Can I put my Center Channel XO in my Towers?

Discussion in 'Home Theater Projects' started by Brett DiMichele, May 9, 2003.

  1. Brett DiMichele

    Brett DiMichele Producer

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    Okay before you say NO listen to what I have to say [​IMG]

    My Center channel is THE EXACT same C-T-C MTM with all
    drivers mounted flush with the baffel and the baffel is
    the same size as my towers.. Everything is exactly identical..

    But..... The crossover in my Center lowpasses the mids at
    70Hz. The XO in my mains Lowpasses the Mids at 100hz..

    My mains take over from 100 down with the 10" subs..

    My center sounds more impactful.. Because it's playing
    lower..

    So could I take my center channel's XO and write down the
    ingreedients and build a pair of XO's for my mains with
    GOOD parts on boards.. And lowpass the mids at 70Hz and
    just do away with the crossover for the subs period since
    my sub amp has a variable XO from 120 down to 40..

    The simple answer should be "Yep" right?

    I can't see any reason not to.. The mids have tons of
    excursion and in thier curent configuration they don't
    even move... (well they don't move much..)
     
  2. Brett DiMichele

    Brett DiMichele Producer

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    Hmmm...

    Brian pointed out about baffle step compensation.. Valid
    point.. I just wonder if they factored it in.. Or did they
    just use the same compensation as the vertical orientation.

    Damn these blasted complimacated things! [​IMG]

    Ahh who knows..
     
  3. Dan Wesnor

    Dan Wesnor Second Unit

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    The center would have less baffle step compensation, which would mean less LF output lost to 4PI space, which means more total output from the same swept volume. That's why they are cut off lower.

    If you do this, you will need to shove the mains back against the walls to keep them from sounding thin and weak.

    Take the center and put it on a stand where one of the mains is to get an idea of what you're in for.
     
  4. Brett DiMichele

    Brett DiMichele Producer

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    Dan I already did that..

    I stood the center channel up where one of my mains sits
    and it sounded fantastic. Much more dynamics, more midrange
    punchiness etc..

    No loss of imaging or any negative effects.. Go figure?
     
  5. Brett DiMichele

    Brett DiMichele Producer

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    The only thing I can think is that the center channel has
    a built in mounting bracket that allows it to be placed as
    a Vertical M-T-M. I wonder if the Baffel Step is factored in
    as Vertical because of this...

    I don't know..

    My biggest gripe is that my mains mids lowpass at 100Hz like
    I previously stated, and from there down they depend on the
    10's to make the rest. It seems to me that the better setup
    would be to have the mids lowpassed at 70 or 80Hz and run
    the 10's from there down.... That would make better use of
    the drivers for thier intended tasks I would think. Why run
    a pair of 10's up to 100Hz when dual 5.25" Mids can do 70Hz
    without breaking a sweat.

    I am going to do some tinkering.. It doesn't hurt to experiment.

    I will take the stock crossovers and put them aside somwhere
    and fab up some experimental crossovers cheaply and if I
    like what they do for the sound I can always do a good pair
    with better parts.

    And then I can run my 10's directly off my external amp.
    Right now I have cascading crossovers since the sub's are
    already highpassed at 100Hz and the sub amp has a variable
    xo that I have been running at 120Hz.
     
  6. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    What I don't get is why would the baffle step be an issue if the enclosures and drivers are identical.

    The only thing separating them apart is the center has a different crossover point and can be tilted on its side. Do those factors affect the baffle step compensation?
     
  7. Patrick Sun

    Patrick Sun Studio Mogul

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    I'd be more concerned about whether AR actually went for accounting for the lobing for a sideways MTM (usually 3rd order slopes are used for this configuration) used as a Center channel speaker, vs. their upright MTM front speakers, whose XOs may have different XO slopes to account for the vertical lobing patterns for their intended use.
     
  8. Brett DiMichele

    Brett DiMichele Producer

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    Is there any way to check and see if they took baffel step
    or lobing into account?

    I had another idea though.

    I can take the stock XO's out and bag them. Build 2 new
    crossover boards based on the originals but lower the mid
    range lowpass that's the only thing I want to change. Plus
    I want to eliminate the subwoofer's section of the XO
    entirely since I have an external variable crossover for
    the subs.

    That way I won't have to worry about circumventing any
    baffel step that may be built in. Just lower the lowpass
    for the mids. Wouldn't that work?
     
  9. Todd Shore

    Todd Shore Stunt Coordinator

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    Active outboard crossover? What slope? Are you then going to bi-amp? You'll probably be changing the roll-offs on your 10's and 5.5(?)'s.

    I would look at the existing highpass to the 10's and see what slope it is using. Going up in order (say to 4th order active from a 2nd order passive) will cause a dip at the crossover.

    Have you measured for in-room bass response? Doing do will tell you where you need to cut or boost. Centering that dip on a room mode is a simple tune. Really tightens things up.

    There should be enough people here that can help you analyze the existing passive crossover. If not here, then other people to talk to at other places like MAD.
     
  10. Dan Wesnor

    Dan Wesnor Second Unit

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    Baffle step is different for center channels because they typically sit on the TV, effectively extending the baffle. At least it should be different, some designers don't put enough baffle step on their mains.

    To compare the tone difference, switch between speakers with pink noise, like that found on Avia audio setup tracks.
     
  11. Ryan T

    Ryan T Second Unit

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  12. Brett DiMichele

    Brett DiMichele Producer

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    Todd,

    They are BiAmped already. The external crossover for the
    subs is built into the sub amp it's variable from 40 to
    120.


    As long as I take the stock passive crossover design and
    just lower the lowpass on the mids what issues will I have
    then? I shouldn't be circumventing any baffle step.

    I hear people bragging up Marchand active crossovers all
    the time. They look interesting but if people here are so
    dead set on Baffle Step Compensation, how do you apply that
    with something like the Marchand Actives??????

    Just curious..
     
  13. Todd Shore

    Todd Shore Stunt Coordinator

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    You can integrate it into the circuit or use really large baffles. You can also use the room and your bass enclosure tunings to tune for flat response by overlaying peaks and dips.
     

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