Introduction

Space is the place.

— Sun Ra

Close your eyes anywhere — a kitchen, a train platform, a forest — and you still know where everything is. The kettle is behind you and to the left. The announcement echoes from above. Somebody's footsteps approach from the right and pass behind your head. You perform this feat constantly, effortlessly, with two ears and no visible antennas, and almost every recording you have ever made throws that entire dimension away and hands your listener a flat pane of glass: left, right, and a line between them.

This book is about getting the dimension back. It is a field guide to spatial audio — the family of techniques for capturing, composing, and delivering sound that has direction and space — written for people who make sound and have never touched any of it. Its center of gravity is Ambisonics: a sixty-year-old idea, born in British hi-fi research and resurrected by VR, that has quietly become the common language of full-sphere audio. If you have seen the word and nodded past it, or been told "just use fourth order, obviously" by someone who didn't explain, this book is for you.

Who this is for

You are comfortable in Max — you can build a patch, you know what dac~ does, mc. cables don't scare you (and if they do, they will stop within a chapter). You own a pair of headphones. That is the whole entry requirement.

You do not need: a loudspeaker array, an ambisonic microphone, a degree involving spherical trigonometry, or any C++. There is real mathematics underneath this field, and the book will always tell you where it lives, but the main text works in pictures, listening experiments, and patches. The formulas appear in clearly marked for the curious sidebars you can skip without losing the thread, and the appendix points to the open-access literature when you want the full derivations.

What a "field guide" means

Spatial audio is a territory, not a technique. It contains at least three competing paradigms (channel-based, object-based, scene-based), a zoo of formats (5.1, 7.1.4, Atmos, AmbiX, FuMa, binaural…), and toolchains that span DAWs, visual programming, game engines, and dedicated hardware. People get lost here not because any one idea is hard but because nobody handed them a map.

So this book behaves like a field guide: it teaches you to identify what you're looking at, and it is opinionated about which tool to reach for in which situation — including the situations where the honest answer is "not Ambisonics." Part V distills that judgment into an explicit decision guide; everything before it earns the distillation.

The playground

You learn a territory by walking it. Our vehicle is AmbiTap, an open-source higher-order-ambisonics library, through its Max package: seventeen ambitap.*~ objects that encode, rotate, decode, binauralize, add distance and rooms, and let you watch a soundfield while you listen to it. Every hands-on chapter is built around a patch you can open and hear in minutes.

The vehicle is not the territory, though. The same objects exist for Pure Data, and Part IV walks the wider world: ambisonic microphones, the Reaper plugin ecosystem (IEM, SPARTA, ATK, Envelop), game engines and XR middleware, and how all of this relates to Dolby Atmos. The concepts you learn in Max transfer whole; only the object names change.

How this book stays honest

Tutorials rot. Prose describes a patch that no longer matches the software; a hand-drawn diagram flatters a decoder that never behaved that way. This book borrows three mechanical commitments from its sibling (the SampleRateTap book) to resist that:

  1. Every hands-on chapter opens a real patch. The companion patches ship inside the AmbiTap-Max package, under patchers/booklet/. The book never describes a patch that doesn't exist in the repository next to the objects it uses.
  2. Every plot of computed data is generated, not drawn. The figures in book/src/img/ are produced by scripts/generate_book_figures.py in the AmbiTap repository, which drives the actual C++ library through its C ABI — the same code path the shipping objects run. The ITD curves in Chapter 1 come from the same embedded KEMAR head your binaural~ object uses. (Purely schematic diagrams — box-and-arrow pictures — are hand-authored SVG and contain no data to lie about.)
  3. Ecosystem claims carry dates. Chapters about plugins, engines, and delivery formats describe a moving landscape; they name versions and say "as of 2026" out loud, so you know exactly what to re-verify later.

The route

  • Part 0 — The flat picture. How your ears actually localize sound, why stereo is a narrow trick, and the three paradigms of spatial audio. No tools yet; this is the map legend.
  • Part I — First sounds. Headphones on: a source orbits your head within fifteen minutes, you rotate the world, and you send a scene to real loudspeakers. Experience before theory.
  • Part II — What's in the bus. What those (order+1)² channels are, why order controls sharpness, and the format paperwork (AmbiX vs FuMa) that makes files from different decades interoperable.
  • Part III — The craft, task by task. Each chapter is a thing you want to do: place sources, add distance, build rooms, decode to speaker arrays, go deep on binaural, monitor a scene you can't see, mix inside it, cancel crosstalk, and fold channel-based beds in.
  • Part IV — The wider world. Pd, microphones, DAWs, game engines, Atmos.
  • Part V — Which tool, when. The decision guide.

What you need

  • Max 9 (the objects need Max's multichannel mc. signals; the optional UI widgets use v8ui). The AmbiTap-Max package, built or downloaded — Chapter 3 covers installation.
  • Headphones. Closed or open, cheap or fancy — but headphones, not laptop speakers, for every binaural experiment.
  • Optional, later: four or more loudspeakers (Chapter 5 onward), Pure Data ≥ 0.54, Reaper (Part IV).

Status of this draft

This is a complete first draft — all parts and appendices are written, the companion patches ship in the packages, and every computed figure regenerates from the library with its claims asserted at build time. What it has not yet had is readers; found something wrong, unclear, or missing, file an issue on the repository like you would for any other bug.