diff --git a/designs/tilting_speaker_wall_bracket/family.json b/designs/tilting_speaker_wall_bracket/family.json
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+++ b/designs/tilting_speaker_wall_bracket/family.json
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+{
+  "family": "tilting_speaker_wall_bracket",
+  "standard": "B-Tech BT77 / BT-series tilt+swivel speaker wall mount",
+  "base_plane": "YZ",
+  "description": "Tilt-adjustable loudspeaker wall mount: a wall plate with a bolt pattern, a standoff arm, a tilt-pivot knuckle, and a speaker-side plate held at a set tilt with fixing holes; optional arm gusset. One connected bracket.",
+  "source": "B-Tech BT77 spec sheet (wall-plate holes, arm reach, tilt); BT1/BT15/BT332 line (reach/tilt ranges); plate/arm proportions",
+  "contributor": "BenchCAD-org"
+}
diff --git a/designs/tilting_speaker_wall_bracket/part.py b/designs/tilting_speaker_wall_bracket/part.py
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+"""tilting_speaker_wall_bracket — the parametric part.
+
+A tilt-adjustable loudspeaker wall mount (B-Tech BT-style): a wall plate that
+bolts to the wall, an arm that stands the speaker off the wall, and a
+speaker-side plate held at a set tilt angle, with fixing holes. An optional
+gusset reinforces the arm/wall joint. Modelled as one connected bracket at a
+fixed tilt position. The wall is the Y-Z plane at x=0; the arm reaches out +X.
+
+Interface + examples: docs/DESIGN_SPEC.md
+"""
+
+import cadquery as cq
+
+
+def build(wall_w, wall_h, plate_t, arm_len, arm_w, tilt_angle, spk_w, spk_h, bolt_d, gusset):
+    # wall plate (against the wall, normal +X), centred at x=0
+    result = cq.Workplane("YZ").box(wall_w, wall_h, plate_t)
+    # wall bolt holes (through the plate along X), a rectangular pattern
+    bx, bz = wall_w * 0.32, wall_h * 0.34
+    holes = cq.Workplane("YZ").pushPoints([(bx, bz), (-bx, bz), (bx, -bz), (-bx, -bz)]).circle(bolt_d / 2.0).extrude(plate_t * 3.0, both=True)
+    result = result.cut(holes)
+
+    # standoff arm reaching out from the wall plate
+    x_arm_start = plate_t / 2.0
+    result = result.union(
+        cq.Workplane("XY").box(arm_len, arm_w, arm_w).translate((x_arm_start + arm_len / 2.0, 0.0, 0.0))
+    )
+
+    # optional gusset: a triangular rib under the arm, wall -> arm
+    if gusset:
+        g = (
+            cq.Workplane("XZ")
+            .polyline([(x_arm_start, -arm_w / 2.0), (x_arm_start + arm_len * 0.6, -arm_w / 2.0),
+                       (x_arm_start, -arm_w / 2.0 - wall_h * 0.28)])
+            .close()
+            .extrude(arm_w * 0.6, both=True)
+        )
+        result = result.union(g)
+
+    # tilt-pivot knuckle at the arm front (a hub on the horizontal Y axis) — the
+    # tilted plate always intersects it, so the bracket stays one connected body
+    x_front = x_arm_start + arm_len
+    hub = cq.Workplane("XZ").circle(arm_w * 0.55).extrude(arm_w).translate((x_front, arm_w / 2.0, 0.0))
+    result = result.union(hub)
+
+    # speaker-side plate, built flat (with its fixing holes) then tilted about the
+    # horizontal (Y) axis to the set tilt angle and set on the pivot
+    spk = cq.Workplane("XY").box(plate_t, spk_w, spk_h)
+    fz = spk_h * 0.3
+    spk = spk.faces(">X").workplane().pushPoints([(0.0, fz), (0.0, -fz)]).hole(bolt_d)
+    spk = spk.rotate((x_front, 0.0, 0.0), (x_front, 1.0, 0.0), tilt_angle).translate((x_front, 0.0, 0.0))
+    result = result.union(spk)
+
+    return result
diff --git a/designs/tilting_speaker_wall_bracket/preview.png b/designs/tilting_speaker_wall_bracket/preview.png
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diff --git a/designs/tilting_speaker_wall_bracket/preview_views.png b/designs/tilting_speaker_wall_bracket/preview_views.png
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diff --git a/designs/tilting_speaker_wall_bracket/spec.py b/designs/tilting_speaker_wall_bracket/spec.py
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+"""tilting_speaker_wall_bracket — the benchmark generator spec.
+
+A tilt-adjustable loudspeaker wall mount (B-Tech BT-series style). PARAM_SPEC
+declares each build() parameter; check() holds the engineering rules a reviewer
+audits. Nothing is coupled, so there is no refine(). Spec: docs/DESIGN_SPEC.md
+
+Sources:
+- B-Tech BT77 (Ultragrip Pro) spec sheet: wall-plate holes Ø6.5/8.5 mm at
+  76/127/145 mm vertical spacing; arm reach 135-280 mm; tilt +-10 deg.
+- BT1/BT15/BT332 line: reach 72-290 mm; tilt +-10 to +-20 deg; loads 5-25 kg.
+- Plate/arm proportions from the BT drawings -> proportion.
+"""
+
+
+# ── 1. PARAM_SPEC ────────────────────────────────────────────────────────────
+PARAM_SPEC = {
+    "wall_w": dict(
+        desc="wall-plate width",
+        unit="mm",
+        range={"easy": (60.0, 75.0), "medium": (50.0, 90.0), "hard": (48.0, 100.0)},
+        source="B-Tech BT77 wall plate ~68 mm wide -> proportion",
+        askable=True,
+    ),
+    "wall_h": dict(
+        desc="wall-plate height",
+        unit="mm",
+        range={"easy": (127.0, 150.0), "medium": (100.0, 180.0), "hard": (76.0, 200.0)},
+        source="B-Tech BT77 wall-plate hole spacing 76/127/145 mm",
+        askable=True,
+    ),
+    "plate_t": dict(
+        desc="plate (wall + speaker) thickness",
+        unit="mm",
+        range={"easy": (3.0, 5.0), "medium": (3.0, 6.0), "hard": (2.5, 7.0)},
+        source="proportion (formed steel bracket plate)",
+        askable=True,
+    ),
+    "arm_len": dict(
+        desc="arm reach (standoff from the wall)",
+        unit="mm",
+        range={"easy": (72.0, 135.0), "medium": (72.0, 200.0), "hard": (72.0, 290.0)},
+        source="B-Tech BT-series reach 72-290 mm",
+        askable=True,
+    ),
+    "arm_w": dict(
+        desc="arm square cross-section size",
+        unit="mm",
+        range={"easy": (20.0, 30.0), "medium": (18.0, 40.0), "hard": (15.0, 45.0)},
+        source="proportion (standoff arm)",
+        askable=True,
+    ),
+    "tilt_angle": dict(
+        desc="speaker-plate tilt from vertical",
+        unit="deg",
+        range={"easy": (0.0, 10.0), "medium": (0.0, 15.0), "hard": (0.0, 20.0)},
+        source="B-Tech tilt +-10 (BT77) to +-20 (BT332)",
+        askable=True,
+    ),
+    "spk_w": dict(
+        desc="speaker-side plate width",
+        unit="mm",
+        range={"easy": (80.0, 110.0), "medium": (60.0, 140.0), "hard": (50.0, 160.0)},
+        source="proportion (speaker-side clamp plate)",
+        askable=True,
+    ),
+    "spk_h": dict(
+        desc="speaker-side plate height",
+        unit="mm",
+        range={"easy": (90.0, 130.0), "medium": (70.0, 160.0), "hard": (60.0, 180.0)},
+        source="proportion (speaker-side clamp plate)",
+        askable=True,
+    ),
+    "bolt_d": dict(
+        desc="wall-bolt / speaker-fixing hole diameter",
+        unit="mm",
+        range={"easy": (6.0, 7.0), "medium": (6.0, 8.5), "hard": (6.0, 8.5)},
+        source="B-Tech BT77 wall holes Ø6.5 / 8.5 mm",
+        askable=True,
+    ),
+    "gusset": dict(
+        desc="triangular gusset reinforcing the arm/wall joint (1) vs none (0)",
+        unit="",
+        range={"easy": (0, 0), "medium": (0, 1), "hard": (0, 1)},
+        source="heavier BT models add an arm gusset",
+        choices={"easy": [0], "medium": [0, 1], "hard": [0, 1]},
+        feature=True,
+    ),
+}
+
+
+# ── 2. check ─────────────────────────────────────────────────────────────────
+def check(p: dict) -> list[str]:
+    """Engineering constraints (empty = valid). Each cites its rule."""
+    bad = []
+
+    # the arm must sit on the wall plate, not overhang it
+    if p["arm_w"] > 0.7 * p["wall_w"]:
+        bad.append("arm_w > 0.7*wall_w: arm wider than the wall plate can carry")
+
+    # the speaker plate must be larger than the arm/pivot it mounts on
+    if p["spk_w"] < p["arm_w"] + 10.0 or p["spk_h"] < p["arm_w"] + 10.0:
+        bad.append("speaker plate smaller than arm+10: plate must cover the pivot knuckle")
+
+    # a slide/plate is a tall standoff, not a stub: reach exceeds the arm section
+    if p["arm_len"] < 1.5 * p["arm_w"]:
+        bad.append("arm_len < 1.5*arm_w: the arm is a standoff, not a stub")
+
+    # bolt holes must fit the plates with edge material
+    if p["bolt_d"] > 0.3 * min(p["wall_w"], p["spk_h"]):
+        bad.append("bolt_d > 0.3*min(wall_w,spk_h): holes leave too little plate material")
+
+    return bad