Speaking of Speakers

Over the past three issues of FOH, we have covered many aspects of loudspeaker horn behavior, so a fitting topic to follow this series is a discussion of the behavior of the devices that feed sound from the compression driver diaphragm into the throat of a horn. These devices are typically known as “phase plugs.”

Last month, we introduced some of the principles behind the horn waveguides that are ubiquitous in professional audio. In this follow-up, we’ll discuss the directional nature of horns, building on the prior discussion about how horns operate and how sound waves travel through them.

When FRONT of HOUSE’s intrepid editor George Petersen suggested I write on the topic of loudspeaker horns, I was immediately interested, and a little overwhelmed. Improving horn behavior is a topic of personal interest. Discussing the operation of horns is a huge subject, and the underlying math that describes how horns operate is complex and poorly understood — even by horn designers. Despite these challenges, horns are too interesting a topic to ignore.

Every year brings more processing power to all aspects of live sound. Modern loudspeaker processing routinely employs equalization, delay, crossovers, limiting and other advanced DSP processing techniques, such as FIR filters. DSP can be found in standalone processors, in amplifiers or built into powered speakers.

There is no escaping the sea change in professional audio, arguably initiated by L-Acoustics, towards widespread use of vertical loudspeaker arrays, more commonly named “line arrays.” Whether for large touring productions or the new generation of column loudspeakers installed in conference rooms, vertical arrangement of loudspeaker transducers is now firmly affixed in the industry’s consciousness.

Neodymium (Nd) is one of the chemical elements employed for the high-strength, permanent magnets in high-output/low-weight loudspeakers. Over the past several years, the small, tight-knit pro audio industry has seen volatile neodymium price changes on the global commodities market. And with Nd becoming an important component of modern, high-performance loudspeakers (particularly in flying systems), this price volatility has created uncertainty in end-user pricing of loudspeaker systems.

Other than dead silence, feedback must be the most hated thing in professional audio. Those little blasts, often at higher frequencies where the ear is very sensitive, disrupt the performance and draw attention to the technology behind it. Feedback has been with us since the speaker first met the microphone, and is something every practitioner of the art has had to face. As long as loudspeakers are returning sound information back to presenters and performers, the potential for feedback will remain. In this article we’ll unpack this pesky beast that forcefully inserts itself into monitor wedges and lapel microphones. We dive into how a monitor loudspeaker’s response can change based on the listening location and how these response changes influence monitor wedge performance.

Column loudspeakers have seen a resurgence of use, especially in the installation world. While the basic design dates back to venerable products like the Shure Vocal Master, advances in driver technology put modern column loudspeakers in a very different class from their historic cousins. Broadly, column loudspeakers consist of arrays of many small, closely spaced drivers. These may be full range drivers or multi-way systems. Column loudspeakers are, by nature, tall and narrow. They are usually installed in a vertically-oriented position, such as against the face of a proscenium, or next to a whiteboard.

Managing low frequencies is one of live audio’s constant challenges. We deal with room nodes, architectural resonances, uneven coverage and unwanted spill. Today’s line arrays provide fairly uniform horizontal coverage with adjustable vertical splay. However, an equivalent vertical subwoofer array that provides low-frequency directivity is enormous. The last decade has brought about the ready availability of digital signal processing (DSP) and with the advent of digital consoles, modest DSP is included in every mixer’s outputs, allowing the easy creation of cardioid arrays with everyday means.

In this age of technology convergence, laptops double as DVD players, video-phones, multi-track recorders and audio analyzers, while cell phones have evolved into Internet-capable computers with thousands of applications. Loudspeaker control and monitoring is also converging. The old modular console-graphic-crossover-amp-speaker systems built from components are merging to become simply consoles and loudspeakers, shedding their outboard racks along the way.

Turbosound's new TFS-900H Flashline is the first true four-way line array enclosure of its type, using cone drivers dedicated to reproducing vocal midrange frequencies in keeping with Turbosound design philosophy, working them within a narrower bandwidth to maximize power handling and improve performance over three-way systems.