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  • Is this spec sheet inconsistent?

    Wolf , tagging you since this is the Missing Link woofer and you may know pretty quickly.

    I want to trace the graph of the Dynavox LW6004HR-N woofer. The top portion of the manufacturer's spec sheet shows sensitivity at 87.92 db @ 2.83V/1m, which is consistent with what WinISD calculates based on mfg's TS parameters.

    BUT...the mfg's frd curve "looks" lower to me. Since the frd curve is not a flat line maybe this curve really is a 87.92 SPL as listed in the top portion. But, right under the impedance graph in the LinearX "Notes" it says SPL = 85.9 db, which is consistent with 1w/1m. (It is a 6 ohm nominal woofer.) If the frd curve is at 1w/1m, I can just adjust for it when tracing, but I don't want to adjust by 2 db if the mfg's frd curve really is at 2.83v/1m. So, which sensitivity rating do you think is accurate for the frd curve shown?



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  • #2
    There's nothing inconsistent in the specs. 2.83V into a 6 ohm load is about 1.33W so a couple dB down at 1W is about right

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    • #3
      Originally posted by devnull View Post
      There's nothing inconsistent in the specs. 2.83V into a 6 ohm load is about 1.33W so a couple dB down at 1W is about right
      Right. So my question is whether the frd plot is at 1w or 2.83v?

      (I'm not saying the spec sheet is"wrong", but if they report sensitivity in the top section at 2.83v but measure the frd at 1w then that is not a "consistent" approach. Nothing wrong with that, just makes it harder for the user to get an accurate view without digging into the notes.)

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      • #4
        Coop used 1.415VAC/1m/7ms window when doing the plots for the measurement files. This yielded ~75.3dB in the 200-300 bandwidth and 81.5dB at 1k. I would wager the 200-300 is at -6dB due to Baffle step loss, or closer to 81.3dB at 1.415VAC. Doubling voltage to 2.83VAC should add +3dB, which is only 84.3dB. My measured impedance calculated 1W/spls are 85.4dB and 85.1dB via my S&L WT2.

        Since 8 ohms is 1W at 2.83V and 4 ohms is 2W at 2.83V, That means 6 ohms should be 1.5W at 2.83V.

        I'll leave you at that to make your decision,
        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*

        Photobucket pages:
        https://app.photobucket.com/u/wolf_teeth_speaker

        My blog/writeups/thoughts here at PE:
        http://techtalk.parts-express.com/blog.php?u=4102

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        • #5
          (For those who aren't aware;) passive XOs need all the drivers' FRDs to be generated at the same voltage (like the 2.83v "standard") or adjusted if not. In a passive XO, all drivers will be driven with a common voltage (from the power amp). This means any drivers measured at "1 watt" will need adjusting UNless they're 8ohm drivers (where 2.83v = 1w).

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          • #6
            Originally posted by Chris Roemer View Post
            (For those who aren't aware;) passive XOs need all the drivers' FRDs to be generated at the same voltage (like the 2.83v "standard") or adjusted if not. In a passive XO, all drivers will be driven with a common voltage (from the power amp). This means any drivers measured at "1 watt" will need adjusting UNless they're 8ohm drivers (where 2.83v = 1w).
            Exactly!
            And I know...I should measure actual drivers, in an actual box, with an actual microphone...in which case if I don't touch the volume knob I have the same voltage (regardless of its actual level) for all measurements. BUT, if I want to TRACE mfg frd curves to simulate, I need the frd curves for woofer and tweeter at the same voltage levels. If the manufacturer doesn't make it clear, or even worse makes it unclear, what conditions the frd curve is measured at then it makes it difficult to work with.

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            • #7
              I don't "quite" agree w/Ben's statement:

              "Since 8 ohms is 1W at 2.83V and 4 ohms is 2W at 2.83V, That means 6 ohms should be 1.5W at 2.83V."

              If 8n(ohms) = 1w @ 2.8(3)v and 4n = 2w @ 2.8v (which is fact), then?

              8n = 1.0w @ 2.8v = SAME SPL
              *6n = [email protected] 2.8v, so EYE would ADD +1dB to 1w plot to get equivalent plot @ 2.8v - for XO design
              5n = 1.6w @ 2.8v (ADD +2dB to 1w plot to get equivalent plot @ 2.8v - for XO design)
              4n = 2.0w @ 2.8v (ADD +3dB to 1w plot to get equivalent plot @ 2.8v - for XO design)

              So ... I'd trace the mfr. (LMS) plot and add +1dB to it to generate a 2.83v equiv. .FRD file for XO design.
              IMO, the FR plot "is what it is" (and it states the sensitivity as about 86dB - which APPEARS to be at 1w).
              If you add +1dB to the plot (for your FRD), it's close to 87dB/2.83v. THIS is what I'd use for a sim.
              The (upper) sensitivity (at 2.83v) is just generated off the calculated T/S parms, and is NOT as "useful" of data as an actual FR plot.

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              • #8
                I didn't do the math before, but I was pretty close.

                You are still not correct, Chris. 2.83*2.83/Z gets equates to power from Ohm's Law.
                2 ohms = 4W @ 2.83V
                4 ohms = 2W @ 2.83V
                5 ohms = 1.6W @ 2.83W
                6 ohms = 1.333W @ 2.83V
                8 ohms = 1W @ 2.83V

                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*

                Photobucket pages:
                https://app.photobucket.com/u/wolf_teeth_speaker

                My blog/writeups/thoughts here at PE:
                http://techtalk.parts-express.com/blog.php?u=4102

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                • #9
                  (I didn't do any math either - oops ;-} )

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