Reverb Basics: What You Need to Know

Today we will be talking a little about Reverbs and their parameters. It is very important to understand reverb as it will help you create professionally sounding mix by placing your music in a 3 dimensional field.

Reverb creates a stereo image by placing many mono signals with a 3 dimensional field

Learning to listen to natural reverb will develop your understanding of the parameters you can control

Reverb Parameters

Decay or Reverb Time ( RT60)

RT60 – Is the measurement of time it takes a signal to fall -60dB. At -60dB is when reverb will no longer be heard.

Benefit the short the RT60 times the closer the reverb will sound the room. In busy or crowed arrangements setting a short RT60 time of

Diffusion

Represents the density of echoes

Each Manufacturer does diffusion a little differently so you will have to play with the give reverb to get a better feel for what diffusion will do.

Generally speaking

• Low diffusion = Thinner
• High diffusion = Thicker

The more diffusion the quicker the reverb will drop below RT60. The less diffusion the longer it will take to drop below RT60 and not be heard any more and the more reflective the reverb generally will be.. This can be affected by location in a given room and size.

Pre Delay

Represents the amount of time it takes before the reverb is reproduced, usually referenced to milliseconds..

Shorter pre delays the quicker the reverb will reproduce for example in a “live room: you will hear more reflections and a quicker pre delay. In a “dead room” you will not hear as much reverb which will create a longer pre delay

Low Pass Filter

Determines the highest frequency that is reproduced by the reverb

High Pass Filter

Determines the lowest frequency that is reproduced by the reverb

Depth

A parameter that adjusts the simulated position of the listener in a space

“Visualize” the “placement” of the listener, you must imagine yourself observing the performance to properly place a voice. For example imagine you are in the 1st row of a concert vs if you were in the 20th row.”

What to look for and think about?

What kinds of surfaces are in the room?

Think about what it sounds like in a bathroom verses your living room when you clap your hands. Better yet go clap in your bathroom and listen.

In the bathroom you generally have tiles which will reflect causing more natural reverb almost like a mini echo chamber.

The room is smaller so it will reflect faster as well. Maybe this is why people say they sing better in the showers?

Let’s translate what you hear into parameter talk

The pre delay would be shorter as the reverb would reflect quicker thus hearing the reverb faster.

There is less diffusion as you have reflective surfaces all around.

The RT60 time takes longer for the reverb to drop below -60dB as there are many reflections going on and not a lot of diffusion.

The low and high pass filters will not be used much at all unless your bathroom has a particularly high or low end sound. That or if there was a lot of low or high end

Now let’s think about your living room and how that sounds

In your living room there is less reflective surfaces and generally more space than the bathroom.

Most living rooms have furniture of some sort a TV and other items.

All of these items will help defuse the natural reverb in the room along with drywall for walls instead of tiles there will be less reflection of sound going on.

Reverb Parameter talk in your living room

The pre delay would be longer as the reverb would reflect slower thus hearing the reverb faster.

There would be more diffusion as you have less reflective surfaces all around and more items to diffuse the sound in the room.

The RT60 time would be shorter for the reverb to drop below -60dB as there are more items to defuse the sound.

The low and high pass filters will not be used much at all unless your bathroom has a particularly high or low end sound. That or if there was a lot of low or high end.

Start listening to different rooms and envision what they sound like and how you would adjust parameters on a reverb plugin to recreate that sound.

Once you got the basic parameters down it is time to talk about types of reverb.

Reverb Types

Acoustic (live) echo chambers

A reverb type originally created by sending sound into an enclosure, with transducers placed inside to pick up the acoustic effect. It is characterized by having a less colored “ tail” decay. Microphones are placed in the room so that they received minimum direct reflections.

A great example of this is at Blackbird Studios in Studio A and D they have two echo chambers. In Studio A the ceiling expands and contracts to adjust the sound of the chamber. These are still used today and sound amazing, however the cost to build one is very high.

Spring reverbs

A reverb type created by sending signals down a coil, typically found in a guitar amplifiers

Plate reverbs

A reverb type that was originally created by fixing transducers on a metal plate, characterized by dense early reflections that end quickly.

These are very popular on vocals and sometimes on snares. I personally use a digital plate reverb in almost every mix I do.

Foil Reverb

A reverb type that was originally created by fixing transducers on a foil membrane, characterized by dense early reflections with a bright longer decay.

Foil Reverbs used principles found in plate reverbs and ribbon microphones. The signal is introduced into a thin piece of gold foil which acts similarly to the plate

Digital Reverbs

Mathematical algorithms that approximate the boundaries and acoustic characteristics of a space. With a digital reverb, you are building a room – walls, ceiling, floor angles, building materials.Then you position the sound source and the listener in that room.

In todays digital audio workstation these are some of the most popular reverbs in the digital age of audio it is what I use on all of my mixes currently but I am still experimenting. They are generally less expensive and if used with a plug in you can have as many instances as needed.

If I could I would use an echo chamber however I simply do not have the money or space for something like this. However our next reverb type could simulate an echo chamber at the fraction of the cost.

Convolution Reverbs

A sample reverb where an acoustic space’s profile mapped by doing the following

Sampling full-bandwidth noise projected into an acoustic space profiling the noise before and after the projection.

Then removing the “ dry” profile from the sampled waveform ( called IR, or Impulse response) resulting in a very accurate simulation of any room’s acoustics.

I am currently experimenting with this type of reverb it does sound very nice as it is very accurate to what is being simulated.

Hopefully this gives you a good foundation to understand the basics of reverbs, and to get you thinking about what a given room will sound like.