Thigpen Rotary subwoofer

There is no comparison between the Thigpen rotary design and a cone based sub.

We've covered this topic at length since I attended the first demo at the 2005 RMAF
ibsubwoofers.proboards51.com/index.cgi?board=general&action=display&thread=1128137922

If you covered the wall with them I'm sure you could do some major SPL at 1hz.

Do the card test.

Wave a postcard slowly. Hear anything? Nope.

Get a nice big board. Wave it slowly. Hear anything? Not much but now your hair is moving.

Now go and stand in front of a fan and move your postcard around in the breeze. Now you can hear something. Turbulence.

Very low frequencies are all about lots of air movement.

Let an 8 x 4 board drop flat onto a smooth surface. That's air movement too.

Now all you need to do is find a way to make a few 8 x 4s vibrate while tightly sealed into the wall surface.

Or use a fan with variable pitch blades.

They need to make a giant sine generator where you install a 30x10 ft sheet of titanium with an extreme excursion surround (a few meters) into a wall of a sealed room. You could hook a bunch of high HP motors hooked to gears to move it back in forth at different speeds. You could mess with the power going to the motors to change the speed it moves at or even maybe use some sort of relay system with an amplifier hooked so that you can play a tone and it will come out on the sheet. It would be very limited...since the excursion would never change, so while 10hz may shake you, 20hz would shake you a lot harder and so on.


Well...I guess a few meters of excursion would require some extremely powerful motors and thick titanium. Still, I'd like to see what SPL levels that would create if you had enough reinforcement and motor strength to get 5 meters excursion at 10khz...it would probably catch stuff on fire, right? Or am I thinking about it all wrong?

Since we are fantasizing a bit here... ;D

A slightly conical polystyrene foam sheet the size of the end wall reinforced with carbon fibre and driven by and supported on a central pneumatic cylinder would produce considerable output and have a stroke of any length you chose. Pneumatics are fast acting and can tirelessly repeat so 10Hz should be possible. Whether you could control the frequency with some sort of programmable electromagnetic air valve I don't know.

It would be far easier just to keep adding conventional drivers (and amps) to an IB. Most rooms can manage 4 x 18" drivers in the height of the ceiling. How many 8 x 18" opposed driver manifolds can you slot into the width of your end wall? At least 8 manifolds? Well 64 x 18" drivers are going to move some serious air!

64 drivers x $300 each is still under $20k! Probably get a nice discount which will pay for your amps and MDF.

This is one serious world class subwoofer for so little real money.
What's holding you back?

OK F = m a

So for 10 hz and one meter of travel, I will keep it to one half meter each way about center, and with some foam carbon fiber composite here is an approximation. We will neglect the weight of the piston and rod in the actuator for now.

The foam could be as little as 4 pounds per cubic foot. Most likely to keep any sort of rigidity at all in a 30 by 10 foot panel the composite skins would have to be space at least 4 inches apart. So we have one cubic foot of foam every three square feet. We have 300 square feet in our driver so that is one hundred pounds.

Now we need skins. About 1/8 inch should do on each side. With a weight of about 70 pounds per cubic foot and with 1/4 inch material every 48 square feet is a cubic foot. Rounding off and giving you the benefit of the doubt we now have about 420 pounds of composite skins.

520 pounds is 16.25 slugs which is the mass of our diaphragm.

Acceleration would have to be 41 g's more or less

That makes our force required about 1880 pounds to start the sine wave at 10 hz.

Lets say we use hydraulics at 2000 psi, then our cylinder would have a volume of approximately 35 cubic inches for the meter stroke. And we would be filling and emptying that cylinder every tenth of a second. So we would be pumping about 29 gallons per minute. A quick search says we would need about a 30 horsepower unit more or less.



Maybe that Thigpen isn't so expensive after all.