THE ART OF CLOSE MIKING
In a series of small articles, we invite you “behind the scene” at REMIC MICROPHONES, in order for us to share with you the latest innovations, knowledge of instrument specific close miking techniques and instrument acoustics.
THE ART OF CLOSE MIKING AN ACOUSTIC INSTRUMENT: VIOLIN/VIOLA
As a sound engineer or musician we are often told that when miking up an acoustic instrument too close, we will leave out a lot for sonic information, since an instrument such as e.g a violin only creates it’s full sonic spectrum from a distance.
In other words, close miking an instrument is often considered to be a compromise to the true acoustic sound of the instrument. The sound of an instrument is usually designed to be experienced at a distance so that all the different elements of the sound are naturally blended into a perfect harmony. Yet often, mounting a microphone directly on the instrument is the most practical solution.
Now – Let’s break down some myths from the past!
Fact is that we can trace these statements or traditions way back to the mid fifties, at a time where the microphones were quite large and heavy, and could not by any chance be mounted on the instrument itself.
Today, microphones can be quite small with a weight of a few grams and they can easily be mounted directly on the instrument itself, which makes it possible to challenge these old traditions. Mounting the microphone directly on the instrument is also quite beneficial, when you utilize the latest knowledge about instruments and technologies.
Along with the latest knowledge of musical instrument anatomy and tonal behavior of classical bowed instruments, we have based our research and developments on “instrument acoustics”, which deviate a great deal from general acoustics and room acoustics.
Today, we also know that the full sonic spectrum arising out of or emerge from an acoustic instrument such as e.g. a violin, spreads out on the whole surface of the soundboard of the instrument, and that the natural balance between the fundamental tone register and overtone registers can be captured within the proximity zone, along the median axis of these instruments.
When capturing the sound of the instrument within the proximity zone, (we’ll get back on this topic later), we will be able to capture every single detail – the full sonic spectrum as well as the full dynamic range and transient response of the instrument – with a minimum of disturbance from ambient sound sources, in order to keep the natural sound of the instrument as clean and undistorted as possible.
What we really want to achieve is to capture the sound of the instrument as uncolored as possible and “move” this sound source to the loudspeaker, from where the sound will fill the room and blend in with the room acoustics of any given location, sounding as if the artist is performing in that very room, whether we are listening to a recording at home or in cases where amplification is added for a live concert.
THE THREE SONIC ZONEs
By splitting up the acoustic environment in three sonic zones, proximity, transition and ambient, we now have a fair chance of knowing where we are going and what we are dealing with.
We could easily make these definitions as a research team, but this would probably conflict with the general opinions of sound engineers and musicians.
So – in 1999 we set up a minor test, incounting 1,378 musicians and 128 sound engineers. This test was set up in order to be able to make a more specific definition of the 3 sonic zones in reference to the human hearing response and psychoacoustics.
Ten recordings were presented to the test persons. The recordings were of a violin captured in two different acoustic environments from five different distances.
The outcome was as follows:
Proximity zone: recordings where more than 75% to 80% of the source signal was represented.
Transition zone: recordings where more than 30% to 60% of the source signal was represented.
Ambience zone: recordings where less than 20% of the source signal was represented.
TRUE CLOSE MIKING
Now having determined the three sonic zones, we can define “close miking” within an average ideal distance to the sound source, from the listener’s point of view.
To be more specific on this point, let’s take a look on how the instrument behaves (in this case the violin).
A violin amplifies it’s own sound acoustically (when one or more strings of the instrument are played, either by use of the bow or picked), due to the vibrations of the soundboard “belly” of the instrument and it’s hollow body (the resonator). The majority of air molecules that generate the instrument sound we hear, are now set in motion by the soundboard (belly), while a smaller part is set in motion by the strings themselves.
The average physical vibration pattern (for the belly of the violin) is approximately 0,2 mm for a standard 4/4 sized violin, tuned in A 440 Hz, carrying steel strings, providing the 9 to 12 kg of down force from bridge to belly, and hereby provides a large potential energy factor. The vibration pattern measured on the soundboard just in front of the end of the fingerboard, were we’ll find the largest vibration pattern.
Now – if we capture the sound within the region of where the sound emerge from the instrument itself, and the sound level is more than 75% louder than the reflected ambient sound in the room, we’re good.
As long as the distance from microphone membrane and the vibrating belly of the instrument stays within a distance of maximum a 100 times the average vibration pattern, we’re safe.
In other terms – if the average vibration pattern is 0.2 mm, the average distance to the microphone membrane should be no more than 20 mm.
Keeping the mic close to the instrument and within the proximity zone at the centre axis, you will have a good chance of keeping clear of most ambient sound sources that tend to desturb and/or distort the finest nuances of the timbre.
Also the distance and angle of the membrane in reference to the vibrating part of the instruments, which creates the final energy pattern of air molecules, are to some point critical, which is another issue that we will address later.
Now – if we move the microphone membrane further away from the instrument, let’s say 50 to 100 mm, we are now working in the transition zone. This zone is an extremely complex sonic area where air molecules from the sound source (the instrument) and air molecules from ambient sound sources colide, creating and forms thousands of other energy patterns and structures, which to some degree distort the source signal, and in this way “wash out” the finest details.
In this zone, we have very little control over the acoustic sound source, bleed from other nearby instruments, stage monitors or PA system. Even the reflected sound from walls, ceiling and floor of the room, will disturb and change the pattern of air molecules coming from the sound source, the violin, before it reaches the microphone, and this way it changes the pattern of air molecules of the most delicate sounds of the instrument.
THE INSTRUMENT SPECIFIC MICROPHONE
The clip-on mics applied with a goose neck that we’ll find on the market today, have been designed from a “microphone point of view” as “general purpose microphone” and they benefit from the fact that they can easily be adapted to different instruments or instrument groups, simply by changing the mounting clip.
The instrument specific microphones, however, have been designed from an “instrument point of view”, based on the behaviour of the individual instrument groups, and benefit from being able to capture even the smallest sonic details emerging from the instrument.
In other words, most clip-on mics designed and used for “close miking” are more or less designed for “transition miking!
In a live or studio situation, we want to capture as much of the natural sound of an acoustic instrument as possible to be able to deliver a good sound without capturing or re-amplifying too much of room reflections and nearby instruments, so the importance of choosing the right microphone tool is essential.
For more information, join the “REMIC MICROPHONES user community”:
https://www.facebook.com/groups/1274102739368320/ where you are more than welcome to discuss, comment and/or write about your experiences in the field of close miking acoustic instruments.