Pneumatic sub

[CBFryman2 5,000+ posts]

1" is nothing unless you have the force to move it 1" in an enclosure tuned to 25Hz, even still I doubt you will get a whole lot more output from it than what some high end drivers will do.

Good idea but I dont think there is much better than mechanical means as of right now. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[CBFryman2 5,000+ posts]

now if you could get 1" on a 20+" cone at 50+ Hz in a 50Hz enclosure I would be willing to bet you would get rather loud. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[JimJ 5,000+ posts]

Who needs an enclosure?

//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[CBFryman2 5,000+ posts]

Dipole SPL...

Not a whole lot of displacement if he does IB for a 15" with only 1" of excursion, especially at 25Hz. He'd be lucky to brake 140dB.

 

[JimJ 5,000+ posts]

Dipole SPL...
Not a whole lot of displacement if he does IB for a 15" with only 1" of excursion, especially at 25Hz. He'd be lucky to brake 140dB.

That's why I said more excursion, mo betta //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[CBFryman2 5,000+ posts]

x Tree

 

[GemaRastem 10+ year member]

lol, this is funny....you of course realize that your subwoofer will cost over $5000 and weigh 400 lbs, probably 100 of those lbs would be hosing, wire and fluid...then the structure for the piston might even be more weight than that. So good luck, im guessing about $80,000 in R&D on that one.

I'm using pneumatics and work in a fluid power testing facility...We have all that stuff laying around. We'll be needing to dig out an air tank out of the basement, already have a valve that can cycle at 65hz or lower, the cylinder is going to be .25" bore, probably weigh about 5 pounds. =$0 //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

for it to be legal at a comp-
1.- has to be an available production sub for sale

2.- has to be powered by standard audio equip.

for it to be cool and a crowd pleaser... anything goes!

hydraulic sub has been done many, many years back. if i remember the story right from the speaker engineer from europe who did it, i think they did a 48" sub +/- for a movie or some effect in one.

1/2" xmax = 1" linear P2P. and 22,000w equivalent @ 25hz i imagine will slam your cone to the end of it's stroke in a bad way.

in your calculations for 300 electrical watts, did you figure in efficiency? that on a good day 300 electrical watts only equates to 3 acoustical watts with a decently efficient speaker?

I'm going pneumatic, easier than hydraulic. I dunno about the cone slamming to the end of it's stroke, definitely gonna have to have a good surround. and yes I did figure in efficiency. we turned 300 watts into horsepower, and then converted it to force, and then to psi.

What company? Actuant?

Which company do I work for? Fluid Power Institute

1" is nothing unless you have the force to move it 1" in an enclosure tuned to 25Hz, even still I doubt you will get a whole lot more output from it than what some high end drivers will do.
Good idea but I dont think there is much better than mechanical means as of right now. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

the enclose won't be tuned to 25hz, we will be playing 25hz sign waves. I don't know how much output we will be getting but it'll be neat and free //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif.

That's why I said more excursion, mo betta //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

I have to see how fast we can get a bigger cylinder to cycle.

 

[00PewterSS 10+ year member]

I also have worked with hydraulic test equipment. The servo-hydraulic systems we use for automotive testing can easily work to 40Hz and probably 100Hz as a subwoofer where there is very little mass to move. I have never considered doing it. When we have run frequency sweeps it excites the bedplates in harmonics, so that sort of act as a subwoofer.

Anyway, with the proper controls you could precisely control the movement. With a good controller with limits, you can limit its travel, and limit the force it exerts. To get a specific response what we do is use software where we create a transfer function between the input and output and physically iterate until the input matches the response as best the equipment can. If you assume the transfer function is perfectly linear you don't need to iterate, but that is unlikely. What signal are you going to try to reproduce? Do you want to input a specific frequency or play music?

Your idea will definately work, but electric actuators (like in a speaker) are far quicker and more precise than pneumatic or hydraulic. The only way this project would make sense to do is if it you want some rediculously large excursion, but then I don't know that you could get that kind of acceleration out of your actuator.

Anyway, cool idea!

Brian

 

[Bolognablake 10+ year member]

Sounds sweet.

I can't imagine how to control the excursion when it has 2500 PSI of force behind it, but I'm in sales, not an engineer. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[reneeb7363 10+ year member]

Is everyone missing the point here? //content.invisioncic.com/y282845/emoticons/uhoh.gif.c07307dd22ee7e63e22fc8e9c614d1fd.gif Did ANYONE see the Mythbusters show where they tried something similiar to this?

This gentleman, and his company/subordinates, just want to expirement and see what will happen when they attempt this crazy stunt! I think it is hilarious. The Mythbuster boys built a STEEL concaved unit and it was able to produce 161.3 Db at 14Hz in that poor Mercedes-- certainly not an enclosure (let alone 'tuned') by any means. Let the man have his fun... who knows what may be learned-- quit trying to over think the situation! Goodness! //content.invisioncic.com/y282845/emoticons/eyebrow.gif.fe2c18d8720fe8c7eaed347b21ea05a5.gif

 

[00PewterSS 10+ year member]

No I haven't seen that episode yet, but I'll look forward to it. Since I haven't seen it I can't speak for what they did. I thought he wanted to try to play actual music with it.

If you are just trying to make a loud sound borrow a garbage truck and drop a dumpster on the ground, that would be loud! (this was a joke)

Brian

 

[regal8r 5,000+ posts]

Is everyone missing the point here? //content.invisioncic.com/y282845/emoticons/uhoh.gif.c07307dd22ee7e63e22fc8e9c614d1fd.gif Did ANYONE see the Mythbusters show where they tried something similiar to this?
This gentleman, and his company/subordinates, just want to expirement and see what will happen when they attempt this crazy stunt! I think it is hilarious. The Mythbuster boys built a STEEL concaved unit and it was able to produce 161.3 Db at 14Hz in that poor Mercedes-- certainly not an enclosure (let alone 'tuned') by any means. Let the man have his fun... who knows what may be learned-- quit trying to over think the situation! Goodness! //content.invisioncic.com/y282845/emoticons/eyebrow.gif.fe2c18d8720fe8c7eaed347b21ea05a5.gif

IIRC it was 16hz //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[CBFryman2 5,000+ posts]

we will be playing 25hz sign waves.

LOLing at Sign Wave.

I understand your desired frequincy is 25Hz, I am suggesting a way to get more than 135dB out put from it.

You mentioned 300w. I hope you are using more pressure than that. The mythwoofer was ~140,000w. //content.invisioncic.com/y282845/emoticons/veryhappy.gif.fec4fed33b4a1279cf10bdd45a039dae.gif