From the same site that brings you AudioMuxer, SpecWeb is a drag and drop stereo to 5.1 converter that retains many of the features of its big brother Spec (The most popular upmix method on the net) but does not require Plogue Bidule.
We believe SpecWeb sounds better (or at least as good) as any commercial stereo to 5.1 solution out there (e.g. better than DTS' Neural Upmix, as good or better than Pento)
SpecWeb is for windows only at this time.
It has both a windows command line and HTML5 web interface, so can be controlled by computers, iOS, and Android devices any where are your local network.
It is designed to be faster and easier to use than the full (Plogue Bidule) version, but has fewer features.
SpecWeb also has an html5 “web” user interface, which works with chrome, firefox, iOS, android, and
windows 10 edge browsers*. You can control SpecWeb from a browser on the same computer or on any
computer or supported device on your local network. For instance, you could sit in your home theater
listening position and control SpecWeb with an iPad.
It’s a great way to get started in making your own upmixes as all you have to do is drag and drop a lossless
stereo file onto the SpecWeb icon and you get a 5.1 multichannel file in seconds.
While not all of the “knobs” from the full version have been included, the most important ones are here and
you can adjust them while you listen to the song, just as you can in the full version, then “record” the results.
SpeWeb is donationware
There is also a free "helper app" which helps automate full album conversions and adds more cool features:
pecWeb has been updated to version 1.4. Same link above applies.
Also, The latest version of AudioMuxer also includes support for batch or single conversion of stereo to surround using SpecWeb: