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Reverberation - the operation, use and history

Reverb processors-the principles of use

The best reverb processor can cost a small fortune. But still, it is worth buying, because without great sounding reverb the music will not sound right. But best sounding reverb is not only depending on the quality of processor. It depends on the quality of... sound engineer.

The importance of ambience in music can not be overestimated. It strictly influences the artistic value of  recording. Each audio connoisseur will be delighted if he will hear the subtleties present in his favorite recording, and when his worth a lot of money listening equipment will reveal them to him, giving the impression of smaller or larger listener's distance from the instrument, or the impression of room, in which the recording was done. It is the precise reason of building the hi-fi systems. Hi Fidelity should be capable to cast such nuances any time.
Why is such a reverberation so important for reception of music? To answer this question we must first realize what is actually a phenomenon of reverb in sound and how the sound reaches out to our ear. The sound of both air jet and human voice or the saxophone is originating from vibrating source. This vibration makes the surrounding air to move, and in the form of acoustic waves reaches our ears.

These vibrations travel in all directions, up and down and 360 degree around the sound source.  The rate of distribution of such waves is very large, it is approximately 300 m\sec, it varies slightly depending on the temperature of air. When the waves reach some surrounding objects such as walls of the room, buildings, trees in the forest, they bounce off. It does not mean they do not finally reach the listener, but because they travel over longer distance then straight waves they come slightly later. The listener's ear, hears both waves running in a straight line from the source as well as those bounced off, having to travel along curved lines. Of course, the waves that are reflected have more distance to go, so they reach the ear slightly later than the waves traveling along straight lines. The human ear can distinguish even very small differences in timing of sound waves and perceives it as the reverb.

Human ear is very sensitive instrument and can also hear that reflected waves have been slightly amended by the material from which they reflected. Hence the color of reverb. Very important here is the type and hardness of the material from which the walls are made of, or other items which could be the cause of sound reflections.
If the room is large, then the waves will travel quite a long way to the walls and then bounce off returning to the listener's ear, so in a large concert hall the reverberation is longer than a typical room. If a room has many bends the wave will often bounce back from them until it looses energy and diminishes. Therefore, in the empty corridors or empty rooms the reverb is very long and therefore special curved objects, for example on the ceiling, are installed to eliminate this reverb. Appropriate and balanced reverb is very beneficial for reception of music, too strong deafening of the room can completely obliterate its reception. Therefore, the recording studios and concert halls and even Hi Fi listening rooms must be properly prepared with regard to the acoustics

From the birth we are surrounded by the sounds. But those sounds are almost never devoid of reverb, as the reverb always occur in a limited space. Even when you are in an open space the different sounds reflected from trees, buildings or land reach our ears, creating the sense of that space. Hence, the sound containing reverb is perceived as natural and listener's brain is able to better locate the position in three-dimensional space.
Therefore the recordings that contain an appropriate amount of the reverb are perceived by our brain as far better than the recordings devoid of reverb. They are perceived as natural, interesting and credible.

In the studio recordings we not always deal with the fully natural reverb. Most often the reverb on studio recordings is of artificial nature. Recording studios use special processors such as reverberation units, chambers and echoes. There are many kinds of such devices, both hardware and software, which came to use recently, but their goal is always the same: to make the recording sounding at it's best and to simulate the natural effect of reverb.

History of reverberation in recording
Originally, the studio recordings were performed through the microphone quite remote from the sound source. This microphone, like the human ear, received the sound waves reflected from the walls of the studio room, and enrolled it into the recording. In the such way the natural reverb of the studio was preserved in the recording. The effect was even more pronounced, when they began to use several microphones, respectively mixed with each other, this way even better results could be achieved. In the fifties the recording studios started to increasingly equip themselves  with special devices for the producing the artificial reverb, which they began to add to the recordings. These were the so-called. reverberation chambers, and spring reverb units. the new approach to the recording was born- to put the microphone close to the source, eliminating the natural reverb from the studio room and then add some artificial reverb in the process of mixing. This gave the technicians and recording engineers greater control over reverberation of their tracks. Each studio had its own technicians and its own solutions to achieve their often unique reverb.

For example, the famous label Tamla Motown studio in Detroit, recording such great soul and funk artists as Stevie Wonder, Aretha Franklin, Jackson Five, The Supremes with Diana Ross, Wilson Pickett and many others have achieved so perfect sound of the the rhythm section - the drums and bass, that the bands used to come there from all over the world just to record their rhythm section using the Tamla Motown studio. When the studio moved  to California in the beginning of the seventies, they cut out the whole room, as the legend says, and took it with them along with the drum set nailed to the floor. 

EMI Studios at Abbey Road in London recording the Beatles or Pink Floyd not only had its own, perfectly worked out sound but also their own reverberation chamber. Abbey Road Studio's reverb chamber was made of a cast iron pipe with the speaker and microphone on both ends. The microphone picked up the sound of this loudspeaker reverbed by the pipe, which was mixed in to the original, direct sound.
At the same time at Abbey Road the very close placement of microphones for recording instruments was introduced, which at the beginning raised great technical objections of studio management, it was feared that the placing such expensive type of microphone as the Neumann U-47 very close to the membrane of a kick drum of the Beatles is not only its desecration, but it can cause damage to the capsule by too much sound pressure levels.
The Beatles were also the only band which was allowed to do that, as mentioned by their sound engineer, Geoff Emerick, and other bands had to record using the traditional method of more distant placement of the microphones.

Close miking gave much more powerful sound to the Beatles' rhythm section, which was even an object of jealousy for the specialists from Tamla Motown, but virtually deprived the recordings of natural reverb of the room. The need for artificial reverberation has become more prominent.
In the earlier days they used two basic tricks to obtain the reverb in the recording session. The first was the use of reel-to-reel tape machine with more playback heads added and the looped tape, which gave the opportunity to obtain both an echo and reverb, depending on the speed of the tape, while the second was to apply tricks of additional, special microphones arranged very far from the instruments and collect an enormous amount of room reverb, which later was mixed back into the close, dry microphones signal,  which gave both very powerful and naturally reverbed sound.


Over time, the first specialized tape reverbs were built, called the echo cameras with many heads offering the possibility of multiple sound and repetition to achieve the effect of reflecting the echoes. Musicians quickly used it as an additional means of expression, and even the whole compositions were sometimes based on the sound of such devices. A good example might be  David Gilmour of Pink Floyd, who used the Binson plate echo effect, or Jimi Hendrix, the greatest electric guitar virtuoso of all times, using very much of artificial reverb and echo in his recordings.

Practical implementation of the reverb in the mix
Generally you can say that the reverb can be used in the mix on the basis of two approaches: either for the purpose of obtaining natural ambience in the mix, simulating a kind of live recordings, or as a special effect, used to obtain special sound textures. Both approaches are widely used and the best way of using reverberation in recording is to take advantage of both of them.


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