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Thread: Model 19 crossover schematics

  1. #1
    Inactive Member Hornluvr's Avatar
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    Question

    Hi, I recently purchased Model 19 speakers in
    good condition and I am delighted by the
    sound- sweet, open, fast and lots of dynamics. They are the perfect match for my
    RadioCraftsmen 1952 triode amps!
    My only (small) concern is the grainy sound
    of strings when I listen to classical music.
    I will dampen the horns and rewire the drivers as described on this board, I am also
    thinking of replacing the old condensers in
    the crossover- would that make sense?
    Does anyone have a schematic diagram of the
    Model 19 Xover or the condensers' values?
    Alas, GreatPlainsAudio know nothing about the "super crossover" there have been rumours
    about here on the board.
    Thanks for your cooperation.

  2. #2
    Inactive Member Richard C.'s Avatar
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    Post

    Hello,
    If you have the same crossover as I have with the 802-8G drivers, I have the capacitor values.
    C1=8 Uf
    C2=16 Uf
    C3=21 Uf
    C4=6 Uf
    These values are from my model 19 crossovers, and from a schematic provided by Jim Easley.
    Richard C.

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    Inactive Member run's Avatar
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    Originally posted by Pat McDermott:
    </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Hornluvr:
    Hi, I recently purchased Model 19 speakers in
    good condition and I am delighted by the
    sound- sweet, open, fast and lots of dynamics. They are the perfect match for my
    RadioCraftsmen 1952 triode amps!
    My only (small) concern is the grainy sound
    of strings when I listen to classical music.
    I will dampen the horns and rewire the drivers as described on this board, I am also
    thinking of replacing the old condensers in
    the crossover- would that make sense?
    Does anyone have a schematic diagram of the
    Model 19 Xover or the condensers' values?
    Alas, GreatPlainsAudio know nothing about the "super crossover" there have been rumours
    about here on the board.
    Thanks for your cooperation.
    <font size="2" face="Verdana, Helvetica, sans-serif"></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Hello,

    Sorry, I posted before I had a chance to actually reply. I have model 19's as well. I changed the caps on the crossover to Jensen oil caps and Solen caps bypased by Jensen on the larger values. I also changed the resistors to Mills non inductice types. The inductors were left in tact. Horns were damped with plasticene (sp?). Wire was changed to 10 awg on the bass and Tara labs solid core on the horn. The improvement was huge. I also completely braced/damped cabinets without changing the internal volume of the cabinet. If you would like more info on what I did you can contact me directly at [email protected]

    Regards,

    Pat McDermott

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    Inactive Member Hornluvr's Avatar
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    [QUOTE]Originally posted by Ho

    rnluvr:
    [QB]Hi,

    Thanks for replying! Over the weekend, I tweaked
    my model 19 as intended: I dampened the horns with
    plastic adhesive tape ,rewired horns, woofers and
    the Xover with 2.5 sq mm OFC wire, and also replaced the caps with new MKT caps from my local
    electronics store. So what happened?
    The coloration that had messed up strings and
    voices is gone, but also a little magic that
    made the 19 sound like no other speaker, its sound
    is now more modern or normal, if you will.
    I guess the coloration was euphonic and had an effect
    similar to an APHEX exciter. ?So, if you are
    considering tweaking, seems you can't have the
    cake and eat it too! Regards, Martin

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    Inactive Member run's Avatar
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    Hello,

    According to Chris Johnson of partsconnexion.com (formerly the designer/owner of Sonic Frontiers), caps take at least 100hrs. to break in, depending on type etc. Some people say that a Jensen cap needs 200hrs before it settles down. When I replaced the caps on my 19's the sound was "bright" for three weeks. Since then, the sound has become much smoother. A word of warning, adding new caps will increase the transparency of what is arguably one of the most transparent speakers ever made. Therefore, the quality of cap used is (in my opinion) critical. You could experiment with Solen caps, as they are not too expensive and physically not too huge for the limited space on the crossover. I changed the resistors to Mills non-inductive types, however, Mills are expensive. Welborne Labs sells a cheaper resistor called Link, which is made by Mills. Personally, I feel the Mills resistors got rid of some of the grain that remained. Hocus pocus? Maybe.

    Regards,

    Pat McDermott

  6. #6
    Inactive Member Hornluvr's Avatar
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    Angry

    Pat, it is interesting that even totally passive
    components like capacitors need breaking in, this
    is a word of consolation for me because the sound
    is now a bit overly bright and revealing, but it
    should get better as you say.
    Still, my hats off to the Altec engineers who
    designed the 19- they knew exactly what they were
    doing, and improving on them without giving up some of the 19's unique virtues is not an easy task. After the changes, I notice a bit less of
    that palpable presence, the "you are there" feeling when listening to a live rock concert.
    I won't undo the changes,though, because with
    classical music the sound is much more natural
    and less tiresome over the hours.
    Regards, Martin

  7. #7
    Inactive Member run's Avatar
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    Hello Martin,

    The more transparent your system becomes the more it will point to weaknesses in the "chain". With my system most things sound very good, however, there are things that sound better on a ghetto blaster-compressed and badly recorded rock music for example. I listen to everything from Philip Glass to John Coltrane. Do you use a cd player or turntable? New cd's will sound quite good. Old re-releases on cd can sound compressed. If you use a cd player I can recommend a very good (and cheap) dac. The dac I'm talking about is a copy of the very expensive dac made by sakura systems (see link below). This dac is a non-over sampling filter less design. There are many people copying it on the net. Scott Nixon sells a copy for about 200US. These dacs sound very natural without the grain or glare of normal cd playback. Of course vinyl is best, however, new music is non-existent on vinyl.

    http://www.sakurasystems.com/articles/Kusunoki.html

  8. #8
    Inactive Member Hornluvr's Avatar
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    Lightbulb

    Pat, thank you for your remarks. I, too, have noticed that the 19 works as a kind of magnifying
    glass for the quality of recordings- 1960's or 70's generally sound impressive, I have some old
    tapes taken from AM radio which I never heard in
    such an astounding quality, it nearly makes you
    shiver. On the other hand, contemporary recordings
    that have been processed, de-essed, compressed,not
    to mention the OPTIMOD sound design that is now
    commonplace with FM radio, sound poor and dull over the 19- you're better off with a ghetto blaster. You are right, source is important, but
    I have a Wadia 850 CD player that is only bested
    by my Oracle IV turntable, not much to be improved
    here.However, here is one more question for you
    (or anyone else who happens to read this):
    When I disassembled the horns, I found a black
    button lying vertically in one horn. Well, the guy
    who sold the 19 had a 3-year old girl, and first
    I thought she had thrown that button in there, kids like to do that. So, I removed the button,
    but on close inspection, that is no button at all,
    it must be that famous phase plug! So, what does
    this thing do exactly? What if I don't have it
    installed at all(which is now the case)? Does it
    make any improvement- I could easily duplicate it
    -would it decrease the the high frequencies, given
    it has only four smallish holes? Any ideas on that
    subject? Regards, Martin Wunderlich

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    Inactive Member run's Avatar
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    Hi Martin,

    I have no idea what this "button" could be. When I took my drivers apart to send to Great Plains, I think the phase plug was orange. From what I recall, there is nothing in the driver that could dislodge itself, never mind anything that fits the "button" description. I'm sure Todd White would be able to tell you what this "button" is,if it is in fact part of the speaker, however, it could very well be a kid's toy.

    Regards,

    Pat

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    Inactive Member Hornluvr's Avatar
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    Wink

    To everyone who has had the nerve to read this thread one last and final remark 4 weeks after my
    initial posting:
    Yes, the caps have broken in, the harshness has given way to sweet and delightful sound.
    The best improvement yet and a strong recommendation to all Model 19 owners: Replace the
    rheostats with fixed value resistors, the "optimum" setting is short circuiting the HF
    rheostat and using a 10ohm, 5watts resistor instead of the MF rheostat. Try it,you will be
    surprised how distortions you might have thought
    to be intrinsic with the horn design simply vanish! Wow, the 19 still is one of the best speakers ever made. Best regards, Martin Wunderlich

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