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Build Thread: SR71-inspired Center Channel

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  • #61
    Re: Build Thread: SR71-inspired Center Channel

    Originally posted by lunchmoney View Post
    Awwww CRAP

    I epoxied one of the magnets in backwards

    Poles being wonderful things, just reverse to corresponding magnet in the grill. If you use metal inserts in the grill, then it doesn't matter unless you are concerned about what the induced magnetic flux in the speaker grill is going to be in about 20 years...

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    • #62
      Re: Build Thread: SR71-inspired Center Channel

      Originally posted by lunchmoney View Post
      Awwww CRAP

      I epoxied one of the magnets in backwards

      Love these moments. Plan everything out precisely then screw up something simple. I usually bang my head on the work bench a couple times and walk around calling myself a dumb ***.
      Might be able to run a screw in from the back side slowly and pop it out. Maybe score around the edges so it doesn't blow out the MDF.
      Dave
      http://www.pellegreneacoustics.com/

      Trench Seam Method for MDF
      https://picasaweb.google.com/101632266659473725850

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      • #63
        Re: Build Thread: SR71-inspired Center Channel

        With magnets, I've had really good success by drilling a press-fit hole for them in the baffle. Spread a little 5-minute epoxy in the hole and press the magnet in so it is about 0.020 below the baffle face, then fill this 0.020 gap with epoxy (mound the epoxy a little proud of the baffle surface, to be sanded flush after drying). The baffle surface ends up being very flat.

        To keep the magnets oriented properly, keep them in a stack as you insert them into their holes, one at a time. Just mark one end of the magnet stack so you don't put any in backwards.

        When it comes time to mount magnets into the grill (assuming magnets in the grill and baffle), place the grill magnets onto the already-epoxied baffle magnets (this gets the polarity correct with no thought at all). Line the magnet holes on the grill with a little epoxy, and pick up the magnets by pressing the grill onto the baffle. Again, use a press-fit hole in the grills, so the magnets stay in the holes.
        Statements: "They usually kill the desire to build anything else."

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        • #64
          Re: Build Thread: SR71-inspired Center Channel

          Originally posted by davepellegrene View Post
          Love these moments. Plan everything out precisely then screw up something simple. I usually bang my head on the work bench a couple times and walk around calling myself a dumb ***.
          Might be able to run a screw in from the back side slowly and pop it out. Maybe score around the edges so it doesn't blow out the MDF.
          Dave
          I'm hoping I can simply shatter the magnet with a flat head screwdriver and a mallet... then I should be able to dig out the chunks.

          I have extra magnets, shouldn't be a big deal.

          These moments happen... as long as they don't happen in the form of an injury, it's all good.
          Form does not follow function
          Form is simultaneous to function

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          • #65
            Re: Build Thread: SR71-inspired Center Channel

            Shattering them could be the start of a new baffle.

            Any way you could glue a block behind, the run a screw in from the back to push even a corner of the magnet out, you're in much better shape. I bet these magnets will not shatter easily without liquid Nitrogen....

            Hve fun,
            Frank

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            • #66
              Re: Build Thread: SR71-inspired Center Channel

              Originally posted by fbov View Post
              Shattering them could be the start of a new baffle.
              Well, I wouldn't smack it THAT hard.

              I'll give it a shot... I think the magnets are quite brittle, it might work.
              Form does not follow function
              Form is simultaneous to function

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              • #67
                Re: Build Thread: SR71-inspired Center Channel

                Just fixed it, I got the magnet out by chiseling out a small slot next to the magnet, then ptying it out with a screwdriver. Then I simply filled the slot back in with the same epoxy that glued the now-correctly-oriented magnet back in.

                Not a big deal... onward...
                Form does not follow function
                Form is simultaneous to function

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                • #68
                  Re: Build Thread: SR71-inspired Center Channel

                  Magnets epoxied in, correctly this time :rolleyes:




                  Adding gaskets to the drivers... thin weather stripping with an adhesive backing...




                  Terminal cup screwed to the crossover door...




                  PE Black Ash vinyl laminate... not my finest work, but it was quick, easy, and doesn't really matter much, since you'll never see any of it anyways (this will be buried in an AV cabinet, and have a grill over it)... prior to applying the vinyl, I hit the edges of the driver cutouts with a black sharpie, in case the drivers sink down a tiny bit below the edge... don't wanna see any mdf poking through...




                  PE grill test fit (yup, it fits)... what a ridiculous coincidence how perfectly this fit...

                  Form does not follow function
                  Form is simultaneous to function

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                  • #69
                    Re: Build Thread: SR71-inspired Center Channel

                    That grill looks nice. I now wish I had rounded the edges on mine!
                    Statements: "They usually kill the desire to build anything else."

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                    • #70
                      Re: Build Thread: SR71-inspired Center Channel

                      Nice, one pristine object surrounded by the mess required to make it. Looks very nice for vinyl.

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                      • #71
                        Re: Build Thread: SR71-inspired Center Channel

                        Soldering the driver contacts, and installing the drivers




                        Drivers installed. It's more or less done, now it's time for test lead mania... next is to hook it up, I'm gonna be trying different values for the woofer inductor and tweeter resistor for a while before finally buttoning it up...



                        Form does not follow function
                        Form is simultaneous to function

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                        • #72
                          Re: Build Thread: SR71-inspired Center Channel

                          Annnnnnd.....done.

                          Well, almost... still voicing, trying different values for the woofer inductor and tweeter resistor, but it's awfully close even with the first attempt (values very close to those of the mains).

                          I'm very happy with it. Quite a bit cleaner and more detailed than the Tritrix center, with much more robust mid bass. Off axis performance seems excellent. Absolutely cannot tell that the driver layout is asymmetrical.

                          It matches my SR71 mains beautifully, so mission accomplished

                          I'll post the final crossover design with final component values after I dial it in and solder it up.

                          Some day I'll spread out the mains a bit more, once my kid is a bit older.

                          Big thanks to Zaph and MikeZ for all their help, and thanks to all those who took a look and chipped in their comments.





                          Form does not follow function
                          Form is simultaneous to function

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                          • #73
                            Re: Build Thread: SR71-inspired Center Channel

                            That is a very nice looking setup.

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                            • #74
                              Re: Build Thread: SR71-inspired Center Channel

                              Originally posted by djg View Post
                              That is a very nice looking setup.
                              Thanks. Ideally the mains would be a bit further apart, on stands, but for now it's a good baby-proof compromise.
                              Form does not follow function
                              Form is simultaneous to function

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                              • #75
                                Re: Build Thread: SR71-inspired Center Channel

                                This seems like an excellent project that a lot of people will probably take notice of. This would be enough to make me want to start pulling together parts and pieces to build four SR-71's and then your center (SR-71-C?) for the basis for an all around excellent home theater setup that can treat music well. Kudos.

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