Announcement

Collapse
No announcement yet.

WinISD Passive Radiator Sub Build -Need Help-

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

  • WinISD Passive Radiator Sub Build -Need Help-

    Hi all,
    I'm probably the newest person to the forum since I just joined. I had a question about a few subwoofer builds that I'm creating through WinISD. I've been an Audiophile for several years and fixed speakers in the past, (refoamed surrounds, replaced drivers, etc.) but I've never built any from scratch. I'm trying to build a passive radiator sub with two radiators. (Dayton Audio DSA270-PR 10' Aluminum cone Passive radiator) (See attached for driver used) However, when I get everything figured out and modeled, WinISD says cone excursion occurs at 35 watts even though woofer is rated for 80 watts RMS. Even when I try to model a sealed or ported sub with the same driver, I run into the same problem. I'm quite stuck on what to do since I'd love to build it, but I don't want to blow the woofer. Any thoughts or ideas?
    Thanks in advance.
    Dayton Audio SD270A-88 10" DVC Subwoofer

  • #2
    That would be because there's no linear relationship between the voice coil thermal rating and the displacement limit. 6mm xmax is very short for a subwoofer. That's one of the reasons why it only costs $40.
    www.billfitzmaurice.com
    www.billfitzmaurice.info/forum

    Comment


    • #3
      Well, you didn't tell us the particulars of your design.
      Using that woofer and a pair of those PRs (w/80g added mass), I've got a box that'll take 80wRMS down below 30Hz at around 105dB.
      The box is 3.0 cf, the radiator pair tunes it to 27Hz, and the F3 is 30Hz.
      6mm Xmax occurs at 26Hz.

      Comment


      • #4
        Originally posted by Skysword View Post
        Any thoughts or ideas?
        Thanks in advance.
        Yup, you typed a lot, but really said nothing. Post up All the details.

        Comment


        • #5
          Sorry for leaving stuff out.
          I simulated a box that is 2.5 cf with an F3 of 32hz. However, the Fh of it is at 30hz. (Problem?)

          Dual PRs with 100g added mass and the Fs of the PRs at 15 hz (w/added mass)

          I'm also planning to use the Dayton Audio SA100 plate amp. 75W into 4 ohms, 100W into 8

          Sub would be run at 4 ohms. HPF on amp set at 18Hz, LPF set at 180Hz

          My xmax occurs first at 60Hz to 35Hz and then from 26Hz to past 10Hz

          Let me know if I left anything else out.

          Comment


          • #6
            For the price of that driver and two PRs you could have the DCS255-4. Put it in a 2 cu ft net ported cab tuned to 32Hz and you're able to handle at least 150w down to 28Hz.
            www.billfitzmaurice.com
            www.billfitzmaurice.info/forum

            Comment


            • #7
              I am SO SOrry ! MY DB had a bad value for Sd for the 10" DVC. (It has the 12"'s Sd, actually.)
              Having said that, just model the 12" instead (in either 2.5 or 3cf). Those 2 drivers have always wanted ABOUT the same size box (which is why I've never really considered a build w/the 10", as the 12" is larger and has (slightly) more Xmax, and power-handling.

              Still, ... Bill's right about the 10" DCS. Even more Xmax, and power-handling. A 4"id x 13" long port should do (unless you're really shooting for a PR design for some reason.

              Comment


              • #8
                There have been a few threads lately on this subject of power vs Xmax. The power rating really is only useful above a certain frequency; below there, Xmax is the limit on power, or you may ram the voice coil into the pole piece.
                Francis

                Comment


                • #9
                  That only happens if you go all the way to xlim, and it's the back plate that the coil hits. If you push past xmax without hitting xlim it just sounds bad, because THD skyrockets. Needless to say that's not a good thing either.
                  www.billfitzmaurice.com
                  www.billfitzmaurice.info/forum

                  Comment


                  • #10
                    So I'm still confused (regardless of which driver I use) on whether or not the cone excursion graph is accurate and if I should follow it? Will the driver blow or can I ignore it or what? I've read other posts regarding this and I've never seen an actual answer.
                    P.S. If the excursion hz (25 Hz) is lower than the lowest frequency response of the driver (31 Hz), will the driver play lower than what it's rated for? Using the DCS subwoofer, same cf of space, same PRs and amp.
                    Thanks
                    Dayton Audio DCS255-4 10" Classic Subwoofer 4 Ohm

                    Comment


                    • #11
                      The excursion graphs ARE accurate (as long as you've got the correct T/S parms in there). When the cone exceeds Xmax, distortion becomes quite noticeable. Many users will allow Xmax +15% (so, 6.9mm for an Xmax of 6.0mm).
                      On a "tuned" box (be it ported or PR'd) exceeding Xmax at the higher freq. (above tuning) will definitely sound bad.
                      If you actually have existing signal content below Fb, and the (plate) amp's HP filter doesn't roll it off, you'll probably not like the results.

                      Comment


                      • #12
                        Originally posted by Skysword View Post
                        Will the driver blow or can I ignore it or what? I've read other posts regarding this and I've never seen an actual answer.
                        I posted the actual answer:
                        (Damage) only happens if you go all the way to xlim, and it's the back plate that the coil hits. If you push past xmax without hitting xlim it just sounds bad, because THD skyrockets. Needless to say that's not a good thing either.

                        If the excursion hz (25 Hz) is lower than the lowest frequency response of the driver (31 Hz), will the driver play lower than what it's rated for?
                        A driver will play, or at least attempt to play, whatever signal you put into it. Keeping out frequency content that's lower than the driver should be attempting to reproduce is the job of a high pass filter, usually incorporated into the amp.

                        www.billfitzmaurice.com
                        www.billfitzmaurice.info/forum

                        Comment


                        • #13
                          Originally posted by billfitzmaurice View Post
                          I posted the actual answer:
                          (Damage) only happens if you go all the way to xlim, and it's the back plate that the coil hits. If you push past xmax without hitting xlim it just sounds bad, because THD skyrockets. Needless to say that's not a good thing either.

                          A driver will play, or at least attempt to play, whatever signal you put into it. Keeping out frequency content that's lower than the driver should be attempting to reproduce is the job of a high pass filter, usually incorporated into the amp.
                          Bill is right, I misspoke and should have said Xlim, not Xmax. Still, if you run the driver past Xmax a lot, the chances of it coming apart mechanically are increased, even if you don't immediately destroy it. The spider can become detached, or the surround.
                          Francis

                          Comment


                          • #14
                            Yep, running a driver even at xmax certainly isn't going to extend its useful life. Headroom in a driver is just as important as headroom in the rest of the signal chain.
                            www.billfitzmaurice.com
                            www.billfitzmaurice.info/forum

                            Comment

                            Working...
                            X