectors aren't doing any good other than to add structural support. They don't "guide" the sound waves around the corners (that's one of many TL myths); the stuffing gets rid of high frequencies, which would be deflected, but the wavelengths of the low frequencies are too long to even "see" those corner reflectors. Also, don't be hesitant to try higher stuffing densities, but not over 1 lb/ft3; you can juggle that and the cabinet volume to get the best compromise between bass response and response smoothness.
    Paul

    Originally posted by Brewski View Post
    I'm toying with a project for next year that would have 2 Peerless 831735 6.5" drivers wired in parallel at the bottom. In a bass reflex enclosure I was thinking of tuning 40L to 38Hz. I also wanted to try to model the speaker as a folded MLTL just to see what going down that path would look like.

    What I'm wondering is if someone could model the enclosure and snag screen shots of how to correctly enter the data into the MLTL Quarter Wave worksheet. When I gave it a shot at home I'm assuming I failed to enter a value(s) somewhere since it was rolling off much earlier than I'd expected and the speakers curve looked somewhat choppy.

    I'm trying to get the mathcad demo installed to give an example of what I was looking at on my laptop. The driver parameters and the idea for the enclosure is in the attached .jpg file.

    Take it easy
    Jay

    I attached what I'm inputting and what the response looks like to see if I'm using the sheet right. What I don't see is how to define what area is stuffed vs not stuffed etc. I figured out 1 mistake my tuning was previously too high I was using the default radius of 2 not thinking about the fact it would be 4" diameter.

    Comment


    • #3
      Re: MLTL help request for 831735 driver

      Thanks for taking a look Paul I wasn't sure if I was making a mistake or not. For the stuffing where in the line should I add a brace to contain the fill? is there a desired distance in the line such as 1/2, 2/3's etc of line length?

      Thanks for the help
      Jay
      "I like Brewski's threads, they always end up being hybrid beer/speaker threads based on the name of his newest creation." - Greywarden

      Breakfast Stout - HiVi RT2 II/Aurasound NS6
      Imperial Russian Stout - Vifa DX25/Fountek FW146/(2) Fountek FW168s - Built by Fastbike
      Ruination 2.5 way - Vifa DX25/Fountek FW168
      Levitation TM
      - Vifa BC25SG15/Fountek FW168

      Comment


      • #4
        Re: MLTL help request for 831735 driver

        Usually in an ML-TL I stuff the first 40-50% of the line's length. If you look at the modeling sheet where the various sections are defined, the first is the Top Section of Enclosure (Driver-->Top of Enclosure), and that one always contains stuffing in all of its 5 segments of Lc0-Lc4. The second section is Open Section of Enclosure (Driver-->Port Position) and you will likely want stuffing in its first two segments, Lo0 and Lo1, and perhaps also the third segment, Lo2.
        Paul

        Originally posted by Brewski View Post
        Thanks for taking a look Paul I wasn't sure if I was making a mistake or not. For the stuffing where in the line should I add a brace to contain the fill? is there a desired distance in the line such as 1/2, 2/3's etc of line length?

        Thanks for the help
        Jay

        Comment


        • #5
          Re: MLTL help request for 831735 driver

          Thanks For the help Paul I'll have to experiment with the fill once I really start building but I've got a model that looks fairly promising. One other question on the worksheet if I'm modeling two drivers changing the TS parameters to model two drivers in the MLTL is there an impact on the drivers X max value in the worksheet? I didn't know if it the X Max needed to be doubled divided etc...

          Take it easy
          Jay
          Attached Files
          "I like Brewski's threads, they always end up being hybrid beer/speaker threads based on the name of his newest creation." - Greywarden

          Breakfast Stout - HiVi RT2 II/Aurasound NS6
          Imperial Russian Stout - Vifa DX25/Fountek FW146/(2) Fountek FW168s - Built by Fastbike
          Ruination 2.5 way - Vifa DX25/Fountek FW168
          Levitation TM
          - Vifa BC25SG15/Fountek FW168

          Comment


          • #6
            Re: MLTL help request for 831735 driver

            You still model with Xmax for a single driver, no doubling or halving of it. Of course the equivalent driver you're now modeling with has twice the Sd of a single driver and that's where the increase in available output comes from. I'll give you a little more advice: model with the stuffing density and length that gives you the best overall system response, however you may define "best", then stuff it just like you modeled it and you should be good. I've never, ever changed the stuffing after I built a TL as modeled.
            Paul

            Originally posted by Brewski View Post
            Thanks For the help Paul I'll have to experiment with the fill once I really start building but I've got a model that looks fairly promising. One other question on the worksheet if I'm modeling two drivers changing the TS parameters to model two drivers in the MLTL is there an impact on the drivers X max value in the worksheet? I didn't know if it the X Max needed to be doubled divided etc...

            Take it easy
            Jay

            Comment


            • #7
              Re: MLTL help request for 831735 driver

              Sounds good thanks again. Hopefully You'll have cooler day out your way today I think we're supposed to get a break tomorrow so I might try to get to work on some other projects at that point.

              Take it easy
              Jay
              "I like Brewski's threads, they always end up being hybrid beer/speaker threads based on the name of his newest creation." - Greywarden

              Breakfast Stout - HiVi RT2 II/Aurasound NS6
              Imperial Russian Stout - Vifa DX25/Fountek FW146/(2) Fountek FW168s - Built by Fastbike
              Ruination 2.5 way - Vifa DX25/Fountek FW168
              Levitation TM
              - Vifa BC25SG15/Fountek FW168

              Comment

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