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i've caught the bug :( Want to make a small as possible BT speaker.

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  • #46
    Originally posted by Chris Roemer View Post
    In WinISD (or any box model program, really) that "-3dB" line is (generally) considered the box's "bottom end". The sound at -3dB is only half as loud as at ZER0, and typically drops like a rock below that. Those PR curves are just down too low (@ 50-60Hz) to really be noticeable. SOMEtimes guys will "tune" that low (aiming for the -6dB line), but that's more with bigger woofers (and maybe counting on more "room gain"). These little guys move such a small amount of air that they'll basically sound like they run out of gas at more like 100 (losing nearly your entire bottom octave of bass).
    hmmm, cant say you havent warned me in the past about a good ported system over a PR. jumped in with both feet on that one, should get the gear delivered tomorrow (and yep, got the peerless). Makes a lot of sense now as in WiniSD, every gram you add to the PR the Hz drops.

    it isnt a huge loss, but stuck with a $17 AUD radiator in the worse case. Back up plan, port. As you've used these drivers before and i think you can gather what i'm going for, do you think a box that size is just right, too small? and do you agree with the 20mm port 5 inch long? I see why Jake suggested 0.08cu.ft as it lifts that curve up about 2db's on the graph, but i'm thinking that i'm getting up in the box size for me to be considering a mini boom box of sorts, its going to be hard to compete with the TEBM's in the boombox as it has been sized nicely to my tastes, if i was thinking of going bigger i would have grabbed a small sub and full ranges and made something to make me smile like a 70's-80's ghettoblaster..

    i wont be cutting anything until saturday/sunday so still have a full day up my sleeve for some last minute CAD work prior to going too far.

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    • #47
      The nd65-8 utilize .05cf. The 4ohm version requires a little more space of .08cf. I wouldn't go with less space on the 4ohm.

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      • #48
        Don't know if jake is using some kind of online "calculator" or what - but nothing wrong with .055cf for the 4ohmer - nothing at all.
        THESE are the specs I'm talkin' about: Qes 0.68, Qms 5.56, (=Qts of 0.606) Vas 0.019cf, Fs 89.5 - 0.055cf box w/a 3/4"x5" port (Fb low 60s)
        Going larger puts more (somewhat undesirable - IF you can avoid it) "ripple" in the rolloff.

        ONE thing you can do (IF you don't have a DATS, or can't measure your own T/S parms) is to model ALL vers. of "specs" you can get a hold of (in WinISD). You'll see that there will be certain "alignments" that won't be HORRIBLE no matter which end of the specs YOUR drivers fall on. That's the alignment EYE would shoot for.

        Here're other specs I've seen (in the past - OR measured):
        Qes 0.80, Qms 5.76 (Qts 0.70), Vas 0.027, Fs 84 - (older specs - possibly orig?)
        Qes 1.02, Qms 4.30 (Qts 0.82), Vas 0.008, Fs 138 - (I measured these - probably an older pair that need MORE break-in !)
        I'd pick an alignment that works "OK" w/either of the 1st 2 sets (ignoring the 3rd - for now)

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        • #49
          Originally posted by Chris Roemer View Post
          Don't know if jake is using some kind of online "calculator" or what - but nothing wrong with .055cf for the 4ohmer - nothing at all.
          THESE are the specs I'm talkin' about: Qes 0.68, Qms 5.56, (=Qts of 0.606) Vas 0.019cf, Fs 89.5 - 0.055cf box w/a 3/4"x5" port (Fb low 60s)
          Going larger puts more (somewhat undesirable - IF you can avoid it) "ripple" in the rolloff.

          ONE thing you can do (IF you don't have a DATS, or can't measure your own T/S parms) is to model ALL vers. of "specs" you can get a hold of (in WinISD). You'll see that there will be certain "alignments" that won't be HORRIBLE no matter which end of the specs YOUR drivers fall on. That's the alignment EYE would shoot for.

          Here're other specs I've seen (in the past - OR measured):
          Qes 0.80, Qms 5.76 (Qts 0.70), Vas 0.027, Fs 84 - (older specs - possibly orig?)
          Qes 1.02, Qms 4.30 (Qts 0.82), Vas 0.008, Fs 138 - (I measured these - probably an older pair that need MORE break-in !)
          I'd pick an alignment that works "OK" w/either of the 1st 2 sets (ignoring the 3rd - for now)
          You cannot appreciate how small these things are until you have them in your hands....the ND65 are tiny...pulled out the callipers and the extent of frame is 2.5" and woofer looks to be less than 2". Interesting to see how these go do like a challenge

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          • #50
            Yup. THESE really benefit from rear-mounting (like on a piece of 1/8" hardboard - Masonite). Be wary of their need to breathe on the BACK side. If you put them on the front of a 3/4" baffle and cut w/a circle-hole saw - they'd barely be able to breathe at all. They ALMOST "exhaust" sideways.

            Also, I had to smear a thin layer of RTV silicone around the frame and NOT over-tighten mounting screws or the frame won't seal properly.

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            • #51
              Originally posted by Chris Roemer View Post
              Yup. THESE really benefit from rear-mounting (like on a piece of 1/8" hardboard - Masonite). Be wary of their need to breathe on the BACK side. If you put them on the front of a 3/4" baffle and cut w/a circle-hole saw - they'd barely be able to breathe at all. They ALMOST "exhaust" sideways.

              Also, I had to smear a thin layer of RTV silicone around the frame and NOT over-tighten mounting screws or the frame won't seal properly.
              I definitely will be rear mounting these, my OCD would trigger seeing a non symmetrical frame on the outside lol. Will mount and either hot glue or silicone, thanks for the tip

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              • #52
                [QUOTE=Chris Roemer;n1405100]Don't know if jake is using some kind of online "calculator"
                It's simply what Dayton reccommends, and what worked for me ;)

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                • #53
                  Started the build, tried to kerf a tight bend than before and it was a nightmare, didnt work at all so pulled out another piece and decided to make a baby version of the bigger boombox. Might try paint the entire thing with a few colours....who knows.

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                  • #54
                    Well after all that and out of frustration not being able to do what I originally wanted, it would appear that I've actually built two 0.065cuft enclosures or a single of 0.14cu.ft without a divider. Guess the width of.the unit was driving this, but guess it can't hurt, except for the fact it is now longer than 300mm (12inches)

                    My other boom box had enclosures of 0.15cuft so without putting them side by side yet, I'm assuming this one will be just less than half the overall size.

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