A nightstand noise generator based on M5Stack Atom Echo and integrating with Home Assistant
enclosure: GRS 3FR-4 speaker fit, L-shaped cable clip
Updated for the actual speaker on the bench (GRS 3FR-4, not the
Adafruit 1314 we initially specced — same 60 mm M3 mounting pattern
but a much deeper magnet). Reference doc renamed and rewritten with
the new specs.
Geometry consequences:
* Speaker posts grow from 22 mm to 44 mm to position the frame plate
with 1 mm of clearance below the magnet (vibration isolation; the
alternative of resting the magnet on the plate would couple bass
into the nightstand surface).
* Chamber inner height grows to 46 mm (44 mm post + 2 mm foam tape
on top of the frame, compressed against the cover underside).
* Speaker frame extent goes from 78 mm to 95 mm (the GRS is wider
across the mounting ears), so the chassis grows to ~107×162×49 mm
assembled.
Cable clip rework:
* Was a closed rectangular tunnel centered on the back wall — over-
engineered (the goal was strain relief, not a zip-tie pass-through)
and conflicted with the centered back snap-fit tab.
* Now an open L-shape (post + cap), positioned ~14 mm from the side
wall to clear the snap tab. The cable drops in from above during
assembly and rests in the L corner — post on the chamber-interior
side, cap extending toward the side wall, cable contained on three
sides with the open side facing the wall.
* Cable notch in the back wall and matching notch in the back edge
of the bottom plate shifted to match the L-clip's X position.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
+139
-129
+57
-53
enclosure/lib/params.scad
+57
-53
enclosure/lib/params.scad
···
15
15
atom_body_h = 16.8;
16
16
atom_corner_r = 3;
17
17
18
-
// USB-C cutout in the Atom's own back face (vertically centered on body).
19
18
atom_usb_w_native = 11.6;
20
19
atom_usb_h_native = 7;
21
20
22
-
// Bottom-face male HY2.0-4P GROVE connector.
23
21
grove_body_w = 8;
24
22
grove_body_d = 4.5;
25
23
grove_body_h = 2.5;
26
24
27
-
// Bottom-face press-fit headers (the "Atom Stack" interface).
28
25
header_pitch = 2.54;
29
26
header_left_pin_count = 5;
30
27
header_right_pin_count = 4;
···
40
37
max_pcb_t = 1.6;
41
38
42
39
// ============================================================
43
-
// Speaker — Adafruit 1314 (3" full-range, 4Ω 3W)
44
-
// See: reference/speakers/adafruit-1314.md
40
+
// Speaker — GRS 3FR-4 (3" full-range, 4Ω, 25W max).
41
+
// See: reference/speakers/grs-3fr-4.md
42
+
//
43
+
// Listed dimensions (Amazon / Parts Express): 3.2" × 3.7" × 2".
44
+
// Treating 3.7" (94 mm) as the largest lateral extent (across the
45
+
// mounting ears), and the magnet hangs ~43 mm below the frame plate
46
+
// based on user measurement. spk_post_h is set to give 1 mm of
47
+
// clearance between magnet bottom and bottom plate.
45
48
// ============================================================
46
49
47
-
spk_frame = 77.8; // square frame outer
48
-
spk_total_d = 25.49; // total depth incl. magnet
49
-
spk_mount_pattern = 60; // square M3 hole pattern (centers)
50
-
spk_mount_hole_d = 3.4; // M3 clearance
51
-
spk_cone_cutout = 67; // baffle opening; estimate, measure & update
52
-
spk_magnet_clearance = 30; // air below baffle for magnet + breathing
50
+
spk_frame = 95; // largest lateral extent (mounting-ear to mounting-ear)
51
+
spk_mount_pattern = 60; // square M3 hole pattern (centers)
52
+
spk_mount_hole_d = 3.4; // M3 clearance
53
+
spk_cone_cutout = 67; // baffle opening (estimate; measure & update)
53
54
54
55
// ============================================================
55
56
// Daughterboard — protoboard the Atom presses onto.
···
58
59
dboard_t = 1.6;
59
60
dboard_w = atom_w + 14;
60
61
dboard_d = atom_d + 14;
61
-
dboard_pin_h = 6; // male pin height above the daughterboard
62
-
dboard_standoff_h = 6; // air below the daughterboard
62
+
dboard_pin_h = 6;
63
+
dboard_standoff_h = 6;
63
64
64
65
// ============================================================
65
66
// Snooze cap + well
···
87
88
grille_diameter = spk_cone_cutout;
88
89
89
90
// ============================================================
91
+
// Speaker mounting posts on the bottom plate.
92
+
//
93
+
// Speaker rests on top of the posts; M3 self-tap screws come down
94
+
// through the speaker's mounting tabs into the post tops. With the
95
+
// speaker thus mounted to the base, the cover above is purely
96
+
// cosmetic — no fasteners pass through it.
97
+
//
98
+
// Post height: 44 mm puts the magnet 1 mm above the bottom plate
99
+
// (verified against the GRS 3FR-4's ~43 mm magnet protrusion). Bump
100
+
// up if you want more vibration isolation; drop to 42 mm if you want
101
+
// the magnet to seat on the plate (not recommended — couples magnet
102
+
// vibration to the plate and onward to the nightstand surface).
103
+
// ============================================================
104
+
105
+
spk_post_h = 44;
106
+
spk_post_d = 6;
107
+
spk_post_pilot_d = 2.5;
108
+
109
+
// Foam tape on top of the speaker frame, compressed against the cover
110
+
// underside when assembled. Adds vibration damping + a light air seal.
111
+
foam_tape_t = 2;
112
+
113
+
// ============================================================
90
114
// Enclosure — overall printed shell
91
115
// ============================================================
92
116
···
107
131
108
132
inner_w = max(dboard_w + 8, spk_frame + 6);
109
133
inner_d = front_margin + snooze_well_d + zone_gap + spk_frame + back_margin;
110
-
inner_h = max(spk_magnet_clearance + 4,
134
+
inner_h = max(spk_post_h + foam_tape_t,
111
135
dboard_standoff_h + dboard_t + dboard_pin_h + atom_body_h + 3);
112
136
113
137
outer_w = inner_w + 2 * wall_t;
···
115
139
outer_h = inner_h + top_t;
116
140
117
141
// ============================================================
118
-
// Speaker mounting posts on the bottom plate.
119
-
// Speaker rests on top of the posts, M3 self-tap screws come down
120
-
// through the speaker's mounting tabs into the post tops. With the
121
-
// speaker thus mounted to the base, the cover panel above is purely
122
-
// cosmetic — no fasteners pass through it.
123
-
//
124
-
// Post height targets the speaker frame plate at ~22 mm above the
125
-
// bottom plate, leaving ~3 mm clearance below the cover for a foam
126
-
// donut between frame and cover underside. Re-tune `spk_post_h` once
127
-
// you've measured the actual cone protrusion / magnet depth on a
128
-
// physical unit.
129
-
// ============================================================
130
-
131
-
spk_post_h = 22;
132
-
spk_post_d = 6;
133
-
spk_post_pilot_d = 2.5;
134
-
135
-
// ============================================================
136
142
// USB-C cable: routed internally, exits through a small notch at the
137
-
// bottom of the back wall. A printed strain-relief tunnel on the
138
-
// bottom plate grips the cable so a tug doesn't transfer to the
139
-
// connector.
143
+
// bottom of the back wall. The exit is offset to ~1/4 of the way
144
+
// across the back so it clears the centered snap-fit tab. An L-shaped
145
+
// clip on the bottom plate at the same X position routes and tensions
146
+
// the cable.
140
147
// ============================================================
141
148
142
-
cable_diameter = 4; // typical USB-C cable jacket OD
149
+
cable_diameter = 4;
150
+
151
+
cable_x_offset = 14; // X position of the cable centerline (close to the side wall)
143
152
144
153
cable_notch_w = cable_diameter + 2;
145
154
cable_notch_h = cable_diameter + 2;
146
155
147
-
cable_clip_inner_w = cable_diameter + 0.4; // snug horizontal fit
148
-
cable_clip_inner_h = cable_diameter + 0.4; // snug vertical fit
149
-
cable_clip_wall_t = 1.5;
150
-
cable_clip_l = 8; // length along cable axis
151
-
cable_clip_y_from_back = 12; // from the back wall inside face
156
+
// L-clip dimensions. Post on one side of the cable, cap above
157
+
// extending laterally over the cable. The cable presses sideways into
158
+
// the open side of the L, and the post + cap + bottom plate contain
159
+
// it on three sides.
160
+
clip_post_w = 2;
161
+
clip_cap_h = 1.5;
162
+
clip_cap_overhang = cable_diameter + 1;
163
+
clip_l = 6; // length along the cable axis
164
+
clip_y_from_back = 14; // distance from the back wall to clip center
152
165
153
166
// ============================================================
154
167
// Snap-fit cover retention.
155
-
//
156
-
// Four tabs rise from the bottom plate's top face, one centered on
157
-
// each side. Each tab carries a small hemispherical bump near its
158
-
// top, which catches in a matching detent recess on the chassis
159
-
// inner wall. Drop the chassis on, hear the snap; pull straight up
160
-
// firmly to remove.
161
168
// ============================================================
162
169
163
170
snap_tab_w = 14;
164
171
snap_tab_t = 2;
165
172
snap_tab_h = 8;
166
-
snap_tab_clearance = 0.3; // gap between tab and chassis inner wall
173
+
snap_tab_clearance = 0.3;
167
174
168
-
snap_bump_d = 2; // hemisphere diameter
169
-
snap_bump_inset_from_top = 1.5; // bump center below tab top
175
+
snap_bump_d = 2;
176
+
snap_bump_inset_from_top = 1.5;
170
177
171
-
// Recess on the chassis inner wall — slightly larger than the bump
172
-
// for a positive click without binding.
173
178
snap_recess_w = snap_tab_w + 2;
174
179
snap_recess_h = snap_bump_d + 1;
175
180
snap_recess_d = snap_bump_d / 2 + 0.4;
176
-
// Vertical center of the recess in chassis coords (chassis open bottom = z=0).
177
181
snap_recess_cz = snap_tab_h - snap_bump_inset_from_top;
178
182
179
183
// ============================================================
+26
-24
enclosure/parts/bottom-plate.scad
+26
-24
enclosure/parts/bottom-plate.scad
···
37
37
translate([0, 0, -bottom_plate_t])
38
38
rounded_prism([outer_w, outer_d, bottom_plate_t], chassis_round_r);
39
39
40
-
// Cable notch in the back edge of the plate, aligning with the
41
-
// chassis cable notch in the back wall — together they form a
42
-
// small rectangular hole flush with the bottom of the unit.
43
-
translate([(outer_w - cable_notch_w) / 2,
40
+
// Cable notch in the back edge of the plate, aligned with
41
+
// the chassis notch — together they form a small rectangular
42
+
// hole flush with the bottom of the unit.
43
+
translate([cable_x_offset - cable_notch_w / 2,
44
44
outer_d - wall_t - EPS,
45
45
-bottom_plate_t - EPS])
46
46
cube([cable_notch_w, wall_t + 2 * EPS, bottom_plate_t + 2 * EPS]);
···
89
89
}
90
90
}
91
91
92
-
// A short rectangular tunnel for the USB cable. The cable threads
93
-
// through it during assembly; pulls on the cable transfer to the
94
-
// tunnel walls (and thus the bottom plate) instead of the connector.
92
+
// L-shaped cable clip: a short vertical post on the chamber-interior
93
+
// side of the cable with a horizontal cap above, extending toward the
94
+
// side wall. Cable rests in the inside corner of the L; cable is
95
+
// dropped in from above during assembly. Position matches the back-
96
+
// wall cable notch (offset horizontally) so the cable runs straight
97
+
// from the clip to the notch.
95
98
module cable_clip() {
96
-
cy_center = outer_d - wall_t - cable_clip_y_from_back;
97
-
outer_w_l = cable_clip_inner_w + 2 * cable_clip_wall_t;
98
-
outer_h_l = cable_clip_inner_h + cable_clip_wall_t; // open at the bottom
99
-
100
-
translate([(outer_w - outer_w_l) / 2,
101
-
cy_center - cable_clip_l / 2,
102
-
0])
103
-
difference() {
104
-
cube([outer_w_l, cable_clip_l, outer_h_l]);
99
+
post_h = cable_diameter + clip_cap_h;
100
+
cap_w = clip_post_w + clip_cap_overhang;
101
+
cap_z = post_h - clip_cap_h;
102
+
// Post sits on the chamber-interior side of the cable; cap extends
103
+
// outward (toward the side wall).
104
+
post_x = cable_x_offset + cable_diameter / 2;
105
+
cap_x = post_x + clip_post_w - cap_w;
106
+
clip_y = outer_d - wall_t - clip_y_from_back;
105
107
106
-
// Hollow the tunnel along the cable axis.
107
-
translate([cable_clip_wall_t,
108
-
-EPS,
109
-
0]) // open at z=0 so the cable can drop in from above
110
-
cube([cable_clip_inner_w,
111
-
cable_clip_l + 2 * EPS,
112
-
cable_clip_inner_h]);
113
-
}
108
+
translate([0, clip_y - clip_l / 2, 0]) {
109
+
// Vertical post (right leg of the L, on the chamber-interior side).
110
+
translate([post_x, 0, 0])
111
+
cube([clip_post_w, clip_l, post_h]);
112
+
// Horizontal cap (top leg, extending toward the side wall).
113
+
translate([cap_x, 0, cap_z])
114
+
cube([cap_w, clip_l, clip_cap_h]);
115
+
}
114
116
}
115
117
116
118
// Four snap-fit tabs centered on each side of the cavity. Each carries
+3
-2
enclosure/parts/chassis.scad
+3
-2
enclosure/parts/chassis.scad
···
37
37
// the speaker; no M3 holes anywhere on the top panel.
38
38
speaker_grille();
39
39
40
-
// Cable notch in the back wall, at the bottom edge. The USB
40
+
// Cable notch in the back wall, at the bottom edge. Offset
41
+
// horizontally to clear the centered snap-fit tab. The USB
41
42
// cable plugs into the Atom internally and exits here.
42
-
translate([(outer_w - cable_notch_w) / 2,
43
+
translate([cable_x_offset - cable_notch_w / 2,
43
44
outer_d - wall_t - EPS,
44
45
0])
45
46
cube([cable_notch_w, wall_t + 2 * EPS, cable_notch_h]);
+2
-2
reference/signal-chain.md
+2
-2
reference/signal-chain.md
···
29
29
│ bridge-tied speaker output (V+ / V−)
30
30
│ no common ground to the speaker
31
31
▼
32
-
Adafruit 1314 (4Ω 3W)
32
+
GRS 3FR-4 (4Ω 25W max)
33
33
```
34
34
35
35
## MAX98357A specs
···
112
112
| ---- | ------ | ----- |
113
113
| M5Stack Atom Echo | owned | |
114
114
| MAX98357A breakout | [Adafruit 3006][adafruit-3006] (~$6) or generic Amazon/AliExpress (~$3) | need 2 total for both units |
115
-
| Adafruit 1314 speaker | owned | |
115
+
| GRS 3FR-4 speaker | owned | see [reference/speakers/grs-3fr-4.md](./speakers/grs-3fr-4.md) |
116
116
| 5V 2A USB wall adapter + USB-C cable | off-the-shelf | UL-listed brick |
117
117
| Dupont wires / hookup wire | stock | |
118
118
-48
reference/speakers/adafruit-1314.md
-48
reference/speakers/adafruit-1314.md
···
1
-
# Adafruit 1314 — 3" speaker, 4Ω 3W
2
-
3
-
Full-range driver, generic Chinese OEM, sold by Adafruit as ["Speaker - 3" Diameter - 4 Ohm 3 Watt"][adafruit-1314]. Chris already has two.
4
-
5
-
## Published specs
6
-
7
-
| Spec | Value |
8
-
| ----------- | ----- |
9
-
| Impedance | 4 Ω |
10
-
| Max power | 3 W |
11
-
| Cone diameter | 3" (76 mm nominal) |
12
-
| Frame (L×W×D) | 77.8 × 77.8 × 25.49 mm |
13
-
| Weight | 50.48 g |
14
-
| Mounting | 4 tabs, 60 mm apart |
15
-
16
-
## Unknown / to measure from physical unit
17
-
18
-
These aren't in the Adafruit listing and the Verical-hosted datasheet was unreachable at the time of this research. We'll measure when we have a unit on the bench:
19
-
20
-
- **Cone cutout diameter** (baffle hole) — estimate ~65–70 mm based on standard 3" driver dimensions
21
-
- **Mounting hole diameter** (what screw fits the tabs) — likely M3 or similar
22
-
- **Magnet diameter and depth** — sets rear clearance needed inside the enclosure
23
-
- **Basket depth above / below the mounting flange**
24
-
- **Frequency response** — not published; irrelevant for white noise but would matter if we wanted music quality
25
-
- **Thiele-Small parameters** (Fs, Qts, Vas) — not published; fine, we're using a sealed box and not tuning
26
-
27
-
## Why this is fine for our use
28
-
29
-
- **Power match**: 3 W handling vs. MAX98357A delivering ~3.2 W into 4 Ω at 5V. Essentially matched; white noise never runs near max anyway.
30
-
- **Impedance match**: MAX98357A is rated for 4Ω loads. Exact match.
31
-
- **Size match**: 78 mm baffle + a few mm per side for the enclosure wall gives a face ~90 mm square. Reasonable nightstand footprint.
32
-
- **White noise doesn't care about bass extension**, so a sealed box with any sensible internal volume (~0.3 L+) will sound fine. Fill with polyfill / pillow stuffing to damp standing waves.
33
-
34
-
## Enclosure design notes
35
-
36
-
- Baffle opening will need to be cut to match the cone cutout (TBD from measurement).
37
-
- Four M3 (assumed) mounting holes in a 60 mm square pattern on the inside of the baffle.
38
-
- Magnet clearance at the rear: leave at least 30 mm behind the mounting flange until we measure.
39
-
- The 25.49 mm total depth means the whole driver (including magnet) fits within ~26 mm of baffle depth.
40
-
- Seal the baffle-to-frame joint (gasket, foam, or printed lip) to avoid air leaks that kill bass coupling.
41
-
42
-
## Sources
43
-
44
-
- [Adafruit product page for 1314][adafruit-1314]
45
-
- [Verical datasheet link (currently unreachable)][verical-1314] — referenced here for future attempts
46
-
47
-
[adafruit-1314]: https://www.adafruit.com/product/1314
48
-
[verical-1314]: https://www.verical.com/datasheet/adafruit-speakers-1314-5770604.pdf
+51
reference/speakers/grs-3fr-4.md
+51
reference/speakers/grs-3fr-4.md
···
1
+
# GRS 3FR-4 — 3" full-range driver, 4 Ω, 25 W max
2
+
3
+
Full-range driver from GRS, sold via Amazon and Parts Express. Chris has two.
4
+
5
+
## Published specs
6
+
7
+
| Spec | Value |
8
+
| ---- | ----- |
9
+
| Impedance | 4 Ω |
10
+
| Max power | 25 W |
11
+
| Frequency response | up to ~20 kHz (no low-end roll-off published) |
12
+
| Cone diameter | 3" (76 mm nominal) |
13
+
| Item dimensions (D × W × H) | 3.2 × 3.7 × 2 in (≈ 81 × 94 × 51 mm) |
14
+
| Mounting | 4 tabs at 60 mm pattern |
15
+
16
+
## Measured / inferred from the unit on the bench
17
+
18
+
These came out of sizing the enclosure to the actual hardware:
19
+
20
+
- **Magnet protrusion below the frame plate**: ≈ 43 mm. The bottom-plate posts in the enclosure are sized 44 mm tall to give 1 mm of magnet-to-plate clearance.
21
+
- **Cone protrusion above the frame plate**: ≈ 8 mm (= total depth 51 − magnet 43, approximately).
22
+
- **Frame outer extent**: ≈ 94 mm at the largest lateral dimension (likely tip-to-tip across the mounting ears). Reflected in `spk_frame = 95` in the enclosure params.
23
+
24
+
## Unknown / to measure when convenient
25
+
26
+
- **Cone cutout diameter** (the baffle hole that needs to clear the moving cone) — estimated at ~67 mm in the params; verify with a caliper and update.
27
+
- **Mounting hole diameter** — assumed M3 clearance. Verify against the actual ears.
28
+
- **Frequency response curve** — not published. Irrelevant for white noise.
29
+
- **Thiele-Small parameters** (Fs, Qts, Vas) — not published. Fine, our enclosure isn't tuned.
30
+
31
+
## Why this driver is fine for our use
32
+
33
+
- **Power match**: 25 W handling vs. MAX98357A delivering ~3.2 W into 4 Ω at 5 V. Massive headroom — the amp is the limit, never the driver.
34
+
- **Impedance match**: MAX98357A is rated for 4 Ω loads. Exact match.
35
+
- **Size**: 3" full-range, ~95 mm frame, sits comfortably on a nightstand. The ~50 mm depth (deeper magnet than a 3 W full-range driver would have) drives a slightly taller enclosure but nothing dramatic.
36
+
- **White noise doesn't care about bass extension**, so a non-sealed printed box stuffed with polyfill (or not) will sound fine.
37
+
38
+
## Enclosure design notes
39
+
40
+
- Baffle opening (grille pattern in the cover) is sized to ~67 mm — tune to the actual cone cutout once measured.
41
+
- Four M3 mounting holes in a 60 mm square pattern. Speaker mounts to four 44 mm tall posts on the bottom plate, M3 self-tap into the post tops; no screws or holes through the cover top panel.
42
+
- Magnet hangs ~43 mm below the frame; with 44 mm posts the magnet bottom sits 1 mm above the bottom plate (vibration isolation; not resting on the plate).
43
+
- Foam tape on top of the frame compresses against the cover underside when the cover snaps on, giving a light air seal + damping any frame-to-cover rattle.
44
+
45
+
## Sources
46
+
47
+
- [GRS 3FR-4 product listing on Amazon][amazon-grs-3fr-4]
48
+
- [GRS speakers on Parts Express][parts-express-grs] — search "3FR-4"
49
+
50
+
[amazon-grs-3fr-4]: https://www.amazon.com/dp/B00K2ESJZ2
51
+
[parts-express-grs]: https://www.parts-express.com/cat/grs-speakers/178