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Anyone ever seen one of these or played with one before? Its been floating around for quite some time now. I found it a few years ago and just stumbled upon it a few days ago. I'd imagine if you took one of these in a public area you'd probably get some funny looks and perhaps a bit of trouble...

The physics behind how it works is awesome.

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The PDF gives cross sections and rough instructions on how to build one. I'd love to hear one sometime, but it looks like quite the project to build one.

Download the pdf here

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Simply amazing! –  Andrew Spitz Mar 11 '10 at 5:59
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Any chance of finding a recording somewhere? If so, please post it here :-) –  Andrew Spitz Mar 11 '10 at 9:23
    
Haven't been able to find anything like it anywhere, so I'm going to try to make one myself. See answer below for a pic of what' I've got so far... –  Colin Hart Mar 12 '10 at 5:57
    
See my comment below for an update –  Colin Hart Mar 17 '10 at 4:25
    
I am curious to know whether or not pvc will work the same as aluminum. It would be the deciding factor for whether or not I build my own. please let me know. –  user478 Aug 5 '10 at 1:25
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8 Answers

So, I felt rather adventurous today, and, having successfully made a hydrophone earlier this week, I felt fairly confident in my building skills as well. So, I decided to attempt to make one of these. The article calls for aluminum tubing, but although I felt confident, I didn't feel confident enough to drop $200 on this project. I, like Selcuk, often turn my DIY projects into RIY projects. So I decided to make a prototype out of PVC pipe (which dropped the construction price to $25 - a admission fee worth the fun even if I fail...). So, if it works, and fairly well, I may venture into making one out of aluminum. We'll see...

I bought the pipes today, as well as epoxy and such. I've gotten the main pipe system almost put together, but I ran out of epoxy around midnight, so I'll give it a rest til I can get some more tomorrow.

Here's what I have so far: alt text alt text

Once I'm done with the project, I'll post a blog about the whole process, as well as recordings (however they turn out...)

Wish me luck!

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BTW, for reference, the longest tube is 36" long –  Colin Hart Mar 12 '10 at 6:05
    
Wow, thumbs up for doing it. I'm so excited to see how this comes out. Good luck! –  Andrew Spitz Mar 12 '10 at 10:52
    
So, I've found out that 1/2" pvc pipe is actually 3/4" because of how thick the walls have to be. I'm already cheating a little because the article asks for 3/8". So, my model will be the same length, but twice as thick as the one they made. Theoretically, this should only change the amplitude (and hence the dynamic range) of my mic, which could end up being a good thing. Hopefully it won't adversely affect the directionality. It'll be interesting finding a pickup big enough to work with it. We'll see... –  Colin Hart Mar 12 '10 at 14:40
    
Amazing. Really looking forward to hearing the recordings! –  Lachlan Harris Mar 13 '10 at 3:02
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Finally got up the blog post with more pics and a few recordings: bit.ly/c6mVkm I'll hopefully have a few more recordings up soon. –  Colin Hart Mar 17 '10 at 4:24
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Ok, this is a cool looking thing, but I agree that you would get a hell of a lot of funny looks, and possibly time in a cell, if you walked around with it. Check this link out http://www.tunedcity.net/?page_id=1356 it's not quite a 'shotgun' mic but it certainly looks similar!!

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Very interesting project. I have seen these plans posted in other places. The weakness of this design is that you will actually need a separate microphone at the end of each tube, instead of a single mic at the end of the funnel. The tubes may resonate and amplify, but whatever gain they have is lost in the "collector"--i.e. the area inside the funnel where the tubes join.

The length of the tubes are set this way to allow each microphone to pickup a different frequency. So let's say you had this attached to a graphics equalizer. You can then separate frequencies.

This design can also be used if you use a funnel at the end.

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Looks amazing!

Whenever I start a DIY project, it usually ends up being a RIY (Ruin it Yourself) Project. So I always prefer an industry standart equivalent which is a better investment in the long-run.

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RIY, I like that. Funny. It's true DIY will probably not be worth your while if a good sounding final product is what you're after, but it's an awesome feeling to build your own and see how it's done. –  Andrew Spitz Mar 11 '10 at 11:59
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This looks pretty crazy. Did you end up completing and testing it? Love to hear some recordings.

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I did. I have a few recordings on my blog. Didn't come out exactly how I expected it to (I explain why there...) so I'm planning to eventually make some modifications to try to improve on it. Let me know what you think! colinhartonline.com/?p=141 –  Colin Hart May 1 '10 at 23:57
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I build and tested the design in PVC tube years ago, when the original article came out. It works OK, but the sound is strange, like you are in a tunnel. Building it in aluminium would be worth a try.

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I have one built in aluminum! Someone in my family built it years ago. I never tried it myself. It it for sale, but I think it would be very expensive to ship it! I live in Sweden

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If you can get hold of it (public library?), an original construction article:- Popular Electronics June 1964 (!). Used 37 , 3/8" ext diam Ali tubes Only one microphone is used.

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