Hi Mattes,
Your petal baffles look to have created a successful solution to many of the OB compromises and with a curved baffle and appear to be the front half of the torus with 'scalloped edges' to form the 5 petals - have you built these from resin/fibre and added the 'flock' finish?
If the diameter of the bass driver is 12" (?), this would make the outer diameter of the torus about 3 ft (1 metre)?
I have been tempted to apply the 'planet 10' EnABL treatment to my Coral Beta 8 drivers to tame the cone resonances but unsure of final result.
Your petal baffles look to have created a successful solution to many of the OB compromises and with a curved baffle and appear to be the front half of the torus with 'scalloped edges' to form the 5 petals - have you built these from resin/fibre and added the 'flock' finish?
If the diameter of the bass driver is 12" (?), this would make the outer diameter of the torus about 3 ft (1 metre)?
I have been tempted to apply the 'planet 10' EnABL treatment to my Coral Beta 8 drivers to tame the cone resonances but unsure of final result.
Greg - yes, John was lots of fun - bless him where / whatever he's up to
- maybe he created his own acoustic even horizon and is inside enjoying the hell out of his system, just can't report back
Indeed! I no longer can get much in the way of event timing right and all our correspondence, both on and off the forum is on my damaged HDs, but the way I remember it is that not long after there was a hurricane that wasted CR and he never responded to any of my emails afterwards...........
GM
Hi James,
The baffles have been built from EVA foam with a density of 100kg/m³, from 4 cm sheets glued to a stack of 16cm (for the bass baffle) with black epoxy. The petal form has been routed in 1 mm increments and then has been sanded to a smooth surface, the baffles have a very luxurious appearance in nature, like being made from a block of suede.
The bass driver is an 18" AE Dipole 18, the bass baffle is 93 cm in diameter.
If you´re in the lucky situation of having a good pair of Coral Beta 8, I would strongly suggest not to do any physical changes to a historic driver like a Beta 8. Taming the resonances with an either active or passive filter of sensible attenuation and of high quality is IMHO the better way to get a balanced representation out of these very good drivers. This is not easy nor cheap, but to match these driver´s quality, all correction approaches shouldn´t incorporate any compromises.
All the best
Mattes
Oh, much bigger than I thought - much work to build those - that's a really heavy density of that EVA soft 'foam-rubber' material, yes? Absorption coefficient?
I am about to start cutting shapes in multiple layers of 75mm thick Expanded PolyStyrene sheets that's used for external house wall cladding out here (you can cut it with hot wire knife) - medium density, I think.
Then bonding front & back sides to a central 18mm plywood layer (to mount the driver) and seal the surface - just a beginning ...
And yes, keeping the beta8 drivers natural - found best results in 16"dia (40cm) spheres and tuned cavities to reduce cone resonances and with the Xover >150Hz - still very good performer after 50 years use!
I am about to start cutting shapes in multiple layers of 75mm thick Expanded PolyStyrene sheets that's used for external house wall cladding out here (you can cut it with hot wire knife) - medium density, I think.
Then bonding front & back sides to a central 18mm plywood layer (to mount the driver) and seal the surface - just a beginning ...
And yes, keeping the beta8 drivers natural - found best results in 16"dia (40cm) spheres and tuned cavities to reduce cone resonances and with the Xover >150Hz - still very good performer after 50 years use!
Hi James,
The density of the material used was chosen due to the fact that the baffles should fulfil a mechanical job as well, separating front from back waves. Too "sloppy" would have probably not been of any good... and a certain rigidity has helped insofar that I was able to route and sand the complex shape.
With the flowers, I didn´t really mount the drivers onto them, instead I mounted the baffles onto the free-swinging drivers by means of a rear ring of the same material which clamps the whole thing onto the drivers frame. The baffle and the ring have wooden inserts to provide rigidity when the clamping force is applied by a set of screws, but contact with the frames is only by 2,5mm sorbothane inserts.
All the best
Mattes
The density of the material used was chosen due to the fact that the baffles should fulfil a mechanical job as well, separating front from back waves. Too "sloppy" would have probably not been of any good... and a certain rigidity has helped insofar that I was able to route and sand the complex shape.
With the flowers, I didn´t really mount the drivers onto them, instead I mounted the baffles onto the free-swinging drivers by means of a rear ring of the same material which clamps the whole thing onto the drivers frame. The baffle and the ring have wooden inserts to provide rigidity when the clamping force is applied by a set of screws, but contact with the frames is only by 2,5mm sorbothane inserts.
All the best
Mattes
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It's a shame you don't still have the measurements. There is a nice large radius round over on them too. DonVK has been doing some simulations of a torus on my thread here Did Siegfried Linkwitz miss a trick? and it seems to have some potential, more than many expected.
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