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  • Boombox help

    My brother snagged a 5 of each audax HM100C0 woofers, and audax tw025m1b tweeters. We were thinking of making two boom box's or two sets of bookshelf speakers with these. Do you guys think these drivers are worth messing with or is it a waste of time? I've attached what specs I could dig up about these. Thanks for any assistance. He is coming up this weekend, thought I could help him cut some baffles and let him finish the boxes at home when he has time.
    Attached Files

  • #2
    Mostly due to their pretty low Q(ts), almost down to .20, they aren't prone to generate much bass in a box. Probably BEST used at mids in a 3-way, that said . . .

    For small bookshelf (or desktop) speakers, you CAN get them to have output down to around 80Hz (where handing them off to a small sub (think TangBand W5/W6) could make for a nice, compact, full-range system). A vented box about 0.10 cu.ft. w/a 1-1/4" ID port tube that's 5" long will accomplish that. They wouldn't take more than about 8w RMS to reach Xmax in that cab, so a small amp (Lepai 2020) should be just about right. That tweeter should cross well near 2.5kHz. I believe they came with "ferrofluid", hopefully it hasn't dried out (which isn't exactly normal, but CAN happen). An impedance sweep could indicate that, by looking at the Fs peak. To get the most out of them, I'd go with a "custom" crossover, not an "off-the-shelf" (pre-made) unit.

    A pair would make for a 0.2cf boombox, a rather nice size. The port tubes can exit the box ends, if that helps to fit them in there. They were considered VERY good drivers - about 20 yrs. ago. Nothing wrong w/using them today either. Those woofers are carbon-fiber w/(NOT "foam")rubber surrounds IIRC, and have REALLY gone up in value over the years.

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    • #3
      Thanks for the advice Chris. I conjured up a simple crossover using this http://www.calsci.com/audio/X-Overs1b.html as a guide.

      Off topic, I've been building some Dayton 8's MTM's, just waiting on a few back ordered components and they'll be complete. Really looking forward to testing them out!
      Attached Files

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      • #4
        That one won't do (same as a prebuilt or "textbook" XO) since they assume the drivers hava a flat response AND impedance profile, neither of which are true.
        I'll whip one up for you, though. A day or two.

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        • #5
          Right on, thanks man. Attached is a photo of the size of the box we are building for the speakers. I'll send you a beer or two for your time if you like.
          Attached Files

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          • #6
            That's for your boombox, right (a woofer & a tweeter on each side)?

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            • #7
              Originally posted by Chris Roemer View Post
              ... where handing them off to a small sub (think TangBand W5/W6) could make for a nice, compact, full-range system).
              Maybe a 2.1 system with a center TB in the boombox as the sub ...

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              • #8
                High Pass (for tweeter): a 6.8uF series cap, a 0.40mH shunt coil (to gnd, cheapest is OK here), and an L-pad using a 5 ohm series resistor and a 4 ohm parallel.
                The woofer wants a 1.5mH low DCR coil, w/a 4uF shunt cap, and a Zobel across the woofer using 10 ohms and 5uF.
                Around 84dB w/full BSC, crossing near 2.5kHz. Reverse polarity is NOT indicated on the tweeter.
                Last edited by Chris Roemer; 05-13-2017, 10:44 AM. Reason: changed polarity

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                • #9
                  Yea, we'll have to adjust the front a bit vertically to account for the giant flanges on these drivers. Thanks for the help Chris. I'll post some photos when we get it all done.

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                  • #10
                    Maybe try tweeter polarity both ways on this one, and go w/your ears?

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                    • #11
                      Does this schematic look correct? Thanks again for the help. Here is a link to what we put together today. https://drive.google.com/file/d/0B7J...ew?usp=sharing

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                      • #12
                        Your missing the 5 ohm series resistor.
                        Jeff

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                        • #13
                          Yup, and it belongs between the shunt coil and the 4n to ground.

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                          • #14
                            Ah, he must of left it out when I had him re draw it legibly so we could post a photo of it. Thanks again for all of the help. My brother seemed to really take an interest in this hobby. He is particularly interested in learning how to design a crossover like you did for us Chris. He is ordering the parts today so it'll probably be a few weeks before I see him again, but I'll be sure to post a final photo of the finished product. He spent a few years painting cars and aircraft, so I'm anxious myself to see what kind of finish he puts on the box. 

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