Altec Lansing ID? 802D, 803B

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 ).

https://www.parts-express.com/data/d...-254_ALT_0.jpg

:)

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 .

Quote:

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Originally Posted by Earl K

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 ).

https://www.parts-express.com/data/d...-254_ALT_0.jpg

:)

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 .

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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

Attachment 84687

(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)

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.

Attachment 84688

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 ).

:)

Quote:

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Originally Posted by Earl K

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 ).

:)

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Understood, thanks! :bouncy:

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

http://www.audioheritage.org/vbullet...1&d=1175580320


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 .

:)

Getting there.

Attachment 85064

A few more wires ...

Attachment 85074

Installing the pots in the terminal cups ...

Attachment 85075

Attachment 85076

Mounting to the back panel ...

Attachment 85077

Move over, L200Bs ...

Attachment 85078

WOW! They sound AMAZING! :bouncy: Detail, imaging, unreal. Bass is fantastic. SO happy with them! :applaud:

Attachment 85072

(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.)

Attachment 85073

Nice !

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

Good show on your persistence.


:)

Thanks so much for sticking with me the whole way through!