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Sealed small sub with a Linkwitz transform. How to do it right?

Discussion in 'Home Theater Projects' started by Javier_Huerta, Feb 6, 2004.

  1. Javier_Huerta

    Javier_Huerta Supporting Actor

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    I'm thinking about this... I have a 12" driver (C-V HED-12) with a high Vas (192 L), and 22Hz Fs. WinISD shows me I have a -12 dB response at 20 Hz using a 60 liter box. This driver really wants something bigger...

    How about a Linkwitz transform? WinISD shows you the correct excursion data when using the transform (I'm aiming for -3dB at 20Hz), but it doesn't show power requirements. Also, I'd believe the driver really needs to be very beefy in order to withstand the beating.

    I have been using this driver for a while in an 84L box, with 180W RMS. So far, no problems. It has a (supposedly) 34 mm Xmax so I guess this would help a bit...

    Does anyone have any extra info on Linkwitz Transformed setups?

    Thanks a lot!
     
  2. ThomasW

    ThomasW Cinematographer

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    One shouldn't create a LT circuit base on a sim, particularly a WinISD sim.
    Build the box, measure it's performance in the room, then design the LT circuit.

    HERE's a link to a TL design program
     
  3. Dan Wesnor

    Dan Wesnor Second Unit

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    I agree with Thomas. You will need to get a copy of SpeakerWorkshop and learn how to measure Fs and Qts to get the best results. You can use the sims to generate this, but T/M parameters provided by manufacturers are often not very accurate. Also, when working in small, stuffed boxes, there are lower tolerances on your gross volume estimate, which means you need to know pretty accurately what the driver and bracing volume is. Easier to just measure the thing.
     
  4. Javier_Huerta

    Javier_Huerta Supporting Actor

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    Dan, Thomas, thank you very much for your help. I do believe you are right - I don't trust C-V's parameters anymore. My sealed sub died with less than 100W yesterday (it's making a loud rapping noise).

    No big deal - I guess. I already knew this could happen... the sub's specs seemed too good to be true. I don't think it's a great candidate for a Linkwitz Transform project, but I guess I could use it to learn new things (I have a couple of them in storage).

    I surely hope measuring the sub isn't too hard...
     

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