Maximizing wind from subs

[leo.nerd]

Hello. For a multimedia exhibit project I am exploring subwoofer options that maximize the "wind" felt from it.
Intuitively, I'm thinking: the lower the frequencies and the higher the SPL => more wind.
BUT are there other factors to consider? Like: a particular cabinet type or configuration, or the presence of port holes? Or even perhaps the type of signal that would maximize the felt "wind" impulse?

Are there sub models you recommend for this application?

And finally: what theoretical laws do we know that link air velocity and SPL from the sub?

Thanks a lot.

[resistorman]

I would use a fan in a fake sub cabinet next to the real one with its speed controlled by an inverter

[Drew Stephenson]

I would use a fan in a fake sub cabinet next to the real one with its speed controlled by an inverter

Definitely the easiest way of doing it! A sub is designed to produce vibration in the air, not gusts of wind.

[Hugh Robjohns]

I third it. If you want a breeze, use a fast-acting fan (more than one, probably) with a speed controller.

[Wonks]

Intuitively, I'm thinking: the lower the frequencies and the higher the SPL => more wind.
BUT are there other factors to consider?

You’re feeling air movement because the speaker in the sub is physically shifting enough air at a speed that you can feel it.

So to move a lot of air fast, you need to give it a big impulse, so lots of power and a signal with a big initial transient like a kick drum.

But the effect is very momentary and the sub needs to be very loud for someone close by to feel an effect. So loud, that for an installation, you’d probably fall foul of noise at work laws if you had the sub playing for any length of time. Fortunately the dB(A) weighting severely filters out bass frequencies, so you might just get by if there was only the sub and no top to go with it.

But any neighbouring buildings may well complain.

Do you want the boom and the wind together as part of the experience or is it just the pulse of wind? How often do you want the pulse of wind?

You don’t want a fan unless you want a continuous wind. Their inertia stops them from giving a sudden blast and it may tale a couple of seconds for them to get up to speed. For wind-only pulses, I’d be looking at an air compressor and a solenoid valve controlling blasts of air, which will be pretty much instantaneous. Compressors are noisy but can be a good distance away with an air line running to the installation.

If you want a noise as well, you could combine a smaller, quieter sub with a compressor air blast to simulate the effect but without excessive noise.

[Arpangel]

You wouldn’t even need a fake sub, a small stage fan strategically placed would do the job fine.

[Sam Spoons]

I'd have thought an air cannon would be just the thing. Toy ones are manually operated but it should be possible to build an electrical version.

https://en.wikipedia.org/wiki/Air_vortex_cannon

[Hugh Robjohns]

You don’t want a fan unless you want a continuous wind. Their inertia stops them from giving a sudden blast and it may tale a couple of seconds for them to get up to speed.

It's called a ROTARY WOOFER and several manufacturers make them, including Eminent:



http://www.rotarywoofer.com/howitworks.htm

The fan runs at a constant speed, but the angle of the blades is controlled continuously by a voice coil to generate different (low) frequencies, right down to 1Hz, at different amplitudes.

This arrangement can move substantial amounts of air, equivalent to a huge conventional subwoofer but much more efficiently and with much better LF extension. The fan idea offers a near perfect impedance match with the air, while a conventional cone driver has a huge impedance mismatch.

I've seen and heard rotary woofers used with electronic pipe organ replacements to generate 32/64ft voices with real power and clarity, and was extremely impressed.

If the OP wants trouser-flapping bass, this is the way to do it.

If the air puffs don't need to be generated by audio directly, a compressor tank venting through an automated valve would be more effective.

[Wonks]

Interesting!