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  • Please help with a new sub woofer project.

    I am planning to convert a leather ottoman into a subwoofer. A few things that I know and bunch of questions:

    1. Ottoman measures 39' x 39' x 19" (h). Estimated intern space for speaker box: 33" x 33" x 13", in case of using 3/4" mdf, internal volume would be 6.6 ft3.
    2. To use external Amp, the ottoman sits a good 5-6' from TV and amps, so easier just to run speaker cable than power+signal cables.
    3. Pairing to exiting KEF main that good for til about 100 Hz. Would love it if the sub can go down to say 20Hz or 25Hz.
    4. Prefer sealed design or passive rad, not for audio reason but didn't want anything to make a home in that ottoman. I know, it's a lol requirement.

    Help:

    1. In case of external amp, does it main Receiver sub out ---> power amp ---> driver posts? So there should be some sort of protection filter etc.?
    2. Driver or drivers recommendation needed.
    3. Can seal design with 6ft3 go low enough?

    Thanks for helping.

  • #2
    What's your budget? You can definitely get down to 25 in 6.6 cubit ft, with a big sub and DSP. I'd think with an ottoman your drivers would be down-firing, in which case you'd need a PR with lots of XMech. If you're worried about animals (ferrets?)or toys finding their way through the port, you can always add a grill outside or a screen at the inside end of your port.

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    • #3
      6.6ft^3 can host a pair of RSS315HF-4 drivers. I would recommend side firing one to either side of the ottoman, and you do have enough height to do so. This will cancel out the vibrations of the cabinet itself. I'd also place a main partition down the internal diagonal as a major brace, and then square-brace up the corners to either side of it. If you want the PRs, you have the other 2 sides for those and the option to get much lower in frequency. Sealed (PR is not a sealed box) will not give you the extension you desire. PRs should not go on the bottom. A simple cloth grill over the drive units/PRs will suffice for stealth purposes.

      Click image for larger version

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      Hope that helps,
      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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      • #4
        Thanks guys, I haven't set a budget yet, I think the wood work would be $100 or so? Basically a sheet of 3/4 and another 1" or just two 3/4" sheets? Haven't get down to drawing yet. And I do have unused power amps, assuming I don't need additional filter or such. Got to be down firing though, the thing is leather and side firing won't pass the aesthetic of you know who ....

        I live in the desert so we have lots of crickets, didn't want them to get too comfy in the enclosure, but ported is of course doable, if it helps the driver to deeper. So far, I found this driver by browsing Part-Express's catalog, it might do the trick, but there must be others too?

        https://www.parts-express.com/dayton...-coil--295-512

        Sealed Volume: 2.8 ft. Sealed F3 ~34 Hz
        Vented Volume: 5.58 ft. Vented F3 ~ 17 Hz




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        • #5
          The DCS380 will do the same f3 sealed. With a lower roll off slope sealed might be the way to go when including room gain. The crown XLS1002 (a separate amp) will include protection plus a programmable high pass.
          John H

          Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

          Comment


          • #6
            Originally posted by jhollander View Post
            The DCS380 will do the same f3 sealed. With a lower roll off slope sealed might be the way to go when including room gain. The crown XLS1002 (a separate amp) will include protection plus a programmable high pass.

            Thanks for the tip on Crown, sounded like a plan. Got a question on DCS380, per P-E's product page:

            Sealed Volume: 3.84 ft.³Sealed F3 ~ 40 Hz
            Vented Volume: 12.77 ft.³Vented F3 ~ 21 Hz

            The F3 with 3.84 ft3 sealed was quoted at 40hz, How does one figure out the F3 at bigger enclosure, in my case 6ft3? Vented volume of 12.77ft3 is impossible in my ottoman.

            Comment


            • #7
              To model a driver in another volume you need a box modeling program. The picture below is of unibox. There are several other free ones online. Many people here will do a quick box sizing if you ask
              John H

              Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

              Comment


              • #8
                Thanks jhollander, it took a bit for this newbie to figure out that you have done my ca l!!! vb is the volume, isn't it. 174 litre or 164 litres are close to 6ft3. If I read the data correctly, with 174 litre, the F3 would be 35 Hz in standard enclosure? or 163 liters with 34 Hz under design by Vb and Q. Did I get it right?

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                • #9
                  Yes you have it correct. The first portion of the spreadsheet shows the suggested 173.4 liters. I put in the 164 liters.
                  John H

                  Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

                  Comment


                  • #10
                    Thanks again jhollander! Much appreciated it.

                    Seems like it's coming down to two Dayton drivers, and take very different approach:

                    1. Dayton Audio UM12-22 12" Ultimax DVC Subwoofer 2 ohms Per Coil ---- $180
                    (https://www.parts-express.com/dayton...-coil--295-512)
                    With ported enclosure of recommended 5.58ft3 ported, it can achieve F3 of 17Hz.


                    2. Dayton Audio DCS380-4 15" Classic Subwoofer 4 Ohm ---- $90
                    (https://www.parts-express.com/dayton...4-ohm--295-470)
                    With sealed enclosure of 5.6ft3 (164l), it can achieve F3 of 35Hz.

                    jhollander and others, what could I expect performance wise from these two different approach? They will be used either with KEF iQ5 main or a pair of vintage Allison three. in a home theater 5.1 setting, But I watch chick flicks and music videos, I do enjoy the loud action stuff but few and far in between.
                    Dayton Audio UM12-22 12" Ultimax DVC Subwoofer 2 ohms Per Coil

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                    • #11
                      Sound wise the UM12-22 will vibrate a few more windows. It's probably best to tune it a bit higher in a smaller box. Because the UM12-22 works in smaller boxes either ported or sealed it might be easier to fit in an ottoman. If you port take a look at the port length to see how you will make it fit in your box.
                      John H

                      Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

                      Comment


                      • #12
                        May one expect faster and cleaner bass from DCS380-4 being15" in a sealed box. I was under the impression (could be entirely wrong impression) that seal box encourages tighter and faster bass, but smaller driver encourages faster and tighter bass. For my main speakers, the antique Allison was good for 40Hz but would like to protect it for stuff below 80Hz, The KEK iq5 didn't have much below 100Hz, so got to set at 100Hz if not a bit higher.

                        Comment


                        • #13
                          We're getting into some subjective areas. Clean bass could be described as low distortion and free of port noise. Both sealed and ported designs can accomplish this. Faster could be describe by group delay, both sealed and ported designs can be designed to have the same delay. Ported is just not as easy to get right as sealed imo. Both drivers work well sealed.

                          Blending to your existing speaker by using a subwoofer in an ottoman would not be my first idea. I'd lean toward 2 premade subs with plate amps first, then the UM12-22 because it's versatile, then the DCS380 sealed.

                          There are no really wrong decisions.
                          John H

                          Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

                          Comment


                          • #14
                            Have you considered the Ultimax 18? 6.6 cubic feet is about perfect for it's sealed requirements. And it has an f3 of 27hz before room gain or dsp. With any of these subs, I would get an amplifier with dsp.

                            Click image for larger version

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                            Dayton Audio UM18-22 18" Ultimax DVC Subwoofer 2 ohms Per Coil
                            All about Speaker Design YouTube Channel

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