Halls, rooms, and chambers will have a three-dimensional quality due to the three dimensions in which sound can reflect (in those spaces). Plates and springs will exhibit a two-dimensional character as a result of the vibrational mechanics of the physical plate and springs.
Using natural analog reverb
The natural reverb in a bathroom, concert hall, or studio environment can be used to augment your dry tracks. Although doing so is far more laborious than tossing a plug-in on a track, it can give you unique reverb unobtainable with your software or hardware reverbs. The following steps outline the process of using natural reverb in the mixing process.
1. Find a (preferably quiet) room or space that has an interesting reverb.
2. Go to that place with your computer, audio interface, one or two speakers (for mono or stereo playback), one or two microphones (for mono or stereo recording) and stands, and all necessary cabling. (speaker quality will affect the results of course)
3. Connect your speaker(s) to your audio interface, preferably to outputs other than your main mix outputs.
4. Set up the microphone(s) if recording in stereo, preferably using a stereo miking technique that does a good job portraying the stereo field in the room and connect them to your audio interface.
5. Create a new mono or stereo audio track (depending on how many mics you use). Set its input to receive the mic(s). Make sure that the output does not feed your speakers; you do not want the hurting that a feedback loop would put on you!
6. Use an auxiliary (aux) send to route the dry signal to the speaker(s).
7. Adjust your mic preamp levels and listen to the reverb.
8. If desired, move the speakers and/or microphones to capture the room differently (tweak gain as needed).
9. Record the reverb to the new track.
Note: It’s a smart idea to create an aux track to control your reverb, as opposed to placing the reverb directly on your instrument track. Why? If you want to use this reverb on multiple instruments, you can just create a bus on the track and send them to the aux, giving you more control over your mix and saving valuable CPU.
Using artificial digital reverb
An easier and more flexible way to add reverb is to use digital hardware reverbs or reverb plug-ins. There are two primary types of digital reverb—algorithmic and convolution.
Algorithmic Reverb: reverb simulated through mathematical calculations (an algorithm). Algorithmic reverbs may attempt to imitate the sound of real rooms and equipment or create reverbs that don’t exist outside of the digital realm. Examples of algorithmic reverbs include the venerable Lexicon reverbs, TC Electronics, Exponential Audio’s PhoenixVerb, Sonnox Oxford Reverb, and Valhalla DSP’s Valhalla Room, just to name a few of the many.
Convolution Reverb (a.k.a. IR or Sampling Reverb): reverb created through processing an impulse response (IR), which is a recording of a signal that was played in an actual room or sent through a piece of gear. The signal typically either contains all frequencies or is swept across all frequencies, allowing analysis of how the room or gear affects the signal over time. Examples of convolution reverbs include Audio Ease AltiVerb 7 and HOFA IQ-Reverb, though there are many more. When compared to algorithmic reverbs, they are incredibly flexible and deliver more varied reproductions of real rooms and equipment, but require substantially increased CPU resources and involve more latency (they are basically sample players).
iZotope’s Nectar 2 combines algorithmic and convolution reverbs, taking the best of both worlds. As explained in the Nectar 2 help documentation:
“Rather than just use pure convolution, we’ve used a hybrid DSP algorithm which utilizes both convolution and algorithmic methods of generating reverb. Convolution is used to accurately generate the early reflections of the plate while an algorithm has been written to synthetically generate the late tails of the reverb. Using this sort of hybrid DSP provides continuous control of parameters like the damping in real-time, which isn’t possible with pure convolution. Additionally, this hybrid DSP is significantly more CPU efficient than pure convolution.”
The following audio clip toggles between algorithmic and convolution reverbs without dry signal. The first snare hit is through an algorithmic reverb, while the second one is through a convolution reverb. Then the loop toggles bar by bar between the two reverbs (algorithmic/convolution/algorithmic/convolution/algorithmic/convolution). Both reverbs were from the same plug-in manufacturer and were configured to the same settings (where possible).