Difference between revisions of "GVerb"

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(ANWIDA SOFT DX REVERB LIGHT: add direct links)
(The presets)
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== The presets ==
 
== The presets ==
  
Experience has been that the GVerb defaults are not very good for the obvious approach of mixing reverb into a track. The basic idea of the presets seems to be that you duplicate your track and convert the double to reverb-only by appling GVerb to it, leaving the original track untouched. Then you control the reverb amount in your mix by adjusting the volume levels of the dry and reverb-only tracks. This is a professional yet conservative studio-like approach. A professional sound engineer would pick up the original signal from the board, send it through a reverb unit and return it through a separate input channel of his mixing board.
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It's certainly true that the GVerb defaults don't seem very good at all for the obvious approach of mixing reverb directly into a track. The basic idea of the presets seems to be that you duplicate your track and convert the double to reverb-only by appling GVerb to it, leaving the original track untouched. Then you control the reverb amount in your mix by adjusting the volume levels of the dry and reverb-only tracks. This is a professional yet conservative studio-like approach. A professional sound engineer would pick up the original signal from the board, send it through a reverb unit and return it through a separate input channel of his mixing board.
  
The basic advances are that this approach is non-destructive - you keep the base track as it is. You can further manipulate the reverb-track e.g. with compression, expansion, equalization, gating. You could also make the reverb change over time by editing the reverb track e.g. with Audacity's envelope tool.
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It is true that this approach is non-destructive - you keep the base "dry" track as it is. Yet that is not really the reason to mix reverb in this multi-track method. The big advantage is that you can mix in the amount of reverb "wet" signal in real time using just the gain control on the reverb track. This is a big advantage, because reverb processing is not real-time, it may take 30 or 40 seconds just to process. Reverb is a tricky effect to get just right, too much sounds corny, too little isn't satisfying. Unless you know exactly what you want from previous experience, you will spend a lot of time experimenting, processing, listening, undoing, changing parameters, re-processing, listening, etc. There is a 2-second preview on effects but that is not really enough to appreciate the full effect. Other advantages are that you can further manipulate the reverb-track e.g. with compression, expansion, equalization, gating - again without affecting the base "dry" track. You could also make the reverb level change over time by editing the reverb track e.g. with Audacity's envelope tool.
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So this is why the default parameters in GVerb have the dry level (original signal) all the way down.
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It's also possible to do two or more reverb tracks, say one with the Early Reflection only and a second with the Tail only. In this way, you can mix all three in real time and really fine-tune the exact sound you're going after with immediate feedback. Going even further with this approach, you can try different parameters on different sets of tracks, muting and unmuting them to compare one set with another in A/B fashion, again with immediate feedback.
  
 
The hiccups of this approach is you're using more disk space, and that it is more complicated in the beginning. In many cases, you just want to get the obvious result: transforming a non-reverb track to a track with mixed-in reverb.
 
The hiccups of this approach is you're using more disk space, and that it is more complicated in the beginning. In many cases, you just want to get the obvious result: transforming a non-reverb track to a track with mixed-in reverb.

Revision as of 22:34, 6 September 2007

GVerb is a free (GPL) reverberation LADSPA plug-in written by Juhana Sadeharju and ported to LADSPA by Steve Harris. Audacity 1.2.0-pre3 to 1.2.4/1.3.0 releases of Audacity included the GVerb plugin. Although currently still included in the 1.2.6 Windows release, it is now a separate download (along with many others) in the LADSPA effects collection for Windows or for Mac

The presets

It's certainly true that the GVerb defaults don't seem very good at all for the obvious approach of mixing reverb directly into a track. The basic idea of the presets seems to be that you duplicate your track and convert the double to reverb-only by appling GVerb to it, leaving the original track untouched. Then you control the reverb amount in your mix by adjusting the volume levels of the dry and reverb-only tracks. This is a professional yet conservative studio-like approach. A professional sound engineer would pick up the original signal from the board, send it through a reverb unit and return it through a separate input channel of his mixing board.

It is true that this approach is non-destructive - you keep the base "dry" track as it is. Yet that is not really the reason to mix reverb in this multi-track method. The big advantage is that you can mix in the amount of reverb "wet" signal in real time using just the gain control on the reverb track. This is a big advantage, because reverb processing is not real-time, it may take 30 or 40 seconds just to process. Reverb is a tricky effect to get just right, too much sounds corny, too little isn't satisfying. Unless you know exactly what you want from previous experience, you will spend a lot of time experimenting, processing, listening, undoing, changing parameters, re-processing, listening, etc. There is a 2-second preview on effects but that is not really enough to appreciate the full effect. Other advantages are that you can further manipulate the reverb-track e.g. with compression, expansion, equalization, gating - again without affecting the base "dry" track. You could also make the reverb level change over time by editing the reverb track e.g. with Audacity's envelope tool.

So this is why the default parameters in GVerb have the dry level (original signal) all the way down.

It's also possible to do two or more reverb tracks, say one with the Early Reflection only and a second with the Tail only. In this way, you can mix all three in real time and really fine-tune the exact sound you're going after with immediate feedback. Going even further with this approach, you can try different parameters on different sets of tracks, muting and unmuting them to compare one set with another in A/B fashion, again with immediate feedback.

The hiccups of this approach is you're using more disk space, and that it is more complicated in the beginning. In many cases, you just want to get the obvious result: transforming a non-reverb track to a track with mixed-in reverb.

Instant reverb settings

If you want to apply GVerb directly to your track, here are some settings that sound a lot better as a starting point:

Roomsize: 40 m²
Reverb time: 4 s
Damping: 0.9
Input bandwidth: 0.75
Dry signal level: 0 dB
Early reflection level: -22 dB
Tail level: -28 dB

The following settings will also produce a nice hall effect in Gverb:

Roomsize: 40 m²
Reverb time: 20 s
Damping: 0.50
Input bandwidth: 0.75
Dry signal level: 0 dB
Early reflection level: -10 dB
Tail level: -30 dB

If you want to apply more or less amount of effect, try changing the Early reflection level (dB) and the Tail level (dB) values (Thomas Economou).

Parameters

In GVerb, the parameters seem to be intertwined. This makes up for the quality of the reverb simulation of GVerb but may also be quite confusing. Kurt hasn't reviewed the code. His observations are derived from "good knowledge" and testing. In either approach of reverb generation in your mix mentioned above, the parameters seem to work as follows:

Roomsize: Controls the overall characteristics of the reverb effect. In general, this parameter influences both the simulation of early reflections and the sound of the tail.

Reverb time: Controls the approximate duration of the reverb floor. In general, this parameter affects the simulation of the reverb tail. Very small settings cause the tail to almost disappear.

Damping: This parameter controls the response of the early reflections and the decay of the reverb tail. The higher the value, the less intense is the reverb.

Input Bandwidth: Provides some kind of "tone" control. Small values cause a smaller frequency range to be processed. In general, the effect of this control can be heard in the treble band. Smaller values cause a "muffled" and less bright reverb.

The last three parameters are volume controls. They allow you to attenuate destinctive portions of the processed signal.

Dry signal level: A volume control that determines the amount of original sound in the reverb. Please note that the standard presets choose this setting to be on the lowest value, whereas the suggested instant reverb settings propose a very high setting.

Early reflection level: A volume control that determines the amount of early reflections. Early reflections are similar to slapback echos. Though they are not responsible for the typical hall effect generally linked with reverb, they contain lots of acoustic information about the setup in which the sound occures.

Tail level: A volume control that determines the amount of the hall effect of the reverb. The volume of the tail determines how intense the reverb appears to be.

Tips for playing around

Generally, an ER level about 10 to 20 dB higher than the tail level gives a typical reverb effect. When you choose the ER level to be considerably smaller than the tail level, you can simulate a distance between the source and the listener.

When mixing reverb and dry signal into a single track, I suggest to decrease the dry signal level of 1 or 2 dB, because the added reverb can exceed the dynamic range and cause clipping.

You can vastly increase the stereo effect when you apply a reverb effect with slightly different settings for left and right channel separately.

To determine the final amount of reverb use monitor speakers instead of headphones. The reverb may sound far less intense when listened to over headphones than over speakers, resulting in adding to much reverb to the mix.

Some other settings:

Singing in the sewer

Roomsize: 6 m²
Reverb time: 15 s
Damping: 0.9
Input bandwidth: 0.1
Dry signal level: -10 dB
Early reflection level: -10 dB
Tail level: -10 dB

Last row of the church

Roomsize: 200 m²
Reverb time: 9 s
Damping: 0.7
Input bandwidth: 0.8
Dry signal level: -20 dB
Early reflection level: -15 dB
Tail level: -8 dB


Please, feel free to modify this page and include documentation on what all of these parameters do, and sets of parameters you have used successfully in various projects. Comparisons to Freeverb and other reverb plug-ins would also be welcome.



ANWIDA SOFT DX REVERB LIGHT

User report: An alternative great sounding free reverb is Anwida Soft DX Reverb Light. You need the VST version for Audacity, here are the downloads for Windows and OS X. Anwida also sell a full version with more reverb types and more parameters, but the free version sounds excellent and its simplicity makes it hard to get a bad result while minimizing your fiddling-around time.

Unlike other reverbs I have tried, which sound pretty bad unless the settings are just so, Anwida sounds good at almost any setting; you just have to decide how much is enough. Really the two most important parameters are Mix (wet level) and Decay. The difference in Predelay can be subtle, but is the main determination of "room size." An increase in Mix can be accompanied by a decrease in Decay, in order to keep the reverb from getting too muddy, chaotic and corny sounding.

Settings

For a good acoustic, fairly subtle natural sounding reverb (I use it on stereo miked classical guitar) try starting with the following settings:

MIX 0.350
PREDELAY 0.400
DECAY 0.500
LP CUT 0.100
VOLUME 1.000

The only drawback to Anwida is that the Volume setting maximum of 1.000 pretty much always results in a slight loss of volume. Actually the perceived volume is about the same, though the waveform graph will look a little smaller and have lower peaks.