For those new to mixing audio, I decided to address some basics on using and understanding the need for ambient effects. Though this is very basic for some, I think it is still a topic that needs a little explanation for the novice or new-comer to live mixing. This topic is one that is probably a bit harder to deal with in written form, as it is best understood and demonstrated when situated in front of a mixing desk. “Ambient effects” refers to the use of what are commonly called “reverb” and “delay.”
The primary reason for the use of ambient effects in mixing audio is to introduce a sense of depth and space into the dry, flat, and sterile set of musical elements that are usually either close-mic’d or directly input to the audio console. Some forms of music naturally require very little in the way of ambient effects, while other forms of music require a more generous dose of these effects to best present the sound and style of the particular music being mixed. So, first off, be familiar with the how the musical style you are mixing is typically treated.
Another critical deciding factor is the acoustical characteristics of the hall or room where the sound is being reinforced. Smaller, dryer acoustic environments usually require a more liberal use of ambient effects (commonly referred to as “grease” in pro-audio circles) to breathe life into a mix, while larger, more ambient spaces may require the addition of very little (or none) because the room acoustics are already adding room reverb, slap-back, or flutter echoes to the dry sounds coming from the PA. This is something that you must determine as you listen to how the room acoustics are interacting with the sound being reinforced by the PA. Yet another one of the many critical judgment calls that a sound engineer has to make in the course of his/her work.
The key to effectively using most ambient effects is knowing how to hide the fact that you are using them at all. In most cases, the addition of reverb and delay to a mix is to be done as discreetly as possible. The idea is to subtly extend and fill in the gaps between the “dry” sounds with artificial space. By adding just the right amount of reverb to the dry sounds, the illusion of depth and width dramatically enhances the overall sound.
The use of delays is another great way to add depth and interest to a mix. A single 1/6th note, 1/8th note, or 1/4 note delay can be subtly added to an instrument or voice, or in some cases, using the regeneration control to allow several cascading delays to follow the dry sound is just the ticket. Sometimes, the idea is to allow the delay(s) to be a very obvious effect that jumps out to make a statement but in most cases the delay should be carefully hidden just underneath the dry sound. Sometimes the effect is tucked underneath until a strategic moment in the song, where it becomes apparent for a short period of time (a common but effective use of delays).
Another trick often employed is the use of EQ to reduce the brightness of the delayed sound, which also helps to further hide or disguise the effect, as well as de-emphasizing noises that might be exaggerated when reinforced with delay (useful on reverb, too). Of course, if you want extra punch, impact, or sizzle, a bright reverb is a good idea; or the EQ can be set to emphasize just the midrange portion of the delayed sound, giving the delay a vintage or phone-like sound (a fun sounding effect ). It’s also a good idea to roll-off the low-end EQ to keep the delay free of excess build-up in the lower frequency range (important for reverb as well – keeps the mix cleaner).
In the case of reverb, it’s important to remember that the length of the reverb decay time is yet another key factor to explore. Some mix elements will benefit from a short or medium decay time (.5 to 1.5 seconds), while other elements sound better with a longer decay (2 to 4 seconds usually). So, it’s beneficial to have more than one reverb at your disposal, if possible. This way, you can have one set to a shorter decay, and another one set for a longer decay time. Also, reverb units (and plug-ins in the digital mixers) are not all the same in terms of the quality of the sounds they produce. Some are very grainy sounding (particularly the cheap ones), and some are more lush sounding (shop carefully).
There is no magic prescribed formula for the use of these effects; it is largely a matter of experience, experimentation, and knowing what the song or musical style calls for, as well as understanding what the room acoustics will contribute to the overall sound. Just use discretion…and have fun!
Happy Mixing!
-Michael Grosso, Technical Director/Audio Engineer-Calvary Chapel Fort Lauderdale
Tags: audio, condenser, dynamic, engineer, Microphone, mix, monitor, sound
Thanks so much for this excellent article – I use a Yamaha MC7L and I have needed guidance on using delays – this was perfect!!