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Old December 1st 20, 12:28 AM posted to rec.audio.tech
gregz
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Posts: 131
Default Onkyo Precise Acoustics

Dave Platt > wrote:
>> I have some nice speakers made with remnants from Parts Express excess. 8
>> inch woofers have a rubbery type surround. Just in the last two years the
>> surrounds started breaking what looks like tearing apart. I have redone the
>> two sets with rubber replacements think they are working well. Just
>> wondered if anyone knew what type of rubber they used. I guess they were
>> made in late 80s by Onkyo, so that would be about 30 years old. The driver
>> was on the front cover of a Speaker Builder Magazine with Keith Johnson.

>
> From what I've seen, speaker surrounds are most commonly made either
> of a closed-cell foam, or of butyl rubber.
>
> They are not necessarily interchangeable. Rubber surrounds are (I
> believe) both heavier and stiffer than foam surrounds of the same
> dimension. Their weight, and lower compliance can change the acoustic
> characteristics of the speaker - quite possibly enough to de-tune the
> speaker/enclosure relationship and throw off the speaker's frequency
> response. This would be more of an issue with vented/ported/
> bass-reflex enclosures than with sealed (acoustic-suspension) systems.
>
> Rubber surrounds seem to have a longer lifespan than foam surrounds,
> but they can go bad over time. I had to replace the rubber surrounds
> on a pair of 4" drivers in some Optimus AV mini-monitors - I believe
> they'd been used outdoors, and sunlight and heat had caused the rubber
> surrounds to become stiff and brittle.


Someone on this group might have known about these drivers. I don't have
many rubber surrounded speakers, but these were a first for me. All of hese
drivers seem to have failed about the same time regardless of use,
including being in original shipping container.

Greg
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