I’ve been thinking a lot about the specifics of diffuse field recording with omni-directional microphones recently. I generally prefer the sound of a well placed pair of omni-directional microphones over recordings made with more directional microphones. To me, omni recordings tend to sound much more real and involving than cardioid or other directional microphone recordings. But, omni-directional mic recordings sound much better when the mics are placed closer to the sound source then is possible sometimes.
What got me started thinking about it was my recent experiments with modifying Chinese SD condenser microphones. Typically these microphones, for example the MXL 603, CAD GXL1200, Nady CM-90, and Avantone CK-1, to name a few, have a pronounced presence boost around 6kHz to 9kHz.
Many microphone manufactures make omni-directional microphones and capsules specifically designed to be used the in diffuse field. These microphones or capsules typically have a presence boost in the 6kHz to 9kHz range. Now, for those manufactures, the diffuse field generally means that the microphones will be placed a little further away from the sound source than near field microphones would typically be placed. For example, when recording an orchestra with mics placed closer to the stage lip or just off stage rather than right over the conductors head.
The diffuse field as it relates to tapers often means recording from a much greater distance to the sound source than the diffuse field omni microphones are meant to be used from. A pronounced presence boost in the higher frequencies can make the source sound closer than it really is from a less than ideal recording distance. This may account for why some tapers prefer brighter mics. If they generally record from far away, they like the reach that the brighter mic gives them. So, tapers knowingly or maybe unknowingly like and specifically use the brighter sounding microphones when recording concerts in the very diffuse field that they often find themselves recording in.
I have been doing some controlled tests with stock and modified cheap Chinese condensers. I’ll play noise or music through my home playback system and record that using the different microphones that I have. When comparing the Chinese mics with the omni capsules to my reference AKG C-480 with CK-62 capsules the Chinese mics, sound much more up front than the AKG’s from the same distance. They also don’t have as much omni room boom as the AKG’s.
Some people have found that by modifying the Chinese mics either electronically or physically they can tame the brightness and make the mics sound more neutral in near field recording applications. But, the modifying to eliminate the presence peak inherent in the microphones can only take you so far.
I got to thinking about how to tame bright mics when used closer to the sound source. So, I started to experiment with several different foam wind screens I have bought over the years. I noticed that I prefer the sound of the Chinese mics with small foam windscreens installed over the sound of them without the wind screens. I will start using them more because of this.
I generally don’t like the sound of my AKG’s with windscreens. When recording indoors I don’t usually put the screens on if there is not a lot of air movement in the venue. But, they are closer to neutral sounding then the Chinese mics.
That extra brightness I hear in the Chinese mics can be used to advantage when recording from further away with the omni capsules. I can also tame that brightness with various foam wind screens when recording closer to the source.