September 23, 2018

How My “Sound Snooper” turned out…

Last week, I wrote about the “Sound Snooper” homemade “shotgunish” microphone from an Electronics journal published in 1965. I thought it looked awesome and I wanted to know how it sounded, so I decided to make one. I did not, however, want to pony up the $200 for the aluminum piping used in the journal. At least not for the first time around. Instead, I decided to spend a mere $4.68 on PVC piping, and about $20 on epoxy. Far cry from $200. I used 1/2″ PVC instead of the 3/8″ Aluminum (couldn’t find 3/8″). I figured the difference was somewhat negligible.

So I started construction:
Snooper

I played around with a few different types of glues. Found out that the 5 minute epoxy in the plunger works best. You just have to work quickly or it will set in the plunger itself! After working for a few hours on it (it was a slow process, as I could only put a few together at a time and had to let them set before I moved on), I started realizing that it was turning out a little on the large side (larger than I expected). So I started measuring some things. It was at this time that I realized that PVC pipe was measured by the inside diameter, while aluminum is measured by the outside diameter. This means that my PVC contraption would be twice the size as the aluminum one made in the journal. This would pose to be a bit of a problem because I can’t find a diaphragm that big, unless it’s dynamic, which kind of defeats the purpose of a long distance mic…

Anyways, I was to continue anyways, because I must finish what I start.

Here’s some pics of the mic coming along:

I finally finished the body, and moved on to the electronics. As I said before, there isn’t a condenser capsule big enough for this application, so that’s out of the question. The journal used a crystal mic, but the biggest one of those I could find was 2 inches, which is big enough for the one they made, but my mic was almost 6 inches in diameter. So, I went down to my local electronics surplus store and bought myself a 4.25″ dynamic driver. It was made to be a speaker, most likely the woofer driver in a small pair of speakers, but I decided to use it as my mic capsule. Unfortunately, I didn’t take a picture of it before I put everything together.

Anyways, I soldered a lead with a 1/4″ TRS connector on it to the mic capsule. I found a funnel that was about 5.24 inches in diameter, which was the biggest one I could find, and mounted my dynamic capsule in it by drilling holes in the funnel and running solid copper wire through the holes. I then cut up the diameter of the funnel every few inches so I could fit it around my mic body. I fitted everything together and manhandled some gaff tape onto it to make it stick (this wasn’t an easy process…). Everything was together, and I decided to try it out. Here’s a pic of the finished product:

So, as you can imagine, it didn’t sound terrific, being dynamic and all. My plan is to make a better one some time (hopefully soon) and order a crystal mic or something to use with it. But for now, I’m just working with what I’ve got.

Below are a few recordings I did with the mic. It sounds fairly cool, because it’s really saturated. It’s fairly directional as well, but I’m guessing if it were much more sensitive, I’d be hearing the directionality a lot more. I found that going directly into a preamp rendered a fairly high level signal, but it was very bass heavy, and didn’t have a lot of high end response. It sounded very “tubey”. I then tried it through an impedance matcher / balancing circuit. I lost a very significant amount of level, but it fixed the frequency response almost completely. It sounded almost normal.

Here’s a recording of a fire cracker with just the “Tube” mic:
Tube Mic

Here’s the same recording with the CSS-5 and a contact mic mixed in:
4 Mics

Speaking of my contact mic (the one I made and blogged about a few weeks ago, it met its untimely doom during this recording. I decided to gaff tape it directly to the firecracker to get a cool impact sound. Granted, I knew it would break, I just didn’t know how long it would last. I reinforced the sides of the firecrackers with tape so the explosion would be directed to the ends, minimizing the impact on the mic. It lasted 4 takes. I’m proud of it. $1.00 of parts down the drain, but I made a new one, so all is good.

Here’s a pic of the dead mic:

Here’s a recording of the final moments of its life. It was a good mic. It always listened, never talked back. It has a short life, but maximized its effectiveness despite its shortcomings:

RIP Contact Mic

I’ll get some more recordings up as soon as I have time to do a few. I can try to entertain requests if you’re interested, since it’s a one-off. Anywho, hopefully I’ll get around to making a new and improved version sometime soon. Wish me luck!

Comments

  1. It might be interesting to hear someone talking or a recording at a set volume at different distances to see how accurate it keeps.
    I suppose you could also record with a normal mic at the same distances for comparison.

  2. I’ll have to try that! Thanks for the comment!

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