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Issues with a Overnight 2.5 build.

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  • Issues with a Overnight 2.5 build.


    Built another pair of 2.5way Overnights for a buddy at works', father in law. Everything's finished except for the feet so I decided to bring them in and give everything the once over.

    Measurements were taken with REW @1 meter, on the back patio. They measure pretty close to each other. 1/48th smoothing.

    Click image for larger version

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    DATS shows this. Nice little wrinkle @180hz. and I need to adjust the box tuning a little .
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    Without much time listening things sounded ok till we got to Madonna's Vogue. There are these bamboo sounding percussion pieces that are outside the right speaker, then her voice comes in outside the left speaker. Her voice didn't. Percussion was outside the right speaker, and her voice was instead in between the speakers. Not good. Reversed the channels and her voice was outside the right and the percussion was between the speakers.

    Measurements show I have a little work to do, but not that bad for a beginner.

    So what went wrong? Something to do with phase? Would that not show up on these plots?

    Click image for larger version

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    ... and is there an easy way to rotate that pic?


    http://techtalk.parts-express.com/fo...khanspires-but
    http://techtalk.parts-express.com/fo...pico-neo-build
    http://techtalk.parts-express.com/fo...ensation-build

  • #2
    Did you DATS each individual woofer?
    That lower Z-plot (below tuning) SEEMs like an air "leak" to me (woofer gasket, maybe)?
    Your tuning freqs. DO match.

    Comment


    • #3
      Is that made from pine? If so, did you deaden it? If you don't you will have resonance problems. I;m not quite sure I understand your problem fully, but just an FYI in the future, pine, being a soft wood can really resonate, it is best to line it with some MDF or hardboard.
      All about Speaker Design YouTube Channel

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      • #4
        Originally posted by Altoid View Post
        Is that made from pine? If so, did you deaden it? If you don't you will have resonance problems. I;m not quite sure I understand your problem fully, but just an FYI in the future, pine, being a soft wood can really resonate, it is best to line it with some MDF or hardboard.
        Yes, no2 yellow pine from the local lumber yard, I'll go through their stash and pick out the straightest and knottiest pieces. Last time I used three h-braces and glued small pieces of cement board to the walls. This time only one h-brace and large pieces of cement board glued to the walls with some carpet padding and a little pillow stuffing. I'm sure the cement board's no miracle worker, but it adds considerable mass, and I think it helps quite a bit.

        The problem is, with the mentioned song, certain sounds should be floating to the outside of the speakers, one pulls the trick off, the other doesn't.

        Didn't consider a leak. I did use the supplied gaskets that came with the b4n's on one speaker and weather stripping on the other. I thought the gaskets looked too small, but they're what was supplied with the woofers. I'll check that out.

        aha ... how did I miss this?




        Thinking I got one tweeter reversed, but why didn't it effect freq response @ crossover?
        Last edited by Kornbread; 03-05-2018, 04:27 PM.
        http://techtalk.parts-express.com/fo...khanspires-but
        http://techtalk.parts-express.com/fo...pico-neo-build
        http://techtalk.parts-express.com/fo...ensation-build

        Comment


        • #5
          It sounds like something is out of phase. I would test the driver terminals with a battery, and ensure that the cones go out when + on the battery is attached to + on the terminals. (AA or AAA battery and a foot of speaker cable and you have a testing jig)
          Isn't it about time we started answering rhetorical questions?

          Paul Carmody's DIY Audio Projects
          Twitter: @undefinition1

          Comment


          • #6
            Originally posted by Paul Carmody View Post
            It sounds like something is out of phase. I would test the driver terminals with a battery, and ensure that the cones go out when + on the battery is attached to + on the terminals. (AA or AAA battery and a foot of speaker cable and you have a testing jig)
            I had this exact issue when building my OS TMM's. One of the drivers had the polarity reversed.

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            • #7
              Sorry for the large double posted phase/spl graphs, for some reason I can't seem to edit the post. The lower trace in the graphs is phase. Look what it does above 3k.

              Did the ole battery test, all woofers are in phase. I'll pull the woofers and check their seal, and check the tweeter polarity at the same time. The woofers were a tight fit, didn't router the recess large enough to allow for the lacquer buildup, they're going to be a real bear to pull out without damaging something.
              http://techtalk.parts-express.com/fo...khanspires-but
              http://techtalk.parts-express.com/fo...pico-neo-build
              http://techtalk.parts-express.com/fo...ensation-build

              Comment


              • #8
                Your were right Chris, it was an air leak. Those small gaskets the b4n's come with are just to thin to do the job, replaced them with some dense window foam seal tape, and now both speakers impedance traces overlay. Weather has changed for the worse, and I like to do the freq (with phase) measurements outside, so those will have to wait.

                Click image for larger version

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                Switched the tweeter polarity on the left speaker, things are better. But for the life of me, I can't figure out why the right side places images outside the speaker much better than the left. When inputs to the amp are reversed, the right side still places those images better, when amp channels are reversed, when the speakers themselves exchange places ... it's still the right speaker that places those sounds outside the bounds of the speaker and into the corner of the room.

                Next attempt to correct this will be draping some quilts over some of the stuff sitting near the speakers and see what that does.

                Then things get scary.

                I'm wondering if my hearing may be coming into question.

                http://techtalk.parts-express.com/fo...khanspires-but
                http://techtalk.parts-express.com/fo...pico-neo-build
                http://techtalk.parts-express.com/fo...ensation-build

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