spartanmanor
Lunatic Member
Does anyone have a copy of this? For Altec Valencia 846A's
Altec n-800 f crossover schematic
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Above was copied from somewhere on LH forum. Can't locate it at the forum directly at moment so here's my copy. Apparently this is part of a (poor quality) scan of orig Altec dwg. Note that this is the "later" version. The "earlier" version used a 10 or 10.5uF cap at both HF and LF locations. This schematic shows 4uF at HF position and is probably an improvement. Note too that while this schematic shows 3.5mH for both LF and HF inductors, my actual xover characteristic meas match up with a model where Ls are 3.75mH.
spartanmanor
Lunatic Member
Thanks! I did find your old post on the N800-f I assume this is a better crossover then the problamatic one you posted about: http://audiokarma.org/forums/showpost.php?p=1102415&postcount=12
It's actually the very same xover with the change of the hipass cap from 10.5uF to 4uF. I believe the 4uF cap version removes a bit of the midrange prominence or "shout" as Zilch would describe it. Having experiemented with both versions, I prefer the 4uF version. Presumably so did Altec since it was a non-public, running change to the N800-F.
My primary gripe about the N800 is that Altec used it on systems with both 8 ohm and 16 ohm bottom ends and 16 ohm tops. It seems best for one consistent 16 ohm load top and bottom.
spartanmanor
Lunatic Member
Right now I have 8 ohm bottoms 416-8c's not original to my Valencias and am contemplating going with 416z's all 16ohm.
Am I to assume the 25 ohm 20 ohm areas in the schematic is an L pad, going to the High frequincys?
Am I to assume the 25 ohm 20 ohm areas in the schematic is an L pad, going to the High frequincys?
25 ohm is an L-pad.
20 ohm is a separate resistor, in SERIES with the GROUND terminal of the L-pad (ie, between terminal '1' or ground of the L-pad, and ground/negative terminal of the input).
This is done to reduce the "sensitivity" of the L-pad... to make it have a little less total effect. Turning down the L-pad all the way, does NOT completely shut off all the output, this way... the additional resistor limits the total "gain reduction" available on the L-pad.
Regards,
Gordon.
20 ohm is a separate resistor, in SERIES with the GROUND terminal of the L-pad (ie, between terminal '1' or ground of the L-pad, and ground/negative terminal of the input).
This is done to reduce the "sensitivity" of the L-pad... to make it have a little less total effect. Turning down the L-pad all the way, does NOT completely shut off all the output, this way... the additional resistor limits the total "gain reduction" available on the L-pad.
Regards,
Gordon.
bowtie427ss
Lunatic Member
FWIW, consider that Altec, for whatever reasons, used the same model number for crossovers that were indeed for different applications and made with different value components.
Here's the N-800K as equipped for the Milano using all 8 ohm components.
Here's the N-800K as equipped for the Milano using all 8 ohm components.
spartanmanor
Lunatic Member
similar yes but not the same.
avguytx
Lunatic Member
Yep, that's the sheet I have and what I am using for ordering new caps and coils to experiment with "replacing" the original crossover. I just want to see how much new components make a difference in place of the originals on these Altecs (my Milano's) like the differences were on a dozen or more other speakers I've done that on. On the others, the differences were there. So, for $100 worth of parts, it's a pretty easy thing to do. I'll keep the original crossover/l-pad completely intact for originality's sake and build a separate board for them.
spartanmanor
Lunatic Member
Thanks Gordon,
I am still new to reading schematics. I am not afraid to go for it but surely I will make a mistake unless I ask.
spartanmanor
Lunatic Member
Yeah I am trying to figure out if I want to keep the 416 -8c's and mess with the 16 ohm 806A tweeter where I would use the N-800k crossover with the ad on crossover for the 16 ohm tweeters or go for a more original woofer like the 416z. or replace the 806 A for BMS? I may end up trying all options. Decisions, decisions.
Comparing the schematics, observe that the filters are the same, scaled by a factor of two for 8- vs. 16-Ohm impedance.
In the later 8-Ohm version, Altec abandoned the limited-range potentiometer plus resistor attenuation scheme in favor of a conventional L-Pad. When building N800-F, I just use a conventional 16-Ohm L-Pad instead. It appears Altec ultimately did that, as well, or switched to a wire-wound pot, at least.
The N800-F schematic scan is in one of my posts in the LHF "Babies" thread. It was provided to me by an Altec Forum member, credited there, and is apparently an official document also having an Altec title block.... :yes:
*****
"Shout" is Don McRitchie's word for it, as I recall. For others, it's "Emphasis," "Vocal clarity," or "Magic," apparently....
:
In the later 8-Ohm version, Altec abandoned the limited-range potentiometer plus resistor attenuation scheme in favor of a conventional L-Pad. When building N800-F, I just use a conventional 16-Ohm L-Pad instead. It appears Altec ultimately did that, as well, or switched to a wire-wound pot, at least.
The N800-F schematic scan is in one of my posts in the LHF "Babies" thread. It was provided to me by an Altec Forum member, credited there, and is apparently an official document also having an Altec title block.... :yes:
*****
"Shout" is Don McRitchie's word for it, as I recall. For others, it's "Emphasis," "Vocal clarity," or "Magic," apparently....
:
spartanmanor
Lunatic Member
That would make things easier :thmbsp:
Actually, in the N800F schematic the 25ohm thing really is a pot...and a wirewound one at that...at least it is in the four xovers I've deconstructed.
The resistor/pot combo provides a pseudo constant impedance characterisitic to the upstream xover. I used to view this circuit as a low cost sub for a real L-pad. After having measured the so called "constant" impedance characteristics of affordable commercial L-pads, this pot/resistor scheme isn't really that bad in comparison. The real L-pads are better but not by the margin one might believe from just looking at circuits.
