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RE: Coral 4" speaker

Re "One great mod which some people do to the series 2 is to replace the aluminium dustcap with one made from paper (as has been done to the one in the ebay link mentioned). It makes the top end slightly sweeter and is what Coral did to the final batch of 500 or so Flat 5's before the company closed down (or was taken over). If your cone has a aluminum dustcap you may wish to try this tweak yourself."

From 1975 to 1985 I was involved in the production of Audiosphere concrete sphere enclosure loudspeakers using the Coral Flat5-II driver (Sphere2). The original prototypes were built around 1976-77, using the earlier version of the Flat5, which was unlistenable due to severe cone resonance problems. Coral resolved this problem with the Flat5-II, with improved treatment of the cone surround. We were still aware of some 'shout' being caused by the duralium dust cap, and around 1979-1980 placed a special order for 300 modified Flat5-II's fitted with the paper dust cap from the Coral 4A-60. Most Audiosphere Sphere2's are fitted with this driver.

I agree with the comments in the post about the Flat5-II - despite its modest specifications, it remains one of the best fullrange drivers ever made. It required an enclosure like the Sphere2 to achieve its full potential, and could sound very thin and nasty in conventional boxes. It was ideally suited for use with low-powered triode valve amps and solid-state Class A amps (eg Sugden A21). Its rendition of pianos and voices is still unsurpassed by most commercial loudspeakers.

Several Sphere2's were purchased by people who had previously owned Quad's - the Sphere2's achieved the transient performance of the Quad's without the dynamic range limitations typical of electrostatic loudspeakers.


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  • RE: Coral 4" speaker - dgjones 05:20:37 03/04/09 (0)

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