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2nd Build, First fried tweeter?

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  • 2nd Build, First fried tweeter?

    I've just completed a rush build of an MTM with Fostex FW137s and FT28Ds. I finished one, REALLY liked it, then built the next, hooked it up with the other, listened for a few minutes to hear that they worked (quietly- it was 3:00 AM), then went to sleep. This morning I woke up, hooked them to a different amp, and noticed one of the tweeters not functioning. Double checked everything and swapped it with the other tweeter. Apparently I have a blown tweeter.
    SO.... I THINK it worked the night before. I cannot be certain. Is there something I could've done to ruin it with just normal (quiet) usage for a few minutes? Thanks for any advice.

  • #2
    Re: 2nd Build, First fried tweeter?

    use a meter to see if it's within spec. If it comes back open it's blown. Tweeters are the easiest to blow. could be simply driver failure.

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    • #3
      Re: 2nd Build, First fried tweeter?

      Originally posted by Neis View Post
      I've just completed a rush build of an MTM with Fostex FW137s and FT28Ds. I finished one, REALLY liked it, then built the next, hooked it up with the other, listened for a few minutes to hear that they worked (quietly- it was 3:00 AM), then went to sleep. This morning I woke up, hooked them to a different amp, and noticed one of the tweeters not functioning. Double checked everything and swapped it with the other tweeter. Apparently I have a blown tweeter.
      SO.... I THINK it worked the night before. I cannot be certain. Is there something I could've done to ruin it with just normal (quiet) usage for a few minutes? Thanks for any advice.
      X-over schematic?
      “I cried because I had no shoes until I met a man who had no feet”

      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

      Comment


      • #4
        Re: 2nd Build, First fried tweeter?

        What were they hooked to overnight?

        I had a freak thing like this happen with both tweeters in my shop speakers when I changed my computer settings to hibernate a year or so ago. Apparently when I put it into hybernate before leaving the garage it began putting out some high frequency I couldn't hear and fried both of them at some point overnight. I had left the amp on as I always do, I know it wasn't a matter of spl's b/c I've put those xt19's through some serious punishment in that system and they just keep giving. The sound card is a middle of the road asus 196/24 model... I think it *may have to do with the el cheapo ECS motherboard in that computer. I've been pretty loyal to Gigabyte for several years but cheaped out the last time I upgraded that unit. I really need to go with some kind of outboard DAC/sound card solution.
        Buyout MTMWW

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        • #5
          Re: 2nd Build, First fried tweeter?

          X-over schematic?
          Click image for larger version

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          The two things that aren't labeled are .50 inductors. The two x-o's are identical. One works really nicely.
          What were they hooked to overnight? Nothing.

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          • #6
            Re: 2nd Build, First fried tweeter?

            Originally posted by thekorvers View Post
            X-over schematic?
            That's why this is the best forum for problem solving... people here will QC a XO for a stranger. Bravo.

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            • #7
              Re: 2nd Build, First fried tweeter?

              Originally posted by Neis View Post
              X-over schematic?
              [ATTACH=CONFIG]51603[/ATTACH]
              The two things that aren't labeled are .50 inductors. The two x-o's are identical. One works really nicely.
              What were they hooked to overnight? Nothing.
              Don't see anything here that would blow your tweeter. I would say that you have a bad tweeter, which is a shame as they are pretty pricy.
              “I cried because I had no shoes until I met a man who had no feet”

              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

              Comment


              • #8
                Re: 2nd Build, First fried tweeter?

                Thanks for the input. The X=O was suggested by Chris Roemer, so I figured it was solid. Does anyone see a place where I could've shorted it out or... anything? I don't want to buy another tweeter just to fry it. I'll go back and re-do all the connections in that X-O, but I would like to learn from any mistake I may have made.

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                • #9
                  Re: 2nd Build, First fried tweeter?

                  If any of the filter components were shorted, the worst case would be that it got a full-range signal (and all THREE components would need to be shorted for that to occur). Even that shouldn't hurt the tweeter at low listening levels.

                  If either of the caps went open, the tweeter would get no signal at all. If the coil went open, it'd be the equivalent of a single 4uF series cap (like a 1st order filter), and you'd still be -12dB down at Fs (1000 Hz).

                  Both amp channels still sound good? The remaining good tweeter still sounds good connected to either XO? The tweeter might measure (w/a cheap DMM) zero (shorted), or around 6 ohms (nominal), or open (infinite). Which is it? If "open", maybe one of the voice coil leads broke off the connection tab?

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                  • #10
                    Re: 2nd Build, First fried tweeter?

                    Took a while to get back to it. I double checked all the connections in the "bad" XO, tried the tweeter again... nothing. Tried it in the other cabinet... nothing. Tried the good tweeter in the "bad" XO... just fine. Also switched channels on the amp just to be sure. Bad tweeter. Multimeter shows infinite. If it is a broken tab, I cannot see any way to get in there to fix it. If someone here would like to take a crack at it... it is yours for the price of postage from MN. I have another on order. Should be in tomorrow. I will get it all set up and publish a build thread.

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                    • #11
                      Re: 2nd Build, First fried tweeter?

                      if you've a time and patience
                      maybe you could try to open the tweeter
                      look the voice coil lead

                      sometimes the voice coild lead and terminal not properly terminated

                      you should scrape the vc lead and resolder to the tweeter terminal

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