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Micro Sub build - Epique E150

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  • Micro Sub build - Epique E150

    Here's another build I have on the table. This is for a buddy of mine, targeting a Chevy industrial truck cab under the passenger seat

    Insert catchy project name here
    I have a 6.5x10x12 space to use under the passenger seat in the Chevy 1500 cab. We've installed a Pioneer head unit in the dash, no power amps and only 2 main speakers in the cab. That leaves 2 channels of head unit amplification unused and the built in capability of a 2 way crossover in the head unit. The goal is to get as deep of a response as possible under there, driven by the relatively small amount of power available from the head unit. To do that, I wanted deep response without cabinet gain for maximum efficiency, and a pair of 4 ohm loads to get as much power as possible. After some modeling of what is available, the new Epique E150 stood out as an excellent choice. The downsides are only the low efficiency, but I'm hoping the cabin gain makes up for some of that and we're not really looking for SPL here, just good deep bass. This is also an under-use of the Epique that could take a whole lot more power and deserves some more space and rigid cabinetry, but worth it IMO.

    I'm maximizing volume at the expense of a solid cabinet by using 1/2" MDF. Even with that there's only a quarter of a cubic foot to deal with. That gives me an F3 of 40Hz with a slot port. There are no excursion limits and I'm only hitting about 50W of real RMS power for reaching perhaps around 100dB peak in the cab.

    Click image for larger version

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    I attempted passive radiators as well, but we opted to save the cost and do a slot port with a 90 degree bend around the back.

    Click image for larger version

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    The port walls will be 1/8" hardboard with a slot routed into the top and bottom to keep them in place. If possible, I'll add a vertical brace in the form of a 1x2 to stiffen those largest panels.

    Boards are all cut, pending the 1/4" rabbet routes and the slot port guides.
    Electronics engineer, woofer enthusiast, and musician.
    Wogg Music
    Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

  • #2
    Are you concerned about the port walls vibrating?

    Comment


    • #3
      Originally posted by devnull View Post
      Are you concerned about the port walls vibrating?
      Perhaps a little, but not really. For reasons...

      Port tubes are generally thin and work fine with even flimsier materials, however being round has inherent stiffness so these flat walls are more suspect
      Designs like KEF intentionally use flexible port walls, though they model and design that on purpose so I can't claim that either
      I'll use a 1x2 at the corner to glue the heck out of and provide a reference for that 90 degree bend, that's where I'm most concerned
      I doubt the audibility of any port wall flexing in the final application, this is targeting a noisy and vibration filled truck cab
      Electronics engineer, woofer enthusiast, and musician.
      Wogg Music
      Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

      Comment


      • #4
        I am a newb when it comes to speaker design but am a retired mechanical engineer and would play it safe with some simple 1" x 1" bracing. (actually 3/4" x 3/4") If the 1/4" material is dadoed into the top and bottom of the cabinet the simpler solution would probably be okay. Just an opinion, no science behind it.

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        Comment


        • #5
          Originally posted by randyohoh View Post
          I am a newb when it comes to speaker design but am a retired mechanical engineer and would play it safe with some simple 1" x 1" bracing. (actually 3/4" x 3/4") If the 1/4" material is dadoed into the top and bottom of the cabinet the simpler solution would probably be okay. Just an opinion, no science behind it.

          Click image for larger version Name:	Brace.jpg Views:	0 Size:	33.8 KB ID:	1490453
          Not a bad idea. I'd like to avoid it if possible, every brace takes out net volume which is at a premium here, which is why I'm shooting for the thin hardboard in the first place.

          Curious if anyone has direct experience using thin wall slot ports.
          Electronics engineer, woofer enthusiast, and musician.
          Wogg Music
          Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

          Comment


          • #6
            I would think a spline of 1/8" hardboard down the middle of each port section (from port wall to cab wall) would be plenty to stiffen it up. And barely affect volume. JMHO.

            Comment


            • #7
              Made some progress on this build over the last couple weeks. It's been hard to find the time in between life and what not.

              I'm dealing with lots of limitations on my tooling capability, so this is a bit jankier than I'd prefer but should work alright. I'm going to risk the thin port walls and report back how it does when I seal it up and hit it with some power. Like I stated, the likelihood of hearing any artifacts from the cabinet in a noisy truck cab is pretty low. If I had the space and was putting this in a position like a under desk sub for a 2.1 setup, I'd increase the size and use the 1/2" stock for the slot port.

              Squish it together and clamp it quick!

              Click image for larger version

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              Inside dado'd port walls.

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              Baffle fit test, have to seal the inside before gluing this sucker. Ran out of glue to do that quite yet.

              Click image for larger version

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              Up next (after internal sealing and baffle glue down):
              Lots of filler and sanding to hide all those terrible tolerances. Then testing and Duratex!
              Attached Files
              Electronics engineer, woofer enthusiast, and musician.
              Wogg Music
              Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

              Comment


              • #8
                Any chance you'll be able to do an impedance measurement on the finished sub?

                Comment


                • #9
                  Definitely! I'll be looking for blips indicating resonances in the cabinet as well as validating the tuning.

                  Pretty much all my boxes und up tuned a little lower than designed, this one is probably no exception.
                  Electronics engineer, woofer enthusiast, and musician.
                  Wogg Music
                  Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

                  Comment


                  • #10
                    High aspect ratio ports will do that. :-/

                    Comment


                    • wogg
                      wogg commented
                      Editing a comment
                      Oh yeah... wall drag and all that. This one will definitely lose some efficiency in the port choice. The funny bit is my tubes also end up low... luckily I really like low bass so EBS alignments + a little EQ work well for me.

                  • #11
                    I'm curious to see how the 1/8" HDF ends up working. It's a lot stiffer than probably many people may think it is. I've made cabinets with curves that had only 2 layers of 1/8" HDF with no issues.

                    Just a thought experiment here, but I suspect that if the slot vent were curved slightly, not even that much, it would take away any chance of the port wall vibrating.

                    I love that driver and I'm curious to see how it works out.

                    TomZ
                    Zarbo Audio Projects Youtube Channel: https://www.youtube.com/channel/UCEZ...aFQSTl6NdOwgxQ * 320-641 Amp Review Youtube: https://youtu.be/ugjfcI5p6m0 *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

                    Comment


                    • #12
                      Sealed and tested before I work on wood fill and finish. I wired it in series and hit it with a test sweep to see if the cabinet rattled or otherwise sounded unacceptable. I measured 15.5VRMS at 60Hz for this test for about 30WRMS. This video is from 60 down to 30 and back up.



                      Edit: I didn't want to post that to YouTube or Facebook, so this is a direct link to my site. The video player doesn't seem to like it so try this:
                      http://woggmusic.com/download/TestSweep.mp4


                      Definitely chuffy down low, even with pretty low power and vent velocity. That's due to the 90degree slot port bend with no rounding and a fairly sloppy corner joint that I can't do much about. Not super awesome, a PR on the top would have been sweet for this thing and solved the box volume and chuff issues. That would have cost some more and been a bit tricky to fit in with that giant motor of that E150 in the way. That thing takes up nearly all the vertical space in the enclosure since the magnet is about the same size as the driver cutout.

                      Here's the impedance sweep, tuning landed at 35Hz and the curve looks good. No weird anomalies. This is without break in, so I expect a small amount of movement as it's put into use.

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                      This slot port design is definitely a major compromise for this little woofer.
                      Electronics engineer, woofer enthusiast, and musician.
                      Wogg Music
                      Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

                      Comment


                      • #13
                        I wonder how much the chuffing will be audible given the lower wattage it will see. Also, the fact that it's in a truck environment with the other speakers playing, and seeing how it will be under the seat, maybe the chuffing won't really be an issue?

                        That little thing can really move some air, can't it? Makes me laugh every time I crank mine up.

                        TomZ
                        Zarbo Audio Projects Youtube Channel: https://www.youtube.com/channel/UCEZ...aFQSTl6NdOwgxQ * 320-641 Amp Review Youtube: https://youtu.be/ugjfcI5p6m0 *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

                        Comment


                        • #14
                          Check out the 6 inch passive membrames on alieexpress. 2 of them can handle the full 200 watt of the epique e150

                          Comment


                          • wogg
                            wogg commented
                            Editing a comment
                            Those would be great for standing this thing up on a narrow end and using for an under the desk sub with the passives dual opposed on the sides. I was pondering a single designer series 8" passive but wasn't sure if it would handle the weight required to get the tuning low enough.

                        • #15
                          Originally posted by tomzarbo View Post
                          I wonder how much the chuffing will be audible given the lower wattage it will see. Also, the fact that it's in a truck environment with the other speakers playing, and seeing how it will be under the seat, maybe the chuffing won't really be an issue?

                          That little thing can really move some air, can't it? Makes me laugh every time I crank mine up.

                          TomZ
                          I don't think the port noise will be much of an issue in this case either.

                          I had some odd behavior with my test connection. I was hearing some distortion in the test, and hooked up my oscilloscope to see why and it was definitely clipping. I couldn't get the real amount of power that little woofer could take. I use the speaker connection to my studio monitors, which are fed through a SPA500 DSP amp that manages a sub before sending the signal through my Crest pro audio amp. I just bypass the high pass and fade the sub all the way down in the software to run tests. The amp should easily push 200+W into 8 ohms, rated at 450RMS per channel into 4, but I was seeing clipping at an extremely low level. I'll have to bypass the DSP amp for the next test to make sure that's not what is clipping my signals. It also could have been the test lead situation, I was using little clippies for the connections that could have been dropping a lot of voltage. The odd part is that the setup sounds just fine with music and the high pass / low pass setup as intended (which would point to the leads more than the amp).

                          Once I've got it together with the terminals I'll do another push with some real power to see just how much air that thing can really push
                          Electronics engineer, woofer enthusiast, and musician.
                          Wogg Music
                          Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

                          Comment

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