I was looking at the purifi drivers with their weird-o surrounds and thought it might be possible to treat normal looking surrounds with thin sections of silicon caulking to damp surround oscillations. A stripe on the front then one on the back, maybe a dash dot pattern, maybe a pattern on the front inside edge or outside edge? I know people dope the edge of the cone, but this would be doping the surround in a pattern.
Would this do anything? Would it damp any resonances or just lower the Q by adding mass? Or, is enabl damping the cone more effective?
Anyone try something like it?
Would this do anything? Would it damp any resonances or just lower the Q by adding mass? Or, is enabl damping the cone more effective?
Anyone try something like it?
Absolutely.
Possibly. Depends on the nature of the resonances, what, how & where you apply any additions.
Likely do that too, or primarily depending on the specifics above.
It's not technically meant as damping in a broad sense, or wasn't intended to be so, although it does do that and I suspect the slightly asymmetric nature and placing them at key mode regions is a critical part of that.
At the risk of using the word 'depends[ing]' again 😉 -depends on the specific resonance. Cone edge damping is usually applied to soft cone types when the suspension is unable to prevent the periphery from resonating & it goes into antiphase, producing an obvious mode that plagues many midbass units (but not rigid cone types). Some damping on the suspension can help with that, though the culprit itself is almost always the cone. An exception can be a reflection from a wide roll surround, so some periphery damping on that may assist there. This is why Vifa came up with their asymmetric suspensions and / or cone edge shapes. Wideband drivers are a little different in that a much wider part of their operating BW is meant to be produced by controlled TL modes in the substrate -at least until you hit the VC point-source frequency when it's either a central cap or a very small area around the neck of the cone where it's bonded to the coil. So the modes tend to be distributed over a wider part of the cone itself & when problematic can need tracking down individually.
Purifi was not the first with “weird -o” patterns of alternating pleats, etc on driver surrounds: Fostex EZ series to name at least one. Of course, those also incorporates structural ribs on cones and dust caps, and IIRC, something special in the lower spiders as well?
Yes! I remember. There are several with wrinkly surrounds. Does anyone know if a variable thickness would help stop resonances?
I remember in the 70's Hitachi released a speaker with a pleated surround on the woofer. It was the first 'odd looking' surround I had seen.
Also, there seems to be no real recognition of the interesting rear of cone ribs that the classic Tannoys used >
it certainly did something good for the lovely 'firm & present' midrange sound.
Also, there seems to be no real recognition of the interesting rear of cone ribs that the classic Tannoys used >
it certainly did something good for the lovely 'firm & present' midrange sound.
Fostex has been playing with the concept of a surround that behaves in a linear manner no matter where it is in its movement. The shaps such that “ins" & "outs” cacel out the differences, I first saw it at AES 1999. Since then there have been other maker splaying with the concept.But poictures of Fostex are easy to pull out.
It woulkd be, i expect that one could change the behaviour of the surround to sorta imitate what they ar etryting to do. Very tricky to figure out exacly how. Someoine good with Cosmos maybe, or a ton of cut n try.
dave
