Steady-state simultaneity test: 60 captures, mask constant at 0.5099, fir constant at 0.5241, actual cut -10.32 dB. Ratio actual/fir = 1.839 ≈ ×1.805 from 23e/24e. Two independent error sources identified: 1. Mask computation: 0.209 vs 0.510 (×2.44, LUT issue) 2. Application: per-bin vs FIR convolution (×1.805, OLA)