Re: Test what you think you know: Part 2
Jay,
1) Open cell foam similar to what is used in windscreens is used for packing material in many microphone shipping boxes. It has very low vibration transmission acoustically isolating it from the bridge and soundboard. The material can simply be wrapped around the mic and put under the bridge, it has no effect on the sound of the mic.
2) The soundboard acoustically amplifies the string vibrations, as well as being a boundary for a bridge mounted mic.
3) The sound of the bass has similar frequency content to pink noise, no argument there. The proximity of the mic in relation to the sound producer is the element of discussion, a non-variable D cardioid has a totally different bass response at one inch from a sound source than at one or three feet.
4) The EV nd487 has lots of low frequency bass boost proximity effect, no doubt it can produce thundering bass. All the techniques you mention are good, though they may not provide as much vibration decoupling as foam. They do provide far more flexibility to find the "sweet spot", given the time to experiment, and the lighter mics will have less acoustical effect on an instrument than a heavier mic.
The examples below show various mics response at the same close distance to a 10" speaker on a large baffle. The RTA-420 is a omni test mic (no proximity effect), the speaker was equalized for roughly flat response for it, other mics were compared. It is interesting to note the 7 dB 35 Hz low frequency proximity effect boost the AT37 has. Also interesting is the Shure Beta 58 low frequency response looks almost the same as the RTA-420, just 3-4 dB less, while the latter Beta 58A and Beta 57 show a greatly reduced low frequency proximity gain. They make for less boomy vocals, but way less LF thunder.
Also noteworthy is the difference in phase response of the condenser mics (RTA-420, AT37) compared to the dynamic mics. When mixing a mic and a pick-up transducer, the two phase responses never are the same, but either a condenser or a dynamic may better compliment the particular transducer .
Art
