Subwoofer Selection

Redwolf · January 20th, 2004, 11:54 PM

Here's an unusual request for ya. I need a Subwoofer. For under $20.

Basically, I'm building an Air Cannon. My plan is to use the subwoofer to create the necessary force. Thsoe of you who know what a Vortex Ring Generator (What it's called?) is probably know what I'm talking about. All I want to do is to hook it to a 9-volt batter and everytime I hit a switch, have it displace large volumes of air.

So...It needs to be big. 12" is good, 15" is better. I don't care at all about quality, since it isn't going to be used for sound. I do want it to be airtight, because the cannon is supposed to be airtight except for the hole the air is forced through. The more air it can displace (bigger sdurace area of the speaker I guess), the better. Oh, and did I mention I'm on a budget?

I put this in the Community, since it's a strange request and I don't know if it's appropriate for the Multimedia and Audio forum...since what I have planned involves neither multimedia nor audio.

thekingofpain · January 20th, 2004, 11:58 PM

Id used compressed air---or something else---only thing you will blow with a 12" driver and a 9v batt is your mind...

cbuddha42 · January 21st, 2004, 12:00 AM

without some serious necking down (going down to 1/2 an inch or so) i dont think you would really generate the kinda of force you are looking for

whats the air cannon for?

Redwolf · January 21st, 2004, 12:01 AM

Perhaps pictures will help explain what I'm trying to do:

http://www.amasci.com/amateur/vortgen.html
http://home.comcast.net/~grundmann/vger/
http://van.hep.uiuc.edu/van/demos/Vo...tor/vortex.htm

I have built a little version with a mini-CD, a ballon, and a soup can. It works REALLY well for something so small. It's not really an air cannon I guess, so that was a bit misleading.

thekingofpain · January 21st, 2004, 12:11 AM

Might be easiest to scale up what you have that works already...

Warthog · January 21st, 2004, 05:19 AM

A $20 subwoofer, hell, a $80 subwoofer wouldn't have even close to the xmax (excursion) you need to produce an acceptable sound wave, IMO.

For $20 you get the BOTTOM of the barrel...pretty much anything you get is gonna be utter shite. There is no use even recommendinga nything because it's all the same

rsisson · August 4th, 2005, 07:19 PM

But they dissapate very fast... in 4-6 feet.

I am going to try to ugrade the Woofer to a piston driven by a solenoid, but don't have much hope.

IThe woofer I am using is a 10" dual 4ohm 1000W Pyle that I am driving with 2 x 12v car batteries to get the voltage I need. I may try upping it to 48V and throw it a -/+/- pulse using some relay logic... (That would be max excursion in both directions)

But after my experiment, I agree, I don't think a 10" woofer has the excusion to get the volume necessary...

a 15" MIGHT, but you would need to neck it down a LOT to get the "slug" of air you and I are both looking for...

Bob

OuTpaTienT · August 4th, 2005, 07:38 PM

I think a sub-woofer driver would indeed work for a device like that. It should be able to move enough air. I know the air coming out of the port on my sub-woofer with two 6.5 inch drivers is capable of blowing out a match at at nearly 15 inches away.

You say you need 12" or bigger. Why? What's more important is the excursion of the driver. A smaller driver with good excursion can easily move more air than a larger one with limited excursion.

Warthog · August 4th, 2005, 08:23 PM

I dunno...For some reason, Donn, I'm thinking that a year and a half later, 'ol Redwolf here has either already completed his project or is no longer interested.

But maybe "it's just me" *shrugs*

Warthog

rsisson · August 4th, 2005, 10:54 PM

The Prop that Redwolf was trying to build, was the same one I am(was) trying to build. It is called a "Vortex Generator" and basically blow smoke rings.

Some of the Larger system are capable of blowing a 3=4" smoke ring 30-40 feet.

My hope was to be able to send a smaller, but denser smoke ring 15-20 so that it would look like I was shooting a "death ray" at someone if I put a pin-spot in the port along with some smoke...

I was going to combine the impact of the smoke ring with a sound effect and possible a sub-sonic impact to the walking surface to create a "death ray prop" that people could feel...

So far, all I have been able to produce is a faint "wisp" at 8'.

I was using a 10" Pyle 1000W dual coil sub-woofer, being driven with a 24V DC pulse. Well within what the sub can take, so I may up the voltage and use some relay logic to send it a negative pulse (retract) followed by a positive pulse (extend) and then neutral again, basically double the displacement I was getting

Not your normal "audio Application" but neat to play with....

Just for fun I took a 18V AC power supply and put it across the coil... the house vibrated, and that was only 18W (18v x 1 amp)

Fun to play with....