Dear speaker manufacturer, the “parachute-style” diaphragm is 5 times lighter than a speaker cone and it can add 13 dB of sensitivity to your subwoofer, yet it is not susceptible to the problems associated with speaker cones like audible resonances, distortions, oil-caning, etc.
So why wouldn’t you prefer it??
How it works: please note that we went over the math quite thoroughly so if something does not seem right please don’t hesitate to ask, figure 1 is a cross-sectional view of a speaker with a parachute-style dome-shaped diaphragm and surround (colored red) that is [uninterruptedly] held taut due to a small positive air pressure maintained in the enclosure. Like a parachute, the diaphragm relies on air pressure and tensile stiffness to maintain its shape, so a 12” subwoofer diaphragm can be thinner than 30 microns of carbon fiber or aramid and still be extremely “acoustically-stiff”, a carbon fiber ring (colored purple) with high compression stiffness circles the diaphragm, this ring separates the diaphragm from the surround and is supported from multiple angles at every point so that it cannot bend and the diaphragm has nowhere to flex.
The thin diaphragm is extremely “acoustically-stiff”, this is because acoustical forces will never exceed the force applied on the diaphragm by the air pressure inside the enclosure (which may be around 1 psi), thus the stiffness of the diaphragm remains equal to its tensile stiffness, which is orders of magnitude greater than typical bending-stiffness which has a leverage advantage and which plagues conventional cones, the surround also benefits from this air pressure which allows for extreme excursion without any buckling.
To hold the diaphragm and surround taut requires a force that is constantly pulling on them, this force can be created in several ways, the simplest way to create this force would be to add a DC current to the voice coil.
However a much more efficient way to create this force is with specially designed lever(s) that pull on the diaphragm and surround, these levers are special in that they don’t utilize hinges or any parts that can wear out over time, or make noise, also, they contribute only a minimal amount of mass and stiffness to the diaphragm assembly, these levers (see figure 1, colored light-green) don’t use hinges instead they are held at one end completely by very stiff (spiral) springs, and although these (spiral) springs are stiff enough to hold the levers the leverage created by the levers makes them appear very compliant and light from the perspective of the diaphragm assembly, the effects of leverage on mass and compliance is proportional to the SQUARE of the leverage, so only the ends of the levers really add undesired mass to the diaphragm assembly, but that mass is small (a fraction of an ounce for a 12” subwoofer).
This leverage allows the (spiral) springs to have more mass so that they may store more potential energy, this allows the levers to pull on the diaphragm with significant force while still remaining compliant i.e. the force from the levers change very little with diaphragm excursion.
Stresses on the (spiral) springs are kept well below their steel-fatigue-limit allowing them to last forever, the same is true for the tension members that connect the levers to the former. The (purple) tapered former holds the voice coil inside the (blue) magnet assembly, tension members arranged in the shape of a cone connect said former to the diaphragm and surround.
The spider too is specially designed in that the heavier parts of the spider, i.e. the parts that store the potential energy, don’t need to move as much, It is also worth stating here that although it is commonly said that half the spider’s mass gets added to the diaphragm assembly mass, this is simply not true (see more on this below).
Published as well as unpublished patent applications are pending, we believe all these patents will be granted.
Manufacturers, please contact us, we will try to make it worth your while: email@example.com
Regarding spider mass, although it is commonly said that half the spider’s mass gets added to the diaphragm assembly mass, this is simply not true, e.g. points on the spider that are halfway between the former and the basket would ideally be moving at half speed and should therefore offer half the inertial resistance however that inertial resistance force does not fully apply itself to the former, instead only half of it is applied to the former and the other half is applied to the basket, the end result is that only one quarter of its mass can be felt, additionally, the spider’s contact area with the former is smaller than its contact area with the basket, this too has a big effect.