Institute of Communication Acoustics
Prof. Dr.-Ing. Rainer Martin



  1. Introduction
  2. Features
  3. Screenshots
  4. Download
  5. Source Code
  6. References


HybridReverb2 is a convolution-based reverberation effect which combines the superior sound quality of a convolution reverb with the tuning capability of a feedback delay network. The sound quality of a convolution reverb depends on the quality of the used room impulse responses. HybridReverb2 comes with a set of room impulse responses which were synthesized with tinyAVE, an auralization software which was developed at the Institute of Communication Acoustics, Ruhr-Universität Bochum (Borß and Martin, 2009; Borß, 2009a). These room impulse responses are designed for a speaker setup with two front and two rear speakers (Borß, 2009b). For a full surround sound effect, you will need two plugins, one plugin which uses a "front" preset for the front channels and a second plugin which uses the corresponding "rear" preset for the rear channels.

Christian Borß (eMail:



screenshot: main tab The "Main" window contains the most frequently used operational controls. The user can select a preset either by the "+/-" buttons or by the categories of the "Preset Selector". The upper-right part of the screen displays some background information about the selected preset.
The "Dry Gain" knob adjusts the level of the direct sound (by replacing the value of the first impulse response sample - HybridReverb2 treats the first sample of each impulse response as contribution from the "direct sound", i.e. the dry audio signal). The "Wet Gain" adjusts the wet level (by multiplication with a constant gain factor). The "Master Level" can be used to adjust the output signal of the plugin.
The envelope of the impulse responses which are shown in the lower-right part of the screen can be manipulated either by the red sliders or by directly entering the desired value. The impulse responses are displayed in three different resolutions: a high resolution for the initial part, a medium resolution for the transition range, and a low resolution for the late reverberation part. The intention of this is to have a better control over the early reflections which may introduce some unwanted coloration.
screenshot: main tab The "Timbre" window contains a graphical equalizer with 1/3 octave resolution which can be used to tune the timbre of the wet part. The impulse response of the generated linear-phase filter is shown in the lower part of the screen. By increasing the smoothing factor (at the bottom of the screen), the duration of the filter impulse response can be shortened.
screenshot: main tab The "Preset Editor" can be used to add, modify, or remove presets or to load and save different preset databases.
screenshot: main tab The "Preferences" window contains only a few items: the name of the preset database which is loaded on startup, the processing latency, and the segmentation strategy. The help text on the right-hand side explains the meaning of these parameters in more details.
screenshot: main tab Last, but not least: the "About" window which gives some background information about me and this plugin. Enjoy!


HybridReverb2 is available for download at the KVR Developer Challenge '09 homepage. Thank you in advance for voting for my plugin!

The room impulse responses (presets) which come with HybridReverb2 are property of the Institute of Communication Acoustics, Ruhr-Universität Bochum, and are free for non-commercial use. The VST plugin is available under the GNU General Public License (GPL).

The DC'09 packages contain only a small impulse response database. If you are interested in a larger database (193MB), download the following archive and extract it to your HybridReverb2 folder. Under MS Windows, this is the directory which you specified during installation. Under Mac OS X, the HybridReverb2 folder is located in /Library/Audio/Plug-Ins/VST/HybridReverb2.vst/. Under GNU/Linux, the HybridReverb2 folder is located in /usr/share/HybridReverb2/. In order to use the updated preset file HybridReverb2_presets.xml, open it with the HybridReverb2's Preset Editor and save a copy of it in your user directory ("save as..."). The Preset Editor should list 118 presets now.


Source Code:

The following files are useful for experts only who want to compile it from source code.

Download: HybridReverb2-2.0.2_20091104.tgz (source code for the VST plugin)

Download: WisdomGenerator-0.2.1.tgz (source code for the initial benchmark, graphical version)

Download: WisdomGeneratorNogui-0.2.1.tgz (source code for the initial benchmark, console version)

In order to compile HybridReverb on a Windows machine, you will need:

  1. Visual C++ 2008 Express Edition from Microsoft
  2. VST Audio Plug-Ins SDK 2.4 Revision 1 from Steinberg
  3. FFTW 3.2.1

Linux developers will need this patch for the VST-SDK to compile VST software using GCC.

Download: libHybridConv-0.1.1.tgz (source code for the convolution library)

This archive contains the source code for the convolution library libHybridConv (included in "HybridReverb2-2.0.2_20091104.tgz") which is available under the GNU Library General Public License (LGPL). The included Makefile can be used to compile it under GNU/Linux. The file hcTest.c implements a benchmark which measures the processing performance for various segment lengths. The functions hcBenchmarkDual(sflen, lflen) and hcBenchmarkTripple(sflen, mflen, lflen) in libHybridConv.c serve as example for a segmented convolution with two or, respectively, three segment lengths.


Borß, C., Martin, R. (2009). "An Improved Parametric Model for Perception-Based Design of Virtual Acoustics", in AES 35th Int. Conference, London, UK, Feb. 2009.

Borß, C. (2009). " A Novel Approach for Optimally Matching a Late Reverberation Model to an Image Source Model - Or: What Does a Football Have to Do With Shoebox Shaped Rooms?", in Proc. Auralization Symposium of the European Acoustics Association, Espoo, Finland, Jun. 2009.

Borß,C. (2009). "A VST Reverberation Effect Plugin Based on Synthetic Room Impulse Responses", in 12th Int. Conference on Digital Audio Effects (DAFx-09), Como, Italy, Sep. 2009.


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