Using a speaker to drive air for Halloween prop

vbimport

#1

I’m building a Halloween prop to send a puff of air using a 12" woofer speaker. The speaker is mounted in a 12" cardboard tube that is 2 feet long. The other end is plugged with a piece of plywood with a 2" hole. My problem is that the speaker is not moving enough air. The air puff is weak and only can be felt a few inches away.

How can I drive the speaker to the maximum movement forward in a quick motion?

Presently I’m using a switching power supply (110v AC) input with a 15w 12v 1.25amp output.

I tried a 15 amp 12v output power supply and this actually produced less air movement.

Any ideas?

Randy
randall-davis@cox.net


#2

Depending on the wattage, you may need to go to more than 12 volts, though beware, as the DC resistance will be lower than the stated impedance.

Short term, you could exceed the RMS power by 50-100%.

Using a charged capacitor to deliver a kick, may be a way to deliver a good transient jolt without the problem of sustained power dissipation.

Another possibility, though it would probably need electronic switching, would be to bias the speaker the opposite way just before firing, so the excursion is doubled.

The other thing, the tube may be working against you, maybe funneling the narrow end somehow might improve things, as a flat stop with a hole is probably reflecting a pressure wave back.

Another approach springs to mind, if you could engineer it - flap valves and drive the speaker from an AC transformer, so it works like a gaint sized vibrator pump.