I want to damp a tweeter....

Discussion in 'Home Theater Projects' started by Dave Poehlman, Sep 17, 2003.

  1. Dave Poehlman

    Dave Poehlman Producer

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    Is there a formula for how much a driver will drop in dB's per ohm of resistance added?
     
  2. Patrick Sun

    Patrick Sun Moderator
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    Is it being done with an L-Pad resistor network?

    http://lalena.com/audio/calculator/lpad/

    If you're only using a resistor in series with the tweeter, it gets more complicated, and the response can get skewed as the series resistance value changes.
     
  3. ThomasW

    ThomasW Cinematographer

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    What you should do is use an 'L-pad'. If you just slap a single resistor in the signal path 1/2 the power goes to it and it will change the XO point.

    If you know exactly how much attenuation you need HERE'S a link that tells how to calculate the values for the 2 resistors neded to create a fixed amount of attenuation.

    If you don know the exact amount of attenuation needed go out and buy an variable 'L-pad'
     
  4. Dave Poehlman

    Dave Poehlman Producer

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    Thanks for the info, guys! I'm going to hunker down with the SPL meter tonight and figure out what my attenuation should be!

    And I've bookmarked that L-pad calculator! Haaaaandy!

    I've got another question since you guys are so quick... I've read about notch filters taming unwanted frequency peaks, but I can't find any information on how to calculate/construct them. Is there a formula and a diagram that covers notch filters? Let's say I have a 5 dB spike at 1500 Hz, how would I knock that down electronically?
     
  5. ThomasW

    ThomasW Cinematographer

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    I did a quick google search for notch filters and found THIS
     
  6. Dave Poehlman

    Dave Poehlman Producer

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    I've seen that article, Thomas. But, what if my peak is due to the physical construction of the driver rather than the driver's resonance? Is there any way to account for that in a circuit?

    Here's my situation: I have a 5 1/4" woofer that has a hard plastic dust cap on it.. well, this dust cap is causing a standing wave spike around 5.5 KHz. The reason I know this is the case is because a friend had measured the driver before and after he added a small bit of modelling clay to the center of the dust cap to break up this wave. I was wondering if there was a way to compensate for this peak electronically rather than physically modifying the driver's dust cap.
     
  7. ThomasW

    ThomasW Cinematographer

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    In the long run you're probably better of to physically solve the problem. So a bit of blutack or something similar would IMO be the best fix.
     
  8. Dave Poehlman

    Dave Poehlman Producer

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    Okay.. I wanted the drivers to look presentable.. I was thinking of putting a drop of black satin paint in the center of the cap and letting it dry upside down to sort of form a "nipple" on the cap. That way it would match the poly cone.

    Thanks again for all the info!
     

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