11--Transient Response
One of the most important factors in a microphone is it's ability to respond to rapidly changing sound waves. This is known as "transient response".
The acoustic sound wave physically moves the diaphragm. The amount of time it takes for this to happen depends on the weight of the diaphragm material. Of course, the response time is longer for the heavier diaphragm material of the dynamic to react over the lightweight, thinner condenser element.
One of the new and important technologies of the new Heil PR series microphones is a larger diameter of much lighter weight materials. The wizards at Heil discovered that if they fused two different types of metals for their new large diameter diaphragms it would keep the weight down and bring the transient response of their new dynamics close, or equal to, many of the inexpensive condenser microphones. This changes the way many producers and leading sound engineers think about dynamic microphones.
We now can use the new technologies of Heil dynamic microphones for overhead cymbals and other instruments with sharp fast attacks. This new dynamic does not bring the baggage of overly sensitive condensers that pick up sounds and instruments from across the stage. The new Heil dynamics can be much better controlled, with very fast transient responses similar to the condensers. The new Heil PR series finally brings overhead cymbal microphones that hear just crystal clear sounds---never before attainable with old technology dynamic microphones.
Electrical Impedance
Another important characteristic of a microphone is its output impedance. This is a measurement of the ac resistance-to-current flow that would be observed looking back into the microphone. Source impedance determines the size of the load that the microphone can comfortably drive. It is important to recognize that the impedance of a microphone should not be matched to the impedance of the device to which it is connected. Doing so will cause a significant loss in signal level. Ideally, a microphone should be connected to a mixer's input whose input impedance is higher than the output impedance of the microphone.
Microphones are usually divided into two basic classes: low impedance 50-1,000 ohms (also called Low-Z) and high impedance 10,000+ ohms (also called High-Z). Most professional microphones designed for long cable runs are low impedance devices. This means their source impedance is below 600 ohms. Properly connected, they are far less susceptible to extraneous noise pickup in the cable and can be used with long cable runs (over 1,000 feet) with very little loss in sound quality. High impedance mics are limited to about twenty feet before degradation.
High impedance microphones require a buffer amplifier or transformer when using low impedance inputs and/or long mic cables. A microphone's impedance is not necessarily an indicator of quality or performance. it is simply a factor that must be weighed for any given application and the characteristics of the input to which it will be connected.
Wiring: Balanced Or UnBalanced
Microphones can be balanced or unbalanced. An unbalanced connection uses two wires. The center conductor carries the audio signal while the shield carries the ground wire.
A balanced connection uses three wires. Two separate signal wires inside the shield carry the plus and minus signals (opposite polarity). The shield is connected to ground. It encases the signal wires and protects them from outside interference. This makes the system more immune to noise from poor lighting equipment, electric motors, computer hash and RF interference because they hit the shield and are directed to ground.
With an unbalanced configuration one of the signal wires is the shield, the other is the + signal. Any noise picked up on the shield will be fed directly into the amplifier or mixer input. Balanced configurations are the preferred method, especially over long cable runs and noisy environments. The added bonus is that noise induced on the microphone cable will cancel since the two signal lines are out of phase from each other and the shield is not connected to any of the signal input lines. |
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