The View Up Here

Random scribblings about kites, photography, machining, and anything else

An Inexpensive Shock Isolation Mount

Posted by Tom Benedict on 17/06/2016

One of the problems with building a funky microphone setup is that off-the-shelf gear won’t always work with it. It’s pretty straightforward to find wind protection for a shotgun mic or for a single omni. No one makes wind protection for do-it-yourself SASS arrays. (And no, that’s not what this post is about. That’s still a work in progress.)

Up until now I’ve run my DIY-SASS without shock isolation. It’s worked after a fashion, but any time I position my gear in foliage I wind up with tap-tap-tap noises of branches or long grass touching the tripod legs. More than one person has pointed out that even rudimentary shock isolation would get rid of most of that.

Unlike wind protection, it’s possible to adapt other shock isolation mounts to my DIY-SASS. Any of the lyre-style mounts for handheld recorders would work fine. But most of these are relatively tall. I wanted something more compact. And cheaper, if I could swing it. Here’s what I came up with:

Microphone Shock Mount Top

It’s adapted from an anti-vibration camera mount for a multi-rotor. As I received it, the mount consisted of two carbon fiber plates with four vibration damping balls (yes, that’s the real term). The balls are replaceable, and can be swapped out for harder or softer ones. The mount had 1/4″ clearance holes top and bottom. I wanted this to fit between a tripod and my DIY-SASS, or between my DR-70D and my DIY-SASS, so I needed a threaded hole on the bottom and a threaded thumbscrew on top.

Microphone Shock Mount Bottom

Adding a threaded hole to the bottom was relatively straightforward. This would’ve been prettier with a round piece of metal, but I had the plate stock in-hand, and it was almost the right size. I squared it up, transferred the hole pattern from the carbon fiber plate to the aluminum, and added a 1/4″-20 threaded hole in the middle.

Adding the thumbscrew to the top was a little more involved. I had some 2″ 6061 aluminum round on-hand, so I knurled it at that diameter, faced off the front to leave an 0.250″ diameter x 0.375″ long boss, and threaded it with a 1/4″-20 die.

Normally you’d want to single point thread a boss like that to avoid all the normal ills of die cut threads: drunken threads, off-axis starts, offset threads, etc. But since this only had to screw into a 1/4″ T-nut to hold my microphones in place, a die cut job was fine. I parted the thumbscrew off the bar, flipped it around, and faced off the other side.

The damping balls that came with the mount turned out to be a pretty good match for my DIY-SASS. I’d have to swap them out for softer ones if I used it with my DR-05 handheld recorder. But since this is probably going to be a permanent addition to my DIY-SASS, it’s fine as-is.

I finally had the opportunity to test this in a systematic way. I put two contact mics on my tripod legs and tapped the center column while adjusting the gains on those channels until they both read the same. Then I moved one of them to the top of my SASS and tapped the center column to see how much attenuation the isolator provided. I recorded both configurations so I could compare in Audacity. The isolator very consistently provided 21dB of attenuation. I don’t know how that compares to a commercial isolator like one of the lyre mounts I mentioned earlier, but it’s a darned sight better than the zero dB attenuation I’ve had up to this point.

I always feel a little weird posting a DIY that requires the use of a machine tool. In this case it involved both a lathe and a mill. But the core idea of this is to adapt a multirotor camera mount to microphones for field recording. There are other ways to get that threaded hole and thumbscrew. Imagination and ingenuity are powerful tools of their own.

Have fun!

Tom

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3 Responses to “An Inexpensive Shock Isolation Mount”

  1. Greetings! What make & model anti-vib plate did you use?
    Thanks!

  2. […] contact mics are useful for other projects as well. June last year, I wrote an article about a shock mount for my SASS I’d made from a re-purposed multi-rotor anti-vibration mount. I used contact mics to […]

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