Bill WhitlockBill WhitlockDisturbance signals, such as hum, buzz, or noise, can be extremely frustrating. And troubleshooting them is oftentimes a time‑intensive process of trial and error. Until I learned of Bill Whitlock and his education[1] on Audio System Grounding and Interfacing.

Whitlock recommends relatively simple means to — methodologically — identify causes for disturbance signals. And while his teachings have always appealed to me, I never got to the point of actually building some of the tools myself. Until recently.

Why do certain channels on a mixing console featuring transient signals (like drums) run hotter than other channels (e.g., strings) even though they all sound equally loud? Let us look at duty cycles.

Redistributing The ErrorSome audio professionals find power alleys, which are associated with left‑right subwoofer deployments, objectionable. This is somewhat ironic considering that modern full‑range loudspeakers also go down to 63 Hz (and lower). And their — bottom octaves — are subject to the same artifacts when deployed left and right. Despite this, left‑right mains are still the standard in typical PA systems and continue to be widely accepted.

Double standards set aside. If one insists on minimizing power alleys while sticking to left‑right subwoofer deployment, using — low‑directional — systems per side, one can consider using signal post‑processing to minimize the interference patterns (spoiler alert: processing will come at a cost). But first, let us address the elephant in the room.

The potential merits of using analyzers, for calibrating and voicing sound systems as well as loudspeakers, include (but not limited to):

  • validation
  • actionable data
  • reconciliation with the—subjective—listening‑experience (eye‑to‑ear training1)

This article focuses on the importance of—actionable data—capable of providing guidance on chores such as aligning pass‑bands, i.e., crossovers, like a "full‑range" loudspeaker and a subwoofer. And whether to use time‑ or frequency‑domain information, or both.

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.