Brahma 15 EXTREME, and 18! (1 Viewer)

[Brett DiMichele]

Cam,

Yes it would displace a "Shitload" of air.. Is that a
technical term?

A crank is an interesting idea and perhaps when linked to
a servo motor and some advanced computer system it could
work like a suspension. I don't see why just a servo motor
coupled to some fancy processing couldn't be all the more
"cone control" you need.. The motor can move the piston in
and out..

 

[Ryan Schnacke]

The engine piston idea is a tempting one. But remember that in order to produce varying volume (SPL) levels you have to vary the distance that the piston moves in each cycle. An engine piston moves the exact same distance every time the engine turns over.

Speed of movement controls frequency.
Distance of movement controls volume (SPL).

So it can't work exactly like an engine. But maybe something close. The motor turning the driveshaft could just twist a bit in one direction, then the other for each cycle, rather than making complete revolutions in one direction. 90 degrees of revolution in each direction would give you 180 degrees total. This is where you reach Xmax.

The bonus is that it would be impossible to bottom a well-designed piston woofer.

 

[MichaelAngelo]

Brett,

just theorizing, but could the "suspension", the return force, be a "repel" magnet at end of designed xmax?
Im thinking a + on the cone, with - around it for suspend, with + on the ends to provide a "centering" effect. Anyway, I'm out on a limb here, more like a leaf, and thought I'd put the idea to better minds than mine.
Thanks,

Mike

 

[Bill Fagal]

Pistons would be great if someone could come up with a way to eliminate static friction.

When one surface slides over another, there is always some amount of friction. When those surfaces aren't moving in relation to each other, static friction dominates, which is more difficult to overcome than dynamic friction (this is why antilock brakes work better than skidding.)

So static friction would make a piston subwoofer nonlinear because it would take a disproportionate amount of energy to start the piston sliding.

Magnetic suspension would be cool, but the way you describe it I think the centering force would rise exponentially from dead center instead of being linear. Hartley uses a magnetic suspension in some of his designs to apply restoring force, along with a spider for lateral VC positioning. It's a thin layer of iron on the former under the VC windings that is magnetically attracted to the zero excursion point.

Hey, keep brainstorming! Free thinking leads to breakthroughs.

 

[Steven Kephart]

Pistons would be great if someone could come up with a way to eliminate static friction.

When one surface slides over another, there is always some amount of friction. When those surfaces aren't moving in relation to each other, static friction dominates, which is more difficult to overcome than dynamic friction (this is why antilock brakes work better than skidding.)

So static friction would make a piston subwoofer nonlinear because it would take a disproportionate amount of energy to start the piston sliding.

Yeah, I agree. The crankshaft idea is interesting, but there would be a great deal of mass for the motor turning the crankshaft to overcome, not to mention the friction mentioned above. Efficiency would be much lower wouldn't it? Not to mention that you would have to oil it up every once in a while. Plus as the sides wear, your going to lose SPL over time as the backwave starts leaking out around the sides.

But maybe someone has an interesting idea to overcome these problems.

 

[Brett DiMichele]

Steve good points...

But would it be cool to say "Well my Sub has 110 thousand
miles on her.. Time to bore her out 0.010 over...