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  1. #1
    Member qcautosports's Avatar
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    Question L-pad delete how to...HELP!

    What's up people. I hope everyone is safe and healthy.
    I recently acquired a pair of L88 Nova speakers. Physical shape is awesome. Issues:
    1. Lpads are wonky. Tried opening and cleaning. Some areas lose sound.
    2. One tweeter (LE25-1) only read 0.6 ohms. I guess its fried although gives out small amount of sound. Should I get a new replacement or a good used one? Any difference between the LE25 and the LE25-1?
    3. How do I bypass the lpads?
    It's been years since my last post and visit so, hello again to everyone. 🤗
    ---::: Pioneer PL71/Empire 999 ev/x/ GE RPX Mono/ Scott Type 299C/ Pioneer CS88A :::---

  2. #2
    Member qcautosports's Avatar
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    Quote Originally Posted by qcautosports View Post
    What's up people. I hope everyone is safe and healthy.
    I recently acquired a pair of L88 Nova speakers. Physical shape is awesome. Issues:
    1. Lpads are wonky. Tried opening and cleaning. Some areas lose sound.
    2. One tweeter (LE25-1) only read 0.6 ohms. I guess its fried although gives out small amount of sound. Should I get a new replacement or a good used one? Any difference between the LE25 and the LE25-1?
    3. How do I bypass the lpads?
    It's been years since my last post and visit so, hello again to everyone. 🤗
    Bump😃
    ---::: Pioneer PL71/Empire 999 ev/x/ GE RPX Mono/ Scott Type 299C/ Pioneer CS88A :::---

  3. #3
    Senior Member grumpy's Avatar
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    An L-pad is (normally) a three terminal device that is functionally the same as the picture below where one terminal is the "+", one is the R1-R2 junction, and the other is the "-" ... the difference being the circuit below has R1 and R2 fixed, where an L-pad allows for them both to be adjusted while it's knob is rotated. If you want to replace an L-pad with fixed resistors and have a good L-pad that's set where you like, just measure the resistance between terminals. Of the three possibilities, you'll get R1, R2, or R1+R2... double check this with a calculator like the one below to see that it makes sense.

    For an 8 ohm L-pad: At one extreme R1 should get close to 8 ohms and R2 very small. At the other, R1 should be minimal and R2 perhaps tens to hundreds of ohms.

    sourced from https://www.erseaudio.com/L-Pad-Attenuation ... one of many such online audio L-pad calculators.

    Name:  Screen Shot 2020-06-05 at 11.33.05 AM.jpg
Views: 928
Size:  72.5 KB

    See also:

    http://www.bcae1.com/lpad.htm

  4. #4
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    If you were previously running the L-pads "wide open" you only need to solder the input lead to the output lead and disconnect the ground. When an L-pad is run wide open, the input lead "touches" the output lead and the secondary windings are by-passed.

  5. #5
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    Quote Originally Posted by grumpy View Post
    An L-pad is (normally) a three terminal device that is functionally the same as the picture below where one terminal is the "+", one is the R1-R2 junction, and the other is the "-" ... the difference being the circuit below has R1 and R2 fixed, where an L-pad allows for them both to be adjusted while it's knob is rotated. If you want to replace an L-pad with fixed resistors and have a good L-pad that's set where you like, just measure the resistance between terminals. Of the three possibilities, you'll get R1, R2, or R1+R2... double check this with a calculator like the one below to see that it makes sense.

    For an 8 ohm L-pad: At one extreme R1 should get close to 8 ohms and R2 very small. At the other, R1 should be minimal and R2 perhaps tens to hundreds of ohms.

    sourced from https://www.erseaudio.com/L-Pad-Attenuation ... one of many such online audio L-pad calculators.

    Name:  Screen Shot 2020-06-05 at 11.33.05 AM.jpg
Views: 928
Size:  72.5 KB

    See also:

    http://www.bcae1.com/lpad.htm

    Also, keep in mind, the reason an l-pad is used is to keep a constant impedance across the output of the passive crossover the same throughout any adjustments so that the crossover frequency isn't affected.
    This may help to understand it's function better other than just reducing the output of whatever type of transducer is on that leg.

  6. #6
    Senior Member grumpy's Avatar
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    Yep... has to serve both functions.
    That said, once a satisfactory setting is found, they just become a maintenance issue.

  7. #7
    Member qcautosports's Avatar
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    Thanks for the great information. Ill stay with Lpads. Question now is where t o get a couple of new ones. Im replacing both pots.
    ---::: Pioneer PL71/Empire 999 ev/x/ GE RPX Mono/ Scott Type 299C/ Pioneer CS88A :::---

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