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Low-cost Spherical Speaker Array

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Picture of Low-cost Spherical Speaker Array
Acoustic instruments radiate sound in a wonderfully complex, 360 degree fashion, while conventional loudspeakers radiate in a much more boring, spotlight of sound. You could spend a ton of money on fancy products:

Hemisphere from Electrotap
Experimental Meyer Array

or you could follow these instructions to build a cheap array out of IKEA salad bowls and surplus automotive speakers. It won't sound as "accurate" as those other speakers, but it's surprisingly good and looks pretty cool on stage.

Special thanks and apologies to Dan Truman and the researchers at CNMAT, who's scientific work directly inspired this project.

P.S. Here's another cool loudspeaker array.

P.P.S The Stanford Laptop Orchestra built some nice ones here.

P.P.P.S. This one is nice, too .
 
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Step 1: Acquire the Materials

The goal of this project was to be as cheap as possible. You'll want eight (8) loudspeakers. I would have used these speakers:

$5.50 speaker

but All Electronics was out of them. I got these, instead:

$7.50 speaker

The important considerations were an impedance of 8 ohms (which is normal for home stereo speakers) and good frequency range. (in this case 70-10k Hertz). Sound localization is more acute at higher frequencies, so response >1k Hertz is especially important. It would be better to add a sub-woofer to make up for thin bass, than to have no high end.

While at All Electronics, get some Speaker Terminals.

I used four (4) "quad"  terminals, but the four-pair ones look good.

(NB: If all electronics doesn't have these anymore. Try Parts Express or Radio Shack)

The other major elements in this project are the bowls. They cost $5 at IKEA:

Reda Bowls

Insanely cheap. Get two (2) sets because you need two of the biggest bowl. They also come in white. I imagined using one of each color, so this project would look like a big fishing float. Ultimately, though, solid red seemed best.

UPDATE: These bowls are no longer sold by IKEA.  Sorry.  

Finally, the miscellaneous hardware. 8 speakers x 4 mounting holes = 32. My local Ace hardware provided 32 machine bolts, locking nuts, and washers. Also, pick up 8 small nuts and bolts for the terminals. Most of the speakers were fine with 1/2" bolts, but the top and bottom ones needed longer (1 1/2") ones, as you'll see later. This may vary, if your parts are different.

Also:
- weather stripping
- speaker wire ( I had some 18 gauge stuff lying around the house, the project only needs a few feet.)
- heat shrink tubing

Step 2: Assemble your tools

For this project, I used:

A "high-speed rotary tool" with the following bits:
- #409 cutoff wheel
- #561 Cutting Bit

Soldering Iron, Solder, and heat shrink tubing
Wire Cutters, strippers
Scissors and a Pencil
Ear plugs and Safety Glasses

I'll emphasize ear plugs here. It wouldn't do to deafen yourself in the process of building a snazzy speaker array, would it? I like to wear earplugs when I do any work with power tools. (Or when I work with stupid fools.)

And of course, working with many of these tools is inherently dangerous. Just because I did this project without injury doesn't mean you won't hurt yourself. Be careful; as the agreement says: By using Instructables, you may be exposed to Content that is offensive, indecent, objectionable or unsafe. Each user must evaluate, and bear all risks associated with, the use of any Content, including any reliance on the accuracy, completeness, or usefulness of such Content.

Step 4: Make a template

Since the hole for the top speaker was the perfect size, I used it as the template for all the other holes. Trace either the hole or the part that was cut out onto a piece of paper. Use scissors to cut out the template.

Step 5: Mark the locations of the speaker holes

The speaker holes should be cut evenly around the sides of the salad bowl.

To make sure they are exactly 120 degrees apart, used a piece of heat shrink tubing (or the like) to measure the circumference of bowl. Then divide the circumference by three, and used the same tubing to mark where the center of each speaker should be.

NB: For one hemisphere I centered a speaker on the handle and measured from there. The other hemisphere has a speaker centered on the spout. That way, the speakers are offset when you put the hemispheres together. Also, make measurements from both directions to make sure there aren't any errors.

I decided to put the speakers an inch away from the rim of the bowl. That left me clearance to put the lids back on, if I wanted to. Don't put them any further away, or they will wack into the top speaker.

Use your template to trace the speaker hole onto the bowl.

Step 6: Cut and adjust the speaker holes

Picture of Cut and adjust the speaker holes
step6b.jpg
Again with the dremel cutting bit, cut along the lines you drew in step 5. There is quite a bit of inaccuracy introduced by trying to draw a flat template onto a curved surface. The first hole you cut is going to be too small. Test fit the speaker, and cut out more material where it rubs against the speaker. Don't worry about ragged edges, they will be covered by the speaker flange.

NB: This might be a better time to do step 13.

Step 7: Take a break

Picture of Take a break
Actually, I made the hemispheres one at a time, over a number of days.

Step 9: Prepare your speaker wire

Cut a short (6-8 inches) length of speaker wire for each speaker. Strip the insulation about 1/2" back on each end of the wires. Tin all of the ends.

Step 10: Solder the wires to the speakers

It will be easier to solder the wires to the speakers before they are attached to the bowl.

Cut some short lengths (3/4") of heat shrink tubing and thread them on one end of a speaker wire. Solder the ends to the speaker terminals, slide the tubing over the solder joints, and use a heat gun to shrink the tubing.

RE: Polarity
My speaker cable has a reddish wire and a silver wire. I connect the red wire to the positive (+) terminal and the silver wire to the negative terminal. Some wire has colored insulation, or just a stripe on one wire. Conventionally, one connects a red or striped wire to the positive terminal. If you are inconsistent about this, you might accidentally reverse the phase of some of the speakers. While this will probably have no audible effect in this system, it would be a problem in a more scientifically calibrated setup.

For all the Rules of Hacking, see:
''Handmade Electronic Music: The Art of Hardware Hacking'' by Nicolas Collins, pp. 225-6.

Step 11: Prepare the speakers with weather stripping

Picture of Prepare the speakers with weather stripping
step10b.jpg
This step is optional, and cosmetic.

I ran a line of open foam weather stripping around the edge of all of the side speakers. (The flange of the top speaker sits flush against the "foot" of the bowl.) The purpose is to cover the gap between the speaker flange and the bowl, and hide any messy edges.

Step 12: Attach the speakers to the bowl

I started this process with the top speaker. Fit the speaker into the hole, and use a pencil to mark where the bolts should go. Remove the speaker and drill holes that are the same size as your bolts. If you get the right size, the bolts will actually cut some threads on the way through the plastic. This isn't very strong, of course, so on the back put a washer and a locking nut. I used locking nuts because there will be a lot of vibration in this system.

There is going to be a fair bit of muscle and bending in this step. As you can see, both the speakers and the bowl are a bit bent by the end. That's fine, it just makes the whole thing stronger. :-)

Repeat for the three side speakers.

BTW: It's possible that by this point you accidentally poked a speaker, and dented it.
Here is an instructable on "unpoping" dented speakers.

Step 13: Attach the terminals to the bowl

It would have been neater to cut the holes for the terminals back in step 6, but that's not how I did it. The terminals each need a hole big enough for the connections to fit through. Hold the terminal in approximate location, and mark the place to cut with a pencil. The terminal block is much bigger than the necessary hole, so a little imprecision is fine.

I was imagining this speaker hanging from the handles, so I kept the terminals as close to them as seemed reasonable. Check out the photograph to see how the positions are different on each hemisphere. There are two terminals on each hemisphere. On one, the terminals are close together near the handle. On the other, they are on either side of the speaker that is centered on the handle.

Since you've already got the weather stripping, stick some to the bottom of the terminals.

Finally, fit the terminal blocks, drill holes for the small bolts, and bolt the blocks in place.

Step 15: Enjoy the sweet, sweet music

This array can be used either as a hanging sphere(oid), or as two hemispheres. Either way, the radiation pattern can be quite interesting. I like to put the lids in when they're in hemisphere mode.

You're going to need a few things to use your speakers, now that you've got them.

-- Eight channels of amplification. With the money you saved on speakers, you could by a Stewart DA-70-4 for each hemisphere. Or, to keep the whole thing on the cheap, get four t-amps .  Currently, I'm running some class D amplifiers I found on ebay.

-- A source of interesting sound. I am a MaxMSP user, so I've used that software with the nbody~ from the PeRColate collection to create simulated body resonances of string instruments. You can also do this all for free with Pd .

-- I use it to make electronic instruments, or electronically processed acoustic instruments, sound more "real" and blend with other instruments.
hey didnt kipkay do something like this?
mzed (author)  applefanatic1 year ago
That comment comes up periodically here. In 2009, I wrote:

"Kipkay did a weekend maker video based on my article in Make. However, I am far from the first person to do this. Check out the link to Dan Truman."
leothelion2 years ago
do you guys think a metal bowl would work well in terms of how it resonantes etc?

ikea now sells these: http://www.ikea.com/us/en/catalog/products/50057254/

pretty good price.
thoughts?
what terminals are you useing in this project, the link you posted doesn't have those terminals.
imolenaar2 years ago
i cant get it everyone says just hook up one speaker to an amp output but normal boxe`s of my radio has 4 speakers in each and just one cable
TOCO3 years ago
Hey, great instrucable. It reminds me of a weekend project a while back. By the way most of your links appear to be broken.
mzed (author)  TOCO3 years ago
Thanks. Mostly fixed now.
TOCO mzed3 years ago
You are the first one that has actually fixed the links when I tell them that they are broken. You did it so fast to. Now the instrucable is even better.
mg0930mg TOCO2 years ago
Some people posted instructables in 2007 and never came back. It also takes time, and some things that go missing, you can't ever find anything with the same information.
mzed (author)  mg0930mg2 years ago
I'm still here. Ikea stopped selling these salad bowls, though. Making an exact replica of a project doesn't seem to me to be very important, anyhow. Hopefully there's enough here to get the idea out and somebody can make a nicer version with whatever is available at the time.
Phoghat mzed2 years ago
Okay, I just saw this and wan't something similar. I've got some questions:
1 Does the one speaker do stereo ? Or am I missing something. If it's not stereo = 1, why are there 2 sets of terminals?

2 I live in Mexico and you can buy bowls like that everywhere for a dollar or 2. About how big are the bowls in diameter ?

mg0930mg mzed2 years ago
Yeah, I see what you're saying.
TOCO mg0930mg2 years ago
Man, it has been forever since I actually did anything on this site. I come and glance at the first page once every couple weeks but it has changed so much from when i joined I dont really like it.
mg0930mg TOCO2 years ago
Same.
hvargas2 years ago
how much did this end up costing you?
krish98.sai2 years ago
This is so cool, did you know it was presented on make magazine videos with Kipkay
Madsengell3 years ago
Hey check out this project from stanford laptop orchestra (SLORK), I believe they are also referring to this project:
https://ccrma.stanford.edu/~njb/research/slorkSpeaker/index.htm
Great work by the way!
hey kipkay did thi project great job it a exact replica lol cool :)
is this a pretty common project? did kipkay rip it off? I just saw the vid too
Johenix3 years ago
Why not use 12 speakers arranged in a dodecahedron (solid of 12 pentagonal faces)? The speaker case could be made from card stock or foam core. Or get the type of speakers TerraCycle gets to make speakers in recycled cardboard cases.
Make it, although you might find if the speakers are perfectly arranged (as in same spacing between each one) it could look dull. Plus try different sized speakers that would give it a cool twist.
FrozenStar3 years ago
Interesting design, looks great.
ya i get it but how i will conected to the radio
You could solve the whole input problem and wire up a headphone jack to the speakers. That is, if your radio has a headphone output jack. But then I guess you would have to give the speakers there own power supply.
you need to put it through an amp and connect the speaker outputs to the red & black inputs on the sphere
Connect it to your stereo on the connectors like in the instructable
vez873 years ago
what sort of amplifier would you use for this as I'm looking to make something similar to wire to a 3.5mm jack for mp3 use, and I doubt that the player will be able to power the speaker all on its little ownsome.
tomigm3 years ago
Only 1 word.... C.O.O.L
Jeff K3 years ago
dont use anything but the batting. Cloth or foam is too dense and will deaden the sound. You can stuff the insides, just dont pack it. You need the sound to resonate thru the polyester dampenig material. The key is that all the gaps from the seams and mounting around the speakers is air tight.
 It's a very creative idea, BUT the sound waves of the speakers will work AGAINST each other...!

A speaker (when in use) sends sound waves to the front but also to the back. SO when you put 2 or more speakers with the backs  +- facing each other in the same space, you get a loss of sound and quality.
In such a project, the space in which the speakers are needs to be divided.

Also, the casing is to light for such and so much speakers, the vibrations will cause the casing to resonate, and resulting in a a unclear sound. It will just work well on low volume... but with these kinds of speakers i do not suppose you want to turn the volume down!
Stuff it full of foam?
Jeff K tim_n3 years ago
Not foam, polyester. And be sure the 2 halves are sealed. They need to be well sealed, or you will lose your base.
Polyester like a wall between the 2 hemispheres of the ball? it will already work better, but sparating each speaker from the rest would still be better.
Polyester like batting, acts as a dampener inside the sphere. My GB-1E's had a large piece covering each speaker inside the sphere plus wadded up inside. Dont pack it , lightly stuff it. You can get the polyester at radio shack, or spend half the money at a fabric store or walmart. No wall betweem the halves, my comment was related to the seal of the system because this is not a ported speaker. The term the origional speakers literiture had was "Hermetricaly Sealed", similar to a passive radiator type speaker system. Depending in your skills, a 1/8 in thick bead of clear silicone will work just fine. Its your choice as to weather you let it cure (24 hours) prior to assembly, or use it as an adhesive seal. Just be sure all the speakers are working prior to addhearing the two pieces togeather. Worst case, the silicone can always be cut to seperate the halves with a razor knife, if repair is needed
Exactly: a dampener. Separating the speakers from each other, so the soundwaves dont ''mess' with each other, and put like: wads (i hope this is the correct word...), cloth, or something soft inside which damps the sound, resulting ina fuller sound. =)
How do mean sutff it full? also the backsides of the speakers?
Jeff K3 years ago
FYI, I have a set of speakers that I bought overseas back in the late 60''s. they still sound as good as a set of Bose 901's. There are 8 speakers, of which 4 are hi dome tweeters with a built in crossover inside. Optimum placement is each globe is suspended in a corner, and the legnth of the chain should be the same distance from both walls and the cealing. The principal is the same as the Klepsch Infinate Baffel, where the walls and cealing are the final projector of sound. I tell you there is a huge difference in the sound as opposed to being on the floor. You google Nivico GB-1E, You can see several others like it at http://www.flickr.com/photos/teddy_qui_dit/4190293419/in/set-72157622584019059/
Madsengell3 years ago
in order to simplify the amplification, these speaker distrubutional hubs (or the like) might do it, although i don't know how it affects the amplification. Can anyone help there?
http://www.nextag.com/speaker-distribution/compare-html
will they be connected in parallel then, and in that case would it still be sufficient just to connect to your amplifier?

rugnor4 years ago
i think you could also use a buoy  if you find it floating in the sea, the rule of the sea find it , keep it
3rdmike4 years ago
Excellent instructable.  And bonus points for humor; beer and espresso are what fuels the DIY'er. 
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