All physics in this tool is taken from: M. Moleron & M. Haguet, “Estimating Room SPL with WaveForming”,
Trinnov Audio White Paper, March 2026. SPL: eq. (6), p. 4 · Wavenumbers ky,0/kz,0: eq. (8)-(9), p. 5 · Qtot: eq. (5), p. 4 · Wall impedance: Delany-Bazley model, p. 5.
User input — room dimensions basis for all calculations
These three values are the only quantities the user must provide. Every other number — wall impedances, kx,0, optimal listening position, speaker geometry — is derived from them via the paper formulas after you press Recalculate.
Physics components view-mask, all on by default
Three components of the room's SPL field. Toggle each as an overlay; intensities sum. The full picture (all three on) is what you'd measure in the real room. Each speaker is calibrated to deliver the reference SPL at 1 m in free field — what the spec sheet means.
Bass traps active absorbers
Active bass-trap units placed in room corners. Their absorbing area at each frequency comes from manufacturer-published curves. Higher counts = more modal damping when "Classical room modes" is enabled.
Reference level & system calibration target
Reference SPL is the target level at the listener — the monitoring convention. Pick a calibration system preset to load its standard SPL target (with the verified reference signal and weighting curve), or enter a custom value. Default is K-20 = 83 dB C-weighted per channel @ −20 dBFS pink (Katz 1999) — the de-facto mastering standard.
Subwoofer array Ns → Qtot in eq. (5)
Regular array, flush with the front wall, in-phase — the three assumptions on p. 3 that reduce eq. (1) to the plane-wave eq. (2). Q per sub is computed by back-solving eq. (6) for the reference SPL target above.
Wall treatment d, Rf → Zy, Zz → eq. (8)-(9)
Side walls & ceiling: rigid-backed porous absorber, uniform along the room length. Floor stays rigid (paper p. 4: “the ground is perfectly reflecting”, “the treatment of the left and right walls are identical”, “acoustic treatment applied homogeneously”).
Rear wall paper assumption: Bn = 0
Paper p. 3: “absorbers located at the rear of the room absorb the incident acoustic field, removing any backward reflection.” The COMSOL validation (p. 6, Fig. 1) used a Perfectly Matched Layer there. Use deep porous or membrane traps to approach that.
Listening & analysis x in eq. (6) · 20-100 Hz (paper p. 6)
Paper p. 8 evaluates SPL at 1 m above the floor, midpoint of the room width. The analysis frequency band 20-100 Hz is the validated WaveForming range (p. 6).
If checked, the chair follows the gold ring automatically — the x/y sliders below become readouts. Uncheck to manually position the listener.
★ Three-step optimization snap pipeline
Snap speakers → AVAAs → listener in order. Each step depends on the previous. "Snap All 3" iterates until the listener position converges (≤ 0.10 m).
Main speakers
Speaker specs come from manufacturer manuals (Kii THREE, Genelec 8240A/8250A/8351A/8260A, PSI AVAA reference). The selected model drives the SPL ceiling, the bass-extension feasibility check, and — for the cardioid Kii THREE — a reduced transverse-mode coupling in the pressure field.
Override the spec's recommended wall distance — useful when the desk/console limits how close the speakers can be to the front wall. Blank = use the speaker's manufacturer-recommended value. Snap 1 uses this as the lower bound for speaker x.
Subwoofer (optional, combined with mains)
Add any sub from the manufacturer list to the mains above. The sub contributes its own monopole sources to the SPL field. Use this for a 2.1/2.2 setup (mains plus discrete sub).
Output recommendations
Methodology & equation map
From paper, p. 3-5: starting from the full modal decomposition eq. (1), three assumptions reduce the field to the forward plane-wave eq. (2):
regular sub array excites only n=0 (plane wave)
rear absorbers ⇒ all Bn = 0
subs in-phase, same plane, rigid front wall
The dispersion relation eq. (3) gives kx,0 = √(k² − ky,0² − kz,0²). The transverse wavenumbers come from eq. (8) and eq. (9), solved numerically (Newton's method) per the assumptions on p. 4.
Wall impedance Zy, Zz uses the Delany-Bazley empirical model (paper p. 5) for a rigid-backed porous layer.
Amplitude A0 from eq. (4), total volume velocity Qtot from eq. (5). Final SPL from eq. (6).
Uncertainty (paper p. 10-11): up to +2 dB overestimation from filter RMS variation across subs; up to 2 dB from wall impedance modelling error (Figs. 4-6).
Outside the paper: main speaker placement is conventional ITU-R BS.775 guidance; the paper addresses subwoofer arrays only.
Bibliography & supporting research
The Trinnov paper is the primary source for all SPL physics in this tool (eqs. 1-9, Delany-Bazley impedance). The optimal listening position calculation combines that paper's plane-wave model with three independent research traditions:
Moleron, M. & Haguet, M.(2026) “Estimating Room SPL with WaveForming” — Trinnov Audio White Paper. Primary source. Plane-wave model, eq. (6) for SPL, eqs. (8)-(9) for wall impedance, validated 20-100 Hz against COMSOL with error < 2 dB.
Welti, T. & Devantier, A.(2006) “Low-Frequency Optimization Using Multiple Subwoofers” — J. Audio Eng. Soc., vol. 54, no. 5. Foundational study on multi-sub placement for modal control. Confirms that listening positions in the rear half of the room (≈ 5/8 L from front) give the flattest seat-to-seat low-frequency response with symmetric sub arrays. Used here as one of the x-position candidates.
Cardas, G.(1990s, refined) “Cardas Room Setup” — Cardas Audio. 38 %-of-length rule for listener distance from front wall. Originally derived from modal-stimulation analysis; widely cited in mastering and audiophile practice. Used here as a candidate x-position.
Toole, F. E.(2017) “Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms” — Routledge, 3rd ed. Synthesises decades of perceptual research: listener centered laterally (y=0) is optimal for stereo imaging; ear height 1.10-1.20 m for a seated listener; the “first 30 ms” reflection pattern dominates timbre perception.
ITU-R BS.775-3(2012) “Multichannel stereophonic sound system with and without accompanying picture” — International Telecommunication Union. Main L/R speaker placement: equilateral triangle, ±30° from forward axis, tweeters at ear height. Used here for the purple main-speaker positions.
EBU Tech. 3276(rev. 2004) “Listening conditions for the assessment of sound programme material” — European Broadcasting Union. Listening-room standards for broadcast/mastering: room volume, RT60, geometry ratios, and seat-positioning guidance referenced for the “1.5 m front-wall clearance” constraint.
Delany, M. E. & Bazley, E. N.(1970) “Acoustical properties of fibrous absorbent materials” — Applied Acoustics, vol. 3. The empirical model the Trinnov paper invokes for Zy, Zz. Implemented here directly (Zc, kc coefficients) for the rigid-backed-porous case.
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SPL @ listener eq. (6), calibrated
—dB
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Per-wall absorption coeff Delany-Bazley
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Q per source is back-solved (paper eq. 4 + 6) so the SPL at the listener equals the reference target (e.g. 80 dB). Per the paper's plane-wave model, the field across the rest of the room is nearly uniform — pressure-zone bobbles will read within ~2-4 dB of the reference, with mode-shape pile-up at corners and small x-decay toward the rear.
Mains are full-range; their bass adds in parallel with the WaveForming array.
SPL heatmap @ ear height — blue < target, green = ${'80'}, red > target
★ Best listening position — gold ring + gold-to-wall vectors
Pressure zones — red bobbles at calculated high-SPL peaks