Audio people often revere equipment and sounds which are old. The best reverb I’ve ever heard is also the oldest. On a trip to the south of France I visited the Abbaye du Thoronet. A 12th century monastery with a chapel famous for its acoustics. Hearing the guide sing in that space reminded me that we take good reverb for granted these days but really exceptional reverb is rare and amazing thing.
I used to be a college lecturer and when talking to students about reverb I used to hear some say “I don’t like reverb” but when working in nearly anechoic practice booths they always left the door open - why was that? It’s because while they might not have liked the kind of reverb they were noticing on records (the fact they were noticing it suggests there was too much…) they liked no reverb at all even less.
Reverb, the sound reflected back to us by our environment, is so important to our perception and understanding of our environment. It is there all the time and we are so finely tuned to interpreting these tiny timing differences between the reflections which get bounced back at us that artificial reverberation will always face a unique challenge because it is trying to fool reverb experts (us) into believing that a sound has been recorded in a space other than the space it was actually recorded in. If the spatial cues we are hearing and interpreting sound “fake” the illusion of reality we are trying to impose on a recording will collapse. No wonder so much effort has been put into creating these tools.
We talk about “go to” effects meaning a first choice but through the history of recording, reverb has literally been a “go to” effect, in that the choice of venue is so often chosen for its acoustic character. Recording an ensemble in reverberant spaces is of course the highest quality reverb we will ever experience, something of which I was reminded when I visited the Abbaye du Thoronet and heard proof, if it were needed, that however good digital reverb is, stone and air and actually being there still wins. That being said, the best artificial reverb is very, very good. Lots of hard work and ingenuity have gone into creating convincing artificial reverb for those of us who don’t have room for a 12th century Cistercian abbey in our studios!
The sound of large spaces is what most of us think of when we think of reverb, possibly because these are the spaces we associate with performances and possibly because they sound impressive and are outside our usual, everyday experience. The characteristic features of a hall include a slow initial build up of reflections. This is because halls are large. In a large space there is an appreciable gap between the direct sound reaching your ears and the first reflections from the closest walls which might be tens of meters away. An additional effect of this is that when they do reach the listener, these early reflections are more widely spaced than other types of reverb because of the distances involved.
Halls also usually have a longer decay time at low frequencies compared to high frequencies. This is an effect of the size of a large hall. Air absorbs high frequencies due to frictional losses, and because many halls contain soft materials which absorb sound, unlike for example a church.
The spaces with which we are most familiar and therefore the category for which we as listeners are least likely to tolerate a fake. This category varies so much that it is difficult to generalise but probably more than any category the early reflections and the character these impart to the sound are crucial to the illusion the reverb is trying to create. Often used to “put a space around a sound” these reverbs often don’t feature any appreciable reverberant tail. Room Reverbs tend to have short decay times, fast build ups of early reflections, resonances caused by standing waves and parallel walls and low ceilings There are as many variations as there are types of room but the thing with this category is that whatever you are using had better be good as this is the environment with which we are most familiar.
The desire for control led to engineers using a real reverberant space as a reverb generator but instead of placing the performers in that space, by putting a speaker fed from a send on the recording console and placing microphones in that space to capture the effect the reverb chamber had on the audio sent to it, a very controllable reverb effect could be created. Some studios became well known for the sound of their reverb chambers, Abbey Road and Capitol being two examples. Reverb chambers can be any size but are typically small, highly reflective with hard surfaces throughout, often with non-parallel walls or with additional surfaces introduced to break up reflections, for example sections of large ceramic pipe to introduce curved surfaces.
The characteristics of a Chamber are almost the opposite of a Hall, a small space with a rapid build up of reflections and a high density. They can be bright and because of their small size classic chambers often had the low end attenuated with filters. If you’ve never tried a DIY reverb chamber then I recommend you do, even if it is just for fun, one drawback of using stairwells and the like is that they have to be very quiet. Don’t try this in a shared stairwell!
Any discussion of electromechanical reverb has to include springs, even if only as a footnote to plates. While there have been a few studio spring reverbs, plates have always been a better solution to those who could afford and accommodate such things in the the pre-digital days. Created by connecting a transducer and a pickup at opposite ends of a spring, the resulting sound while “sproingy” has a charm and character but beyond use on electric guitars, for most (though definitely not all) springs remain a low-fi character effect.
What a spring reverb wants to be when it grows up. The plate reverb was the first really professional artificial reverberator. While today we marvel at how big and impractical a 2x3m sheet of tensioned steel in an isolating box is, in 1957 I suspect people were marvelling at how compact and convenient the EMT 140 reverb was compared to a concert hall!
Plate reverb has a very characteristic high initial diffusion followed by a bright, coloured decay which, while not sounding like any particular shape of space, gives a very pleasing, generic reverb effect which works very well on percussive sources. Because the decay is controlled by dampers which mute the vibrations of the vibrating sheet of steel there is a characteristic damping of high frequencies at shorter decay times which adds to the thickening effect commonly associated with plates.
Analogue electronic devices, while held in high regard compared to digital alternatives were never really the right technology for reverb. The sheer number of delay lines necessary to simulate a convincing reverb were simply too many to be practical. Digital reverb first became available in the seventies. EMT, the plate reverb EMT, were technically the first to market. The EMT144 released in 1972 was the very first but the EMT 250 was the first digital reverb of a quality able to challenge that offered by a plate. Nice as it was the EMT250 was expensive. The people who had the right product at the right price were Lexicon and their 224 defined the sound of pop reverb for decades to come. How much the hardware cost compared to its competition in 1978 isn’t a concern to us today but the foundations Lexicon laid with those algorithms which from the 224, through the revered 480L and to the modern PCM96 are still in use today is definitely of concern to anyone who uses reverb. And everyone uses reverb!
These famous Lexicon algorithms are available for use in your productions in software form as the PCM Native Reverb plug-ins. These are exactly the same algorithms as those found in the PCM96. Real Lexicon reverb. Seven algorithms are available:
The seven algorithms available in the PCM Native Reverb Bundle are:
Rather than give examples of all seven I have created four examples of very different algorithms. Rather than provide these with settings typical for each type I have matched the delay times all to 1.5 seconds. That is long for a room and short for a hall but it does illustrate the differences between the algorithms themselves in a different way.
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