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Thread: Great Plains Audio

  1. #1
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    Great Plains Audio

    Hi

    I own a pair of 605-B. one of these was blown by a problem in a Luxman amp...it really burned it. ..so well I tried reparing it.

    I ordered to Great Plains a recone Kit and a Diaphragm, and where installed by an Altec representer here in Mexico City, and the sound quality of the diapragm, +comparing it with the old one is not even near. donīt know why. Several persons told me Great Plains Audio was the best option. Bill Hanuschak told me there is no reason to the sound to be different, I believe him and since then I have been trying to explain what happened.

    The original diaphragm was covered or made with a silver color "tape" around the voice coil, this in the new one is copper color and there is no "tape" just the coil..this causes a small diference between the 2 speakers

    the sound in the original one is different and superior...

    Does anyone has tried changing the old dipragms for brand new Great Plains Audio ones???

  2. #2
    Senior Member spkrman57's Avatar
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    Symbiotik vs aluminum

    Which one did you order?

    What you describe is the symbiotik which handles more power, but less HF response.

    Ron
    JBL Pro for home use!

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    My guess is the magnet needs recharging. If the luxman went DC at the output, that could have been enough overcurrent to somewhat discharge the alnico magnet.

    How far was the speaker disassembled for repairs?

    Disassembly of the HF driver beyond removal of the cover and diaphram will render the magnet in need of recharge.

    Low magnet charge will reduce both sensitivity and HF response.

    AFIK, Bill does not offer/build symbiotik diaphrams, however i'm not positive on this.

    At any rate, with the alnico drivers/speakers from Altec i strongly recommend sending the entire unit to GPA for rebuild.

    Since there was a known amplifier problem it might also be a good idea to check that all crossover components are still within spec.

    Just my 2 cents worth..........

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    Can you post a pic of both the old and new diaphrams?

    The new phram from GPA should have required changing the terminals on the lead wires to a 1/4 inch push on spade rather than the old style screw type which is what the old phram should be.

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    Senior Member louped garouv's Avatar
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    Quote Originally Posted by bowtie427ss View Post
    AFIK, Bill does not offer/build symbiotik diaphrams, however i'm not positive on this.
    pascalite is the higher powered version now methinks

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    pascalite is the higher powered version now methinks
    Right on! I have GPA 26420 Pascalites in my 802-8G's, the look identical to the all aluminum versions and i cannot hear a difference, but that doesn't mean there isn't one. Either way, far superior sound to the symbiotik.

    If the OP does indeed have a symbiotik, something "fishy" happened somewhere other than on GPA's end.................. IMO.

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    Senior Member louped garouv's Avatar
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    that diaphragm change puts you in "quasi 808-8B" territory....

    IIRC

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    You're correct in the respect that by changing the diaphram to a pascalite doesn't make it exactly an 802-8G, but rather an 802-8GHP. The 808's in stock form use the orange mylar surround in lieu of the all metal tangential surround, the symbiotik's have a much lower and steeper HF rolloff, not doing much above 14k. I've read where it's claimed that HF extension on the symbiotik was intentionally limited.

    From my understanding the cheif difference between the aluminum and pascalite phrams is the actual metallic alloy known as "pascalite", and stronger "lead in" conductors. It's supposed to have a higher fatigue resistance than the all aluminum type. In all other respects, they're the same.

    first 2 pics are symbiotik (left) and pascalite (right).

    second 2 pics are a never before opened 806A from a 9844A studio monitor with original 16 ohm aluminum phram.





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    Senior Member spkrman57's Avatar
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    According to Bill H at GP..

    Pascalite is hardened aluminum.

    He said some think it is too forward, others like it.

    I have Pascalite diaphrams in my 902's and 399's.

    I like them!

    Ron
    JBL Pro for home use!

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    Quote Originally Posted by spkrman57 View Post
    Which one did you order?

    What you describe is the symbiotik which handles more power, but less HF response.

    Ron
    I ordered the original one, I will post some photos of both

  11. #11
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    [quote=bowtie427ss;143551]

    How far was the speaker disassembled for repairs?

    Disassembly of the HF driver beyond removal of the cover and diaphram will render the magnet in need of recharge.

    Low magnet charge will reduce both sensitivity and HF response.

    AFIK, Bill does not offer/build symbiotik diaphrams, however i'm not positive on this.
    quote]

    ---------------------------------------------------------------------

    I donīt know how far was dissasembeld, but as far as I know they did a very bad work, so I expect anything . first they tried to fool me installing a non original recone kit..the diaphragm was altec made (I saw the box)....later I ordered the hole kit and diapraghm from GPA...a long story...they also bad serviced my Mcintosh (also representers) at the point the amp does not function any more ...

    your post has beeen very usefull:

    the one I ordered was the aluminium type (right one of the first two pics)
    the original one (as I have in the other speaker and has never been opened) is like the one in the 3rd pic

    BUT the original one taken from the speaker does not looks like the one sended by GPA only in the voice coil color

  12. #12
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    Thinking it well. I dont even think the diaphragm was burned, it sounded...they only changed it for billing me a new one...after all the story I asked them to return the original one and it was all damaged because of bad storing but the voicecoil was intact.

    The woofer was parcial-burned, it sounded but not as It was meant to be..it sounded like a burned speaker

    - Itīs kind of hard to explain some of the terms I want to in English - Hope I make my point.

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    So.......In order to conclude this thread.

    Maybe the HF unit was totally opened, I checked the invoice from GPA and they send me the original one With itīs corresponding conversion Kit "802C HF 34852 Aluminum 16 ohms"

    The sound is not weaker..is just different; less smooth, a more metal sound, less warm. harsh in peaks....not as the fine clear sound from the original one

    My plan is firts try to repair it completely here in Mexico if it is not posible I will defenetely send it all the way to Oklahoma

    * How does a HF driver is re-magnetized? - maybe here in Mexico I can find someone who can do that

    *How do you verify if the magnets need re-charge (how to meassure) and how can you know itīs optimal charge point?

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    Ice thawed today!

    Ummm...probably no need to ask the obvious, but I have new-found respect for redundancy; have you verified all components are connected properly? Sounds to me like an out-of-phase issue, which happens a lot when people install the wiring conversion mods needed for new 'frams. I've done it myself.

    Like NOS crankshafts for '49 Plymouths, there are essentially no more NOS exact replacement diaphragms available. Likewise, each item went through nearly annual production refinements (see older parts references), so there were likely instances where even Altec wouldn't have had (or recommended) exact replacements for every variant. What you got then was the current version of the original part.

    GPA started (continued) making the same versions that Altec made when it died, though there may and likely will be continued developement. I'm fully confident saying they continue customer support in the manner that Altec did in the old days, maybe better.

    Your local tech obviosly wasn't too excited to do the job your way. After all, it's kinda like taking your own groceries to a restaraunt so you only have to pay them to cook it...doubt if you'll get a lot of warranty work there.

    (Add/edit) Always recone, re-fram or similarly service items in pairs if that's how you're going to use them. Makes for happy camping!

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    Moldyoldy makes a great suggestion here, and refreshes me on the importance of always verifying/eliminating the simplest possibilities frst.

    Thanks moldy, you've just reminded me that as with most troubleshooting, issues are often far simpler than we assume.

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