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  • Power to drivers in unconventional wiring scheme...

    So, my brain just isn't working right now, but I'm wondering about an unconventional wiring scheme and how much power is seen by each driver. Given:

    - Three DVC drivers, each with dual 3.5 ohm voice coils
    - Target the lowest impedance possible without dipping under 1 ohm

    Option 1) wire each set of voice coils in series to get three 7 ohm loads, then parallel all three to arrive at a final load of 2.3333 ohms. Given the symmetry of loads, I'm pretty sure each voice coil receives the same amount of power from the amplifier.

    Option 2) wire two of the drivers' voice coils in series to get two 7 ohm loads, then parallel those two loads with the other two 3.5 ohm voice coils for a final load of 1.1667 ohms. My brain is telling me that even though my final impedance load is closer to what I want, the voice coils may not be receiving the same amount of power. I think the two voice coils not wired in series will be receiving twice as much power as the other two drivers. But then I second guess myself and think that perhaps since all of the voice coils are the same impedance, they will get the same amount of power.

    I know there was a thread on here a little while back asking a similar question, but IIRC, the question was about wiring drivers together with different impedances.

  • #2
    Your brain is correct.
    Go with option 1.

    You could short one voice coil on each woofer and just wire the three remaining coils in parallel, but then your power handling would be cut in half.
    But if the amp you're driving them with can't supply the combined power handling of the three coils, you'd be fine.
    R = h/(2*pi*m*c) and don't you forget it! || Periodic Table as redrawn by Marshall Freerks and Ignatius Schumacher || King Crimson Radio

    Byzantium Project & Build Thread || MiniByzy Build Thread || 3 x Peerless 850439 HDS 3-way || 8" 2-way - RS28A/B&C8BG51


    95% of Climate Models Agree: The Observations Must be Wrong
    "Gravitational systems are the ashes of prior electrical systems.". - Hannes Alfven, Nobel Laureate, Plasma physicist.

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    • #3
      Thanks, Pete. I figured that was correct. There are some discrepancies in published MFG data and listed specs for the drivers I'm planning on using, so as for how much power they can take - well, I'm not exactly sure. I'm guessing its due to this being a driver revision. I've emailed both the MFG and the retailer for some clarification. At 2.3 ohms, the amp I'm planning on pairing them with will pump out plenty of power to get close to (or maybe exceed by a hair) the rated power. But, again, that depends on which spec I go by. Getting closer to 1 ohm would give me more power on tap as overhead, but, realistically, I would probably only ask for the much power a couple of times a year. So the amp loaded at 2.3 ohms would be plenty.

      Right now, I'm flogging one of them with a bash 300 and it's happy right up to clipping as far as power goes. Currently, excursion on the driver is kept in check everywhere but between 12 and 15 hz (I think); the filter and box take care of it everywhere else up past the 300 watts the bash and supply. What's the second lowest bass note in the opening zinger on the show, Edge of Tomorrow? That's the one it doesn't like... The rest of them it takes in stride, even, amazingly, the lowest note (which I think is 10 hz)

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      • #4
        WinISD "Pro" can show you how excursion varies by power & freq. I'm guessing these are in ported boxes.
        In a vented box, it's not uncommon for a v.c. to "hit the stops" at some freq. above Fb, then be FINE through Fb and a bit below, until (ultimately) it surpasses Xmax at and below its lowest reproducible note.

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        • #5
          Thanks. Yes, it's a vented enclosure. I used WinISD Pro to model the enclosure and monitor cone excursion and port velocity at different power levels - also including the stock filters for the Bash 300 - before I built the box. According to WinISD, at full power, Xmax is breached between 20 and 16 hz, but only by a few mm. The peak Xmax was around 18 hz, but the box tuning shifted down a few hz when I built it and measured it with my DATS (resonance was 2 or 3 hz lower than expected) - hence the uncertainty of exactly what frequency Xmax becomes a problem at. I also don't have an Xmech spec for the driver, so I didn't know where the hard limit was. What I described above was confirmation from the real world of what I had modeled on paper. Edge of Tomorrow is the only movie or song thus far that has given the driver fits - and that was at levels far beyond what I expect from the driver. Normal listening levels haven't caused any issues.

          If I were to gamble on the Xmech being fairly large, each driver could easily handle around 400 watts before Xmech is breached at driver resonance in this alignment. I could shift the tuning around and adjust the filter on the Bash amp, but that would get rid of my beautiful response curve and I was going for the flattest and lowest tune. Now, I also modeled a PR with some interesting results... I just might have my cake and eat it too But that's for a different thread..

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          • #6
            Your brain is correct.
            Go with option 1.

            You could short one voice coil on each woofer and just wire the three remaining coils in parallel, but then your power handling would be cut in half.
            But if the amp you're driving them with can't supply the combined power handling of the three coils, you'd be fine.
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            • #7
              Shorting the winding keeps the TS parameters the same. Leaving one open will change the way it behaves in a tuned enclosure.

              The reason for this is due to the fact that the coil will see a low impedance source in both cases; connected to the amp, or not.

              Electrical braking in this case is inconsequential. But that effect is what keeps the TS parameters the same.

              Putting a variable resistor on the disconnected coil will allow you to vary the TS parameters to your liking.
              R = h/(2*pi*m*c) and don't you forget it! || Periodic Table as redrawn by Marshall Freerks and Ignatius Schumacher || King Crimson Radio

              Byzantium Project & Build Thread || MiniByzy Build Thread || 3 x Peerless 850439 HDS 3-way || 8" 2-way - RS28A/B&C8BG51


              95% of Climate Models Agree: The Observations Must be Wrong
              "Gravitational systems are the ashes of prior electrical systems.". - Hannes Alfven, Nobel Laureate, Plasma physicist.

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              • #8
                A mains
                The Ventures
                Open Invit8tions
                RSR
                Sound Troopers
                Acorns
                442
                DGBG's
                The Monuments

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                • #9
                  Originally posted by 6thplanet View Post
                  As for all the testing I’ve done with DVC drivers powered by one of the coils, shorting out the unused coil was the worst option. The driven coil is fighting the shorted coil, drastically reducing bass output.
                  It's not fighting the shorted coil. There's almost nothing flowing in that coil. It's a lousy transformer at the frequencies you're driving them at. The reason for the drastic reduction in bass output is that now you have twice the normal impedance compared to running the coils in parallel. If you measure TS parameters with the coils in parallel, and then open one, and measure again, you will see a big change in Qts. Qts will go up significantly with one coil open. Shorting the second coil brings Qts back to normal.

                  Like I said originally, option 1 is the preferred option, even if you can get closer to 1 Ohm by driving only one of each coil. But if you want the TS parameters to properly match the box when driving only one coil, then shorting the unused coil is what you need to do.

                  http://www.diy-audio.narod.ru/litr/D...oilDrivers.pdf
                  R = h/(2*pi*m*c) and don't you forget it! || Periodic Table as redrawn by Marshall Freerks and Ignatius Schumacher || King Crimson Radio

                  Byzantium Project & Build Thread || MiniByzy Build Thread || 3 x Peerless 850439 HDS 3-way || 8" 2-way - RS28A/B&C8BG51


                  95% of Climate Models Agree: The Observations Must be Wrong
                  "Gravitational systems are the ashes of prior electrical systems.". - Hannes Alfven, Nobel Laureate, Plasma physicist.

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                  • #10
                    Your link says what I'm getting at. The shorted coil wants to resist moving due to back EMF through that coil, hence my terminology of " fighting " that coil.
                    A mains
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                    DGBG's
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