Too Much Of A Good Thing
As live recording began to take a back seat to multitracking and layering of parts, a room’s acoustical characteristics became less important – in fact, in some cases acoustics began to be viewed as something of a liability.
Studio design began to emphasize acoustically “dead” spaces, and recording techniques began to favor placing mics close to each instrument to capture as much direct sound as possible, with minimal reflections from the room. A chamber or plate reverb was then used to create an artificial “room” ambience. (Why yes, this does sound a bit backward, doesn’t it?)
These days, as digital audio workstation technology has evolved, and signal processing power has become cheap and plentiful, even the most basic, entry-level programs offer a multitude of reverbs and DSP, allowing us to easily plug in several different rooms, halls and chambers on any given track.
The challenge now is no longer which reverb to use, but what combination of reverbs will work together to create a cohesive and natural sound.
Not surprisingly, the availability of technology has made it all too easy to overdo it. Excessive or poorly applied reverb is one of the most common mistakes heard in amateur recordings. An instrument’s direct sound is critical in establishing definition and directionality – add too much reverb and your mix can quickly devolve into a lush soup of mush. Generally speaking, it’s best to approach reverb with a “less is more” philosophy; unless you’re after a cavernous special effect, try and make it almost imperceptible within your mix.
Breaking It Down
At first blush, the many parameters of a reverb unit or plug-in can appear pretty complex. Let’s try and simplify it by breaking it down to its basic physics.
Like throwing a stone into a pool of water, sound emanates from the source in waves. Those waves eventually hit multiple surfaces (walls, ceiling, floor, seating, whatever) and echo back, mixing with the original sound. The way we perceive that sound is dependent on a number of different factors, including how far away those various reflective surfaces are, what they’re made of, where our ears are located in relation to the original and reflected sound waves, and a host of other, more subtle factors like temperature, humidity, altitude and more. In most cases, what we hear is the product of thousands of echoes, reflected many times.
Our brains decode this information in a number of different ways:
—The first echoes that occur when sound waves hit surfaces (early reflections) and the amount of time between the initial sound and those first reflections (pre-delay) work together to tell us how large the space is, and our position within that space.
—The length of time until the echoes die away (decay) also helps determine the size of the space, but the way that decay interacts with the early reflections also makes a difference. For example, a small but reflective room (e.g., a tiled bathroom) can have a decay time similar to a larger hall, but the smaller room’s early reflections will arrive sooner.
—The tonal color of the reflections also plays a critical role. The reverb in that tiled bathroom will be considerably brighter sounding than a larger room with wood or fabric-covered walls. Larger halls will also attenuate different frequency ranges at different rates, and the combination of which frequencies last longer also affects our perception of the space.
—Other factors also affect our perception, including density (how tightly packed the individual reflections are) and diffusion (the rate at which the reflections increase in density following the original sound). A large room with parallel walls will usually have a lower diffusion rate than a similarly sized room with non-parallel or irregularly shaped walls.
As you can imagine, creating a natural sounding ambience is a complex, multi-faceted process that involves programming dozens of interdependent parameters.
Generally speaking, unless you have a degree in advanced acoustics, it’s best to find a reverb program that comes close to what you’re looking for, and keep the tweaking to a minimum.