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TB W3-2141 Measured vs Published Specs

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  • TB W3-2141 Measured vs Published Specs

    Published (bottom) vs measured specs (below) don't add up...I guess that is what I've been reading from you guys all these years ...

    Now that I have a DATS.... this is what I've measured (Drivers been playing in garage for 4-5 months... Call them A and B samples )

    TB2143 (A) | TB2143 (B)
    Re: 6.907 | 6.685
    Fs : 107.7 | 109
    Qts: 0.5283 | 0.4944
    Qes: 0.6549 | 0.6038
    Qms: 2.734 | 2.728
    Le : 0.1782 | 0.1739
    Mms: 2.179 | 2.204
    Vas*: 2.086 | 1.925

    *added mass method (dime 2.268 g)

    One question: Drivers with open cone and center metal pole piece (as opposed closed center cap) -- Is it Ok to position the weight on one side of paper cone (unbalanced) as opposed to center of cone ??

    If not what do you guys recommend for added mass positioning?

    Tang Band Specs:

    Re 6.5
    Fs 75 Hz
    Vas 3.3 Liters
    Qts 0.39
    Qes 0.46
    Qms 2.51

  • #2
    For drivers with phase plugs I generally used Play-Doh. Measured out a mass of it on my postage scale and then rolled it into a worm and then joined the ends to form a ring. Smooshed the ring to the cone firmly enough to stick it well enough for testing (so it wouldn't be bounced about, which is why I ended up using this method for all my smaller woofer testing but that's another story) and let the measuring commence.

    shawn
    My favorite woofer is a Labrador retriever.

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    • #3
      Out of curiosity, were these drivers broken in? The sound of mine seemed to change drastically after ~50 hours of play time. I'm not even sure which (if any) of the specs would change during the break in period so if someone wants to share their wisdom on the topic it would be much appreciated.

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      • #4
        Originally posted by downfallat111 View Post
        Out of curiosity, were these drivers broken in? The sound of mine seemed to change drastically after ~50 hours of play time. I'm not even sure which (if any) of the specs would change during the break in period so if someone wants to share their wisdom on the topic it would be much appreciated.

        Yes plenty of break in...gentle at first, then thru series baffle step 0.56 mh |15 ohm and ocasional Loudness On garage receiver

        thank You Shawn ...heading to Walmart tomorrow for the Play-Doh....

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        • #5
          Here's the kicker-
          A lot of times my measured T/S of the TB drivers I've used come out modeling about the same as the manufacturer's spec T/S.

          I tend to use a medicine bottle or small plastic jar laid over-top/around of the voice coil former for phase plug drivers. I just measure and label it's mass, and add the typical 5g nickel or 3 in a stack atop of it. This avoids the imbalance issues, the phase plug, and other problems.

          The Play-doh is a good recommendation as well to get around the plug issue.
          Later,
          Wolf
          "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
          "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
          "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
          "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

          *InDIYana event website*

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          http://techtalk.parts-express.com/blog.php?u=4102

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          • #6
            If you model both sets of specs in a vented 0.12cf box, your measured drivers reach down near 80Hz (1.5"id x 5" long vent), whereas TB's "spec" can go about 10Hz lower (1.5"id x 7" long vent). Either set is Xmax limited to around 2w RMS at their F3. You can basically get the same results as the "spec" by going larger on the box (0.18cf) using a 1.5"id x 3-1/2" long port.

            A well broken-in driver will typically see Qts drop, w/a complimentary drop in Fs, and a rise in Vas. "Complimentary" to the point where the box models won't end up significantly different.

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