STEREOLABSL-1400
MOD-02MONITOR GEOMETRYPAGE 2 OF 14

Stereo Triangle & Listening Geometry

Optimize monitor spacing, sweet-spot intersection, toe-in axis, side-wall mirror reflections, and front-wall SBIR cancellation.

OSC-1: 440 Hz
BENCH PRESETS:
UNITMeasurement System
SPAN
0.8 mSide Wall Gap: 1.05 m3.9 m
FRONT
0.15 mSBIR Null: 132 Hz2.3 m
TOE-IN
RM-W
2.2 m10 m
RM-L
2.5 m12 m
ARCHITECTURAL TOP-DOWN ACOUSTIC GEOMETRY BLUEPRINT
Listener @ 47% Room Depth (Target: 38%)
38% Zone1st Reflect Panel (1.56m)Span: 2.10 mSWEET SPOT (2.47m from Front)FRONT WALL (4.2 m Wide)REAR WALL (Rear Clearance: 2.73 m)
Sweet Spot Depth
1.82m
2.47m from front wall
SBIR Front Null
132Hz
1/4-Wave Cancellation
1st Reflect Mirror
1.56m
ITD Delay: +7.2 ms
Room Depth Pos
47%depth
Avoid 50% Null Center!
TECHNICAL MANUAL // MOD-02 REFERENCE SHEET

How It Works & Acoustic Engineering Principles

#sweet spot#equilateral#cardas#rule of thirds#sbir#first reflection
GOVERNING ELECTRO-ACOUSTIC EQUATIONSI / IMPERIAL VERIFIED
Y_sweet = (D_span / 2) × tan(60°) | f_SBIR = c / (4 × d_front)
D_spanCenter-to-center acoustic distance between Left and Right tweeters
Y_sweetPerpendicular distance from the speaker plane to the listener’s ears
f_SBIRQuarter-wave Speaker Boundary Interference cancellation null frequency (Hz)
d_frontDistance from speaker baffle woofer center to the rigid wall behind it

Physical Mechanism & Theory

Phantom stereo imaging relies on precise interaural level and arrival-time symmetry. By forming a 60° equilateral triangle between the left monitor, right monitor, and listening position, high-frequency dispersion patterns intersect cleanly at the listener’s head without creating a "hole-in-the-middle" soundstage or overly narrow monophonic presentation.

Simultaneously, low frequencies radiate omnidirectionally (`4π` space) from the speaker cabinet, strike the wall behind the speaker, and reflect forward. When the round-trip path equals half a wavelength (which occurs when speaker-to-wall distance equals 1/4 wavelength), the reflection arrives 180° out of phase, carving a deep 10–18 dB notch known as Speaker Boundary Interference Response (SBIR).

Studio Bench Rules of Thumb

  • 01.The 38% Rule (Wes Lachot): Place the mixing chair at 38% (or 62%) of the room’s front-to-back length to sit between the deepest 1st- and 2nd-order axial nulls.
  • 02.Acoustic Focal Point: Aim tweeter axes slightly behind the listener’s head (about 20–30 cm behind the ears) to widen the usable sweet spot across a mixing console.
  • 03.Tame Side-Wall Early Reflections: Treat the side-wall mirror points so reflections arriving within the first 15 ms (Haas fusion window) are attenuated by at least 10–15 dB.