Choosing Vocal Microphones - Understanding Technical Specifications

!±8± Choosing Vocal Microphones - Understanding Technical Specifications

This article provides an overview on five important measures that are typically listed in microphone specification sheets: frequency response, sensitivity, impedance, self noise level, and signal to noise ratio. Understanding these specs can help when trying to decide on the best microphone to purchase for a specific application.

Frequency Response

Frequency response measures how a microphone reacts to different sound frequencies. An ideal "flat" response (equal sensitivity) microphone would respond equally to all frequencies within the audible spectrum. This results in a more accurate reproduction of sound and produces the purest audio. The truth is that even microphones which are advertised as having a "flat response" can deviate somewhat at certain frequencies. Typically spec sheets will list frequency response as a range like "20Hz to 20kHz", meaning that the microphone can reproduce sounds that fall within that range. What this does not explain is how accurately the various individual frequencies will be reproduced. Some microphones are purposely designed to respond differently to certain frequencies. For example, instrument microphones for bass drums are generally engineered to be more responsive to lower frequencies while vocal microphones would be more responsive to the frequency of a human voice.

As a general rule of thumb, condenser microphones have flatter frequency responses than dynamic. This means that a condenser would tend to be the better choice if accuracy of audio reproduction is the main goal.

Sensitivity

Microphone sensitivity measures how much electrical output (measured in "millivolts" mV) is generated for a given sound pressure input. Typically when measuring microphone sensitivity the mic is placed in a reference sound field where a sound pressure level (SPL) of 94 dB (1 Pascal) at 1000 Hz is maintained at the microphone. (Some vendors like Shure use 74 dB 0.1 Pascal). The distinction is that 94 dB SPL is the typical sound intensity of someone speaking twelve inches away while 74dB SPL would be the same speaker one inch away. A typical condenser microphone might have a value listed either like "7mV/Pa" or -43dBV in the technical specification. These two values mean the same thing - they're just expressed differently.

If two microphones are subject to the same SPL and one generates a higher output voltage, that microphone is said to have a higher sensitivity rating. Although knowing how to read/compare microphone sensitivity (output) is important, the actual sensitivity rating usually is not a major consideration in mic selection. Typically the design of a microphone for a particular application plays a role when manufacturers determine the appropriate output level. For example, dynamic microphones are typically less sensitive than condenser mics as they're generally used fairly close to the sound source. Listed below are the typical specifications for three different microphone transducer types:

Condenser: 5.6mV/Pa (high sensitivity)

Dynamic: 1.8mV/Pa (medium sensitivity)

Ribbon: 1.1mV/Pa (low sensitivity)

Impedance

Impedance is how much a device resists the flow of an AC current (such as audio signal) and is measured in ohms. Typically when referring to microphones, "low impedance" is considered anything under 600 ohms. "Medium impedance" would be 600 ohms to 10,000 ohms and "high impedance" would be greater than 10,000 ohms. All microphones have a specification regarding their impedance - sometimes the value is written on the mic somewhere, other times you might need to consult the technical manual or manufacturers' website to determine the number. Generally speaking, low impedance microphones are better than high impedance, and quite often you can use impedance as a rough gauge when determining overall quality. The advantage of low impedance microphones is that they can be used with very long cable runs and negligible signal loss. Mics with hardwired cables and a 1/4" jacks are high impedance, while mics that require a balanced audio cable and xlr connector are low impedance.

When connecting your microphone it's important to know the corresponding ohm level of the sound mixer or amplifier. A low impedance microphone should always be connected to an input with a higher impedance value, otherwise signal loss will result. Typically "low impedance" audio mixers have inputs with impedance levels between 1000 and 2000 ohms, and are designed to work with the lower level microphone impedance levels.

Self Noise Level

Self noise is the electrical hiss that a microphone produces. Typically the self noise spec is "A weighted", meaning that the lowest and highest frequencies are flattened in the response curve, to better simulate the signal response of the human ear. (We tend to perceive mid range sound frequencies as louder.) As a general guideline, an A Weighted self noise spec of 18dB SPL or less is excellent (very quiet), 28dB SPL is good, while anything over 35db SPL is not well suited for quality audio recordings.

Because dynamic microphones do not have active electronics (no phantom power requirements) they have very low self noise when compared to condenser microphones. Most spec sheets for dynamic microphones do not include self noise measurements.

Signal to Noise Ratio

The signal to noise ratio (S/N) is the difference in dB between a microphone's sensitivity and self noise. A higher S/N means that the signal is cleaner (less noise) and that the microphone has more "reach". Reach can be defined as the accurate pickup of quiet/distant sounds due to high S/N. Typically reach is not listed as a metric on a tech sheet as any microphone can pick up a distant sound if the source is loud enough. For example, even a very inexpensive mic can pick up a thunderclap from far away.

As a general rule when evaluating S/N ratios, given 94dB SPL, anything over 74dB is excellent, a S/N spec of 64dB is considered good.

Summary

Hopefully these definitions have helped to provide some understanding about typical microphone specifications. The truth is that there is no "ideal" microphone that is perfect for every situation. Manufacturers design their microphones with specific audio applications in mind - such as live performances or studio reproduction, and as a result have tailored the specifications so that the mic sounds the best that it can with a given hardware configuration. Generally speaking, more expensive microphones are engineered with better hardware, which results in better specifications and performance.

Choosing Vocal Microphones - Understanding Technical Specifications

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Korg Kaossilator Dynamic Phrase Synthesizer

!±8± Korg Kaossilator Dynamic Phrase Synthesizer

Rate : | Price : $108.99 | Post Date : Oct 08, 2011 05:15:08
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Meet your new musical addiction: the KAOSSILATOR from Korg. Play it alone or add it to your rig for over-the-top, music-making mayhem. The KAOSSILATOR's user-friendly touch-pad lets you create musical and rhythmic phrases using any of its 100 synth programs, such as leads, basses, realistic instrument sounds, playable drums and drum patterns. Each time you add a phrase, KAOSSILATOR stacks it on top of the previous phrases you created. The results are as simple--or complex--as you desire. Choose from the 31 available scales, and play in any key. Lay down your groove with any 50 gate-arpeggiator patterns for even more KAOSS! The portable, travel-friendly KAOSSILATOR runs on batteries or a 4.5v adapter. Use the it as a multi-instrumental musical instrument, sample source, live rig addition, or just a fun way to get your groove on!

Meet your new musical addiction. Click to enlarge.

Innovative touch-pad control controls separate parameters along X and Y axes.

Features stereo RCA output and headphone jack.

100 Playable Synth Programs
The KAOSSILATOR offers 100 unique patches for you to play, from nautral instruments to synth basses and leads, including ten drum patterns and 31 musical patterns. Sounds include:

• Preset drum/bass grooves with flexible effects
• Fat synth lead sounds
• Acoustic instruments like trumpet, digeridoo, sitar, and more
• Tap-able drum voices
• Extra thick and juicy basses
• Complete chords with filters and other effects
• Space-age sound effects to send your loop beyond the cosmos

Innovative Touch-Pad Control
This is what defines Korg's entire KAOSS PAD/KAOSSILATOR series, and what made 'em such a hit. You play the KAOSSILATOR by moving your finger around on (or tapping on) the touchpad, thereby controlling the sound. The parameters controlled by the X axis and Y axis depend on the preset (for example, a bass synth might feature pitch along the X axis and filter resonance along the Y axis).

Scale/Key Controls
It may not have keys, but the Kaossilator can still play a hook. It lets you control a full two octaves of notes just by touching the pad. To make sure you're playing in the same mode as everyone else, you can choose what kind of scale to use, from 31 different options. You can also set the root note, including flats and sharps, so you're always in tune no matter how wacked out you get on the effects.

Adjustable BPM and Gated Arpeggiator
To get the beat to your desired BPM, you can select a normal MIDI tempo or enter a tap tempo with your finger. The built-in Gate Arpeggiator repeatedly triggers sounds in sync with the tempo. The slider controls either the gate time or gate speed. 50 different gated arpeggiator types are included.

Loop (Phrase) Recording
The KAOSSILATOR can record and playback phrases and patterns that you play on the touch pad--loop style. During playback, you can play along. You can even add another layer to the loop recording. This process can be repeated, adding several new layers. Recorded phrases can be up to 8 beats (2 bars of 4/4) in length.

Portable KAOSS
Create some chaos anywhere you go. The KAOSSILATOR is eminently portable, weighing in at 5.43 oz without batteries, and with dimensions of 4.17 x 5.08 x 1.14 inches. It's powered with four AA batteries, for up to about five hours of operation. You can also snag an optional AC adapter for plugging it in.

RCA/Headphone Outputs
The KAOSSILATOR features a dual RCA stereo line out, for quick connection to mixers or interfaces, and a mini headphone out, for using on the go.

What's in the Box
Owner's Manual, parameter sheet, four AA "test" batteries

• Korg PXPS Power Supply for PX4 Pandora Models
• Korg mini-KP Kaoss Pad Dynamic Effect Processor
• Korg MONOTRON 16-Key Synthesizer
• Korg KP3 Kaoss Pad Dynamic Effects Sampler
• Hosa CPR201 Dual 1/4 To Dual RCA Cable 3.25 Ft

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