Wednesday, July 25, 2007

On Suspension Mounts

The suspension mount, AKA "the shock mount" is sometimes a wobbly gadget.

Suspension mounts do work to attenuate conducted acoustic energy that might travel up a mic stand or from a boom or other attachment, and into the body of the mic. The principle is simple: Make the inner portion of the mount have a resonant frequency, with microphone attached, below the lowest recorded sound.

Now that can be pretty low. I see all kinds of mic figures that seem to say that mics have significant output well below 10 cycles per second (Chladnis). Ours certainly do. So that would mean that the mount ought to resonate at that fequency, or lower. Of course this is where the low cut switch comes in.

How do you lower the resonant frequency of mount + mic? Adding mass to the mic will do it. In fact, the heavier the mic, the lower the resonant frequency. It's called mass loading. So, a heavier mic has some advantages.

Suspension mounts have some other problems with heavy mics: those rubbery things you see are usually made of what I call ponytail bands. They are apparently the same rubber string with braided covers you find in Rite Aid. The Shure KSM44 avoids this, partly, by having an elastomeric, form fitting sling type mount. Perhaps it could be extened out to the stanchions, eliminating the strings entirely, but that might not look as nice.

But you could also theorize that a heavier mic would benefit from a firmer mount and have fewer conducted sound pollution problems in the low range in any case. This might indeed be true, as some devotees of the rigid ring type mounts assert. You might be interested in reading other opinions regarding solid mounts, and in particular, about the Enhanced Audio M600 Mount, which fits our largest microphones well, on this thread in gearslutz.com.




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