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Cylindrical Wave Behavior - When and WhereFigure 1Cylindrical waves loose only 3 dB rather than 6 dB per distance doubling, making them very marketable. After all, they cut the expected propagation losses known of point sources in half!

And as a consequence, ever since the advent of modern line arrays—in the early 90s—many subsequent claims about cylindrical waves may have been exaggerated.

So much so that newcomers, at the time of writing, continue to get indoctrinated with a firm belief that line arrays simply work by virtue of cylindrical waves without questioning:

  • when, i.e., for what frequencies, and;
  • where, i.e., up in the air (above the audience), or in the audience plane (across the audience), or both.


This article explores whether or not real‑world line arrays exhibit expected line‑source behavior. And more importantly, when and where in space such behavior is observed. Up in the air (above the audience), or across the audience—in the audience plane—or both (Figure 1)? The distinctions will not be trivial.

In closing, the article will question if referencing "cylindrical waves"—in the context of line arrays—has been hyped for its marketability. And whether or not it is the most concise term for describing a line array's unique behavior across the audience—i.e., in the audience plane—rather than up in the air (above the audience).

The reciprocal relationship between time and frequencyFigure 1What constitutes a group of frequencies and how does that relate to the word "group" in group delay.

Artistic Impression of Time Smearing: Phase & Group DelayFigure 1Many seminar attendees are pretty indiscriminate at first about a loudspeaker's phase response. And tend to be shocked once you point out that typical full‑range loudspeakers (including studio monitors) with decreasing frequency are "smeared out" in time by a couple of dozen milliseconds (Figure 2).

In part 2 of this article series, we will explore how filters — that invariably change level or phase as a function of frequency — can affect crest factor. Towards the end, you can download a MS Excel Workbook for free that contains all relevant calculations and graphics used in this article.

Crest factor is an important metric associated with phenomena such as (but not limited to) headroom, distortion, instantaneous power consumption, and loudspeaker driver excursion.

In part 1 of this 4‑episode series on crest factor, we will begin by defining crest factor first. Towards the end, you can download a MS Excel Workbook for free that contains all relevant calculations and graphics used in this article.

Subsequent episodes will cover crest factor and filters, crest factor and power consumption, and crest factor in the air: measuring sound levels.