GVerb

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GVerb is a free GPL reverberation plug-in, originally written by Juhana Sadeharju then ported to LADSPA by Steve Harris.


Contents


Feel free to improve the documentation on what all the effect parameters do, and to add alternative sets of parameters you have used successfully for different types of audio, in various projects. Additional comparisons to the alternative plug-ins listed would be welcome.


Obtaining and installing

GVerb was previously included in Audacity releases for both Windows and Mac. Current Audacity releases from 2.0.4 onwards now have a built-in Reverb effect which replaces GVerb.

GVerb is still available as a separate download inside a suite of LADSPA effect plug-ins. This suite is available for Windows, Mac and Linux.

How to install: After downloading from the appropriate link above, the plug-ins should be installed as follows:

  • Windows - Run the .exe installer and set the installation path to the Plug-Ins folder inside your Audacity installation folder. This installation folder is normally in your Program Files folder, so in that case install the plug-ins to:
    C:\Program Files\Audacity\Plug-Ins.
  • Mac - The plug-ins should be installed to:
    /Library/Audio/Plug-Ins/LADSPA/ or
    ~/Library/Audio/Plug-Ins/LADSPA/.
  • Linux - The plug-ins should be installed in:
    /usr/lib/ladspa/ or /usr/local/lib/ladspa.


Usage: two approaches

Apply reverb directly to the original track

The more obvious approach of applying reverb directly to a track works badly with GVerb's default settings, but there's an excellent reason for this. Specifically, the "dry" level (no effect applied) is set to zero. Why? This is based on the assumption that you are going to duplicate your track and convert the duplicate to reverb-only by applying GVerb to it, leaving the original track untouched. Then you control the amount of reverb by mixing in different 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.

There are some advantages to applying reverb directly. It means less disk space and CPU  usage, and lessens the possibility of playback problems on slower machines. It can give you a quick, reasonably useful reverb, if you know suitable instant reverb settings that you can apply.

Duplicate and mix together

The alternative "duplicate and mix" approach has two major advantages:

Quicker to get exactly the effect required

There are a very wide variety of sounds possible on a reverb, and it can be difficult and time-consuming to determine the parameters required for a particular sound, instrument or project. Reverb processing is not real-time: even on fast machine it may take 30 seconds or more to process a four-minute stereo track in 96000 Hz, 24 bit quality. Audacity does have a preview for effects (limited to 3 seconds in Audacity 1.2.x, but with configurable length in 1.3.x). Even so, the reverb parameters cannot be modified during preview, so unless you already know exactly what you want from previous experience, you may spend a lot of time experimenting, processing, listening, perhaps undoing, and changing parameters. To get the exact sound you want more quickly, it is actually very useful to utilize the sound engineer's method of duplicate track reverb layering. Once a chosen reverb has been processed into the duplicated track, you can mix in the amount of reverb "wet" signal in real time using just the -....+ gain control  on the reverb track.

Non-destructive, and expandable

You always keep the base "dry" track as it was originally. As well as being important in its own right, this gives you the option of working with multiple reverb tracks, without destroying either the dry track or the individual reverb tracks. As a simple example, you can further manipulate the reverb track with compression, equalization or noise gating (via a third party plug-in such as Dr.Expander ), without affecting the "dry" track.

Working with more than one reverb track opens up several possibilities. You could make the reverb amount change over time by duplicating the reverb track, applying a more extreme reverb to one of them, then use Audacity's envelope tool  to gradually adjust the volume of each reverb track. Or you could prepare two different reverb tracks, (say one with the Early Reflection only and a second with the Tail only). This way, you could mix both types of reverb with the dry original in real time and really fine-tune the exact sound you want with immediate feedback. Going even further with this approach, you can try different sets of parameters on different sets of tracks, muting and unmuting them to compare one set with another in A/B fashion, again with immediate feedback in real time.


Instant reverb settings

If you want to apply GVerb directly to your track, here are some settings for immediate gratification that sound a lot better than the GVerb defaults:

The Quick Fix
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


Bright, small hall
Roomsize: 50 m²
Reverb time: 1.5 s
Damping: 0.1
Input bandwidth: 0.75
Dry signal level: -1.5 dB
Early reflection level: -10 dB
Tail level: -20 dB


Nice hall effect
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


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


Electric guitar and electric bass
Roomsize: 1 m²
Reverb time: one beat ¶
Damping: 1
Input bandwidth: 0.7
Dry signal level: 0 dB
Early reflection level: -15 dB
Tail level: 0 dB
the amount of time for one beat of the song. For example, a beat in a 151 beats-per-minute song is 0.397351 seconds


Hints:
  • For a quick way to apply more or less reverb, try changing the Early reflection level and Tail level values.
  • Applying GVerb can clip your track, so Effect > Amplify. If the Amplification (db) is a negative value when the "Allow Clipping" box is not checked, press the OK button to decrease the amplification.
  • For settings that increase the reverberation, you may need to click at the end of the region you want to reverb, Generate > Silence, then include the inserted silence when applying GVerb.


Explaining the Parameters

In GVerb, the parameters seem to be interdependent to some extent. This needs to be considered, whichever approach you take to generating your reverb.

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 distinctive portions of the processed signal.

Dry signal level: A volume control that determines the amount of original sound in the reverb. Note that the standard presets place this setting to at its lowest value, whereas the suggested instant reverb settings propose a very high value at or close to 0 dB.

Early reflection level: A volume control that determines the amount of early reflections. Early reflections are similar to slapback echoes. 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 occurs.

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 early reflection (ER) level about 10 to 20 dB higher than the tail level gives a typical reverb effect. When you set the ER level considerably smaller than the tail level, you can simulate a distance between the source and the listener.
  • When mixing reverb and dry tracks together, decrease the dry signal level by several 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. Reverb may sound much less intense through headphones, because (with good design), little or none of the output of each channel should reach the opposite ear. As a result, too much reverb may be added for reproduction through speakers.


Mono and Stereo reverbs

GVerb is a mono rather than "stereo" reverb, meaning that it applies exactly the same effect to both channels. If you apply a mono reverb to a stereo source, the position of individual instruments in the stereo field tends to become more diffuse, and phasing effects can occur.

You can demonstrate that GVerb is a mono reverb by taking a mono track, Edit > Duplicate it, "Make Stereo Track" in the Track Drop-Down Menu to produce a "dual mono" track with both channels identical, then apply GVerb to the tracks. Now use the Track Drop-Down to Split Stereo to Mono, and Effect > Invert one of the channels. Playing will produce silence, indicating both channels are still identical.

Of course, there are workarounds.

  • You can use the Track Drop-Down Menu to "Split Stereo to Mono" then apply GVerb separately to each track. Optionally you can use the L....R Pan Slider to pan each track as required, then Tracks > Mix and Render.
  • For mono source material you could duplicate the mono track then apply subtly different GVerb settings to each of the two tracks to make a stereo effect.


Criticisms

Monty (one of the former Audacity developers) has this criticism of GVerb:

"GVerb is more a building block that you could use to build a good reverb than it is actually a good reverb. The typical problem with geeks writing free software: once they get something that proves they can solve an interesting puzzle, they lose interest in making the software usable. There's nothing wrong with GVerb, but it's a lot like a car that's nothing but an engine, wheels and gas tank on a frame, with a rope for steering and a milk crate to sit on."

Monty goes on to say that the GVerb's "room size" label is incorrect; it does not affect the waveguide depth, only the damping. So, the room size is really always the same size in gverb. As a result, GVerb can't be used for the common task of softening and pulling back vocals, which is more about "close" reflections than what most people think of as reverb, which is primarily the long tail echo.


Alternative reverb plug-ins

Anwida and Freeverb mentioned below are stereo reverbs.

Anwida Soft DX Reverb Light

User report: An alternative great sounding free reverb is Anwida Soft DX Reverb Light. Note that you can no longer download DX Reverb Light from that page, so use the download links below for the VST version of the application.

Downloads:

  • Windows (zip)
  • Mac OS X (sit) - This is for PowerPC only. You might get this to work on Intel Macs with slow performance under Rosetta. Note that Rosetta cannot be used on Mac OS X 10.7 or later.

After extracting Anwida, see below for how to install VST effects in Audacity.

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.

Freeverb

Freeverb was originally coded by Jezar at Dreampoint. Freeverb 2 was the reverb plug-in used in earlier versions of Audacity. Some users find Freeverb easier than GVerb to get a decent-sounding reverb with minimal time spent.

Downloads

Original Freeverb
Freeverb2

Only a tabular interface is provided. See the Freeverb2 help from the 1.2 Audacity Manual.

Freeverb3

Freeverb3 is the latest version of Freeverb. It now comprises a suite of different reverb effects including an impulse response (IR) convolution reverb plus a soft knee/hard knee compressor and soft knee/hard knee limiter.

Installation (VST)

Until Audacity 1.3.8, VST effects in Audacity required the additional VST Enabler, but this is no longer required. You can obtain the latest Audacity version for your system here.

Using current Audacity, place the Freeverb or Anwida .dll file (or .so file on Mac OS X) in the Audacity Plug-Ins folder inside the Audacity installation folder. On Windows computers, the installation folder is usually under "Program Files". On Mac OS X, it is usually under "Applications". Then go to the Effects tab of Audacity Preferences, check "Rescan VST effects next time Audacity is started", and restart Audacity. Freeverb or Anwida will be visible underneath the divider in the Effect menu. If you need a utility to extract from the zip, try 7-Zip. To extract on OS X from the .sit folder, try Stuffit.

Using legacy Audacity prior to 1.3.8, place the Freeverb or Anwida .dll file (or .so file on OS X) in the Audacity Plug-Ins folder inside the Audacity installation folder. On Windows computers, the installation folder is usually under "Program Files". On Mac OS X, it is usually under "Applications". Download the Windows VST Enabler or OS X VST Enabler as appropriate. On Windows, set the installation path for the Enabler to the Audacity Plug-Ins folder as above. On Mac OS X, double-click the .dmg file to mount it, then drag the vst-bridge.so file inside the .dmg into the Audacity Plug-Ins folder as above. Restart Audacity, then Freeverb or Anwida will be visible underneath the divider in the Effect menu.

Installation (Mac OS X Audio Units)

Audio Units plug-ins require Mac OS X 10.3 or later and any Audacity version after 1.3.1. You can obtain the latest Audacity version for your system here.

Double-click the downloaded .dmg containing Freeverb and drag the plug-in files into either:
/Library/Audio/Plug-ins/LADSPA or
~/Library/Audio/Plug-ins/LADSPA.

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