Carl Blare

Building a radio station requires many choices to be made. The antenna design, the grounding scheme, the audio system, to name several. Let’s look at audio.

Building a radio station requires many choices to be made. The antenna design, the grounding scheme, the audio system, to name several. Let’s look at audio.

The audio network within a radio station is not a simple plug and play sort of thing, it involves complex architectural considerations, i.e., balanced or unbalanced lines, line level matching, mixing, patching, equalizing, signal processing, and stereo/monaural. We will focus on the stereo-mono subject.

CD recordings and many downloaded audiofiles arrive as stereophonic source material, and some audiofiles arrive in mono form. Original studio recordings made by the radio station must be captured one way or the other, at the choice of the recording engineer. Finally, the transmitter will dictate the ultimate product as either stereo or mono.

The leading advocate for stereophonic AM is RFBurns whose KROCKS specializes in AM stereo. At the same time, Carl Blare (me) is sold on mono radio, and that’s where this discussion heats up.

My station, KDX Worldround Radio, is mostly talk, so let’s look at the human voice. The human voice is what? It is a monaural instrument. When I see double-capsule stereo lapel mics pinned onto a performer I already know that the engineering policy is ignorant of the fact that the voice, already mono, will suffer from some phase-cancelation when those two capsules are mixed down to mono. The clearest and most distinct reproduction of a human voice can only be done in mono with a single microphone.

Even music features any number of monaural instruments…. and by instruments I am talking about acoustic “natural” instruments, not electronic “artificial” instruments, which are nothing more than P.A. systems driving loudspeakers and already present in electronic form right into an input plug – no mics needed.

A clarinet is a monaural instrument.
A trumpet is a monaural instrument.
A bass is a monaural instrument.
Each piece in a drum set is a monaural instrument.

What is stereo? Stereo is the acoustic sense of space in between the various instruments in an orchestra and the reverberation of the concert hall. It makes a group performance more natural and quite pleasant, when well recorded. But even the best stereo recording must mix-down clearly to a monaural version for the portable radio listener who is hearing an L+R mixdown (left+right=mono).

An ideal broadcast plant would be capable of perfect mono during spoken voice portions and musical solos, with a fade-over to stereophonic sound for orchestral events or sports crowd ambiance.

But the technology, as I understand it, is presently an either-or proposition – either mono or stereo, not inter-mixable. That limitation applies to online streaming, and AM/FM technology. In FM the sub-carrier generators required for stereo actually detract from the stability of mono reception, especially on the outer fringe area of the station signal.

In webcasting a stereo stream occupies more bandwidth per listener which has its own trade-offs.

The bottom line for KDX is that mono = clear talk quality and robust music quality, with the slight disadvantage that the spacial effect is not present for ensemble music. If we were a music station it would be the other way around.