BREAKING DOWN THE BASICS OF MICROPHONE SPECS TO HELP YOU BUY SMARTER
Reading through microphone specifications can be overwhelming and confusing even for the experts. This is a quick guide to help you sift through the specs and figure out what model is best for your purposes.
Keep in mind, a microphone’s specifications are only that – detailed numerical information. Beyond the numbers, certain models will deliver different sonic experiences that may resonate more with each individual user and performer. You want to find a microphone that not only captures the sound accurately, but also inspires a performer to go further and discover more nuances to their delivery.
THE DECIBEL SCALE
The decibel (dB) scale is the starting point for discussing microphone specs. The dB scale serves as the best guide for how the human ear perceives sound pressure changes. It calculates a given pressure in proportion to a reference pressure. For example, 0 dB does not mean zero sound. It simply represents the inability of the human ear to detect sound and pressure changes at that range.
The frequency response curve grades the microphone’s ability to accurately transform acoustic energy into electrical signals without adding or losing tone or coloration. Do not confuse frequency response with frequency range (which is often called bandwidth). Manufacturers of professional equipment will always provide more than one frequency response curve, as it is essential to see how the microphone will respond to sound coming from different directions and in different acoustic sound fields.
This specification measures a microphone’s ability to respond to sound coming directly at it, on-axis, towards its diaphragm (0°). It is important to understand that on-axis response may be measured from different distances, which may impact the response because of the proximity effect. Each model should state at which distance the directional microphone has been measured.
DIFFUSE FIELD RESPONSE
How does the microphone respond in a highly reverberant sound field where the acoustic sound is not coming from a specific direction but from all directions? Imagine sound ricocheting off walls and floors and other surfaces contrasting with a direct sound. Consider omnidirectional microphones with their ability to register the full frequency range at lower frequencies. The diffuse field response will demonstrate a microphone’s ability to capture across frequencies within a reverberant environment.
This measurement is a corollary to On-Axis Response. It measures the microphone’s response to sound coming at it from different angles. Off-axis coloration can greatly impact your recording, so, if you need a good directional microphone, you’ll want to consider how well the model eliminates sound coming from other angles.
It is important to have smooth and symmetrical gradients of sound levels across frequencies and different angles. A polar diagram uses a reference point to determine the amount of coloration and strength of signal. Extreme peaks and valleys are unwanted and the response curves should not cross each other.
From the polar plot, you can also see how omnidirectional microphones usually become more directional at higher frequencies (the bigger the microphone, the more directionality at high frequencies).
EQUIVALENT NOISE LEVELS
Every microphone brings its own “self-noise.” This is called the equivalent noise level – the sound pressure level that represents the same voltage the microphone model actually generates by itself. Ideally, you are looking for the lowest noise level to limit unwanted sound – especially when working at low levels of incoming sound. The self-noise also dictates the lower limitation in the microphone’s dynamic range.
The sensitivity of a microphone is the electrical response at its output to a given standard acoustic input. This is expressed as the ratio of the input pressure to the electrical output (voltage or digital word). The standard reference input signal for microphone sensitivity measurements is a 1 kHz sine wave at 94 dB sound pressure level (SPL), or 1 pascal (Pa, a measurement of pressure). A microphone with a higher sensitivity value has a higher level output for a fixed acoustic input than a microphone with a lower sensitivity value. Microphone sensitivity in decibels (dB) is typically a negative number; therefore a higher sensitivity is a smaller absolute value.
It is important to note the units presented with the sensitivity specifications of the microphone. It is incorrect to directly compare the sensitivity of two microphones if the sensitivity is not specified for the same unit. For analog microphones, the sensitivity is typically specified in units of dBV, that is decibels with reference to 1.0 V rms. For digital microphones, the sensitivity is typically specified in dB FS, that is decibels with reference to full-scale digital output (0 dB FS). For digital microphones, a full-scale signal is defined as the highest signal level that can be output from the microphone.
SPL HANDLING CAPABILITY
SPL refers to the Sound Pressure Level that a microphone can handle. It is important to know the SPL at which a certain Total Harmonic Distortion (THD) occurs. You want to have a good sense of the limit before the point at which audible distortion can be detected.
FIND THE MODEL YOU NEED WITHIN YOUR PRICE RANGE
It’s not enough to like your mic. We want you to love it. We want you to find a model that you swear by. That you rave about to every performer and producer you know. To help you find your ideal model, shop from a wide assortment of top brands for every budget at https://www.fullcompass.com/category/live-sound/microphones/. Or contact one of the Full Compass Sales pros at 800-356-5844 for experienced answers and expert advice.