Hi,
@John
right, it would be more complicated and probably costier in manufacture. But these aren´t intended as mass market drivers anyway. The sheer size of 15" to 18" discloses them from mass market home hifi.
@KSTR
The setas are no solution. If I wanted such a design I´d just glue a large dustcap onto a existing driver or spray foam on it.
This ´Patent´ is another showpiece in my collection of ´ridicules´.
KEF´s B139 was built this way and the claim of a broadened dispersion character because of the domed shape simply doesn´t apply in praxis. I remember a 12"-subwoofer of mbl germany that featured such a dome shaped membrane in the mid 80s. There is nothing new, let alone smart or special in this work. Too pity that trees lost their lives in spending paper for it.
As I said in the starting thread the idea is to increase the membrane area with a given basket size and to get a certain ´dome´ look. This look demands a different construction of the surround or the complete omittance of it.
jauu
Calvin
@John
right, it would be more complicated and probably costier in manufacture. But these aren´t intended as mass market drivers anyway. The sheer size of 15" to 18" discloses them from mass market home hifi.
@KSTR
The setas are no solution. If I wanted such a design I´d just glue a large dustcap onto a existing driver or spray foam on it.
This ´Patent´ is another showpiece in my collection of ´ridicules´. KEF´s B139 was built this way and the claim of a broadened dispersion character because of the domed shape simply doesn´t apply in praxis. I remember a 12"-subwoofer of mbl germany that featured such a dome shaped membrane in the mid 80s. There is nothing new, let alone smart or special in this work. Too pity that trees lost their lives in spending paper for it.
As I said in the starting thread the idea is to increase the membrane area with a given basket size and to get a certain ´dome´ look. This look demands a different construction of the surround or the complete omittance of it.
jauu
Calvin
John,
As you say, a "constrained U" surround has limitations. High pressure differentials will cause it to lift away from the walls and "slap" (make noise). This can be reduced by making the surround membrane thicker / stiffer so that the pressure against the walls is increased, but this increases the moving mass. A heavy surround is also undesirable because the moving mass is assymetric (mass is higher on outward excursions than inwards).
As for the ability of such a surround to keep the diaphragm centred, the actuator I saw used it as the rear "spider". (The front support was a carriage on rails supporting an array of disk drive heads.)
Personally, I'd prototype the design first, by modifying a conventional driver. It needn't be pretty, for example the rings could protrude outwards instead of inwards to clear the basket. It would need a flat face or solid diaphragm to brace the moving ring. Properly constructed, it could be tested with both conventional half-round and "constrained" diaphragms to measure the actual effect on parameters and noise.
Calvin:
Your original design (first post in this thread) would be quite noisy due to the sharp edge of the cone. Whatever surround design you use, plan on having the edge of the diaphragm thick / tall enough so that it is always within the edge of the basket, even at full outwards excursion. Otherwise you will get "cork from a bottle" noise as the diaphragm clears the basket.
As you say, a "constrained U" surround has limitations. High pressure differentials will cause it to lift away from the walls and "slap" (make noise). This can be reduced by making the surround membrane thicker / stiffer so that the pressure against the walls is increased, but this increases the moving mass. A heavy surround is also undesirable because the moving mass is assymetric (mass is higher on outward excursions than inwards).
As for the ability of such a surround to keep the diaphragm centred, the actuator I saw used it as the rear "spider". (The front support was a carriage on rails supporting an array of disk drive heads.)
Personally, I'd prototype the design first, by modifying a conventional driver. It needn't be pretty, for example the rings could protrude outwards instead of inwards to clear the basket. It would need a flat face or solid diaphragm to brace the moving ring. Properly constructed, it could be tested with both conventional half-round and "constrained" diaphragms to measure the actual effect on parameters and noise.
Calvin:
Your original design (first post in this thread) would be quite noisy due to the sharp edge of the cone. Whatever surround design you use, plan on having the edge of the diaphragm thick / tall enough so that it is always within the edge of the basket, even at full outwards excursion. Otherwise you will get "cork from a bottle" noise as the diaphragm clears the basket.
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