Introduction To Effect Part 3, Reverberation and reverbs
Introduction To Effect Part 3, Reverberation and reverbs
Sep 28 2007, 10:23 PM
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Effects part 3 – reverberation
Most guitar players have used a reverb(eration), usually the one fitted to a guitar amp whether it’s a spring reverb or a digital one. It’s a nice effect as it adds the impression of space and depth – or distance - to a sound. With well chosen reverb a guitar or a mix can come to sound just that little bit ‘larger then life’. It works on the basic principle of adding time delay to a repeated signal. (Rather like the sense of space you get in big cathedrals where your voice echoes) Reverbs generally offer a time delay of over 1 second – here they differ from a delay unit which usually operate in the 0-2 second range.
Types of reverb
There are a number of types of studio quality reverb units available. Ones that you may come across include hardware units and software ones. Hardware reverb units are either analogue or digital. Analogue reverbs may be spring, plate or some form of delay. An example of a spring reverb is the Accutronics unit found on many guitar amps. It works by sending the guitar signal down a spring that’s fitted with two transducers, one at each end of the spring. The vibration of the spring causes the reverb effect and the quality of the sound is often improved by adding springs to the unit. A plate reverb is literally a large metal plate fitted with transducer and several pickups dotted about it. A signal from a mixing desk’s auxillary send makes the plate vibrate and the vibrations are picked up by the pickups and sent to a preamp and then on to the mixer’s aux return. Two pickups used at the same time give the impression of stereo Interestingly plate reverbs have a fixed delay time and don’t have a spatial character. Instead they have a tonal characteristic: they sound metallic rather than say sounding like a cathedral. This metallic characteristic often requires eq. The first studio quality reverb I ever used was an old Wem Copycat tape echo. This worked because it was effectively a multiple headed tape machine. By changing the distance between the record head and the playback ones you could emulate reverb.
Digital units may either be hardware or software. Lexicon is one of the best known hardware digital reverb brands. Many digital reverbs have presets that emulate plate, spring and tape reverbs along with different room types. Some software reverb plugs focus on modeling a specific hardware reverb however – Universal Audio for instance have a plug in emulation of the old Roland Space Echo.
Digital reverbs and delays often sound quite bright and individually may need some eq’ing but often this ‘brightness’ disappears in a complex mix. Most digital reverbs offer a multi-tap feature that give a reverb the impression that the sound is reflected off different points in a space, thus adding to a sense of depth. The more taps, the more points, the more sense of depth. Note though that really complicated reverb – one with lots and lots of taps – can start to sound unfocused and indistinct.
The Lexicon PCM81
The SIR1 Convolution Reverb Plug-in.
Convolution (modeling/emulation) reverb is a relatively new system that makes use of the processing power of modern computers. In essence any space has a reverb characteristic that can be recorded, mathematically modeled and then reproduced. The better the modeling the better the quality of the reverb but – and this is the sting in the tail, high quality convolutions are cpu intensive and so tend to need a reasonably powerful pc to work.
Many convolution reverbs are software plug-ins and, as a bonus it is relatively easy to get additional room samples (or Impulse Resonance recordings – IRs- for them).
Typical controls for a reverb are:
This sets the amount of time that elapses between the initial sound and the start of the reverb. Typical range is between 0-100ms.
Room size and/or type
The size of a room may often be varied between 20-100%. The room type may range from a large cathedral through to a small room or intimate jazz club. Convolution IRs very often will give specific details of exactly what space they model and how they were produced.
This allows you to filter out high frequencies from the reverb signal and allow you to produce a more natural, less bright reverb. The range is often –15 to 0 dB.
Filters out unwanted low frequencies and can help reduce boominess in larger room sizes and longer reverb times. Range is often –15 to 0 dB.
Reverb or decay time
Sets the duration of the reverb from 0.2 – infinity.
Determines how much of the wet (with reverb) signal is mixed with the dry (original no effect added) signal. 0% is fully dry and 100% fully wet.
Reverb is, in my opinion, a great effect if used sparingly. Too much can make a mix sound muddy and indistinct. Furthermore once applied it is difficult to remove so with this in mind it is often better to record guitars, vocals and so on dry with no reverb and then add reverb at the mixing stage.
It’s also worth noting that any space has a reverb characteristic unless it is fully acoustically dead. Try to be aware of the inherent natural reverb that probably already exists in your recording space. You might aready have good natural reverb suitable for recording the type of music that you like.
With software I would add an additional caveat – software reverbs, particularly convolution, are cpu hungry. The more individual reverb simulations you use in a mix the harder your pc has to work. So I would advise you to really think about applying reverb globally to a mix or to groups of instruments via a buss send, rather then individually to single instruments in a mix (see elsewhere for a tutorial on how to set up a buss). In a software sequencer like Reaper you can also opt to ‘freeze’ tracks that you have recorded for a mix but are not currently working on. This neat feature can help reduce cpu load – particularly if it had a complicated convolution IR.
To be honest if your pc struggles to find processing power when you record then you may well be better of considering upgrading your pc and/or getting a hardware reverb unit rather then use software reverb.
Apart from creating a sense of space (for instance a cathedral IR modeled on a convolution or digital reverb gives a different sense of space to a small room IR) reverb also add a sense of distance. The shorter a reverb time is, the shorter the delay before you hear the repeated signal. This will make the signal appear nearer and more distinct to you then one recorded with a long reverb time. You can make a reverb sound bigger by adding some pre-delay ( the gap between the dry signal, without reverb, and wet signal, with reverb). The early reflections of a signal are less complicated then the more densely packed ‘tail’ of a reverb. So if you want a sense of space but without too much detail then you should focus on the early reflections and use less of the tail.
How you set a reverb (or reverbs) and the type you choose really depends on the mix you are producing. It’s really a case of trying out different settings to see which works for your particular mix but without overdoing so that you end up with an indistinct, muddy mix. If you set the reverb time to the tempo of a song you can add a sense of depth without the reverb being too noticeable. Personally I would err on the side of caution – too little reverb, to me, is better then too much.
Some possible settings to start from are:
Rhythm guitar – pre delay of 10=50 ms. 1.2 sec delay time. Little high band filtering. Bright digital reverbs sound good to me here.
Guitar solos – 100-150ms of pre-delay. 2-5 sec delay time. Some high band filtering 5-10 dB.
Editorial note: published 8 October 2007
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