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POC #3 - tapped-horn build using the Dayton PA310-8

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  • POC #3 - tapped-horn build using the Dayton PA310-8

    Hi Everyone:

    I decided to make another attempt at building a tapped-horn, using some of the knowledge I gained from my "Proof of Concept #2" build. I opted to use the same driver, the Parts Express PA310-8 , but this time I opted to use a different folding technique, one that was used for another popular DIY tapped-horn build, the SS15, the main reason for this being that I needed to come up with a design that was a bit more transportable than POC#2, which threatened to break the back glass in my SUV every time I went over a bump in the road. I also decided to build it partly out of 12mm ply to reduce the weight of the box.

    To assist with coming up with the best dimensions for the new tapped-horn, I put together a spreadsheet that would allow me to adjust the various dimensions until I came up with a smooth expansion curve. The spreadsheet then gave me the appropriate parameters to insert into HornResp to simulate what the results would be like. By varying the dimensions in the spreadsheet and updating the simulation accordingly, I was able to come with a decent-looking alignment in a reasonably-sized box.

    I then proceeded to build the box. Ingredients: one sheet of 4 x 8 18mm ply, one sheet of 4 x 8 12mm ply, a box of drywall screws, wood-glue, a few bricks (to act a temporary table), some mounting screws for the driver and of course the driver. This time around I left no removable panels, as it's possible to mount the driver in the box without having to remove any panels. This build was a bit more difficult than my previous POC build due to the number of panels involved, the bracing, and the different thicknesses of ply used.

    Results:
    The tapped-horn seems to be performing as expected, with that "effortless sound" that characterized my previous proof-of-concept builds. Peak output is quite decent considering the capabilities of the driver that I'm using in it but, as per previous tapped-horn build, a steep high-pass filter needs to be used to address the out of band noise. Based on my listening impressions, the results to me appear to be equivalent, if not superior to, what was achieved with my previous POC build, and this is before I've done any fine-tuning, like perhaps adding some stuffing to see if the peak around 160 Hz could be reduced.

    The impedance curve of the built system suggests that further bracing than what's present in the images below may not be required, as the three impedance peaks are well-formed (as compared to my previous build, where the third peak was almost non-existent until I properly braced the box).

    One of the image below shows the measured frequency response (in red) , compared to the HornResp predictions (in brown). Also shown is the measured response with 48dB/oct filters applied at 30 Hz and 120 Hz (blue). The measured results suggest that Fb is between 38~39 Hz, an almost perfect match for the simulation. I suspect that it's slightly lower because the driver's structure is blocking the mouth a bit.

    This was another fun build and works quite well. Now I just need to decide how to finish the box .

    Click image for larger version

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    Project page: http://www.diysubwoofers.org/projects/other/PA310-TH2/
    Brian Steele
    www.diysubwoofers.org

  • #2
    Re: POC #3 - tapped-horn build using the Dayton PA310-8

    Some more images..

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    Brian Steele
    www.diysubwoofers.org

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    • #3
      Re: POC #3 - tapped-horn build using the Dayton PA310-8

      Another image... I decided to paint the POC#3 flat black. I'm still trying to figure out what I should do for a grille...

      Click image for larger version

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      Brian Steele
      www.diysubwoofers.org

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      • #4
        Re: POC #3 - tapped-horn build using the Dayton PA310-8

        Very nice Brian!
        Don't worry, if your parachute fails, you have the rest of your life to fix it.

        If we all did the things we are capable of doing, we would literally ASTOUND ourselves - Thomas A. Edison

        Some people collect stamps, Imelda Marcos collected shoes. I collect speakers.:D

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        • #5
          Re: POC #3 - tapped-horn build using the Dayton PA310-8

          Originally posted by Brian Steele View Post
          Another image... I decided to paint the POC#3 flat black. I'm still trying to figure out what I should do for a grille...

          [ATTACH=CONFIG]46398[/ATTACH]
          Good to see the LF capability of these drivers put to use.

          One small note: Tapped horns still benefit from boundary coupling, like most other horns or direct-radiating designs. Have you tried turning the cabinet 'upside down' so the horn mouth is on the floor? This might smooth out the bass response in your room.
          Best Regards,

          Rory Buszka
          Product Manager, Dayton Audio

          The best way to predict the future is to create it.

          Comment


          • #6
            Re: POC #3 - tapped-horn build using the Dayton PA310-8

            very nice and flat in the passband.
            Weight? and final dimensions?
            "Not a Speaker Designer - Not even on the Internet"
            "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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            • #7
              Re: POC #3 - tapped-horn build using the Dayton PA310-8

              Originally posted by Sydney View Post
              very nice and flat in the passband.
              Weight? and final dimensions?
              I'm going to redo the FR measurement, so don't hang your hat on that yet . It should be pretty close to the pictured measurement however.

              Weight: 55 Lbs.
              Dimensions: 32" x 22" x 14.5"
              Brian Steele
              www.diysubwoofers.org

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              • #8
                Re: POC #3 - tapped-horn build using the Dayton PA310-8

                Originally posted by [email protected] View Post
                One small note: Tapped horns still benefit from boundary coupling, like most other horns or direct-radiating designs. Have you tried turning the cabinet 'upside down' so the horn mouth is on the floor? This might smooth out the bass response in your room.
                Oh, it's only shown that way to give a comparison of its size to the Blastoramas. That and I still have to finish work on that last panel at the bottom . I actually intend to use it on its side, which should be the position that provides the lowest distortion.
                Brian Steele
                www.diysubwoofers.org

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                • #9
                  Re: POC #3 - tapped-horn build using the Dayton PA310-8

                  Here's an image that shows the difference in size between POC #2 (left) and POC #3 (right). POC #3 is lighter, suffers from less panel flex, and has dimensions that are better suited to transportation. It's a definite improvement over POC #2.

                  Click image for larger version

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                  Brian Steele
                  www.diysubwoofers.org

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                  • #10
                    Re: POC #3 - tapped-horn build using the Dayton PA310-8

                    Just updating an old thread with some new information.

                    I've discovered that including a bit of "cone compensation" can improve the performance of the POC3 a bit. In this case, this was done by adding a 3 L triangular piece of wood in the horn right below the driver. The attached graph shows the resulting FR, measured with a calibrated mic very close to the TH's mouth. The graph shows a response that's within +/- 2.5dB from ~42 Hz to about 130 Hz. Not too bad at all.

                    Click image for larger version

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                    Next step up is to try a restriction at S2, to see if I can flatten the response around 110-130 Hz....
                    Brian Steele
                    www.diysubwoofers.org

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                    • #11
                      Re: POC #3 - tapped-horn build using the Dayton PA310-8

                      Hi Brian,

                      Great job on getting such close agreement between modeled and measured responses. I know how hard it is getting HornResp to spit out a model that has a reasonably flat frequency response over a desired bandwidth.

                      Two questions:
                      - what kind of sensitivity are you seeing with this system vs. a sealed or simple ported system?
                      - what are you using for active EQ?

                      Regards,

                      Rob

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                      • #12
                        Re: POC #3 - tapped-horn build using the Dayton PA310-8

                        Originally posted by weinstro View Post
                        what kind of sensitivity are you seeing with this system vs. a sealed or simple ported system?
                        With THs you can shoot for efficiency, extension, or a combination of both, over a vented alignment with the same driver. I aimed for extension with the POC3, so the efficiency's about the same as a vented alignment, but the F3 is quite a bit lower. And of course, being a TH, there's no "port compression" to worry about.


                        Originally posted by weinstro View Post
                        what are you using for active EQ?
                        I'm driving it with a Behringer iNuke 3000DSP pro audio amplifier. The DSP capabilities of that amp are perfect for taming THs . .

                        This build was a learning experience, and I've put what I learned towards my next build - POC4, based on the B&C 18TBX100 18" driver. Of course, as result, POC4 is slightly larger then POC3 . Work is still in progress, but I've got a page covering the design and build here - http://www.diysubwoofers.org/projects/other/POC4/
                        Brian Steele
                        www.diysubwoofers.org

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                        • #13
                          The bandwidth and folding of this one mimics the SS15, but uses a 12" at a fraction of the cost. If the sensitivity can stack up to the SS15, this could be a nice smaller/cheaper alternative? How does the measured efficiency compare? I guess it IS xmax limited. But if the efficiency is there.......like 50-100w from some D amp boards could make this a very portable party speaker!!

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                          • #14
                            Originally posted by blamus View Post
                            The bandwidth and folding of this one mimics the SS15, but uses a 12" at a fraction of the cost. If the sensitivity can stack up to the SS15, this could be a nice smaller/cheaper alternative? How does the measured efficiency compare? I guess it IS xmax limited. But if the efficiency is there.......like 50-100w from some D amp boards could make this a very portable party speaker!!
                            ​The SS15 is a more sensitive and larger box, with a bigger driver. In a direct comparison, the SS15 will go louder. However, with its high resonance frequency, the SS15 can't do 40 Hz, the POC3 can, and it's a bit easier to transport. And you can buy three PA310s for the price of one Kapplite driver for the SS15...
                            Brian Steele
                            www.diysubwoofers.org

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                            • #15
                              Brian - do you happen to have dimensioned drawing for the POC3?
                              Sausage With Meat Sause, Please

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