Can an IB be incorperated physically in the same room?

Discussion in 'Archived Threads 2001-2004' started by Serge Breton, Sep 4, 2002.

  1. Serge Breton

    Serge Breton Supporting Actor

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    Here is my situation:

    The front of my HT is 12 feet wide with a 90" diagonal screen. I have 2 large tube traps in the front corners and i will be building an octagon front out of black masking(felt) to hide these bass traps and to finish off the theater, these will be curtain like. Can i build an IB into the corner? I can build a special box to fit right into the corner and technically i guess the front wave would be seperate from the rear wave and this should work. Advice needed....
     
  2. Rick Guynn

    Rick Guynn Second Unit

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    I'm not sure... but I don't think that a 'felt' curtain would be solid enough to keep the backwave contained. However, if I am wrong about that, then all you need to do is make sure that the volume behind the driver is a min of 4x Vas (preferably 10x) and well-sealed. As long as the backwave cannot bleed through the felt, you should be ok.

    That does beg a question though... if you are using the felt curtains to hide bass traps, wouldn't the felt need to be transparent to bass frequencies for the traps to work? Or am I misunderstanding bass traps? (entirely possible)

    RG
     
  3. ThomasW

    ThomasW Cinematographer

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    If you build a false wall (or box) that encloses an area that's no less than 4X the sum of the Vas of the drivers, then yes you can.

    And as Rick correctly pointed out, the consensus is that the optimal box size is 10X or greater the sum of the Vas
     
  4. Serge Breton

    Serge Breton Supporting Actor

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    Rick,

    bass frequencies use sound pressure levels and are not like mid-high frequencies in this regard. Bass frequencies travel through walls, etc so a curtain will have little to no effect on bass absorption.

    So i have to build a false wall, hmmm. Concerning Vas, i'm unfamiliar with the term, say the dimensions of the said triangular box is like 25"x25", what overall hight of this false wall/enclosure would i need to acheive optimum Vas. What size square opening do i need in a dual tempest IB configuration (for the sound to come out). I plan on employing two tempests drivers for my IB. Another question arised as to if i need to employ an EQ with this configuration. Thanks
     
  5. Dustin B

    Dustin B Producer

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    Vas is the something or other compliance of the driver and measured in units of volume. The Vas of the Tempest is 317L, so the combined Vas of 2 Tempests would be 634L. So the required range in size would be 2600L to 6400L. Or 91 to 226 cubic feet.

    So 2' by 2' it would need to be 22' to 57' tall. But you only want to use half of that (making a triangle) so it would need to be 44' to 114' tall :p)

    You might be able to make it work if you went out 4.75-5 feet in each direction for the triangle. As that would allow you to get over 90ft^3 assuming an 8' height in the room.

    But this isn't so much an IB as just a really really big sealed box that will act like an IB.
     
  6. Greg Monfort

    Greg Monfort Supporting Actor

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    Another thing to consider when building large cabs is the ratios of the internal dimensions, otherwise the eigenmodes (standing waves) will modulate the driver, altering its frequency response and increasing it's distortion.

    GM

    PS: RG, are you related to Randy Guynn of Performance, American Style in Pasadena, Tx?
     
  7. Serge Breton

    Serge Breton Supporting Actor

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    well so much for that idea....
     
  8. Rick Guynn

    Rick Guynn Second Unit

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    Greg, not that I know of... but there seem to be so few people with the last name spelled the way mine is, so he may be somewhere in the same bloodline ;P

    RG
     
  9. Greg Monfort

    Greg Monfort Supporting Actor

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    Thanks, just wondering. It's the same for me AFAIK, if their last name is spelled 'Monfort', then I'm related in some way.

    GM
     
  10. Brian Bunge

    Brian Bunge Producer

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    Greg,

    Let me know if you meet another Bunge!

    Brian
     

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