Placing sources

Part III is organized by job, and the first job is the daily one: take some mono material — synths, samples, stems, live inputs — and place each piece somewhere deliberate. You already own the mechanics (encode~, azimuth, elevation, summed buses); this chapter is about doing it well, at mix scale, and about the one architectural fork the job hides.

Companion patch: patchers/booklet/04-placing-sources.maxpat.

The bus discipline

A workable spatial mix in Max is one habit applied consistently: one mc. cord is the master scene, every source gets its own ambitap.encode~ N, and everything sums into that cord before the renderer. The companion patch lays out three sources this way — noise, a tone, a click pattern — each with its own azimuth/elevation controls, so the mix reads like a mixer: channel strips into a bus.

Practical notes that save real time:

• Give every encoder the same order. One order-1 encoder summed into an order-3 bus doesn't crash — its 4 channels land on the first 4 of 16 — and the result is even legitimate (a deliberately blurrier source, the nesting property from Chapter 7). But do it by decision, not by typo; a source that refuses to sharpen is the classic symptom.
• Set levels before the encoder (a *~ per source, or the encoder's gain attribute — same thing). The bus is a sum; balance is easiest while each voice is still mono.
• Automate angles like any parameter. The azimuth/elevation setters ramp click-free over a few milliseconds (every AmbiTap parameter does — the library's "click-free contract"), so line, function, LFOs, and live dials are all fair game. For fast circular movement prefer driving azimuth from a phasor (Chapter 3's idiom): it wraps cleanly at ±180° where a naive line ramp would spin the long way round.
• Park a monitor on the bus. An mc.meter~ tells you instantly which source just clipped the scene; Chapter 14 upgrades this to real soundfield instruments.

Elevation earns its keep

New spatializers overuse azimuth (the party trick) and underuse elevation (the depth of field). Two placements that transform dense mixes:

• Tilt the pads up. Ambient beds at +30–45° elevation stop competing with foreground material at ear level. The mix gains a vertical layer cake structure that stereo literally cannot express.
• Keep transients near the horizon. Elevation perception (Chapter 1) is spectral and fragile; percussive, broadband material reads its height cues best, but everything localizes most stably at ear level. The horizon is your focal plane.

The fork: through the bus, or around it?

Now the architectural decision this chapter exists to teach. For headphone delivery, there are two ways to render a placed mono source, and the package ships both:

Through the scene: encode~ 3 → bus → binaural~ 3. The source becomes part of the field, subject to the field's order-3 blur (~75° beam, Chapter 7), rotatable with the world, mixable with everything else. Cost: one convolver bank total, however many sources — the renderer binauralizes the whole bus at once.

Around the scene: ambitap.panbin~ — mono in, azimuth/elevation messages, stereo out. It convolves this one source directly with a per-direction HRTF (the full order-5 resolution of the embedded KEMAR set), skipping the bus entirely. No order-limited blur: this is as sharp as the dataset gets. Direction changes crossfade click-free. Cost: one convolution pair per source, and the result is a stereo signal — it can't be rotated with the scene, vmic~'d, or decoded to a dome; it's already rendered.

The trade in one line: the bus scales, the direct path sharpens.

The companion patch wires the same source both ways behind an A/B switch. Listen at 90° azimuth: through the order-3 bus the source is a presence to your left; through panbin~ it is a point. Then imagine forty of them and check the CPU meter. Both instincts are correct; that's why both objects exist. (Game engines reached the same design decades ago — Chapter 21 — rendering foreground objects directly and carrying the ambience in a bus. You are allowed to mix strategies within one patch: panbin~ the soloist, bus the orchestra, sum the stereo outputs.)

Checkpoint

You can place and automate any number of sources on a disciplined bus, you use elevation as a mixing dimension, and you can argue both sides of bus-versus-direct rendering and pick per source. Placed sources still float in an airless void, though: every source is somewhere, but no source is far away. Distance is its own set of cues, and the next chapter manufactures them.