Mono Recording

History

Audio recording gradually emerged after Thomas Edison's invention of the phonograph in 1877. Edison's orginal invention recorded on tinfoil, had poor sound quality, and recordings could not be mass produced. So, it wasn't until Emil Berliner invented his "gramophone", a flat disk that turned as the needle followed a groove, that recordings could be reproduced in large numbers.

Then, around 1901, the technique of metal plating wax masters allowed mass production of reasonable quality records. Before too long, phonographs appeared in the homes of many people, mostly the rich at first. But, soon, the new technology was available to more and, more people. It is at this point that people realised that recording could be a viable business.

As the use of phonographs spread, there was an ever increasing demand for recordings. The techniques to capture these recordings evolved alongside the technology.

Initially, phonograph records were recorded direct-to-disc, with a horn and diaphragm connected directly to the needle that cut the groove in the vinyl. The musicians all huddled around the horn, arranged in such a way as to have all the instruments picked up evenly (see photo). With the single horn and diaphragm as the pickup device, these recordings were inherently mono.

Mono recording can be accomplished with as little as one microphone. The mic, or mics, pick up the sound and it is applied to a single channel, or equally to both channels of a two channel setup, which is then heard equally from both left and right speakers or headphones. So, whether one speaker or two, mono recording is quite common. Even for stereo recordings, lead vocals are almost always recorded in mono, for example.

For recording mono. any type of mic can be used, depending on the need. For vocals, the choice is often cardioid because we want to capture the vocal and reject other sounds. But if the vocalist is isolated, then other mic types are an option.

The General Rule:

If you are needing to isolate the sound source, you use a cardioid mic. If you are trying to record equally from all sources, you choose an omni mic. This applies to instruments, voices, and percussion.

Examples:

Omnidirectional mics pick up sound from all directions. You need to place the mic carefully to avoid leakage from other instuments or voices. However, you can place an omni mic very close because it does not have proximity effect.

Examples are the Shure VP64A, and the excellent Earthworks QTC40.

Cardioid mics, arguably the most common type, are represented by the Shure SM57, SM58, SM7b, and ElectroVoice RE20. These mics capture sound from one direction, the direction the mic is pointed. The opposite direction, the "null", will be less sensitive. We take advantage of this to allow rejection of sounds we do not want to record. The downside, however, is "proximity effect". Proximity effect is the behavior of cardioid mics to exaggerate the low frequencies as the mic is moved closer to the source. Sometimes proximity effect is desireable, such as voice-overs. But it can also make an accoustic guitar sound boomy, if placed too close.

SuperCardioid Mics tend to be used in more specialized situations, such as movie sets and live sound, because of their enhanced rejection of unwanted sound outside fo the pickup pattern. An example is the Rode NTG4 Shotgun mic which is used extensively in video recording.

Multi-Pattern: And we must mention the many mics that have multiple polar patterns selectable by a switch on the mic body. Examples include AKG C414 and Neumann U87. These mics have multi-head capsules and additional circuitry to allow selection of different polar patterns.