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Center channel project

squamishdrocsquamishdroc
in DIY

Working on a center channel build for a friend - am using 2 CF120 woofers and a ND25 tweeter. I am just working on the crossover and was taking some measurement sweeps - I have an ok response straight on but then get a pretty good dip as soon as I hit about 15deg off axis. Crossover is second order on the woofers and tweeter at about 2.7k. The speaker is only 13" wide and 5.5" tall. Am I missing something or is this normal for a horizontal mtm

? I tried reversing the tweeter polarity and all it does is just move the dip down about 1k.

Comments

  • dcibeldcibel

    Horizontal MTM for a centre channel isn't done for the acoustic benefits...turn it vertically and enjoy :)

    squamishdroc
    I'm not deaf, I'm just not listening.
  • WolfWolf

    Try 3rd order acoustic slopes....

    squamishdroc

    InDIYana Event Website

  • rjj45rjj45

    re:I tried reversing the tweeter polarity and all it does is just move the dip down about 1k.
    That just means that you don't have the phase lined between the mids and the tweeter.
    I'd use 2nd order electrical on the woofers and 3rd order electrical on the tweeter
    unless those CF120s have a bad breakup node.

    But Chahly - Stahkist don't want speakers that look good, Stahkist wants speakers that sound good!
  • WolfWolf

    The reason I said 3rd order slopes on a horizontal MTM is so the off-axis nulls fill in.

    As to the drivers' responses, John has shown the CF120 to be a roller coaster ride. The ND25 I've used and found to sound better above 4kHz, even though its performance is not bad to about 2.5kHz.

    InDIYana Event Website

  • squamishdrocsquamishdroc

    @Wolf said:
    The reason I said 3rd order slopes on a horizontal MTM is so the off-axis nulls fill in.

    As to the drivers' responses, John has shown the CF120 to be a roller coaster ride. The ND25 I've used and found to sound better above 4kHz, even though its performance is not bad to about 2.5kHz.

    I will try a 3rd order x/o and see what happens 👍

  • jhollanderjhollander

    Third order runs 90 degrees out of phase at the x-o point, so there will not be a null when you flip polarity

     John H, btw forum has decided I don't get emails
  • WolfWolf

    This is also true. It's not an 'aligned phase' result. I'm not one to prefer the BW3 acoustic because it can lack focus. For a Center Channel this might not really be a problem.

    InDIYana Event Website

  • jhollanderjhollander

    On my center channel projects I've found the BW3 ends up with the same magnitude of dip at the x-o as an LR4. Maybe it's because of the spacing. Any how I seem to end up with LR4s on my center channels.

     John H, btw forum has decided I don't get emails
  • WolfWolf

    I still don't even have a really nice center channel, but I have plans to do one. BW3 is not for everyone.

    InDIYana Event Website

  • squamishdrocsquamishdroc
    edited July 2020

    Well I played around with the crossover a bit in PCD and was able to get rid of my dip by removing the l-pad on the tweeter and just putting a series resistor before the cap. Also helped bring up the impedance low spot up to 5 ohms from about 3. Thanks for the suggestions👍👍

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