Knowing how to use reverb effectively is one of those things that really comes with practice, but we want to help you a get ahead, as poorly balanced reverb is one of the most obvious signs of an inexperienced engineer. So, here’s our guide to how reverb works and how to use it effectively. In this article we will use natural reverb on solo piano, and plate reverb on vocals as two examples.
Put simply, reverb plugins simulate acoustic spaces like cathedrals or concert halls, and reverb equipment like spring or plate reverb units. There are no hard and fast rules as to what type of reverb sounds best on which instrument, so experiment will all the different presets you can find, as they are all distinctive and useful in different ways.
How They Work
Some reverb plugins create a large number of delayed versions of the audio input, which all add together to create a smooth reverb tail which gently dies away to nothing. These delays simulate the individual reflections of sound off all the hard surfaces of a real acoustic space.
Alternatively, rather than using lots of delay lines to imitate reflections in a room, convolution based reverb plugins like Altiverb multiply the incoming audio with the response of a room or piece of equipment. This gives a more realistic sounding reverb, which is perfect for our solo piano example. Almost anything will sound good with convolution reverb, but it does require you to have the response of the right room or piece of equipment first, you can’t just make one up by changing the settings.
Just about every reverb plugin will allow you to choose from several different types of reverb. The acoustic spaces like halls, churches and small or mid-sized rooms are useful for piano or strings to give the feel of genuine space. Plate and spring reverbs are not particularly natural sounding, but they have a unique metallic tone which is useful for guitars and snare drums that need some character. Vocals sound particularly nice with plate reverb, as the distinctive sound is easy to pick out in a mix.
Early Reflections / Size
The first few reflections of reverb are usually quite distinct and clear, and your ears use these to work out how big a physical room is. Most plugins will give you some control over these early reflections in the reverb, even if it’s just labelled as ‘size’. Larger rooms have more pronounced early reflections, so when you select a larger size the plugin will usually make its simulated early reflections louder.
For a solo grand piano with a natural sounding reverb, we want a large sounding space with plenty of acoustic information for the listener to pick up. Early reflections help bring clarity to plate reverb, so a medium to large size would fit vocals quite well.
Also known as ‘pre-delay’, this is the time before the first early reflection arrives, which has a big impact on how big a space sounds; as you increase the pre-delay the room gets bigger. For a concert hall, somewhere around 15ms should be about right to match a real space. For a plate reverb on vocals this can be much shorter or even zero, as we are not trying to create the illusion of space, and just using the reverb tail as an effect.
This determines how dense the reverb tail is, literally how many reflections there are per millisecond. A very diffuse reverb has a lot of reflections which blur into a big, thick and dense sound. Be careful with the diffusion in big mixes as the reverb tail can make the mix sound very muddy if it is too dense. Broadly speaking, about 60-70% is good starting place, listen and then dial it back if it’s too much. For solo piano, we want to keep some character in the reverb tail so about 40-50% diffusion is plenty. The vocal plate reverb should be very diffuse to get a soft and smooth decay, so 100% diffusion is ideal.
This determines how long the reverb tail takes to die away, and is what a lot of people focus on exclusively. For our vocal plate reverb, a decay of just over two seconds is enough to make the reverb heard without being so long that it clogs up the mix. For solo piano, we have the luxury of making the reverb more of a feature, so about four and a half to five seconds should be about right.
Equalisation is a step that is often overlooked when setting reverb. Most plugins will give you control of a high frequency cut or eq, which simulates the hf loss that you would get in a real acoustic space. This is perfect for the solo piano, just dial in a little hf cut so the reverb sounds softer and less brittle. Vocals will usually benefit from some hf reduction on the reverb, particularly on plate and spring reverbs which can be very bright, to the point of sounding harsh. We can’t give you specific frequencies or how much to reduce them because it really depends on the instrument you are using, and the specific type of reverb you choose, so get experimenting.
Cutting the reverb’s low end with eq is a very useful way of thinning it out so that it doesn’t take up too much space in the mix. This isn’t so helpful on vocals as they don’t contain much low end anyway, and the solo piano really needs the low end to sound natural. However on instruments like piano or guitar in a full mix, taking out anything below about 100 Hz in the reverb will stop it sounding muddy and overwhelming.