Townsend Labs Sphere L22, Руководство по аппаратному и программному обеспечению

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Townsend Labs Sphere L22 Precision Microphone System Guide Off-Axis Correction
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Figure 5-3 U87ai measured on-axis frequency response
You can also apply any mic frequency response to any polar pattern. For example, you can combine a
4038 ribbon response (normally figure-8) with a cardioid pattern, or take a U87 model and make it
hyper-cardioid. For the ribbon this can be extremely useful when trying to deal with bleed from
directly behind the mic. Making the U87 hyper-cardioid can significantly reduce room pickup.
Effectively, you have created a hybrid microphone from two different mics that did not previously
exist! This enormous flexibility lets you easily obtain the precise attributes demanded by your
application.
Proximity Effect
All directional microphones have polar patterns that vary with distance at frequencies below about
1 kHz. This is an inherent consequence of the proximity effect. For example, at low frequencies a
typical large, dual-diaphragm, cardioid, condenser mic (e.g., U87 or 414) tends towards a figure-8
pattern close to the mic and omnidirectional farther away. Only at some distance in between will the
mic have a cardioid response. This distance, typically 0.5 - 1.0 m, depends on the capsule design.
To further illustrate the differences in low frequency response, a typical small, single-diaphragm,
cardioid, condenser mic tends to have a figure-8 pattern close to the mic (< 10 cm), cardioid at far
distances (> 4 m), and hyper-cardioid at middle distances (1 – 4 m). However, this is a generalization
that depends on the capsule design of the mic.
It is evident that the polar pattern you want might not be obtained, depending on the distance of the
sound sources from the mic. For example, this can be a problem when you want to reduce kick drum
mic bleed, but your cardioid mic is acting omnidirectional at those lower frequencies.
For this reason Off-Axis Correction has distance controls so you can dial in the desired polar pattern
at the mic’s actual distance. The
ON DIST
control sets the on-axis frequency response to match the
frequency response of the modeled microphone at the selected distance. The
OFF DIST
control sets the
distance at which the Off-Axis Correction Polar Pattern control is most accurate.