Mixing : Delays part 1

Time-based effects include all processes where some form of manipulation of time occurs to the signal. This includes things like delays and echos (obvious time manipulation), chorusing and flanging (short delays with modulation), phasing (shifting signals by very small amounts of time), reverbs (essentially numerous delays and echoes), pitch transposers and Harmonizers (slowing or speeding the signal while adding or removing slices to keep it in time with the music), etc. These effects all change the signal’s timing in one way or the other to produce the desired result, thus they are time-based effects.

Delays

After many failed attempts to use outdoor racquetball courts to create delays, engineers realized they could get a delay from a tape player. You could hear a delay by recording a signal on the record head, then listening to the playback head two inches later. The delay time could be set by changing the tape speed. Engineers used this technique for years. There was also a popular unite called the Echoplex, which fed a piece of tape through a maze of tape heads at different distances, each giving different delay times. Not bad, but the problem with tape is that every time you record over it, you get more tape hiss.

Then came analog delays, which would put a signal through a piece of electronics to delay the signal a bit. The more you put the signal through the electronics, the longer the delay. It was a bucket brigade type of system. The only problem was that when you put a signal through a piece of electronics over and over, it also got extremely noisy after awhile.

Then came digital delays, which record the signal digitally onto a chip, then use a clock to tell the unit when to play the sound back. 

Delay times versus distance 

Before we explore different delay settings, it is helpful to understand the relationship between delay time and distance. Sound travels at approximately 1130 feet per second. That's around 740 miles per hour, which is extremely slow compared to the speed of sound in wires - 186,000 miles per second, the speed of light (approximately 670 million miles per hour). Therefore, it is easy to hear a delay between the time a sound occurs and the time it takes for a sound to travel even a few feet to a wall and back. We can also easily hear a delay when we put two microphones at two different distances from one sound. In fact, chasing the distance between two microphones is almost exactly like chasing the delay time on a digital delay.

The following chart illustrates how different distances relate to delay time. Of course, if you are calculating a delay time based on the distance between a sound source and a wall, the distance must be doubled (to and from the wall). 

                                                               Feet     =      Delay(ms)

                                                               1130            1000

                                                               560                500

                                                               280                250

                                                               140                125

                                                               70                 62.5

                                                               35               32.25

                                                               17.5            16.13

                                                               8.75              8.01  

                                                               4.28                   4

                                                               2.14                   2

                                                               1.07                   1

As distances become smaller and smaller, the distance in feet almost equals the milliseconds of delay. This correlation comes into play when using more than one mic on a sound (e.g., piano, guitar amps, acoustic guitars, horns, or background vocals) and is especially helpful when miking drums. For example, the distance you place overhead miss above the drum set will create a corresponding delay time between the overhead miss and the snare mic (or any of the rest of the mics for that matter). It is also important to note the distance between instruments when miking an entire band live (or recording everyone in the same room at once) since miss may be more than 10 feet away from another instrument and still pick it up.

Besides delay time, you must also consider phase cancellation, a problem that happens with extremely short delay times. We'll discuss more about it later.

if you pay attention to the way that something sounds when miked at different distances, you will eventually become aware of what different delay times sound like. Once you become familiar with the way that different delays affect different sounds, you can control their use in a way you deem most appropriate; that is you can do whatever you want.

You need to learn how each delay time feels and what feelings or emotions each delay time evokes. Then, when you hear a song that has a similar feeling or emotion, you will know which delay time might work.

You can read more about the most important things you need to know about mixing, and how to setup the compressors properly depending on the task you want to realize in Dave Gibson's book "The Art of Mixing 2nd Edition" A visual guide to recording engineer and production.