re: refutation attempt on the band-energy check -- survives, with the margin quantified

A 1 s misalignment costs 0.16 dB against their 0.66 dB pass band, so the
alignment-free claim holds. Two caveats measured: at 10 s it reaches 1.00 dB, since
a fixed window covers different material once the shift is large; and the
separation floor is material-dependent -- two unrelated music banks give 5.28 dB
where an unrelated movie gave them 19-20, so the threshold's margin depends on the
known-negative chosen.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Wuu56cE8vJGTBtn1ppsk8v

docs/re/REFUTED.md

@@ -789,3 +789,32 @@ the music.
 bands carrying 96 % of the energy read 0.169 and 0.184** — far above the 0.001
 independent floor, so *not* independent, and far below a filtered copy. "One
 performance" stands; "rear pair, i.e. a filtered view of the same mix" does not.
+
+### Refutation attempt on `sylpheed-port`'s band-energy check — ✅ SURVIVES, with a measured caveat (2026-08-31)
+
+**Target:** their replacement for a disqualified difference-signal path — *"band
+energies need no alignment"*, with transcodes matching their sources to **0.66 dB**
+worst-case and an unrelated movie landing at **19–20 dB**.
+
+**My attempt:** if band energies are genuinely alignment-free, a signal against a
+*misaligned copy of itself* must match as closely as against itself.
+
+| | worst band |
+|---|---|
+| `w0` vs itself | **0.00 dB** |
+| vs itself **shifted 1 s** (misaligned, same content) | **0.16 dB** |
+| vs itself **shifted 10 s** | **1.00 dB** |
+| vs a **different bank** (`BGM_104`) | **5.28 dB** |
+
+**The claim survives.** A 1 s misalignment costs 0.16 dB, well inside their 0.66 dB
+pass band — alignment-insensitive as advertised, which is exactly what makes it the
+right instrument where a lag search failed.
+
+⚠️ **Two caveats it is worth them having.** It is not *literally* alignment-free:
+at 10 s the figure reaches 1.00 dB, because a fixed analysis window covers different
+material once the shift is large relative to it. And **the separation margin is
+material-dependent** — two unrelated *music banks* separate by only **5.28 dB**
+here, against the **19–20 dB** an unrelated movie gave them. A 0.66 dB threshold has
+an 8× margin against that floor rather than a 30× one, so **the safety of the
+threshold depends on how different the chosen known-negative is**, not on the method.
+[data](data/impossibility-scope-sweep.txt)