Royer Labs R-122 - Manual (Page 9)

The Sweet Spot
Finding and Working with the Sweet Spot
Good engineers know the importance and benefits of finding and working with the “sweet spot”
of a given microphone. The sweet spot is usually defined as the optimum placement (working
distance and angular position) of any microphone relative to the sound source.
Each microphone has its own sweet spot, whether it is a ribbon, dynamic or condenser type. The
sweet spot will vary with the type of sound source and its volume intensity, the polar pattern of
the microphone and how consistent it is with frequency, and the acoustic environment.
Being in the sweet spot means the microphone and the sound source are in a harmony of sorts;
the acoustic information is exciting the microphone in such a fashion that the resulting
reproduction is very desirable, usually without the need for additional equalization or electronic
manipulation.
There are only general rules as to where the sweet spot may be found for any given microphone,
and usually experimentation reveals it. The sweet spot can be extremely variable since it depends
on the quirks of a given microphone and acoustics of a given room. Once the sweet spot is
discovered, this placement can become a “rule of thumb” starting point for future microphone
placement with similar sound sources. Remember this: If it sounds good, it’s probably right. If it
doesn’t, move the microphone. It’s often more effective to reposition the microphone than to
start fiddling with knobs. Knob twisting can affect headroom and phase coherency and add
unwanted noise.
The following is a list of variables that account for “sweet spot” effect.
1. Frequency response variations due to proximity effect.
2. Frequency response variation due to treble losses as a result of absorption and “narrowing” of
the pattern at high frequencies, causing weakening of highs as the microphone is moved
away from the sound source.
3. Variation in ratio of direct to reverberant sound.
4. Tendency of a microphone to favor the nearest sound source due to a combination of these
items, plus the influence of inverse square law. Inverse square law states that for each halving
of source-to-microphone distance, the sound pressure level quadruples.
Other Types of Microphones
For the same ratio of direct to reverberant sound, omni-directional microphones must be closer to
the sound source than cardioid or bi-directional microphones. Microphones should generally face
the sound source head-on; if not, treble losses due to phase cancellation can result. The exception
here is for large diaphragm condenser microphones, which often give the flattest response at an
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