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Speaker Cab Displacement Power Limit?

Discussion in 'Amps and Cabs [BG]' started by StoBro, Jun 24, 2007.


  1. StoBro

    StoBro

    Jun 2, 2007
    Chicagoland
    Speaker Tech help needed!

    I've been thinking about new drivers for some home-made 112 cabs of mine, and I've noticed the term "Displacement Limited to X Watts" in some Eminence Cab Design documents. Does that mean RMS (sine wave) watts? If I power a cabinet that is displacement limited to 100W with a 200W amp, what might happen?

    My boxes are sealed, about 2.9 cu. ft. internal volume, less the volume of the driver, and are currently loaded with Eminence Beta 12LTAs. I believe the -10dB point is around 40Hz, but the power limit is quite low at that frequency due to the low xmax of the driver.

    My plan is to switch to the DeltaLite II 2512 and port the cabs properly based on Emi's published suggested design. But with this alignment, the power is still displacement limited to 125W. My amp is rated for 240W. Am I asking for trouble?
     
  2. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Not if you don't turn it up too loud. But your limitation with the Beta 12s isn't just xmax, it's using them in a sealed box, for which they aren't at all suited. Just properly venting the cab would give another 5dB output on average below 100 Hz. BTW, most drivers are displacement limited to no higher than half their thermal ratings, and many to far less.
     
  3. StoBro

    StoBro

    Jun 2, 2007
    Chicagoland
    Since I didn't have any speaker cabinet design software at my disposal when I built these cabs, I went with a sealed box in a size optimized to fit in the back of my vehicle.

    If I kept the Beta 12LTs in the boxes, how would I determine the proper porting for the box size? Eminence has designs for 2 cu. ft. and 4 cu. ft. boxes, but not 2.9 cu. ft.
     
  4. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Download WinISD at linearteam.org.
     
  5. StoBro

    StoBro

    Jun 2, 2007
    Chicagoland
    That's a fun program. Looks like I'll be spending several hours playing with different driver and tuning combinations. Thanks.
     
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    Primary TB Assistant

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