Saturday, June 18, 2011

IR Reverb Comparisons

This is not a comparison of their features but of how each one of them sound.

Deconvolution Comparison:


The Altiverb sweep generator produces a sweep with a start and end beep (which it uses for identification). Since most other deconvolution tools don’t recognize these beeps, we created two versions of the sweep – one with the beeps and one without and normalized them to -0.3dBFS. The recorded sweep at the venue also included broadband noise and AC hum, which Altiverb’s processor did a good job of neglecting. The other plugins weren’t as good and included the noise along with the impulse. To make the comparison easier we used some amount of noise reduction on both versions of the recorded sweep.

1. AudioEase Altiverb:

AudioEase’s IR Pre-Processor needs to be used to deconvolve a sweep that is usable in Altiverb. The process is very simple – select a folder with the recorded sweep (make sure they are stereo-split SDII files), an output folder (your Altiverb preset folder), an input description file (in this case, “Sweeps, not to be equalized”) and hit “Process”. Re-scan your IR directory in Altiverb and it should show up.

Altiverb Pre-Processor

Here’s what the sweep recorded at the venue for Altiverb sounded like (with beeps, noise reduction and normalization). Make sure you aren’t monitoring too loud:

Recorded Altiverb Sweep on SoundCloud

2.McDSP Revolver:

Revolver has its own utility in the form of an AudioSuite plugin. This is even simpler to use. You need to make sure that both your original sweep and recorded sweep files are imported into Pro Tools. The plugin can then be used to analyze both files and the result can be saved as a preset.

McDSP Sweep Analyser

Here’s the edited and processed (noise reduction) sweep that was used:

Recorded IR For Other Plugins on SoundCloud

3. TL Space:

TL Space has no deconvolution utility. A third party utility can be used – Voxengo Deconvolver on Windows, Fuzz Measure Pro or Space Designer on a Mac.

4. Waves IR1

IR1 has restrictions. It only works with the sweep provided by Waves (on the install CD or downloadable from their website). It’s a 15 second sweep from 22Hz to 32KHz. Because of this, it could not used for this test.

Waves IR1

5. Space Designer:

In the more recent versions of Logic, the deconvolution option in Space Designer is hidden. It can be found by switching the view options of the plugin to ‘Controls’ and scrolling down to ‘Decode IR’ menu. It will then ask for both the original sweep and the recorded and sweep and output a deconvolved response. we used the same edited sweep that was used for Revolver.

Space Designer - 'Controls' mode


The SoundCloud clip below shows the results of the sweep deconvolved by the above plugins. All plugins were running flat with no additional processing. The results were normalized to -1dBFS.

Deconvolved Results on SoundCloud

Altiverb does sound closer to the actual recording in the space. Although, it does lack LF and wideness in those frequencies. My guess is it’s because of the noise reduction, as the results in my previous post (with no noise reduction) sound alright.

The stereo spread in Revolver is a bit skewed across the frequency spectrum.

The result from Space Designer are closer to the source but it also has a lopsided image. It does seem to have a litte more depth though.

What do you think? Which of the results sounds closer to the source to you?

Plugin Sound Comparison:

To compare the sound of each plugin, we used Voxengo’s Deconvolver to create an impulse response that could be used commonly across all the plugins (thereby keeping the effect the deconvolution process has on the sound common across all plugins). It’s a standalone application that runs only on Windows and is simple enough to use – select the two files and hit process. It does come with other options that are useful for batch conversions (normalize, fade in, fade out, high cut, low cut, etc).

UPDATE: Voxengo Deconvolver can be used in OSX using WineBottler (thanks to Ayush Ahuja for the tip).

Voxengo Deconvolver


All plugins had no additional processing and the results were normalized to -1dBFS.

Convolution Plugin Comparison on SoundCloud

The results are definitely interesting! Each plugin seems to be treating the IR very differently. Altiverb & TL Space sound closest to the source and also sound similar. Revolver seems to have some sort of smearing again. Waves IR1 sounds more “wet”. Space Designer has a lopsided image again in addition to having a little more depth (not as upfront as Altiverb and TL Space). It’s also interesting to compare these results with the ones above.

What are your thoughts? Which of these plugins do you use and how do they translate and work for you in a mix?