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Thread: Altec Lansing ID? 802D, 803B

  1. #16
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    Why not use a 16 ohm variable Lpad for attenuation ?( for instance one from Parts Express found in the clickable picture link )
    - Use in place of all fixed value resistors ( between crossover components and the 802 driver ).





    BTW, the N800-D network only offers 4- or 5db maximum of horn attenuation > which typically isn't enough for home listening ( when mated with a 416 type woofer ).

    One wants a network that offers more than that . Something like a max. of 8db or 10db of attenuation is more useful .

  2. #17
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    Quote Originally Posted by Earl K View Post
    Why not use a 16 ohm variable Lpad for attenuation ?( for instance one from Parts Express found in the clickable picture link )
    - Use in place of all fixed value resistors ( between crossover components and the 802 driver ).





    BTW, the N800-D network only offers 4- or 5db maximum of horn attenuation > which typically isn't enough for home listening ( when mated with a 416 type woofer ).

    One wants a network that offers more than that . Something like a max. of 8db or 10db of attenuation is more useful .
    Thank you!

    I guess I never took a moment to appreciate that the N800-D is simply a 2nd order Butterworth with HF attenuation. That being the case I suppose I could use the pots I got after all, in series with the 15 ohm resistors for extra attenuation. If the horn's still too hot I can always increase the attenuation.

    Quick note, I think it's been covered before on here, but FYI running 2nd order Butterworth calculations on the N800D components (C1, C2 are 10.5uF; L1, L2 are 3mH) with these drivers (802D, 803B are both 16ohm drivers), we get an actual crossover around 900Hz with an almost 3dB spike (!):

    https://speakerwizard.co.uk/calcs/Crossover_Calc_v2.php

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    (Also, not that it matters, but another smoking gun that Altec intended these A7-800 components to be used with the N800D, page 12 of the 1954 catalog http://lansingheritage.org/images/al...ome/Page12.jpg and page 10 of the 1964 catalog: http://www.cieri.net/Documenti/Catal...log%201964.pdf)
    Currently: L300, C40 Harkness (030 Load), 4301B

  3. #18
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    So here's how I'll incorporate the resistor and pot into the 2nd order Butterworth that is the N800D. Top is the network w/o attenuation, bottom is the network w/ the resistor and the pot wired in. (Obv the line I drew btw pins 2 and 3 of the pot isn't supposed to be there ...) This just might work after all.

    Unless ... am I still misunderstanding the pot? Does the resistance designation on these refer to the impedance instead of the resistance across it? In other words, should I use a 16ohm pot here and not the 8ohm pot because the 802B is a 16ohm driver?

    Edit: Yes this does appear to be how these things work. From PE, "L-pads adjust the relative volume of drivers connected to them by placing added resistance in series and parallel, keeping impedance at a constant 16 ohm load." Well, I will see if I can exchange my 8ohm ones for those 16ohm ones you linked to above Earl. Thanks again for steering me in the right direction.

    ... a quick thought, wouldn't I not want a constant 16 ohm load? The 802D like any driver will have non-constant impedance as a function of frequency ...

    So just ignore R below and pretend that's the 16ohm pot, and ta-da, that's how I'll build these N800D clones.

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    Currently: L300, C40 Harkness (030 Load), 4301B

  4. #19
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    When designing crossovers it's generally advisable to use ( create ) a constant impedance ( if at all possible ) .

    The variable Lpad will give you that.

    The older Altec diaphragms ( ie; 20275 type ) are actually more like 12 ohms, therefore I think you're better off keeping the 8 ohm Lpads and adding a 4 ohm resistor between the Cap/Coil arrangement and the variable Lpad ( like in your picture ).


  5. #20
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    Quote Originally Posted by Earl K View Post
    When designing crossovers it's generally advisable to use ( create ) a constant impedance ( if at all possible ) .

    The variable Lpad will give you that.

    The older Altec diaphragms ( ie; 20275 type ) are actually more like 12 ohms, therefore I think you're better off keeping the 8 ohm Lpads and adding a 4 ohm resistor between the Cap/Coil arrangement and the variable Lpad ( like in your picture ).

    Understood, thanks!
    Currently: L300, C40 Harkness (030 Load), 4301B

  6. #21
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    Another ( so-called ) 800hz option is to use the N800F network ( it's quite applicable for those older components of yours ).




    The small 4uF cap used in the N800F provides quite a lot of midrange attenuation ( below say about 3.5K ) > cutting down the midrange "shout" of the horn/driver combo .


  7. #22
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    Getting there.

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    Currently: L300, C40 Harkness (030 Load), 4301B

  8. #23
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    A few more wires ...

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    Installing the pots in the terminal cups ...

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    Mounting to the back panel ...

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    Move over, L200Bs ...

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    Currently: L300, C40 Harkness (030 Load), 4301B

  9. #24
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    WOW! They sound AMAZING! Detail, imaging, unreal. Bass is fantastic. SO happy with them!

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    (I wired them in phase w/ + going to "1" for both since they are mounted with the woofer flush with the horn per the following.)

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    Currently: L300, C40 Harkness (030 Load), 4301B

  10. #25
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    Nice !

    It's cool that you are finally enjoying these ( since you started this journey back in early 2918 ).

    Good show on your persistence.



  11. #26
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    Thanks so much for sticking with me the whole way through!
    Currently: L300, C40 Harkness (030 Load), 4301B

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