Dollar Store Parabolic Mic

This is a ridiculously easy way to build a very functional parabolic microphone using mostly items purchased from one of those stores where everything is a dollar. Check out the original design at: .Dollar Store Parabolic Microphone

Step 1 Gathering your materials.

First, gather all the materials you will need. This is very easy. In fact, this whole project is so easy you almost don't even have to have the instructable.

Find a small folding umbrella hat, a regular nine inch paint roller handle, and small microphone. Make sure the umbrella hat is vinyl and not fabric. Fabric is too acoustically transparent and will not reflect the sound properly. Just about any small microphone will do as long as it is reasonably sensitive. Here I am using a stereo "Clip-On" mic from Radio Shack (33-3028).

You will also need a few tools and supplies. This is basic stuff. Get a hammer, side cutter, sharp knife, razor saw, permanent marker, some gaffer's tape, and a few cable ties. The reamer is optional. A file might come in handy. So might a small laser pointer of some sort.

That's it!

A little note for "dollar store purists:"

It is possible to build this whole thing using only components from the dollar store. Many of them sell small earbud headphones that can function like microphones, albeit very poor ones. The also sell little hands-free headsets for cell phones. Those have real microphones in them. They will require a little surgery to work but a dollar store purist won't mind. Using either of these options will give you a true $3 parabolic mic

Comments

[integrator]

I wonder if I could figure out a way to make small whisper dishes, like you see at science centers and such? Two of them pointed at each other, you stand in front of them and talk into them, and the reflected sound is heard at the other one 50 or 100 feet away. If it's to small, you may block it though.

[jurtle]

All of the whisper dishes I have seen are fairly large, usually four feet or larger in diameter. They are passive devices and fixed in location. They tend to work better if the participants in conversation have their backs to each other. In general, the larger the dish, the larger the gain. Once you start getting into the smaller sizes, you will encounter the problem of less gain compounded by the acoustic "shadows" cast by the heads of the participants. If you built two active devices such as the one in this instructable, you could achieve the same effect, except that the communication would be electronically amplified (as well as reflectively amplified through the parabola). Simply have the two participants point their respective devices toward each other and chatter away. Unlike the ordinary whisper dish sets, these would not be fixed in location. and the participants would be facing each other.

Good luck with your experiments.

[bigskyjack]

i like ur style! i made my own parabolic mic a while bak from 1 of those clip-lites for keeping chicks warm, just took out the bulb socket & replaced with a cork with a hole (chem lab style), ran a wooden dowel thru for the mic boom. for the tuning of the mic placement, i found i needed a distant, constant, 'white-noise' source, so i stuck a small transistor radio tuned between stations out the other side of the yard - worked perfectly - & ur rite, the human ear is by far the best sensor for that 'sweet spot' for the mic!

[jurtle]

Thanks. I am glad the project resonated with you. I guess it is clear that I had a ball doing it and even more fun interacting with others who like the project.

[KingOfCatfish]

I love this Instructable!
So you know those really crinkly emergency blankets that resemble foil? Would lining the inside of the umbrella (using spray adhesive or the like) with that help provide better sound? My reasoning with this thought was that the metal-like surface would reflect sound waves better than just the vinyl.

[jurtle]

Glad you like the Instructable. It was fun to put together. As for lining the umbrella with the rescue blankets, I think you would get only marginal improvement if any at all. Those blankets are usually made of mylar, another plastic-like material. Adding another really thin layer of plastic (and glue) to the umbrella might make the whole thing slightly more rigid, thus making it slightly more reflective. My guess is that one would hardly be able to tell the difference in an A-B test. Don't confuse the shiny, almost mirror-like, look of the mylar with good acoustic reflectivity. It will make a much better reflector of light but not of sound.

[KingOfCatfish]

Thank you for getting back to me. My eyes have now been opened, ha-ha. So I was looking at some pieces of Lexan that are at my house from another project and was wondering is forming it into a parabola would work. What do you think the outcome would be?

[jurtle]

I assume you are talking about flat pieces of lexan. Yes, you can fabricate a parabolic reflector from that material. It will require some cutting and gluing. Here is a link that will get you started: http://vzone.virgin.net/ljmayes.mal/var/parabola.htm Otherwise, just do a google search for something like "Make a parabolic reflector." Lots of idea out there. Good luck.

[scraggy12]

Hey , can I use an old direct tv dish?

[jurtle]

Yes, but because the dish is so shallow, the focal point is farther away from the surface. It will work but you won't get as much gain. See an earlier comment/reply on this subject. Good luck

[jacko622]

Could you use a regular umbrella for this? 

[jurtle]

There is a major difference in the configuration of the hat and a regular umbrella. In the case of the regular umbrella, there is the center shaft to contend with. Perhaps instead of removing it, one could re engineer it to be the on-axis mic support. That way you have a support for the ribs and a support for the mic. Then it would be a matter of configuring a handle for the device. Here is where your own builder/hacker/engineer self comes into play. Go for it.

[dakellymon]

 Well done. Great idea.

[wingo395]

Oh one more thing - You showed in the photos but perhaps it is worth mentioning - you want the microphone element pointed IN to the center of the umbrella, not outwards.  This is to pick up all of the reflected sound bouncing off the surface of the umbrella and to the focal point.

[jurtle]

Good call. I did show the mics facing inward in the photos but nothing is said about it in the text. I will probably amend to make the addition. Thanks for the input.

[jurtle]

I have amended the text to point out that the mic should face inward toward the umbrella. Thanks for the input.

[pyro ray]

Ok for those of you interested I found umbrella hats online for like 2.99 ea at a lot of places, from But they are made out of nylon. But you can also take a can of spray paint to the unbrella to close the "pores " of the nylon

[jurtle]

I have not tried that approach but I do think it would work. Anything you can do to reduce the acoustic transparency of the nylon fabric will help. That said, you can still get some detectable isolation of the sound source, even with an untreated nylon umbrella. You might be surprised.

[ilpug]

 use metallic spraypaint to boost the reflectivity of the umbrella... you could even use aluminum foil to line the umbrella. i used a coat of metallic stove black high-heat paint and used a full can... several coats helped alot. i have used these for getting audio on films, and they work great.

[wingo395]

Very nice project!  If you really want to get accurate (as accurate as possible given the flexible nature of the umbrella hat), you can calculate the focal point.  All you need to know is the diameter of the dish and the depth of it.

A simple google search will turn up oodles of info:
http://www.google.com/search?q=calculate+the+focal+point+of+a+parabola

I once bought a parabolic dish (without the mic) from a college, and I bought a very sensitive electret microphone (electets have batteries in them to amplify the signal).  I don't know if it was omni or unidirectional.  My guess is omni might be better, but would need experimentation.  The funny part?  I have yet to put it all together!!

[jurtle]

Glad you liked the project. Yes, one can easily calculate the focal point from diameter and depth in a true parabola. That said, there is no reason to believe the umbrella is actually made to conform to such standards. As I have said in previous posts, the focal point on this device is fuzzy at best. Better to use the methods suggested to get the best result. Much of the physics (and math) that applies to parabolic focus with point sources from infinite distances (therefore parallel rays) just does not apply with variable wavelength sonic sources from variable distances and angles. Too much accuracy is overkill.

[herrdoktor]

 Could you use a large, plastic salad bowl instead of an umbrella?

[jurtle]

Yes. Almost any roughly parabolic surface will work. You just have to find the focus or sweet spot for the dish you are using. Of course, the more accurately it approximates a parabola, the better off you are.

[herrdoktor]

 Thanks, I'll give that a whirl. Have a dollar store down the street, want to try this out with my kids. We live in the country, so hope to capture a number of sounds. Very cool instructable, thanks for posting.

[threedagreexo15]

Hey I'm having some trouble acquiring the vinyl umbrella. Any ideas of where I should look? I tried the dollar store (Dollar General) and few other places and haven't had any success. All i've find is nylon so far.

[tobybirch007]

You could just cover the nylon umbrella with aluminum foil

[jurtle]

Another thought: You might also try looking in a toy store for kids' umbrellas. I think I have seen transparent vinyl umbrellas in places like Toys R Us or Target. Modification of the umbrella would be very different but perhaps worth the effort.

[jurtle]

Sorry you are having trouble finding the vinyl ones. Mine came from a chain called Dollar Tree. I think the items are seasonal so you might have better luck in the coming weeks as the weather warms up (at least in the northern hemisphere). As a last resort you could still use a nylon umbrella if you were willing to coat it some way so as to reduce the acoustic transparency. I think a few coats of shellac would work. The umbrellas are cheap enough to experiment with. Maybe something like Mod Podge, available any hobby or craft store, would work. Good luck with the project.

[threedagreexo15]

Thanks. I just realized that I've been looking at regular umbrellas instead of hats. Is there a major difference between the two? It looks like the regular umbrellas need the rod in the middle in order to hold the rods that hold the umbrella out, so removing that might be difficult.

[jurtle]

There is a major difference in the configuration of the hat and a regular umbrella. In the case of the regular umbrella, there is the center shaft to contend with. Perhaps instead of removing it, one could re engineer it to be the on-axis mic support. That way you have a support for the ribs and a support for the mic. Then it would be a matter of configuring a handle for the device. Here is where your own builder/hacker/engineer self comes into play. Go for it.

[SLUTSONLY]

nice work ....... how do i use one witout being in plain view ....... dose it work threw screens ??? thanks

[SLUTSONLY]

do you , by any chance.. know about a shotgun mic ... and how it works ??? i have hot to hear what the heck my new neighbors across the street are arguing in the driveway about ..... thanks

[jurtle]

Begin your research into microphones here:
http://en.wikipedia.org/wiki/Microphone
I am going to stay out of that business with your neighbors. You probably should too.

[SLUTSONLY]

just bored and she's kinda cute ..LMAO .... thanks for your help ...

[jurtle]

Glad you like it. This is probably not your best bet for secretive recording. It does stand out. My guess is that it will work through a screen but I have never tried it. Good luck.

[hellequin]

Excellent demonstration... In your sample, I found that as with most parabolic reflectors – professional or otherwise that I have on occasion used, there is quite a bit of base rumble in the 40 > 100 Hz area. But a lot of this can be filtered out using various low-pass filters and EQ. A very commendable effort and a great solution... Bravo!

[jurtle]

Thanks. You are right about the low end emphasis. I think a more rigid reflector would probably take care of some of the problem. Some sort of shock mount for the mic would help as well. The challenge would be to make such modifications while staying within the "dollar store" range. Thanks again. Glad you liked the project.

[ee0u30eb]

Two things...

1. http://mscir.tripod.com/parabola/ a great program to calculate the exact focal point so you can put the mic in the right spot.

2. I bought one of those spy listeners sold for kids, opened it up and soldering long leads to its mic. If you use that you have a great instant amplifier and mic for your project. I also suggest removing the button cell (usually 1.5V cell) and solder on an AA battery holder. By using an AA battery you get more current and better amplification.

[jurtle]

Excellent feedback on both counts. Thanks. On the matter of the calculator, finding the exact focal point in this kind of device doesn't always produce the best results but it does give the best starting point. I have found that one has to fudge it a bit because the parabolic surface is imperfect. The best sound is most often somewhere off of the parabolic focal point. The ear is the best tool for the final adjustment. Some of those spy listeners for kids are great. Others are pretty crappy. I have a couple "Supersonic Ears" from Wild Planet toys. They work very well but cost about twenty bucks. Nice idea for an instant mic/amp combination though. If one is inclined to the the soldering and modifying anyway, it might less expensive to get a mic capsule, and one of those mini amps ( Model: 277-1008) from Radio Shack. The output quality would certainly be better.

[ee0u30eb]

We don't have a radio shack in the UK, but I might investigate mini-amps in maplis. Worst case scenario, I will just build my own amp, there are plenty of good circuits out there. There is I believe an instructable about reverse engineering a kids spy listener... so if one had one knocking around they could swap out the transistors to improve its amplification. Great instrctable, thanks