SoundField UPM-1 Stereo to 51 Converter

An easy-to-use, single-rack space hardware unit aimed squarely at audio-for-broadcast applications.
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An easy-to-use, single-rack space hardware unit aimed squarely at audio-for-broadcast applications.

In the world of 5.1 surround sound mixing, there are two basic ways to achieve your end result. The first is to take the multichannel master and break out tracks as needed. The second is to take stereo program material and “convert” it to 5.1.

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With that previous approach in mind, the SoundField UPM-1 stereo to 5.1 converter ($4,500 list) is an easy-to-use, single-rack space hardware unit aimed squarely at audio-for-broadcast applications and targeted for up-converting older (legacy) stereo program for 5.1 HD broadcast standards.


Fully digital, the stereo source material is fed to the UPM-1 via AES-3 to a single 75-ohm BNC connector. The 5.1 surround outputs are then sent out via three BNC connectors — one each for Left/Right, Center/LFE, and Left Surround/Right Surround. There’s also a pair of BNCs for Word Clock I/O, available at 48 kHz only. Onboard sample rate converters will synchronize to the incoming AES-3 streams or you can provide external clocking.

The front layout consists of a master gain (Level) control, a L/R balance trim and a L/R swap button. The UPMIX Controls section features a Select button for either Upmix Mode or Matrix Decode (for previously encoded Dolby Pro Logic material, etc.). Then there are rotary knobs for Direct Sound, Front and Rear Ambience Sound, and a Width Control with an Active button for A/B comparisons. From there you have Center Divergence with an Active button and 5.1 Output Levels for L/R, Center, LFE, and LS/RS. Lastly, there’s a System Bypass button for stereo to 5.1 comparisons and a USB interface, intended to accommodate future software updates.

According to the SoundField, the UPM-1 steers source signal information to its five channels in an interesting way: “The UPM-1 generates 5.1 from two channels by analyzing the original stereo audio using a patented algorithm which separates the audio into its so-called Direct and Ambient components. The former encompasses the ‘dryer,’ less reverberant components in the original sound (for example, those elements that would have been close to the microphone when the audio was recorded), while the latter refers to the more reverberant components (i.e., those sound sources that would have been further away at the time of recording). These elements can then be processed separately and routed in different proportions to the 5.1 mix if required, using the UPM-1’s simple frontpanel rotary controls.”

In Use

The key to any “upmixing” unit is not only the controls offered, but also the quality of the algorithm. However, since it’s primarily a broadcast unit, phase coherency is also critical. The UPM-1 handles all these issues quite well.

Working with engineer Paul Holly at Gizmo Enterprises in New York, we tested the unit out on an upcoming A&E show. Feeding the final stereo mix from Pro Tools, Paul set out to create a useable multichannel mix. “I got a nice 5.1 mix up pretty quickly,” he noted. “Overall, you tweak the knobs a little bit, and you’re up and running. I appreciate the center divergence control with the dialog, as well as the ability to make things wide and/or tight.” I found it to do a good job extracting ambience and leaving the dialog alone, while maintaining good stereo imaging.


As a surround mixer, I’ll be the first to argue for doing a full surround mix in the traditional way. But multitrack sessions are not always available, and for a unit that’s geared toward 5.1 upmixing for live sporting and broadcast work, it does a fine job indeed. With a few minutes of tweaking and some experimenting, you’ll have a downward-compatible 5.1 mix that should please clients and end-listeners alike.

Contact: Transamerica Audio Group (U.S. distributor) | 702-365-5155 |

Rich Tozzoli is a composer, engineer/mixer, and the software editor for PAR.