Matching Sensitivity of Woofers for MMT Speaker

Discussion in 'Archived Threads 2001-2004' started by Daniel Marx, Feb 18, 2001.

  1. Daniel Marx

    Daniel Marx Auditioning

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    I'm planning on buying new drivers for an older pair of MMT speakers I built a while back. The original drivers are pretty shotty, but the cabinet and finish I spent weeks on. So I figure they're due for a tune-up. So upon my search for a pair of 8" drivers and 1" dome tweeters, I find myself ruling out drivers that are too efficient for matching with any tweeter. I am going on the assumtion that 2 woofers in the enclosure increase sensitivity by +3 dB. (Although I have read that it's actually +6 dB). So I need clarification there too. Take for example the two speakers I have currently found: woofer spl 1W/1M 91.5, tweeter spl 92 dB. I plan on wiring the woofers in parallel for a 4 ohm load. The problem I'm seeing is now I'm looking at my woofers being 2.5 dB louder than my tweeter. So what do I do? Find a more efficient tweeter to match or less efficient woofers? And obvisously the option is open for an attenuation circuit on the tweeter, but this only works if the tweeter is more efficient than the woofer. In most cases I have seen so far, the two woofers are going to be more efficient than any tweeter. What to do?
     
  2. Greg Monfort

    Greg Monfort Supporting Actor

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    > I find myself ruling out drivers that are too efficient for matching with any tweeter. I am going on the assumtion that 2 woofers in the enclosure increase sensitivity by +3 dB. (Although I have read that it's actually +6 dB).
    ====
    Efficiency is turning electrical power into mechanical/acoustic power.
    Sensitivity is how much output for a given voltage signal.
    So you get +3dB efficiency (2x cone area), and +3dB sensitivity (2x voltage) gains.
    ====
    > Take for example the two speakers I have currently found: woofer spl 1W/1M 91.5, tweeter spl 92 dB. I plan on wiring the woofers in parallel for a 4 ohm load. The problem I'm seeing is now I'm looking at my woofers being 2.5 dB louder than my tweeter. So what do I do? Find a more efficient tweeter to match or less efficient woofers? And obvisously the option is open for an attenuation circuit on the tweeter, but this only works if the tweeter is more efficient than the woofer. In most cases I have seen so far, the two woofers are going to be more efficient than any tweeter. What to do?
    ====
    Unless you plan to mount them against the wall (not a good plan with typical cone/dome drivers), you've got baffle step diffraction to consider, which can be up to -6dB depending on how far they are from it. So having the LF make it up in part/all is a no brainer for me. If there's too much boost in the LF's upper BW in-room, then attenuate it with an inductor or passband filter to better match the HF.
    GM
    ------------------
    Loud is beautiful, if it's clean
     

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