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Internal Bracing for RSS315HF Sealed Enclosure

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  • Internal Bracing for RSS315HF Sealed Enclosure

    I am looking to build a subwoofer for my overnight sensations MTMs (http://i.imgur.com/FQp23vW.jpg). From what I have read so far, a popular choice is the RSS315HF and pairing it with the SPA500 amp. As I have a Denon AVR-X4300H, it can support a left and a right sub. However, for right now I am going to build one and then a second if need be. As the primary use is music, I have been looking at 2 ft3 sealed enclosure.

    I found some plans from ZaphAudio.com but I like the H bracing in the PE sub kit more. Is it possible to mix and match cross bracing or does that affect the sound? Does anyone else have links to a sealed enclosure for this sub? I don't have the time to get into speaker enclosure design due to life, so I am just looking for a nice design.

  • #2
    Bracing is a very important part of any build. It helps prevent & control resonance. The higher the frequency band expected from a large driver the more important it becomes. My rule of thumb for >80hz x-over points is no panel left unbraced over 7” in any direction. That is based off of some white paper research by Toole, can’t recall the reference specifically right now. Yes it is slight overkill. Since wood is cheap and I am building it, why skimp out right? Combine that with Constrained Layer Damping enclosure, some Rockwool and it is virtually resonance and reflection free.

    I could argue that the CLD and rockwool are more effective in the midbass/midrange, though can still yield some benefits if the bass woofer is used up past 200hz or so.

    In short do some window/matrix bracing that covers every panel and ties all 6 panels together with no wall unbraced by more than 7”.

    Comment


    • #3
      If you make the common cubical sub box with speaker and plate amp, two of your 6 sides will have big holes in them. The other 4 should be braced. H shaped braces with the crosspiece in the middle of the panel are the norm. The elegant cnc cut interlocking braces you see on PE and DIY sound group boxes are very nice. If you don't have a cnc machine it's not necessary to duplicate that style. It's most important to tie the opposing sides together at the panel centers. H shaped braces fabricated from 3 separate pieces are fine, IMHO. Much simpler, using much less material. The most important part of the H brace is the crosspiece tying the opposing sides together. Taking into consideration component clearance of course.

      Your Overnight Sensations show you have some skills. I recommend you make a sub box in line with your tools, skill and aesthetic.

      Comment


      • #4
        Life got in the way of my intention to reply quicker than a week later...

        If I understand you guys correctly, I can copy the below images with the noted modifications? The gray box is just my design in Fusion 360, its taking me a little while to get used to it as compared to Inventor (I used Inventor at a previous job).

        While copying the CNC is overkill, I'm up for the challenge of doing it by hand...well....with the help of a jointer, router, table saw, sliding miter saw, and a bandsaw.

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        • #5
          IMO having clearance between the amp and a brace is not very important - an 1/8" would be fine by me. A bigger problem is obstructing the rear motor vent, which'll probably be at least as large as your thumb. I'd like to see maybe no bracing within 3/4" of that vent hole.

          If I were building that sub box, and had no supplied bracing, 1st I'd run a dowel from top to bottom and another from side-to-side (being exactly centered is not necessary, but you DO need clearance for the driver's rear vent), then I'd be tempted to run 4 dowels from front to back (at the driver's 1:30, 4:30, 7:30, and 10:30 positions - IF that's doable, not forgetting the rear mounted amp as well), IDEALLY (if the driver had 8 mounting holes) putting those dowels right behind 4 of those holes so mtg. screws could bite right into the dowels (behind the baffle).

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          • #6
            If you're inclined and have a set that'll fit your dowel (or purchase dowels that will) a forstner bit at 1/16 or 1/8 depth for each end is an added layer I find works very good. Of course I'm talking large dowels of reasonable length.

            A drill press is ideal, but hand held angle / level attachments are common.

            Once the last dry assembly including mortise depths is complete, this should make the dowels as effective as possible.

            The ones in my main stage are gorilla glued, not just screwed. Yes I love overkill, but I also like things lasting until the sun burns out when I can swing it.

            With the success I've had using them, forstners are now a staple and definitely going in an upcoming build to replace my aging subs. In fact they're now part of my procedure forever.

            Just another 2c.
            Last edited by Thump; 09-03-2018, 07:59 AM. Reason: Typo
            Feel free to rip my assumptions apart when wrong, or fix if close.

            Passive Radiators:
            All PR(s) Vd must be at-least double all woofer(s) Vd. Calc = Sd x Xmax to get Vd for all PR(s) and all woofer(s). A combined PR(s) Vd equal or > than a combined woofer(s) Vd is usable.
            Woofer(s) with large Xmax vs Sd, all PR(s) with Xmax at-least double all woofer(s) Xmax is usable.
            A PR max weight is said to be its Mms x3

            PR Systems - tight focus with key parameters.
            PR Speaker Design - thorough coverage.

            Comment


            • #7
              That driver is vented but I am not putting any bracing directly behind it. It seems like whether I use dowels or MDF it doesn't really matter. As long as all sides are braced?

              I have found people saying to use acousta stuff or sonic barrier or nothing, but it seems like it's just an opinion?

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              • #8
                Thanks to everyone for their comments. The sub sounds awesome!

                Comment


                • #9
                  Looks very nice, but Justin Timberlake?

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                  • #10
                    Wow, nice work ... that's a beautiful ensemble. Recently heard the same sub in the same size enclosure and it sounded terrific. Are you still thinking about a second sub?

                    Comment


                    • #11
                      Very nice and perfect match. You'll be enjoying the absolute hell out of that no doubt. Let the house shaking commence
                      Feel free to rip my assumptions apart when wrong, or fix if close.

                      Passive Radiators:
                      All PR(s) Vd must be at-least double all woofer(s) Vd. Calc = Sd x Xmax to get Vd for all PR(s) and all woofer(s). A combined PR(s) Vd equal or > than a combined woofer(s) Vd is usable.
                      Woofer(s) with large Xmax vs Sd, all PR(s) with Xmax at-least double all woofer(s) Xmax is usable.
                      A PR max weight is said to be its Mms x3

                      PR Systems - tight focus with key parameters.
                      PR Speaker Design - thorough coverage.

                      Comment


                      • #12
                        Originally posted by oldloder View Post
                        Wow, nice work ... that's a beautiful ensemble. Recently heard the same sub in the same size enclosure and it sounded terrific. Are you still thinking about a second sub?
                        My amp does have two sub outputs... One sub sounds great but I bet two subs would fill the space very nicely.

                        Comment

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