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Thread: DIY Altec N1500A

  1. #1
    Junior Member
    Join Date
    Nov 2011
    Upstate, NY

    DIY Altec N1500A

    Hi all, I'm trying to build a set of N1500a's from scratch for a pair of 604e. I've used Markwarts excellent site, but this is my first crosssover from schematic. My question is this: there is no lpad on the parts list, but one is used in the vintage crossovers, is it the 25ohm R-2 component?
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  2. #2
    Senior Member
    Join Date
    Apr 2003
    GTA, Ont.
    R2 is not an Lpad, it's a variable resistor ( Potentiometer / Rheostat ) .

    This part (from Ohmite) will do the job .

    PS ; I think you should ask JeffM( via his website ) for clarification about installing his HF contour circuit to the N1500a ( since it's mentioned at his web-page but not committed to a drawing ) .

    Quote Originally Posted by JeffM
    The N-1500A with MF EQ?
    I next wondered what the addition of Mid Freq EQ would do to the behavior of the N-1500A filter, so I modified the CALSOD filter model with a contour circuit consisting of a 6uf cap paralleled with an 8 ohm resistor, which was then placed in series with the compression driver voice coil. The mid-point of the resistor was tied to ground with a variable resistance of 10-50 ohms. See Fig. 3 below:

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