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Thread: Altec 950-8A duplex speaker spider required.

  1. #1
    Junior Member Michon's Avatar
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    Altec 950-8A duplex speaker spider required.

    Good day folks.

    I am a long time lurker here, but this is my first post. Part of the reason for this is that unfortunately Altec transducers are rare in Southern Africa. Despite this I was lucky enough to acquire a pair of Altec 950-8A duplex speakers recently. Unluckily a spider on one of them produces a resonant/flapping sound when playing low frequencies. I suspect this occurs because the horn had an excessive force applied to it that caused a crease to develop over a few of the corrugations of the spider that is attached between the horn and the woofer diaphragm. I hope that removing the spider, tightening the horn and installing a new spider will fix this problem and that no further damage is present.

    Below is a link to two videos illustrating the fault condition. In the videos I play a 50Hz sine wave through the woofer.
    The data compression applied to the videos by the host site has significantly reduced the resolution of the videos. I apologize for that.

    Are there detailed photos or graphs of the anatomy of these transducers that I missed in my internet searches? An interesting aside: the baskets of the 950-8A look exactly like EVM15L baskets, except that there is a compression driver mounted in the middle of the magnet assembly.
    Is there a company, such as Great Plains Audio, that sells suitable replacement spiders for this model of Altec speaker?

    Link to the videos: https://www.dropbox.com/sh/c54hskdyu...wphUYVgDa?dl=0.

    Internet photos of the Altec 950-8A (for those whom are unfamiliar with them): https://picclick.fr/Vintage-Altec-La...697624460.html.

  2. #2
    Senior Member RMC's Avatar
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    Hi Michon,

    Welcome aboard the Lansing Heritage.

    Unfortunately I cannot help you here. Sorry.

    As for that mention here "... the baskets of the 950-8A look exactly like EVM15L baskets,...", there MAY BE a possible connection about this. Altec and E-V were both owned by Mark IV Audio for a number of years. So there's a possibility the two companies might have shared, exchanged or sold parts to each other? Regards,

    Richard

  3. #3
    Junior Member Michon's Avatar
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    Thank you Richard. I am happy to be a participating member now.

    Once I have sorted out my Altec 950 drivers I will attend to my JBL 2482 units and others.

    I copied this post to a Facebook group called “Vintage JBL/Altec/TAD” and received a response indicating that due to the Mark IV Audio ownership and subsequent merger with Telex, the Altec 950 models are potentially made entirely from EV parts.

    The commenter mentioned that the woofer diaphragm is definitely an EV part. Prompted by the commenter I found a parts number listed by Great Plains Audio for the Altec 950-8A/B/C.


    Accordingly I will contact Great Plains Audio and the local EV agent to enquire about spare parts.

  4. #4
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    Some more info for reference purposes.

    Quote Originally Posted by WhiteBroncoii
    The clover leaf Duplex speakers were the 925-8A / 925-8B (12") and the 950-8A / 950-8B (15"). The "8A" modelsused a shared magnet and the Altec 909 HF driver. The "8B" models were built using all EV parts with the HF screwed on the back (sorta like a 604). Big 511 horns are usually either a 311-60 or 311-90.

    Gary
    Here's the Altec 950-8A spec sheet


    Attached Images Attached Images    

  5. #5
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    I hope that removing the spider, tightening the horn and installing a new spider will fix this problem and that no further damage is present.


    Hi,

    I believe those spiders only serve the purpose of acting as a dust barrier over the voice-coil & gap area.

    Based on that belief, I would explore replacing this type of cover with the older ( felt type ) used by Altec up to the end of the 604-8G duplex model.

    Name:  1566220-6048g-duplex-loudspeaker-system.jpg
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    Mind you. I believe it's harder to make the felt "bib" look good + pro on a retrofit > but black felt is easily obtainable ( + it'll never give the sort of problem you're currently experiencing ).

    I believe it was the 604-8H model that introduced using a spider ( as dust-cover ) .

    GPA should be able to provide either type of dust cover to you.

    OTOH, if mine ( before buying any replacement ), I would first remove that horn and then see if I could reconstitute/reform the existing spider using heat ( hair dryer ) and a bit of moisture.




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