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Large Open-Baffle Dipole Line-Array project underway

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  • Large Open-Baffle Dipole Line-Array project underway

    Hi Folks -
    Starting up previews of an upcoming OB project. Will document build process and post measured results.

    Using Bohlender Graebener Radia75 driver and 6) MB Quart 12" woofers per side (OWC304). Woofers chosen because of very high Q for OB, and excellent price/build quality @ $35 each. May upgrade to better woofers eventually. Some pics of renderings and early baffle construction.Click image for larger version

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    The perspective pic of the finished speakers is a rendering, and not finished work.

    Primary goals:
    1) an open baffle woofer column design capable of f3 @ 40hz
    2) output potential approaching 110db across entire range 40hz-20khz
    3) line source dispersion behavior from 80hz on up
    4) extremely low distortion
    5) audiophile-grade sound quality with pro-audio output potential
    6) imaging and spatial accuracy

    More soon. Ask questions, I'll answer ;)

    (edit) Mostly finished see bottom of post for more pics
    Last edited by Professor Niko; 07-29-2014, 07:25 PM.

  • #2
    Re: Large Open-Baffle Dipole Line-Array project underway

    Looks good! I'll be watching the development of your line array.
    If life were fair, Elvis would still be alive today and all the impersonators would be dead.
    ~ Johnny Carson

    Bungelow Ed's Photo Album http://techtalk.parts-express.com/album.php?u=8594

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    • #3
      Re: Large Open-Baffle Dipole Line-Array project underway

      Sick! I love me some open baffles. Good looking project also.

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      • #4
        Re: Large Open-Baffle Dipole Line-Array project underway

        Regarding woodwork / materials choices on baffles:

        One of my failings is in fine wood crafting. I don't have the patience nor the tools to use high quality hardwoods or veneers, but I won't accept anything that I perceive as acoustically compromised either. I tend to prototype designs by using thick particle board because of its excellent damping properties and low penalty for mistakes. I like to re-purpose materials intended for other applications, like stair treads or workbench tops you can buy at Lowes / Menards because they are typically thicker (1 1/4" or more) and are much cheaper than buying and laminating together 4'x8'x3/4" sheets.

        11-1/2" x 4' x 1 1/8" stair treads @ $7 built these
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        The new dipoles at the start of this thread are being built from $14 workbench tops 24"x72"x1 1/14"

        My hopes are to prototype / measure / evaluate this design making these low-cost choices within my carpentry skill range, and then maybe pay a woodworking artisan later to build some exceptional baffles.

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        • #5
          Re: Large Open-Baffle Dipole Line-Array project underway

          Does anyone know if the Basslist archives are still online? There was a gentleman (John Whittaker I believe was the name) who did quite a few studies of baffle shapes for OB BG75 planars. I bet you could learn a lot from them.
          --
          "Based on my library and laboratory research, I have concluded, as have others, that the best measures of speaker quality are frequency response and dispersion pattern. I have not found any credible research showing that most of the differences we hear among loudspeakers cannot be explained by examining these two variables." -Alvin Foster, 22 BAS Speaker 2 (May, 1999)

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          • #6
            Re: Large Open-Baffle Dipole Line-Array project underway

            Originally posted by Pallas View Post
            Does anyone know if the Basslist archives are still online? There was a gentleman (John Whittaker I believe was the name) who did quite a few studies of baffle shapes for OB BG75 planars. I bet you could learn a lot from them.
            Thanks Pallas -
            I found the whole study. Tons of information and pretty much a must read for anyone thinking about using the B&G Radia RD40 through RD75 drivers. This guy is a monster. Gonna take a few days to process it all. I wonder if the current BG RD75s are the same build as those used in this study from 97-98? They have to have been updated in the last 17 years....?

            http://web.archive.org/web/200807090.../dbsindex.html

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            • #7
              Some Measurements

              I was doing a driver fitment test before routing in all the 3/4" radius on all the edges, and I decided on a whim to wire up the drivers and test it out as a sub / LFE channel.

              I'm running them up tp 80Hz with no EQing / preamp running flat. Straight signal with no processing except 80 Lowpass @ 2nd order. Dayton iphone omni mic with calibrated file loaded in to Audio Tools FFT. Adcom GFA555 with each channel running 3 woofers into 2.66ohms per side.....so somewhere in the 350watt per channel range for each 3 drivers. Pink noise.

              I thought these numbers were very promising IMO for an unEQed open baffle. My design goals included usable flat output to 40Hz At one point I had them pushing 105dB. Once I add in the other side with 6 more woofers there should be some serious output potential. I was impressed on how clean, articulate, and musical this set up was in the deepest bass.

              Click image for larger version

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              • #8
                Re: Some Measurements

                interesting project!
                It"ll bee interesting to see the measured data as well as your crossover development.
                http://www.diy-ny.com/

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                • #9
                  Re: Some Measurements

                  Finally got the BG RD75s in after months of backorder. Some pics

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