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WZLX: Programming a Surround Station

One of the primary concerns over surround-sound radio broadcasting has been the lack of music content produced in 5.1, making it difficult if not impossible to fill the multichannel format in anything close to a full-time fashion.

One of the primary concerns over surround-sound radio broadcasting has been the lack of music content produced in 5.1, making it difficult if not impossible to fill the multichannel format in anything close to a full-time fashion. Reports from one early-adopting station show that it is indeed possible, however.

WZLX(FM), a Boston classic rocker, recently began surround broadcasting on their HD-Radio service — using the MPEG Surround format — and worked with Telos Systems (which represents MPEG Surround proponents Fraunhofer IIS in the United States) to fill the station’s music library with surround content. I recently spoke with Telos President Steve Church about the challenges of such a process.

Church reported that they started by taking everything they could find in the station’s current playlist that had been released in surround remixes on DVD-Audio and multichannel SACDs. Among these were classic rock staples Steely Dan/Donald Fagen, Eagles, REM, Moody Blues, The Doors, Alice Cooper, Blue Oyster Cult, Eric Clapton, David Bowie, Yes, Talking Heads, Foreigner, Dire Straits, Pink Floyd, Santana, Queen, The Who, Deep Purple and Fleetwood Mac. This accounted for about 25 percent of the station’s high-rotation material in true surround.

This content was then ingested into the station’s content management system, a Broadcast Electronics AudioVault. But the process didn’t stop there. The station wanted to utilize the unique capability of the MPEG Surround system to transmit surround content to surround listeners without compromising the stereo/mono content to everyone else.

So as an additional step in the content ingest process, the station’s production team either synchronized the “artistic” mix from the original stereo release with the surround tracks, or they downmixed the surround version to create a stereo mix. This was decided on a case-by-case basis. They found that some songs exhibited speed variations between stereo and surround mixes, making them difficult to synchronize. While time-shifting could have been applied to these cuts, they opted to simply downmix the surround to produce the stereo version in these cases.

So far the station reports that they have received no complaints from listeners about the downmixed cuts, and some at the station feel that these songs may actually sound a bit better than the original CD versions since they came from higher-resolution disks.

But what about the other 75 percent of the station’s playlist? For much of this content, the station looked to third-party “upmixers,” who take stereo material (without access to original multitrack recordings) and creatively remix it to a discrete 5.1 output, which can then be encoded to any surround distribution format.

One such producer is a company called Penteo (, which uses upmixing technology developed by the company’s founder, John Wheeler. It is an off-line, file-based process with a number of parameters that Wheeler manually adjusts for each music piece. The result often approaches the quality of a true surround mix or remix. I’ve heard some examples of Penteo-processed songs on DVD-V (Dolby Digital-encoded), and they are quite impressive.

Getting it on air

At WZLX, all surround content is stored on an AudioVault system in discrete eight-channel form (six channels for the 5.1 surround mix, and two for the synchronized original or downmixed stereo mix). During playback, these are delivered via IP audio over Ethernet to an Axia Element console that mixes and routes the surround and stereo feeds independently.

The console also automatically upmixes any stereo-only material it encounters to surround using a simple copy of the left and right channels to the left surround and right surround channels, respectively. It is also set to downmix any surround-only material it might find to stereo. Studio microphone sources can be individually panned anywhere within the surround and stereo fields.

Regarding the latter point, I heard such an arrangement on a morning zoo-type program with multiple hosts and interview guests over HD Radio via an MPEG Surround prototype receiver in a demo vehicle, and was surprised how much easier and interesting it was to hear all the voices coming from very clearly distinguishable and consistent locations around me, while seated anywhere in the car.

So while one might think that surround content is all about the music (or the spots), announcers’ voices and other continuity can also be effectively presented in surround, and it can provide a big improvement over stereo or mono. One can imagine how radio sports broadcasts might also benefit from surround-sound presentation.

For now, however, music is the primary attractor for surround on HD Radio. Church believes that WZLX is a great station to promote the benefits of surround, given that it is a mainstream station in a major market — which also happens to be the home of several major consumer audio manufacturers. He also thinks that just as the improved fidelity of stereo FM gave the oldies format a successful two-decade run after it had faded on AM, surround broadcasting could add a decade or more to the lifespan of classic rock, allowing listeners to hear familiar material, but giving it a new edge in 5.1 presentation.

Of course the particular format of a station will have impact on how much surround content is available without resorting to upmixing. Classic rock, classical and some other top 40-type formats will likely have an easier time than others in finding surround content. Nevertheless, it is becoming clear that upmixes need not necessarily be considered second-class citizens in this regard.

Meanwhile, record companies might take note, and begin to release more current and catalog content in surround. While DVD-A and SACD formats have languished, new high-resolution HD-DVD and Blu-ray disks can provide even better vehicles for distribution of such content — with or without accompanying video.

Finally it must be acknowledged that very few listeners will appreciate all this effort at any station for some time to come, and they will probably always be a minority of the audience. Thus a broadcaster should ensure that nothing in this process degrades the analog FM or HD Radio stereo service, and WZLX’s owners (CBS Radio) and management were just so concerned. Nevertheless, the process has moved forward there, and as receiver hardware becomes available, listeners in Boston will have at least one source of great surround content, 24×7.

We can only hope that this trend will grow, and we’d like to know if it does. Let RW know if your station is broadcasting surround content so we can share your news in this area as well.

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