Introduction: Build an Infrasonic Subwoofer


Infrasound is sound that is below your hearing threshold which general drops off at 20-30hz, i.e. lower than big booty bass. It can have a profound effect on your body, and should be experimented with carefully! Infrasound is used by the military as a weapon, or science to monitor earthquakes, whales ect.. In this instructable we will walk you through the process of building your own Infrasonic Subwoofer. We created one for our research collective AUDiNT.net on sonic warfare.

from wikipedia:

Infrasound is sound that is lower in frequency than 20 Hz (Hertz) or cycles per second, the "normal" limit of human hearing. Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure must be sufficiently high. The ear is the primary organ for sensing infrasound, but at higher levels it is possible to feel infrasound vibrations in various parts of the body.
The study of such sound waves is sometimes referred to as infrasonics, covering sounds beneath 20 Hz down to 0.001 Hz. This frequency range is utilized for monitoring earthquakes, charting rock and petroleum formations below the earth, and also in ballistocardiography and seismocardiography to study the mechanics of the heart. Infrasound is characterized by an ability to cover long distances and get around obstacles with little dissipation.

Step 1: Speaker Cones

First, You must find an appropriate speaker cones. We decide to build a double speaker system with a cone on each end of the enclosure. You could also build it with only one cone. When choosing a cone it should one that is 21" or 24" in diameter. We chose to use a Pyle 21" speaker. For good sound quality you should use a driver that has a QES of .38 + - 20%. We found Pyle speakers at J&R for only $250.00 which for such a low speaker is cheap!!

What is Qes?
http://www.bcae1.com/spboxad2.htm
http://en.wikipedia.org/wiki/Q_factor

Step 2: Step Two


Select a wood type. We chose 18mm plywood. This is probably the best material. Avoid Chinese plywood if possible because it is not as consistant. Plywood is very sturdy and holds up well the air pressure produced by the large speaker cones. You need enough wood to make both the box and the bracing structure. Each wall should be braced to handle all the bass. You should try to make the box as big as you can. We built ours to be 30" x 30" x 70" It should NOT be square. This will greatly reduce its ability to produce infrasonic frequencies low enough.

Step 3: Bigger the Case

Now build the main box. As mentioned, the bigger the better. Cut all the sides to the proper dimension, and plan out how you will create support system within the box using braces. THere is a lot of pressure exerted on the walls and the stronger the walls are the more efficiently the subwoofer will be able to create such low frequencies.
We used a combination of wood glue, and as few screws as possible. The box should be airtight so each screw increases the possibility of air leaks and rattling. Then we used Kwik Seal to seal all of the corners and potential air leaks.

Step 4: Installation

Install the speakers into the enclosure. Make sure the mounting is solid. Next install the bracing. The bracing should be on all sides of the enclosure and should be glued in using would glue. We created to braces from speaker to speaker, from side wall to side wall, and from bottom to top, and then used clamps to hold everything in place while the wood glue set overnight.

Step 5: Electronics + Test, Test, Test

Test the cone to make sure it works. We connected the cone up to a 1000 watt amplifier and ran sine tones through it in order to confirm that it was working properly. Sometimes when speakers are shipped they are DOA ( dead on arrival), as was our case with one of our speakers. In order to break the cone in we ran a sine tone through ours  for 24 hours. 
You will want to find powerful amplifiers. We chose two livesound amplifiers. Each channel was 500watt amplifier and switch to serial mode to which collectively made one amplifier a mono 1000 watt amplifier.
Once the cone works, then solder together the thick gauge audio cable, connect it from the speaker to a 2 channel Speakon wall-mount connector which we will insert into the wall of the speaker. This will enable you to unplug your speaker but also insert it into a larger live sound system. Then solder on male speakon connecters to thick audio cable and then connect this to your amplifier and add the compatible connector for your amplifier. For us, we used balanced 1/4" connectors.
Test all the wiring by running sine tones through the input to make sure all of your connections wokr.

Step 6: Cabling


Now once you have tested and solder together your cabling install l all the cabling, solder the speakers, cut holes to the exact size of the speakon jacks + corresponding panel. Then test all the wiring by running sine tones through the input again. At this point you may want to add wooden or metal handles to the side of the Subwoofer because its heavy and awkward to lift!! Ours was close to 70lbs. 


Step 7: Seal the Connections

Now you need to seal all possible air leaks in your subwoofer. Seal all joints and corners with silicon or Qwik Seal. Also put apoxy on all connections on the subwoofer prevent connections from loosing. You don't want to have to open up the Subwoofer again because of a loose connections!


Step 8: Step 8

Put the lid on the finished unit and test one last time. Seal all of the seems with silicon as you screw the lid on. If you plan on staining or painting it you will want to cover the cones with plastic to protect them.

Step 9: Step 9

Next, stain the wood and repeat again to get a rich color. If you would like to take the project one step further you can add 100 grams of bondo to the cone you can lower the frequency. To half the resonance double the cones mass. The Pyle's resonant frequency is 22 hz. We decided not to do this but it is certainly worth a try.

Step 10: Rock

Next crank it up but be slow about it to see how you react to the low frequency. A 15hz sine tone is a good start or even better a sliding tone from 60hz down to 10hz and then back up. From this you will be able to tell when your body feels it intensely and also how low the speaker will be able to reproduce a frequency. Enjoy but be careful!!


For more information on our collective AUDiNT go to AUDiNT.net. The subwoofer was build by Toby Hayes and Jon Cohrs, with the help of Steve Goodman. Steve Goodman has recently released a book called Sonic Warfare: Sound, Affect, and the Ecology of Fear (Technologies of Lived Abstraction). Toby will be releasing a book shortly as well.

Comments

author
atpmarcus made it!(author)2017-04-29

i have no background in any of this i have 3 questions:

1. can anybody suggest a generator that can produce 1.05hz for the purpose of producing HGH in the pituitary gland while i sleep

2.can anybody give me some advice via private communication on how to go about making sub audible frequencys

3.is a frequency the same as a sound i.e if i was to use a online tone generator is it the same and if so is simply turing up the volume while it is running make a difference.

I AM NOT A SOUND TECHNICIAN I AM A HEALTH FREAK so dont go judging guys! lol

thanks

author
gefluz made it!(author)2017-04-05

has absolutely nothing todo with ulf. ulf ranges from .01 to to 19.5 hertz

the numbers that currently matter are .8 to 19.2 hertz if your actualyl using ulf. if you want good sounds the lowest sound humans enjoy is 40 hrtz.

author
DahliaJ1 made it!(author)2016-09-26

how can i measure the frequency of the subwoofer because i need a specific frequency in my work

author
skylerdprahl made it!(author)2012-10-05

Yea I don't know why people try to put on a show like that.. There are many many many car audio systems that easily produce sub 20hz frequencies up into the 140+db region and as long as proper hearing protection is worn, nothing bad happens lol. It is a nice subwoofer don't get me wrong, I love bigger than 18" subs, just because of the sheer beast-ness of them lol.

author
mgann1 made it!(author)2016-09-16

Also car audio has cabin gain to help it, the smaller space makes it easier to pressurize the cabin. You put those car audio systems in a large room and they won't play as loud or as low.

author
pgramma made it!(author)2014-10-17

it's not lower than 20 and sine at the same time with the most of car speaker systems...all they do is frying the sound and what comes out is triangular waves

author
vivekgir999 made it!(author)2014-10-26

Is it necessary to play the sound through amplifiers and if so why? I'm asking this because i dont know anything about producing infrasound sound.

author
mgann1 made it!(author)2016-09-16

You need power to drive the speakers. They're rated for 1000w. You can drive them at lower power but they will only be quieter. In this sense you're not suppose to hear the sound, but if you're looking for that feeling that they talk about it giving you I assume it comes from the higher air pressure

author
JanisS made it!(author)2014-11-02

Im a noob and just interested, Is infrasound only playable by special speakers? or could basic earphones, or phone speakers already play infrasound?

Thanks

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mgann1 made it!(author)2016-09-16

Even the speakers in this instructable isnt made to play below 22hz but they get them to. The key to this is that size matters, that's why they started with two 21" cones and to make the largest box for them that you can. Bigger the better. You want large displacement to pressurize the room for low frequencies. While shopping for drivers look for cone size but also for a lower FS parameter. Usually one comes with the other but I've seen some 12" speakers have the same fs as 15" or 18".

author
bradhouser made it!(author)2011-10-16

You don't say if the speakers should be in phase with each other or out of phase. I would think at these low frequencies, with a sealed box, you would want them out of phase, so that one is going in, while the other is going out and vice versa. That would keep the air pressure in the box constant. Or am I missing something?

author
mgann1 made it!(author)2016-09-16

Wow what are these people saying..

They need to be in phase, and it doesn't matter what side the speakers are mounted. Pressure inside the box is a good thing and when he says "no longer compresses air" he isn't just talking about inside the box, this is true for outside the box too. Sound is compressed air, no longer compressing the air is no longer making sound. You want to pressurize the room. That's probably why it effects your body too.

If you wanted to put them out of phase you would have to separate the two chambers so that each speaker can pressurize when it needs. Phase does change with distance, but the frequencies are so low that they will not be out of phase being on opposite sides of the box, this would only be true for higher frequencies. I'll bet that the designer of this box put the drivers on each side of the box to limit any movement that might occur from these large diaphragms moving, if you put the drivers on the same face the box might get pushed around or vibrate distorting the "silence" of the subsonic frequencies. Honestly I would look into designing this as a ported box instead of sealed to get more decibels out of the low frequencies, that's a post for another day. If you keep it sealed though, larger the box the better the low frequency response but you put the drivers at risk, they're only made to reach 22hz or so. Also would recommend applying resin to the cone as they suggested to lower the resonant frequency.

Unless maybe you guys were thinking of reversing the polarity and playing each driver at a different frequency? You can use the frequency cancellation to your advantage, but you must separate each driver into its own chamber. Build this box with a wall in the middle and reverse the polarity as you thought. Then play each driver at different, but at their rated and loud, frequencies they will cancel out some of the waves but not all leaving you with the difference. Hopefully high decibel low frequency waves will be left. If your resonant frequency with the sealed box is 54hz that means the box will play those frequencies the loudest. So with reversed polarity try playing one speaker at 50hz while the other at 60hz hopefully giving you a 10hz overall sound. Actual results might vary, try different tones.

author
Offroadie made it!(author)2011-10-16

If they were out of phase they would cancel out and you would have no bass.

author
keriksen1 made it!(author)2011-10-16

No they won't, since they are facing opposite directions.

author
Offroadie made it!(author)2011-10-17

You guys need a lesson in acoustics...

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bradhouser made it!(author)2011-10-17

Offroadie: Your reply is not very informative. Which part of your acoustics training can you share with the rest of us to better explain your position?

Not being a sound engineer, my understanding is limited. So I welcome clarification based on sound (pun intended) principles.

This is what I think is happening.

In a normal stereo setting, when the woofers are out of phase they tend to cancel each other, an effect that is increased with lower frequencies.

However, this scenario is different. For one, they are not in separate boxes, and they are pointing in opposite directions. Add the fact that the box is sealed, keeping them in phase causes both cones to move in and out together. This increases and decreases the pressure of the air in the box. Being sealed with no port to the outside, this would tend to dampen the sound, making it quieter.

If the two speakers are anti-phase, one moves in while the other moves out, keeping the pressure on the internal air the same. Wouldn't that tend to boost the volume instead of reducing it?

author
ShaneS28 made it!(author)2015-10-11

All I can tell you guys is that I have tinkered extensively with my speaker phase and in the same box, if the speakers move opposite directions it will almost completely cancel the bass response. The idea behind bass (all sound actually) is moving and compressing air. speakers moving opposite directions will reduce the amount of compressed air in the box as well as outside of it. Also, if the two subs are hitting different frequencies at the same time, like say two different brands or different size enclosures, they will "fight"each other so to speak. Kind of the same way ripples in water can be disrupted by other ripples. If they aren't in sync your robbing them of bass.

author
pwnageoldstyle made it!(author)2016-01-01

bass isnt directional below like 60hz . it travels around speakers

author
ChrisW91 made it!(author)2015-09-10

Sounds plausible.

author
psychotron made it!(author)2011-10-19

No, if they were out of phase they would constitute a dipole and at low frequencies they would cancel and give very little output. Try playing bass through a speaker without a box (dipole) and a speaker in a box (monopole) You will generally find that the enclosed speaker makes a lot more bass.

A dipole will augment response at certain frequencies, but it will not be in the infrasonic range unless the dipole were VERY large. Read 'Linkwitzlab' to see the pattern of dipole augmentation and cancellation.

author
keriksen1 made it!(author)2011-10-17

Right, let hear it?
In my humble opinion bradhouser is hitting tha nail on the head :)

author
Offroadie made it!(author)2011-10-18

My first post was informative. My second comment wasn't meant to be rude but I would have thought someone would search on their own if they were interested.

Being stereo or mono has no effect on low frequencies. Also, It doesn't matter what side of the enclosure the drivers are on. Either you are compressing air or you are not. Putting them out of phase no longer compresses air. If you were compound loading drivers then yes the outside speaker(s) would be wired out of phase.

A box is basically an air spring. Each driver has it's own properties that determine how it reacts to this air spring. That's how some work in sealed boxes some in ported and some both. Sealed boxes have to be pretty specific to the driver as well. Wrong size spring, wrong size reaction.

Ports don't dampen sound they reinforce it by putting the rear wave in phase with the front wave by tuning the port.

Hope that helps a little.

author
ChrisW91 made it!(author)2015-09-10

That's why Cerwin Vega invented a Newly designed 21” woofer with Stroker™ technology for increased output and reduced distortion Improved power handling to 2000 w Radial cooling fins located outside the aluminum Stroker™ pole, increase cooling and improve the TS-42’s efficiency Stroker™ pole is vented out the back of the back plate for improved voice coil cooling Aluminum cooling ring above voice coil gap for improved heat transfer from the voice coil, providing improved power handling and reduced compression Stroker™ technology adds a third plane of suspension eliminating cone rocking and allows increased excursion while maintaining a tight gap that provides higher sensitivity The six magnet sections and the tunnels located between them, provide cooling below the top plate Rugged new die cast door provides improved heat dissipation & displays Stroker™ metal badge New curved horn mouth bracing for smoother frequency response Steel front corner bracing to improve cabinet strength Extra handles, ergonomic balanced design, and larger casters for easy handling.
Yeah, It's pretty bitchin'. :-)

author
bradhouser made it!(author)2011-10-18

Thanks for clarifying Offroadie.

So, if they are out of phase it "no longer compresses air", by that I assume you mean the air in the box. Makes sense, but I "am from Missouri". (i.e. show me)

I would be interested to hear if anyone who builds this could try it each way and then let us know if they feel any difference.

author
ChrisW91 made it!(author)2015-09-10

Amen to that. :-)

author
dysynchronous made it!(author)2012-10-08

No they don't. You're wrong. The design is pumping both ends of an air column. That said * Acoustical* phase will change with distance, so like a vented box, some frequencies will be reinforced while others will cancel.

author
bradhouser made it!(author)2012-10-08

Dsynchronous: (1) Who or what are "they", and what don't they do? (2) Who are you referring to when you say "You're wrong."? Your answer makes sense, but please tell me which school of thought you are in. The speakers are either wired in phase, or out of phase. I can't tell from your response. Almost a year after I posted this question, I still don't know what the author intended.

author
dysynchronous made it!(author)2012-10-27

Okay sorry: I was responding to tachyon I think . The issue is whether or not the speakers were to be wired in phase or in anti-phase. I thought that in phase is wrong, because at the wavelengths were talking about resonance coupling would'nt matter. The speakers are mounted both facing outward on opposite sides of the box.
You can view the box as a sealed air column, in which case they should be wired anti-phase (one pushes in while the other pushes out). BUT, you can visualize the box as a point source of pressure variation (makes sense?) in which case you would want the speakers pushing out at the same time and in at the same time.
The correct answer depends on several factors:
Size of room relative to box, size of box relative to speakers and placement of box in the listening environment.
I believe that in a closed room or with placement close (acoustically) to the walls anti phase would be correct. Outdoors or with the sub placed in the center of a LARGE room, or with the listener far away from the sub(s) then in phase would be correct. I haven't modelled the behaviors, but I understand the arguments of both camps.
Solution: Buy a DPST switch and wire in a phase selector>

Sorry 'bout the lack of clarity, it happens when I'm netting at work sneakily.
Gerry

author
ChrisW91 made it!(author)2015-09-10

I agree, I would imagine thats what they did, because otherwise they would be throwing each other off. You are talking about the Push/Pull technique right?
I tried that many years ago in a truck system that I had. It did alright. I needed to build a better box for them.

author
GBMorris made it!(author)2011-10-16

Bradhouser, I believe you are correct. Either you would want the speakers in antiphase or you would not want a sealed enclosure.

author
idydstie made it!(author)2014-03-28

My understanding is that if desired wavelength is longer than the distance around to the back of the box, the speakers should be wired so that they are both pushing out simultaneously.

author
Tachyon made it!(author)2012-04-18

The way the speakers are shown mounted, they should be wired in phase electrically which will cause them to operate out of phase pneumatically which is the correct configuration acoustically.

Make sense?
;')

author
eruger made it!(author)2016-07-18

Infrasound, particularly around 17hz, has been detected as cause in several known 'ghost spots'. It's been demonstrated to cause chills, unease, minor paranoia, sudden sadness, and even slight hallucinations in the peripheral vision.

author
katesisco made it!(author)2016-07-04

I would also like to know if you can build an infrasound detector to monitor hobby drones?

author
katesisco made it!(author)2016-07-04

http://www.infiltec.com/Infrasound@home/

This is what I was looking for when I came here. A home made infrasound detector. Wind farms are now indicted as producing damaging infrasound. I suspect this is going to be a huge health problem science and medicals are ducking as they have zero help to offer.

author
Robert+JC made it!(author)2015-11-01

I'm a Disabled Veteran trying to live in my own Condo. It's only a 26 unit neighborhood but it has 7 affordable 40B (Massachusetts) units of which I own one. Seems the neighbors don't like the people of lower income. I remember that feeling when I got home from the Military in 67. Lot's of cries "Baby Killer" with some spit in the air. Anyway, I need to defend against what I feel is this same type Infrasonic gadget from being used on me before it kills me. I tried to explain it to the cops, the Doctors at the VA Hospital and my own Family all are thinking I'm nuts. What reactions to it are spelled out here exactly and I need to build one to prove to all these asses I'm not lying or nuts and give my upstairs female neighbor some FEEDBACK. I am going to try to download the info but I'd appreciate any personal assistance in how to save $$. Social Security doesn't get me too far when You have a mortgage. Thanks in advance.

author
katesisco made it!(author)2016-07-04

http://www.infiltec.com/Infrasound@home/

What I was looking for when I came here: a home built infrasound detector.

author
pwnageoldstyle made it!(author)2016-01-01

find a used 10 inch or smaller car subwoofer. make a massive stiff cone out of card paper coated with pva glue. glue the cone to the center of the subwoofer on the edges of the dustcap . you might want to have surrounds around the edge of the cone connected to a sealed box. try playing dubstep music or something really bassy through it. you need a subwoofer amplifier or an amplifier with a powered sub output. http://onlinetonegenerator.com/ this site lets you generate constant tones.

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author
pwnageoldstyle made it!(author)2016-01-01

find a used 10 inch or smaller car subwoofer. make a massive stiff cone out of card paper coated with pva glue. glue the cone to the center of the subwoofer on the edges of the dustcap . you might want to have surrounds around the edge of the cone connected to a sealed box. try playing dubstep music or something really bassy through it. you need a subwoofer amplifier or an amplifier with a powered sub output. http://onlinetonegenerator.com/ this site lets you generate constant tones.

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author
rfoster4 made it!(author)2011-10-16

Were you able to discover the elusive "brown note"? :)

author
rallen71366 made it!(author)2011-10-16

When I was in the service (many moons ago) one of my Commo buddies commented that he had done some research like that, but they didn't use normal speakers with a diaphragm. They were spraying propane into the air and detonating it at a rapid speed. They were using a fuel/air explosion as a speaker!

He also said that they had to wear depends. That assignment was the sh*t. :-)

author
ttitus made it!(author)2012-01-16

The Mythbusters did a whole episode on "The Brown Note", with the conclusion being that it didn't exist. Although some tones will make you feel a bit dizzy. I get that way when I listen to bi-naural beats too long. Air explosions though...I don't remember them testing that. I cant imagine that a short blast of frequency, whatever it may be, could make someone shat themselves.

author
Hiwatt+Dr504 made it!(author)2016-04-14

Im probably wrong but didnt mythbusters use a pulsed wave versus a continuous way. I too have experimented bunaural beats. Did you uae audio or audio synced to visual stimului? (I used cheap goggles, mounted my leds). Im a fat old man now but the software i using at the time was i believe was calked wavelab s (?). Even included presents and DETAILED INSTRUCTIONS on how to craft and encode your very own binural beats....im going to hunt around for the software. Im sure i saved it.
Man sorry I just realied I have may hijacked this thread. Im a idiot. Sorry again.



author
MarkK23 made it!(author)2015-08-09

University of Wisconsin in Madison built a 6 foot subwoofer that hits it.
http://soundworkscollection.com/news/the-biggest-subwoofer-in-the-world

author
rallen71366 made it!(author)2012-01-21

Ever been on the firing line when they cut loose with the heavy weapons? A .50 BMG firing shakes you to your bones. Standing too close to REAL heavy weapons (like a Patriot Missile, or Naval cannon) can kill you just from the shock wave (a Patriot is going Mach 6 when it clears the launch tube). Loosening your bowels without killing you is more a matter of control, than power.

author
TrentonG made it!(author)2016-01-11

whats the max db amount for this speaker at 5 hz

I'm looking to eexperiment with the effects

author
Jose+AntonioR10 made it!(author)2015-10-25

Hello guys. Just wanted to step by and say that such a huge subwoofer is not necessary to produce infrasonics with good decibel range. I was able to get a nice rumbling 13hz out of a measly 6.5" subwoofer. This was achieved using a T-line concept. I currently have two 8" Massive audio Summo Subwoofers in a specially designed T-line type enclosure which is capable in output to a standard 15" subwoofer in a big enclosure. But the t-line type enclosure I did is just 20 x 20 x 9. The main box where the two 8" subs sit is just 20 x 9 x 9. The rest of the enclosure is just a placeholder for the multiple PVC tubes that make up the porting system and is what gives the infrasonic response. Each tube is approx. 90 inches in length and are folded on top of each other to be accommodated inside the enclosure. Here is a video of these two 8" subs moving a curtain at 9hz!

https://www.youtube.com/watch?v=ua-PMvLaJ6s

author
pwnageoldstyle made it!(author)2016-01-01

you need to move a lot of air or have your head right next to the subs to actually hear that low. you can hear the difference with good headphones if you dont turn up the volume too loud.if the volume is up too loud you hear different frequencies because the woofer or headphones only makes clean sound when its moving in and out a certain distance. try turning down your subs, they probably go silent or quietly purr.

author
JakeJarmon+ made it!(author)2015-02-08

A lot missing here. This Instructable is very misleading on so many levels. www.billfitzmaurice.com

author
JakeJarmon+ made it!(author)2015-02-08

Pyle is crap, and you don't need anything bigger than 15" to get infrasonic.

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Bio: I teach, work on art projects, and master music. For more info on me go to http://joncohrs.com or for more projects go to ... More »
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