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Let’s Talk About Mono

A commentary on why talk radio stations should be broadcasting in mono, not stereo

Radio World’s “Guest Commentaries” section provides a platform for industry thought leaders and other readers to share their perspective on radio news, technological trends and more. If you’d like to contribute a commentary, or reply to an already published piece, send a submission to [email protected].

The advent of “Talk FM” stations has caused me to question: Why are they broadcasting or streaming in stereo? Many FM stations “and streamers” have monaural programming. This includes most talk and sports formats (yes, some sports are done in stereo or immersive, but lets not talk about that). The prime goal is to send strong audio programing out with the least interference.  

Many FM broadcasters are sending the programming out on both the left and the right channel, plus lighting the FM pilot. Why? They can send the audio out as mono and not have the penalties of L – R. Reception in the Grade B contour would be improved. Nothing would change RF wise, but you would have a stronger signal. You have half the audio chain to deal with! No phase issues!

Streaming is also an issue. The other day while listening to mono programming, the streamer went to a local ad that was obviously in stereo, but out of phase. Why will a mono stream want the commercials to be in stereo? You do not want the ads sounding more inviting than the programming. The stream will require half the infrastructure.

My friend Robert Orban says: “Streaming mono instead of stereo eliminates the bitstream overhead required to encode stereo. For a given bitrate, mono therefore provides higher subjective quality with fewer audible codec artifacts.”

Controlling the audio is more simple with mono as well.  You have half the controls to deal with.  No phase issues, no balance issues either.

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For over the air broadcasts, there is no benefit to lighting the stereo light anymore. With FM talk becoming more prevalent, a strong signal matters. We are no longer spinning the tuning wheel and stopping when the stereo beacon lights or at the loudest thing on the dial. Guess what, a good clean mono audio signal will sound louder than a stereo signal.

By eliminating the stereo signal which is AM modulation, the pure FM signal will generally be receivable cleanly over about 1/4 more area.  Note — it’s not turning off the pilot that makes the difference, it is getting rid of the stereo difference signal. The 19kHz pilot is just to notify the receiver to look for the difference signal and turn on the stereo decoder inside the radio.

Many of us have used a 19 kHz audio signal generator to turn on the stereo light when we had to pull out a stereo generator for repair. Yes, this turns on the light and sends the same mono audio to both the left and right channels.  This can also introduce noise. Is there still a need for the stereo bacon to be lit? Does the audience even know it is there anymore? Talk radio should not be stereo.  A human only has one desirable audio output — the mouth. True mono will sound great for talk radio and improve your coverage, what better argument do you need.

David Bialik is a consultant; co-chair of the AES Technical Committee for Broadcast and Online Delivery; and chair of the Metadata Usage Working Group at the NRSC. He is former director of stream operations for CBS Radio and Entercom. His commentaries appear regularly at Radio World.