As you can probably tell, I love these drivers....and it pains me no end that I can't find another good pair anywhere for love nor money...
When I got these around 2004 there were quite a few of these "new" from spare parts hand assembled ones floating around if you knew where to look and didn't mind paying a bit for them, (I think I paid about $250 US for my pair, roughly the same price as a brand new pair of FE207E at the time) but they must have all gone by now as I haven't seen a single pair for sale in the last 2 years that I've been actively looking again...the only way I will ever find another pair is to somehow find and prize them out of the hands of another full range collector
The reason nobody buys the patent for them is probably because Coral went out of business in the mid 80's never to be seen again. On the other hand that means any patents have expired so it would be possible for someone to make a clone of them...
Yes I see the whizzer cone on yours has crumple damage and that they've had a hard life - I've tested a couple of 8A-100's that have that type of crumple damage and if it's minor crumpling it will reduce the treble a bit, but if it's major that 2.4Khz resonance may appear with a vengeance, however it's possible that cutting out the dome may mitigate or solve that resonance even with the crumpled cone. Without seeing a FR or CSD plot of your driver it's hard to be sure, but the treble wont be quite what it should be with the crinkles in the cone.
Regarding the "Stiff suspension syndrome" that yours have, my Flat 8A have exactly the same problem, their surround was very stiff when I first got them and attempting to dope the surrounds with lubricant and later remove it (with alcohol) has just made them even stiffer.
They're so stiff in fact that the Fs of the driver is 105Hz, with at most 1mm of suspension movement, while the Flat 8 Mk II's have lovely soft supple suspension with an Fs of 38Hz, and about 8mm of total physical travel. They're almost too soft.
Needless to say my Flat 8A's produce next to no bass, making them useless as anything other than a wide range midrange driver, on the other hand the Mk II's with their soft suspension have very good bass for a full range driver.
I use them daily in 44 litre bass reflex cabinets tuned to 43Hz and on paper their F3 is about 50Hz, (and 6dB down at 43Hz) however by the time you factor room gain into the equation they produce pretty damn solid bass right down to 40Hz for an 8" driver, and I still have to use a PEQ to cut down the lowest room resonance at 39Hz by several dB.
I don't know what their exact linear Xmax is but it seems to be around +/- 3mm which is pretty decent by full range driver standards, so they're perfectly usable in a bass reflex cabinet with a bit of baffle step compensation.
I plan to build better cabinets for them one day and running some T/S sims in WinISD suggests that a 55-60 litre cabinet tuned to 40Hz is about optimal and will extend the cutoff frequency a few Hz lower than what I get now, while still maintaining a flat response before roll off.
The stiff suspension syndrome puzzles me, I can only assume that different models or batches had different suspensions. In the 8 years I've had them there has been absolutely no change in stiffness of my MkII's, they're soft as ever, and the 8A-100's which my Dad has are over 30 years old and they are still soft and supple as well, yet my Flat 8A's are stiff as a board.
I don't think it's worth trying to treat the existing surrounds, if you like the sound you're getting now in the mid/treble it may be worth getting the surrounds replaced by someone who does reconing. Although there probably aren't any spare parts for the Flat 8's left, the surround on many current 8" full range drivers such as the Fostex FE207E is very similar and may be almost a drop in replacement.
It's a soft fabric reverse roll that looks like it's almost the exact same dimensions and stiffness as my MkII's, although it's black instead of cream. Someone who does reconing of full range drivers should be familiar with one that might fit.
If you replace that stiff surround with a new soft and supple one I think you'll be amazed at just how much the bass improves, the difference would be night and day.
My MkII's are a yellow not cream colour as well, and look very much like yours. (Most Flat 8's are white/cream) I've attached a couple of pics of how they looked when I first got them. They still look much the same now just slightly dirtier There is also a little bit of cracking of the rubber gasket around the edge for no apparent reason...(I notice the important gap between the dust cap and whizzer cone I mention in the previous message is quite apparent in that picture...)
When I got these around 2004 there were quite a few of these "new" from spare parts hand assembled ones floating around if you knew where to look and didn't mind paying a bit for them, (I think I paid about $250 US for my pair, roughly the same price as a brand new pair of FE207E at the time) but they must have all gone by now as I haven't seen a single pair for sale in the last 2 years that I've been actively looking again...the only way I will ever find another pair is to somehow find and prize them out of the hands of another full range collector
The reason nobody buys the patent for them is probably because Coral went out of business in the mid 80's never to be seen again. On the other hand that means any patents have expired so it would be possible for someone to make a clone of them...
Yes I see the whizzer cone on yours has crumple damage and that they've had a hard life - I've tested a couple of 8A-100's that have that type of crumple damage and if it's minor crumpling it will reduce the treble a bit, but if it's major that 2.4Khz resonance may appear with a vengeance, however it's possible that cutting out the dome may mitigate or solve that resonance even with the crumpled cone. Without seeing a FR or CSD plot of your driver it's hard to be sure, but the treble wont be quite what it should be with the crinkles in the cone.
Regarding the "Stiff suspension syndrome" that yours have, my Flat 8A have exactly the same problem, their surround was very stiff when I first got them and attempting to dope the surrounds with lubricant and later remove it (with alcohol) has just made them even stiffer.
They're so stiff in fact that the Fs of the driver is 105Hz, with at most 1mm of suspension movement, while the Flat 8 Mk II's have lovely soft supple suspension with an Fs of 38Hz, and about 8mm of total physical travel. They're almost too soft.
Needless to say my Flat 8A's produce next to no bass, making them useless as anything other than a wide range midrange driver, on the other hand the Mk II's with their soft suspension have very good bass for a full range driver.
I use them daily in 44 litre bass reflex cabinets tuned to 43Hz and on paper their F3 is about 50Hz, (and 6dB down at 43Hz) however by the time you factor room gain into the equation they produce pretty damn solid bass right down to 40Hz for an 8" driver, and I still have to use a PEQ to cut down the lowest room resonance at 39Hz by several dB.
I don't know what their exact linear Xmax is but it seems to be around +/- 3mm which is pretty decent by full range driver standards, so they're perfectly usable in a bass reflex cabinet with a bit of baffle step compensation.
I plan to build better cabinets for them one day and running some T/S sims in WinISD suggests that a 55-60 litre cabinet tuned to 40Hz is about optimal and will extend the cutoff frequency a few Hz lower than what I get now, while still maintaining a flat response before roll off.
The stiff suspension syndrome puzzles me, I can only assume that different models or batches had different suspensions. In the 8 years I've had them there has been absolutely no change in stiffness of my MkII's, they're soft as ever, and the 8A-100's which my Dad has are over 30 years old and they are still soft and supple as well, yet my Flat 8A's are stiff as a board.
I don't think it's worth trying to treat the existing surrounds, if you like the sound you're getting now in the mid/treble it may be worth getting the surrounds replaced by someone who does reconing. Although there probably aren't any spare parts for the Flat 8's left, the surround on many current 8" full range drivers such as the Fostex FE207E is very similar and may be almost a drop in replacement.
It's a soft fabric reverse roll that looks like it's almost the exact same dimensions and stiffness as my MkII's, although it's black instead of cream. Someone who does reconing of full range drivers should be familiar with one that might fit.
If you replace that stiff surround with a new soft and supple one I think you'll be amazed at just how much the bass improves, the difference would be night and day.
My MkII's are a yellow not cream colour as well, and look very much like yours. (Most Flat 8's are white/cream) I've attached a couple of pics of how they looked when I first got them. They still look much the same now just slightly dirtier
There is also a little bit of cracking of the rubber gasket around the edge for no apparent reason...(I notice the important gap between the dust cap and whizzer cone I mention in the previous message is quite apparent in that picture...)Attachments
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I have 5 Flat 8 MkII is whizzling at certain frequencies, and one in perfect shape, one has a damaged cone, and looks bad but is working, and sound is OK, but I can somehow feel something is wrong.. somewhere
..., and one is whizzling seriously bad. The fifth is in bad condition all over, it plays, but has a hole in the cone, and the middel cone os damaged, miscolored, and so on...So... how ..I mean is it possible to repair them? in ol' days in Denmark where i live, you just went to where you bought them, Audioscan in Copenhagen, and they repaired them, and if I don't remember wrong you could buy a repaired one and then give your own damaged in exchange + a small fee.
and voila you had a new Flat 8".
Today I have searched the net a lot to find someone that can repair ot at least find some kind og a "manual" to how to.. so thaat I don't smash them in first try., BUT so far I have not found anything. The larges speker repair shop in Dk told, me it is not possible to repair be course n spare parts are available at all..
but is that the truth?
I wonder what happend to Coral speakers but the story I heard was, the ingeneers was seriousl old, and the factory was sold to someone that shut it down,,, what a pitty ... seriously..
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