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Subwoofer design question

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  • Subwoofer design question

    I just picked up a pair of Peerless 12" XLS subs from the PE buyout.

    I am at this point just beginning to consider a design for them. Apparently they really shine with a passive radiator. Their Xmax is listed as 12.5 mm.

    Dayton has the RSS315-PR 12 passive, which lists an Xmax of 26mm. Is this adequate as a single passive for the XLS driver?

  • #2
    I haven't modeled it, but I imagine you'd probably be okay with one. If I remember correctly, they're set up to work okay with a single active RS driver of the same size, with about the same excursion.
    I'd wait for a 'for sure' quick sim, though before ordering.

    *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
    *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

    *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF


    • #3
      Originally posted by skatz View Post
      I just picked up a pair of Peerless 12" XLS subs from the PE buyout.

      I am at this point just beginning to consider a design for them...
      Been used in a Tapped Horn as well.
      "Not a Speaker Designer - Not even on the Internet"
      “Pride is your greatest enemy, humility is your greatest friend.”
      "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."


      • #4
        nothing can stop me now


        • #5
          The rule of thumb guide I am remembering, I think correctly, is that the displacement of the passives should be 1.5-2 X that of the active driver. Generally, two passives per active. However in this case the Dayton passive has slightly bigger Sd than the active, but has a little more than twice the Xmax, so its displacement is >twice that of the XLS. So this should work OK, or is there something else I have not considered?*


          • #6
            I just ran the numbers, and you're not going to get super low output from this combo. I think the Qts is too low and the PR's mass, too high. The F3 will only be about 40hz, but the box is 1 cubic foot. Power handling above 25hz is basically unlimited--I tried 1000W and it was still comfortably below Xmax. For music, this would be one mighty little boomer.
            nothing can stop me now


            • #7

              Thanks for running the numbers, I haven't gotten that far yet.*

              Do me a favor and read the application notes that accompany the driver on the PE buyout site. I don't think it matches* up with what you are saying, but I haven't really had a chance to closely compare it.

              I am not too concerned with getting extremely low frequency though. But the app notes seem to say it will get below 40.*


              • #8
                Originally posted by Dirk View Post
                I just ran the numbers, and you're not going to get super low output from this combo. I think the Qts is too low and the PR's mass, too high. .
                Try an EBS alignment with it.

                Brian Steele


                • #9
                  Sure. All of the XLS & XXLS line I've experienced seem to behave similarly. The application notes do kind of "EBS" the boxes, and then use DSP to correct. That is a workable option, and you certainly could increase the volume for a greater shelf. It could probably go as big as 50L. It extends the low end down to the low 30s.
                  nothing can stop me now


                  • #10
                    Thanks I will need to look into this. I may come back to ask you more later on.*


                    • #11
                      You can get mid 20s (unboosted, w/an LP filter at 60Hz) out of a 1.5cf box, tuned to 28Hz. A 4" "Precision Port" that's 26" long will accomplish that; so would a slot port that's 1-1/4" x 11-1/2" x 30" long. Since this (older) driver is only rated at 150w RMS, it models out to 106dB @ 35Hz. A box something like my "Slot Ported 10in" should work OK. Just design a box w/a "chamber" volume of 1.5cf, then add the slot onto the bottom to make something that looks similar to this (THIS slot is about 4-1/2 FEET long) Click image for larger version

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                      • #12
                        Maybe I bought the wrong sub. I could return it to PE and get something else. The 315 sub is rated for 700 watts RMS, maybe I'd be better off with it?


                        • #13
                          I guess it comes down to your design goals. What are you after? As always, Hoffman's Iron Law is at play. The XLS and RSS315HF have similar sensitivity and Xmax. One plays moderately low in a tiny box, and the other goes super low in a box that's literally twice the volume. I know the XLS has a significantly lower thermal rating, but if the primary use is home theater, I would have no problems driving it with 300W or more because the duty cycle is way lower than it is with music.

                          Would I have chosen the XLS over the RSS315? Personally, not at this price. If I had the XLS in hand, would I send it back? Probably not. I still think with that PR it'd be an amazing small sub anchoring a 2.1 music setup.
                          nothing can stop me now


                          • #14
                            They were about the same price. I jumped at the XLS because I remembered drooling over it years ago, but I could never afford it. On the buyout I could, and jumped without really considering its competition. Now looking back I wonder if it is the right choice.*
                            Dirk, you seem to have a lot of experience with this driver, but I want to make sure I have it straight.* When you say that one plays moderately low in a tiny box, is that the XLS or the RS? As you can tell I have not modeled either one, I was going to do it this weekend, but that plan may not materialize this week.*
                            The use is for home theater, not particularly for music. Whatever music would be from the soundtrack.*
                            I am withing driving distance of PE, its just over an hour away, so exchanging it would not be a big deal on a Saturday.*


                            • #15
                              Since the matching PeerlessXXL PRs are NLA, the best match I've found is the ScanSpeak Discovery 30W/0-00 12" Subwoofer Passive Radiator.

                              The design is modeled on the well proven North Creek "Thunder"

                              The combo sounds great for both music and HT use. F3 around the mid 20s @ about 105db

                              Here's how the combo looks: