V.I is a free VST plugin for designed to convert a stereo input to a 5.1 audio output. You can then save this data in a file and encode it into a surround sound file using appropriate software. V.I cannot go back into a recording studio and separate the original multitrack audio into separate channels, but it can extract ambience information embedded in the stereo audio and redistribute it among 5.1 channels. Recording engineers, audio engineers and enthusiasts have been doing this kind of thing for years in one way or another. V.I simply combines some of their techniques in one VST plugin.


  • Width correction helps compensate for source files that were mixed too narrow or too wide.

  • Independent controls for adding ambience to the front or rear soundstage.

  • Pass-through of original left and right signals ensures accurate reproduction of original stereo imaging (when not in Movie Mode).

  • Companion fLfR, CLFE, and sLsR VST plugins duplicate V.Iís effects in channel pairs for VST hosts that do not support multichannel plugins such as V.I

  • Movie Mode switch redirects some dialog frequencies from front left and right channels to the center channel to enhance dialog while still maintaining a good stereo soundstage.

  • On/off control for A-B monitoring of effect.

  • Switchable LFE channel.

V.I has been tested in various multichannel hosts such as Plogue Bidule, Audiomulch, and Steinberg Cubase SX or Nuendo versions 2.x or later. The 2-in/2-out fLfR, CLFE, and sLsR plugins have been tested successfully in Adobe Audition 1.5-2.0, Steinberg Wavelab 5.0, Kristal Audio Engine, Sonar Producer Edition 5, and Sony Vegas 6.

You can download V.I VST Suite here (3.8MB):

V.I Suite version 1.11 Installer or V.I Suite version 1.11 Zip file

February 4, 2006 updates in version 1.11
The updates to the V.I Suite installation package for version 1.11 do not include any changes to the actual plugin dlls. This is just a maintenance release to fix minor problems with the support files and to add information to the manual. If you just want the updated files, feel free to download them as follows:

Plogue Bidule layouts (zip, 13.4K)
(fixed problem with occasional error message when opening layout files in Plogue Bidule)

V.I fxb Preset files (zip, 2.2K)
(fixed problem with occasional error message when opening preset files in Plogue Bidule)

V.I Manual (zip, 316K)
(added information about additional supported VST hosts)

IMPORTANT#1: This installer automatically checks your PC's registry for the current shared VST Plugins folder and defaults to installing the plugin in this folder. Be sure the VST host program you use (Plogue Bidule, Cubase, Nuendo, etc.) is set to read this directory. If your system does not have a default VST directory, the V.I Suite installer will place the files in a subdirectory of your Program Files folder called "V.I Suite." Of course, you can change this during the installation to whatever destination you wish.

IMPORTANT#2: The process of extracting ambience from a stereo recording can result in files that occasionally contain transient peaks exceeding 0dB, resulting in distorted sound. If your playback levels are too high, you may damage your equipment, and at the very least end up with a distorted file. Always use a limiter on the V.I, fLfR, CLFE, and sLsR outputs. These plugins are free to use at your own risk. Steve Thomson assumes no responsibility for any damage as a result of their use or misuse.

Don't let this warning dissuade you, just be careful with your levels and follow directions. For detailed explanations of the V.I controls, see the Manual.pdf file included with the download. The following  section provides the main control information.

December 19, 2006: VI.I
Due to popular request, I'm posting a download link for the .dll file for VI.I, a 6.1 version of the V.I Stereo-to-Surround VST plugin. This is for those with a 6.1 encoder.


Yeah but isn't V.I just "double stereo" with some filters
No, V.I is not just "double stereo." I'll get technical for a minute. To ensure a stable soundstage, V.I starts with the original front left and right channels from the stereo source file, but then it builds on them with a combination of crosstalk cancellation and second-order Ambisonics for the front ambience. Try the slider called Front Ambience and see how you like it. Even without any rear channels, the sound on some recordings seems to jump out of the speakers and take on a life of its own! For the rear surrounds, V.I extracts ambience using a modified second-order Ambisonic approach. In fact, inside the V.I plugin, there are over 300 software connections similar to the kinds you would find in modular programs such as Plogue Bidule, Audiomulch, etc. This may sound complicated but the result is a smooth, natural surround effect.

As for filters, there are only two: one for the LFE if you choose to use it, another for Movie Mode, again if you choose to use it. Any other sound that seems to be filtered is just the natural result of proven Ambisonic techniques.

If you have a computer with a 5.1 soundcard and speakers, try listening to music going through V.I and then switch it off and on a couple of times using the button on the plugin. Whenever you turn V.I on, notice how the instruments and sounds seem to remain in basically the same place but suddenly become three-dimensional as if you were standing in the room with them.

About V.I Controls
Even if you've started with the highest-quality source you can find, carefully removed DC offset, etc., your source fileís stereo mix might not be ideal for a good stereo-to-surround conversion. You can't go back into the studio and change this, but you can adjust the width of the stereo image with the WIDTH CORRECTION control. This helps you in the following situations:

Individual sounds are panned to the extreme left or right
Most conversion methods will spread these sounds out to the side too much, and even to the surround speakers. If this is what you want, great! If not, then it's a problem. To fix this, move the WIDTH CORRECTION control toward its minimum setting on the left.

The unwanted sounds on the side or in the surrounds should move to the front soundstage but the overall mix still maintains a reasonable amount of stereo separation. Many older recordings from the 60s and 70s sound much more natural with this setting.

Another way to enhance old recordings with material mixed to the extreme left or right is to try the MOVIE MODE switch (see below). This is sometimes very subtle, but it could be just enough to make the difference!

The recording is too "dry"
The original ambience is actually there, but it's buried in the mix. Move the WIDTH CORRECTION control toward its maximum setting on the right.

This boosts the ambience information in the recording, which generally gives you a more open, natural sounding mix. Be careful though because too much width can make the recording sound washed out or weak.


Unless you've changed the width of the source stereo signal using the WIDTH CORRECTION control, V.I passes the original stereo signal to its Left and Right outputs unaltered. The center channel is derived by extracting the mono centered sound information. If you wish to add a bit more of a sense of ambience to the front soundstage, the FRONT AMBIENCE control adds some ambience harmonics. In its maximum position, these harmonics start to give a pseudo-surround effect even without surround speakers.


V.I's rear surround channels are derived using calculations based on Ambisonic principles. If you wish to add a bit more of a sense of ambience to the rear soundstage, the REAR AMBIENCE control boosts ambience harmonics already present in the surround signals.


Just as the WIDTH CORRECTION control compensates for problems with the source file at V.I's input, the REAR LEVEL control balances the overall surround effect at the output of the surround channels. If you want to put more emphasis on the front soundstage, reduce this level.


This button toggles the center, LFE, and surround channels on (red indicator appears) and off (no bright red indicator) so that you can "A-B" compare the plugin's effect when adjusting controls. For example, when using the REAR LEVEL control, one well-known approach is to raise the surround level until it becomes easily apparent, and then reduce it slightly. You may then think the level is too low, but if you use the ON/OFF control to switch off the surrounds, you'll notice the sound stage tends to collapse towards the front.


The Movie Mode switch redirects some dialog frequencies from front left and right channels to the center channel to enhance dialog while still maintaining a good stereo soundstage. This works well with movie soundtracks and TV show audio tracks. It can also enhance some music files as well. Try it! The effect is often quite subtle, so for additional clarity, you may wish to add some compression to the center channel output to boost the dialog level without distorting it.


This button toggles the LFE channel on (red indicator appears) and off (no bright red indicator). Some people prefer to leave the LFE channel empty and allow a playback system's bass management to take care of the bass frequencies. This is a wise course of action, but you may also want to use the LFE channel to boost the deep bass level in old recordings. Experiment and find something that works for you. V.I's LFE signal consists of very low frequencies at approximately 60Hz and lower. It does not boost them to any great degree so any negative side effects are minimal. If you want to boost the bass, you can apply some mild compression to the LFE output.

IMPORTANT: if you use an LFE and intend to encode your surround mix as AC3 (Dolby Digital), remember that any signal in the LFE channel will be lost if your work is played on a non-5.1 system such as a Dolby Pro Logic I or II system. When the AC3 channels are "folded down" or downmixed to DPL I or II, the LFE channel is discarded. This is part of the Dolby specification. Therefore, it's important that your 5 regular channels remain full range. You can easily encode a 5.1 file with a blank LFE channel and the results will sound fine! If you want to use the LFE button to add a bit of extra "oomph, go for it. Just remember that 1. Anyone playing the resulting disk on a DPLI or II system won't hear anything in the LFE channel and 2. Too much LFE can make the bass muddy. Remember, "LFE" DOES NOT EQUAL "SUBWOOFER". They are two completely different things. Depending on equipment settings and design, Sound in the LFE channel may be reproduced by your regular speakers and sound in the other channels may be reproduced by your subwoofer. It's amazing how many people confuse the two.

A Balancing Act Ė Using V.I Controls Effectively
The controls on V.I allow you to shape the resulting surround sound output to your tastes. To get the most out of them, you really need some way of monitoring the sounds before processing the files. Even if you don't have a full 5.1 output sound card with speakers, you can effectively monitor your mixes with a bit of practice. Note that most 2.1 or 4.1 systems do not really have a separate subwoofer output. The speaker system's amplification circuit determines the crossover point and sends the sound to the appropriate speakers. Therefore, these are treated as if they were 2- or 4-channel systems. Since the LFE channel does not equal the sound sent to the subwoofer, this should not matter.

PCs with 2- or 2.1-channel sound
If all you have is a two-channel speaker system, you won't be able to effectively monitor the overall surround sound balance, so some "guesswork" is involved. Nonetheless, if you exercise some restraint and don't try any extreme settings, you can still end up with good results. If you're using Plogue Bidule, you would typically monitor the output Left and Right channels through the Microsoft Sound Mapper output and leave the other V.I outputs unconnected to a sound output. Adjust the WIDTH CORRECTION control for the best, most natural sounding stereo output. Avoid the temptation to move the control all the way to the right. Although the wider, more spacious sound might lead you to think it will sound better in 5.1, too much width will make the surrounds too loud and ruin the imaging of the front soundstage.

Since you don't have a way to monitor this effectively, you'll end up with an unbalanced mix. Remember, Width correction is designed to correct the stereo width of the source file.

PCs with 4-, 4.1-, or 5.1-channel sound
If you have a four-channel system, you can generally adjust the balance of the surround mix quite well. Obviously, a 5.1 system will provide the best monitoring environment.

Try combinations of adjustments until you get a nice balanced sound all around. Keep in mind that adjusting the REAR AMBIENCE control to boost ambience harmonics in the surround signals can sometimes result in them becoming too loud. In such a case, use the REAR LEVEL control to back off on the surround level. This still gives you added ambience in the rear, but it also evens out the overall sound image and restores the sense of localization. For example, an acoustic guitar that's intended to seem as if it's in the front left of the soundstage might sound like it's coming from the side. You could use the WIDTH CORRECTION control as mentioned in its description, but this might reduce the overall ambience and sense of space in the overall soundfield. A more effective approach is to use the REAR LEVEL control as described above.

As for the LFE Channel button, it's up to you whether you use it. Remember that V.I sends bass frequencies below 60Hz through the LFE channel when this button is toggled on (red indicator appears). Since these are may also be present in the regular channels, you should only use the LFE channel if you want to give your surround mix a slight added bit of deep bass. A general rule of thumb is that older recordings benefit more from using this because their deep bass response is generally limited. Still, you have to experiment to avoid having too much bass. If you're not sure, or if you're a purist, shut it off. The other channels in V.I are full-range, so if you don't use the LFE channel, the bass in the other channels will be routed to the subwoofer of any playback system by its bass management circuit.

Saving and loading Settings or Restoring Defaults
V.I features standard VST patch bank loading and saving capabilities. V.I comes with several standard patches to get you started. If you change these settings and wish to restore the defaults, simply load in the vi.fxb bank file to restore the original defaults.

The Rest of the Family Ė fLfR, CLFE AND sLsR
If you donít have a VST host that supports multichannel VST plugins, try V.Iís companion plugins:

  • fLfR duplicates V.Iís front channels.

  • CLFE duplicates V.Iís Center and LFE channels

  • sLsR duplicates V.Iís rear surround channels

An extra bonus: stereo playback enhancement
As an added bonus, the fLfR plugin by itself can enhance stereo playback if you use it by itself and turn the front ambience up near its maximum. This won't give you the full V.I effect, but depending on your source material it can have you looking for speakers that don't exist! Just remember to use a limiter on its outputs.

If you have any questions or comments about V.I or its companion plugins, please feel free to contact  


V.I Suite plugins were proudly made with Synthedit


V.I © Copyright 2004-2006 Steve Thomson. All rights reserved.
fLfR, CLFE, sLsR © Copyright 2006 Steve Thomson. All rights reserved.