Infrasonic Speaker - Need advice for undergrad thesis project - Page 7 - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 19th November 2012, 07:25 PM   #61
diyAudio Member
 
myhrrhleine's Avatar
 
Join Date: Jan 2006
Location: Avalon Island
I can think of 2 unrelated possibilities.
One- Use vented enclosures tuned to the desired frequency
You may need more than one tuned to a different frequency.
Two- Use headphones with very small enclosures.
Meaning hearing protectors covering headphone speakers.
__________________
Just because you can't hear it doesn't mean no one can.
  Reply With Quote
Old 19th November 2012, 07:31 PM   #62
diyAudio Member
 
myhrrhleine's Avatar
 
Join Date: Jan 2006
Location: Avalon Island
One more idea
Vibrating water in a swimming pool.
__________________
Just because you can't hear it doesn't mean no one can.
  Reply With Quote
Old 19th November 2012, 07:51 PM   #63
diyAudio Member
 
Join Date: May 2010
Location: was Chicago IL, now Long Beach CA
Quote:
Originally Posted by myhrrhleine View Post
One more idea
Vibrating water in a swimming pool.
The lack of high-frequency requirements allows the use of heavy fluids and radical "hydraulic horn" geometries. Indeed, it you had a large-displacement "driver" of some sort, you could easily use something like water as media for the transform to coupling more surface to more air. Variations on "stick of dynamite in a crater lake".
  Reply With Quote
Old 19th November 2012, 08:05 PM   #64
diyAudio Member
 
Join Date: May 2010
Location: was Chicago IL, now Long Beach CA
...although you were probably taking about more efficient coupling to the underwater ear...?
  Reply With Quote
Old 19th November 2012, 10:18 PM   #65
Nanook is offline Nanook  Canada
diyAudio Member
 
Nanook's Avatar
 
Join Date: Feb 2004
Location: Chinook Country.Alberta
Default one possibility, just a thought

earlier in the thread someone suggested the "Buttkicker" items available at PartsExpress. These are within the $800.00 budget you suggested. And here's an idea. Borrow a tympani from the music department. Use the "buttkicker" to excite the typmani (attach the bottom plate of the Buttkicker to the tympani's kettle (temporarily). You're starting with a drum with the capability to play naturally quite low.If you excite the kettle it should vibrate at the desired frequency.

Another might be to get a good AC induction motor. Make a wheel that could be attached to the end of the motor shaft. Make a connecting rod and attach it to the wheel off-centre (the distance mounted off-centre multiplied by 2 is the stroke of the infra-woofer). The other end of the connecting rod should be mounted to a rigid plate, perhaps plywood or rigid foam or similar. This becomes the transducer's radiating surface.

Attach the rigid plate to a suspension or surround. Perhaps an automotive innertube could be used.The suspension must now be mounted to some sort of baffle. I'd cut one from plywood and reinforce it. Now a "tube" or enclosure needs to be constructed. Something as simple as a vertical tube (maybe a concrete casting?). It must be vertical because I do not believe that you can hold the radiating surface centred if mounted pointing in the horizontal direction.

There are a bunch of alternatives that could be a combination of a tympani drum combined with a motor drive. Oh, you need a method of controlling the transducer. So a frequency generator and the ability to amplify that frequency to a working voltage for the AC motor.

If it seems like I've made this all sound trivial, it is not. I might suggest (as others have) that you get someone in the Engineering or Physics departments involved, perhaps an undergrad looking for a project in acoustics.

If it is successful, it should only be tested outside with excellent hearing protection or within a performing hall capable of allowing wavelengths in the 200 ft range to be reproduced, and under strict supervision. The hall should be completely closed to all except those required to supervise the implementation. If it doesn't shake itself apart it could be very interesting.
__________________
stew -"A sane man in an insane world appears insane."
  Reply With Quote
Old 20th November 2012, 11:43 AM   #66
DrDyna is offline DrDyna  United States
diyAudio Member
 
DrDyna's Avatar
 
Join Date: May 2007
Blog Entries: 3
I'd still be a fan of constructing an enclosure that you can get inside. I did this once when I was younger, using a refrigerator sized box and an old 15" woofer, but I think you could probably build it big enough to get a few people in, so long as you take proper care to seal it up.

You're going for a pressure vessel instead of a room, think "hyperbaric chamber". Maybe find an old fluid or fuel tank that you could get people into and cut out a bunch of driver holes on each end of it.

Or, even something like a short bus with a wall up halfway through it. Seal it up real nice with great stuff and mount a dozen woofers in it at the mid point on a rigid wood wall. Enough room to seat 6 or 8 people and you could EQ it down to pretty much wherever you wanted so long as you pick the right drivers and don't get too wild with the volume.

Edit: Does your college have an old bomb shelter? lmao.
__________________
Thou shalt not commit logical fallacies.
https://yourlogicalfallacyis.com/
  Reply With Quote
Old 20th November 2012, 08:22 PM   #67
diyAudio Member
 
Moondog55's Avatar
 
Join Date: Jun 2007
Location: Norlane; Geelong: Victoria: Australia
Also I do suggest watching the "Brown Note" episode of Mythbusters.
Take a monetary note here I believe that EACH of the drivers in the multiple driver boxes used in that episode cost more than your whole budget ( Meyersound aint cheap)
__________________
QUOTE" The more I know, the more I know, I know (insert maniacal laugh >here<) NOTHING"
  Reply With Quote
Old 20th November 2012, 09:16 PM   #68
diyAudio Member
 
Join Date: May 2010
Location: was Chicago IL, now Long Beach CA
Quote:
Originally Posted by cyclecamper View Post
Danley "Intersonics" brand of rotary-drive subwoofer...start with surplus capstan motors from large mainframe disk drives.
Should have read "tape drives" not "disk drives"...oops.
  Reply With Quote
Old 20th November 2012, 09:34 PM   #69
diyAudio Member
 
Join Date: May 2010
Location: was Chicago IL, now Long Beach CA
Using the most conventional hardware, of course the idea of pressurizing and depressurizing a very small room is the most economical. Could also be difficult to demo to a large audience, possibly dangerous.

You could also look into renting commercialy-available defensive infrasonic weapons. I recently saw the Japanese using them on ships to discourage the Greenpeace folks trying to disrupt whaling and harvesting dolphins and other protected species in international waters.

Finding some Intersonics seems the best bet. Several in a row can get infra-sonic. Most subs don't.
  Reply With Quote
Old 20th November 2012, 09:55 PM   #70
diyAudio Member
 
Moondog55's Avatar
 
Join Date: Jun 2007
Location: Norlane; Geelong: Victoria: Australia
Getting a well sealed room is not going to be difficult tho; just look at dis-used commercial cool-rooms/freezers, hire it for a week or so then setup; conduct experiment take down and go. Just use the door opening as the place to mount the driver array and fabricate a replacement to suit from chipboard and ply the seals on those doors is usually airtight to a large factor.
But I still think your budget is too tight to do a realistic test, it is about what I have budgeted for my new HT setup.
Hiring the gear may be cheaper, have you contacted any of the local sound people to see what is available commercially??
__________________
QUOTE" The more I know, the more I know, I know (insert maniacal laugh >here<) NOTHING"
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Thesis idea: Speaker distortion detection LG Multi-Way 13 10th November 2008 03:19 AM
looking for advice on a first speaker project farkus888 Multi-Way 10 25th April 2007 10:05 AM
My first speaker project. Any advice? Jim85IROC Multi-Way 10 14th December 2003 04:11 AM
Need Advice for Speaker Project Tophet1 Multi-Way 2 11th August 2003 08:39 PM


New To Site? Need Help?

All times are GMT. The time now is 04:48 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2