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Thread: Altec 9844-8B

  1. #211
    Senior Member Skywave-Rider's Avatar
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    Quote Originally Posted by Zilch View Post
    Can it be fixed? I'd say, "probably."

    [Not my job, tho.... ]
    Damnation!

  2. #212
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    A series of passive notch filters?

    Ugh, that's where I draw the line.

  3. #213
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    Quote Originally Posted by geaugafletcher View Post
    A series of passive notch filters?

    Ugh, that's where I draw the line.
    JBL routinely does it, including in TOTL products.

    However, with respect to vintage Altec, a driver swap is more, well, "expeditious...."

  4. #214
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    I opened today my 806A-16 ohms drivers and I find this diaphragm series:
    391046.
    Do you know something about this diaphragms?I can't find any info about that.
    Thanks for tips to all.
    I measure with an ohmeter and the value is something close to 10ohms.
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  5. #215
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    Quote Originally Posted by felixx
    I opened today my 806A-16 ohms drivers and I find this diaphragm series:
    391046.
    Do you know something about this diaphragms?I can't find any info about that.
    Thanks for tips to all.
    I measure with an ohmeter and the value is something close to 10ohms.
    - 391046 is not the diaphragm part number . What you have is most likely a 20275 diaphragm ( which is 16 ohm ) .
    - The 8 ohm counterpart ( to the 16 ohm 20275 ) was the 21597 ( found in the 806-8A & the 802-8D driver ) .
    - What numbers do you see written on the inside of the voice-coil ?

    - You can learn a lot about Altec part numbers by familiarizing yourself with the wealth of info found here ;



    ps; here's a pic of a 23744 diaphragm / note where the number is written .
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  6. #216
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    Notches at ; 3K, 6K, 8K, & 10K



    Quote Originally Posted by Zilch
    I'm suspecting the "TANGERINE Radial Phasing System" is the culprit here. Has no one else ever measured these Altec drivers and horns? Where are the curves?
    - I don't know if I would blame the "TANGERINE Radial Phasing System" as much as suspension irregularities & network incompatabilities .

    - The two pics of yours which I have included, show notches in different spots / with the 3K notch being common to the two drivers / horn combos .

    - Below is a Plane-Wave measurement of the 909 driver . It shows an inherent notch at 3K and one around 9K . ( I doubt we'll ever see the goods for the 902-8B driver ) .

    - FWIW; Yesterday I took my 902s and put them on about 8 different horns. One thing became apparent. The horn ( & it's classification type ) can either exaccerbate or minimize the notches. The included 909 info also reflects this somewhat.
    - I was able to make ( with real CD horn compensation ) a very respectable line/curve ( with only 1.5 db notches at 3 & 8K ) on an RCF 9041 CD-type horn ( which is much like a smaller 2370 ).

    - I came to the conclusion that the network will play a significant role in minimizing or expanding the notches ( into holes ) as large as what's seen with the M19 network . IMO, that network needs to be redesigned for use with the 902/811 combo.

    - Here's someone who has measured ( using Clio ) an 802-8G on a 1000hz Tractrix. One can see that the notches have been minimized.

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  7. #217
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    Might we not expect the resonance frequencies to differ depending upon the diaphragm type as well, Earl?

    Gary's 802s have standard diaphragms, whereas Skywave's are apparently 902 "Lites." :dont-know

  8. #218
    Senior Member Skywave-Rider's Avatar
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    Diaphragm ID

    Relaying some diaphragm info from Dave over at AK:


    "Hi,
    Those are 35480 aluminums, one of my favorite phragms from Altec in 1980, they're stock in the 902-8 ohm drivers. The only driver I like better is the BMS 4552ND for better treble, nice, Dave."

  9. #219
    Senior Member Skywave-Rider's Avatar
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    Quote Originally Posted by Earl K View Post
    - FWIW; Yesterday I took my 902s and put them on about 8 different horns. One thing became apparent. The horn ( & it's classification type ) can either exaccerbate or minimize the notches. The included 909 info also reflects this somewhat.
    Thanks Earl, that's interesting. I wonder if Zilch has tried this on the PT waveguide. I should have, but did not think of it b4 sending the 902s out.

    Quote Originally Posted by Earl K View Post
    - I was able to make ( with real CD horn compensation ) a very respectable line/curve ( with only 1.5 db notches at 3 & 8K ) on an RCF 9041 CD-type horn ( which is much like a smaller 2370 ).
    Using standard 6 dB/octave CD horn compensation?

    Quote Originally Posted by Earl K View Post
    - I came to the conclusion that the network will play a significant role in minimizing or expanding the notches ( into holes ) as large as what's seen with the M19 network . IMO, that network needs to be redesigned for use with the 902/811 combo.

    Could the incorporation of series notch filters into either the N800 or M19 constitute the redesign, or do you mean scrapping, entirely, the HF section of the x-over, making something totally new?

  10. #220
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    Quote Originally Posted by Skywave-Rider View Post
    Thanks Earl, that's interesting. I wonder if Zilch has tried this on the PT waveguide. I should have, but did not think of it b4 sending the 902s out.
    I'm doing additional measurements here, and can add that to the list.

    Also wondering whether there isn't more to the loading cap thing than everyone presumes. You might want to check that once they get back.

    Altec engineering has suprised us more than a couple of times now....

  11. #221
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    Guys, due to work commitments, I'm out of this discussion till late Thurs ( or Fri. ) .


  12. #222
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    Quote Originally Posted by Skywave-Rider View Post
    I wonder if Zilch has tried this on the PT waveguide.
    1) 902-8B #1 on 1" PT-F95HF and MR931 Model 14 horn, and both dialed "flat" using M19 crossover.

    2) On 811B full range with LE14A on axis and 15° off axis.

    3) RTA version of same for comparison to Skywave's measurements.

    4) On 511A full range with LE14A on axis and 15° off axis.

    5) Can 1/3 octave (31-band) AutoEQ fix it?
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  13. #223
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    More gnarly-looking graphs...

    Thanks for the measurements, Zilch!

  14. #224
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    Quote Originally Posted by geaugafletcher View Post
    More gnarly-looking graphs....
    Again, and I believe Skywave has already confirmed this, it doesn't sound bad, rather merely has an inherent coloration, no matter the program.

    If the same is demonstrable with standard diaphragms as well, it's a component of "That Altec Sound" characteristic of these later drivers....

  15. #225
    Senior Member Skywave-Rider's Avatar
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    Briefly had Selenium D220Ti drivers on the 811s, without proper compensation.

    Now that the BMS 4552NDs are back in the box, I have to say that the 9844s are beautiful sounding. Gorgeous. I'm lucky to have found them.

    Won't be able to open N-800-F this week. Have to figure out how to do the goo-softening procedure at my job -- where they live. Seems this is best done outside due to fumes produced.

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