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Thread: My new-to-me 820s

  1. #31
    Senior Hostboard Member cradeldorf's Avatar
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    Re: My new-to-me 820s

    Ummm I don't remember, The 16 gauge 1.5 Mh from parts express. which is actually up from the 1.1 Iron core Erse I was running. It seems like most crossovers I've seen have the same Mh coils on both sides where I was running a 1.5 Iron Core 0n my LF and a 1.1 on my HF.

  2. #32
    Hostboard Member johnny_fever's Avatar
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    Re: My new-to-me 820s

    Whats the time frame on the Cabinet work? Cant wait to see the pics. Thanks for all your help. Rick

  3. #33
    Senior Hostboard Member wws944's Avatar
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    Re: My new-to-me 820s

    Quote Originally Posted by johnny_fever View Post
    Whats the time frame on the Cabinet work? Cant wait to see the pics. Thanks for all your help. Rick
    Soon, I hope. We were thinking they would be done by the end of December, but Life got in his way.
    W.

  4. #34
    Senior Hostboard Member wws944's Avatar
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    Re: My new-to-me 820s

    Update: We spent a fair amount of time this evening marveling over the numerous differences in construction between the two cabinets. Some of which are very visible back in post #1 of this thread.

    Measurements of the DC resistance on the woofers are:

    Gray (1955 - 12 ohm rated) set: 8.6 ohms + 8.6 ohms measured
    Green (1957 - 16 ohm rated) set: 8.3 ohms + 8.3 ohms measured

    Compression drivers are:

    Gray (15 ohm rated): 8.8 ohms measured
    Green (16 ohm rated): 8.3 ohms measured

    Do these DCR values seem low? At least they are pretty consistent with each other.

    Still under discussion is if we should replace the crossover caps in the N800Ds or not. Both N800Ds have 10.5 mfd caps in them, but he has not had a chance to measure them and see if they are still in spec yet. (As a friend of mine likes to say - "To measure is to know".) If the caps are out of spec, it may just as easy to leave them as they are and build new crossovers. Or maybe bi-amp them? (I could buy a cheap Behrenger active crossover for what new crossovers would cost. I already have the amps.)
    W.

  5. #35
    Senior Hostboard Member Earl K's Avatar
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    Re: My new-to-me 820s

    Quote Originally Posted by wws944 View Post
    Update: We spent a fair amount of time this evening marveling over the numerous differences in construction between the two cabinets. Some of which are very visible back in post #1 of this thread.

    Measurements of the DC resistance on the woofers are:

    Gray (1955 - 12 ohm rated) set: 8.6 ohms + 8.6 ohms measured
    Green (1957 - 16 ohm rated) set: 8.3 ohms + 8.3 ohms measured

    Compression drivers are:

    Gray (15 ohm rated): 8.8 ohms measured
    Green (16 ohm rated): 8.3 ohms measured

    Do these DCR values seem low? At least they are pretty consistent with each other.

    Still under discussion is if we should replace the crossover caps in the N800Ds or not. Both N800Ds have 10.5 mfd caps in them, but he has not had a chance to measure them and see if they are still in spec yet. (As a friend of mine likes to say - "To measure is to know".) If the caps are out of spec, it may just as easy to leave them as they are and build new crossovers. Or maybe bi-amp them? (I could buy a cheap Behrenger active crossover for what new crossovers would cost. I already have the amps.)
    I wouldn't let the inconsistent labelling worry you what-so-ever .

    Those quoted dcr values are quite consistent with drivers having a 12 ohm rating ( which is really what most Altec & JBL components were up until around the early sixties ) .

    Some Historical Trivia ( as I understand it ) ;

    - It's after this that Altec moved their line of transducers towards a set of "truer" impedance ratings ( raising the dcr to @ 12 ohms for drivers that were rated as 16 ohms & lowering the dcr to @ 6.5ohms for things rated as 8 ohms ).
    - JBL took a different tack / they retained those mid 8 ohm dcrs and proceeded to still call their products 16 ohms . They then introduced lower impedance drivers ( some having dcrs as low as 3.2 ohms ) and called them 8 ohms ( while in effect they should have been called 6 ohm ).
    - A Lower impedance draw more current & are therefore "louder".
    - It's this deliberate mis-labelling ( or marketing "slight of hand" on JBLs part ) that would help trigger some finger-wagging (& put-downs) directed towards them ( ie; "Just Be Loud" being one of the more "insight-full" ) .

    Last edited by Earl K; January 9th, 2013 at 09:29 AM.

  6. #36
    Senior Hostboard Member wws944's Avatar
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    Re: My new-to-me 820s

    Quote Originally Posted by Earl K View Post
    I wouldn't let the inconsistent labelling worry you what-so-ever .

    Those quoted dcr values are quite consistent with drivers having a 12 ohm rating ( which is really what most Altec & JBL components were up until around the early sixties )...
    Thanks! One less thing to worry about.
    W.

  7. #37
    Senior Hostboard Member wws944's Avatar
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    Re: My new-to-me 820s

    Update: Slow progress. He has pretty much completed stripping both cabinets and repairing the veneer. Last week, we discussed replacing a couple of pieces of wood on the bottom of one that had gotten damaged over the years.

    In the meantime, here is a photo that my cousin found. It dates from about 1957-1958 - when my uncle first bought his first 820C. Mono at the time, of course. It was taken at my grandmothers house. I very well remember this scene from when I was a tot!

    1
    W.

  8. #38
    Senior Hostboard Member wws944's Avatar
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    Re: My new-to-me 820s

    Update: Last night we had a discussion on grill cloth. He is (carefully) removing the old cloth in preparation for the finish. The cloth is held in place on the removeable nose pieces with screwed in strips of wood. While the old cloth is in decent shape and could be reused, now is the time to consider replacing it. I know that the cloth was replaced on one of them back in the 1980s. At the time, my uncle managed to find reasonably matching cloth. (Knowing him, he might have driven over to Altec in Anaheim... But according to my cousins, he may have found a source in the San Fernando Valley.)

    In the Badmaieff and Davis book, they recommend "Newcastle 211-72 aluminum". Since the book was published 10 years after the speakers were built, I have no idea if they are the same or not. Googling around, it turns out that Newcastle is still in business and still making grill cloth. But their product numbers are different than the "211-72 aluminum" mentioned above. I've sent them an email to see if they can identify it and cross reference it to a current product. I also sent an email to Antique Electronics Supply (now called Tubes and More) to see if they have any opinion.

    In the meantime, does anyone here have any ideas on what this cloth is?

    This is the 1955 cabinet - which I believe is the original cloth:

    38

    This is the 1957 cabinet - with newer cloth, but similar to the original:

    39
    Last edited by wws944; March 16th, 2013 at 11:37 AM. Reason: Details, details....
    W.

  9. #39
    Senior Hostboard Member Audio_by_Goodwill's Avatar
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    Re: My new-to-me 820s

    Quote Originally Posted by wws944 View Post
    In the meantime, here is a photo that my cousin found. It dates from about 1957-1958 - when my uncle first bought his first 820C. Mono at the time, of course. It was taken at my grandmothers house. I very well remember this scene from when I was a tot!

    1
    That lamp and dresser are pretty nice looking, besides the 820 in the corner.
    Audio_by_Goodwill
    Michigan, USA

  10. #40
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    My new-to-me 820s


    Alien_Shore's Avatar
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    Re: My new-to-me 820s

    Not sure about the grill cloth, other than I totally agree that you should replace it!
    How cool would it be to have a thread of old pics showing new vintage gear in it's prime. That picture is a fantastic example.
    - Mike

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