Smart Soundbar – ESP32, Bluetooth, Nextion Touch Display, LED Underglow (no glue)

A battery-powered stereo soundbar built around an ESP32, a 3.2" Nextion touch display and an I2S DAC. Play music from your phone over Bluetooth, listen to internet radio or the internal microSD card, control it with the rotary knob, three front buttons, a touch screw on the top or the touch screen – and enjoy the LED underglow shining onto the table under the speakers.

The whole enclosure is designed to be printed without supports and assembled only with screws and heat-set inserts – no glue anywhere. Every electronic module sits in its own printed holder, so everything can be taken apart and serviced.

The complete build is fully documented in the included PDFs – no guessing: Assembly Guide (24 pages, picture-only, step by step), Wiring Guide (25 pages, one connection per page with tables and drawings) and Nextion Build Sheet (display project in Nextion Editor). Follow them in this order and you will end up with a working soundbar.

Features

• 2× 4" full-range drivers (Roadstar VO-401) in two separate sealed chambers (~0.9 l each), TPU-sealed joints and fronts

• PCM5102 I2S DAC → PAM8403 amplifier, level dividers for clean sound, automatic bass boost at low volume

• Nextion NX4024K032 3.2" touch display with a custom dark UI (home / player / stations / SD browser / settings)

• Rotary encoder with knob, 3 front buttons, capacitive touch screw (stainless M3) on the top

• 1S2P 6400 mAh Li-ion battery, USB-C charging, main rocker switch, battery level on the display

• BME280 (temperature, humidity, pressure) and BH1750 light sensor (automatic dimming)

• WS2812B underglow in a clear PETG diffuser bar under the case

• microSD card stays inside – music goes in over WiFi

• Android app for control over WiFi – currently in development, will be added later

• Splash-resistant design (louvres, sealed port cover, TPU gaskets) – not waterproof

What's included

• 36 STL files, numbered in print order and named with colour + material:

  • 01–10 black PETG – body (3 parts), fronts (3 parts), speaker grilles, port cover + knob, encoder knob

  • 11–21 orange PETG – holders for ESP32, charger, microSD, PCM5102, PAM8403, BME280, battery, buttons

  • 22–32 TPU 95A – gaskets, cable grommets, feet, button caps, display gasket

  • 33–35 clear PETG – underglow diffuser bars, light-sensor window plug

  • 00 – speaker hole template (print first to check your speakers)

• Assembly Guide (PDF, 24 pages) – picture-only, step by step

• Wiring Guide (PDF, 25 pages) – one connection per page with tables + detail drawings

• Nextion Build Sheet (PDF) + 14 UI images for Nextion Editor

• Test firmware (PlatformIO) – Bluetooth speaker + test of display, inputs and battery

Printing

Printed on a Prusa CORE One (every part fits 250 × 220 mm). Layer height 0.2 mm, no supports for any part.

• 01–03 body – PETG black, back wall on the bed, 4 perimeters, 25 % gyroid

• 04–06 fronts – PETG black, face down, 100 % infill or 6 perimeters (a stiff front = better sound)

• 07–21 – PETG, orientation as in the STL, 3 perimeters, 20–25 % infill

• 22–32 – TPU 95A, textured sheet, Prusament TPU 95A profile (gaskets are 0.2 mm thicker than the gap on purpose)

• 33–35 – PETG Clear / natural, open side down

• Files ending in x2, x3, _x4 → print that many

Hardware (all countersunk hex DIN 7991)

• 46× heat-set insert M3 (CNC Kitchen M3 × 5.7)

• 30× M3×16 (fronts), 10× M3×25 (speakers through the grille + port cover knob), 20× M3×12 (body joints + holders through the back wall), 25× M3×8

• 2× M3×10 stainless A2 (touch screw), 30× M3 nut DIN 934, 20× self-tapping screw 2.2×6 for plastic

• Polyester damping fleece for the chambers

Components (where I bought them)

• ESP32 DevKitC 38-pin (ESP32-WROOM-32D) – 1× – dratek.cz

• Nextion NX4024K032 3.2" Enhanced touch display – 1× – hadex.cz

• PAM8403 2×3 W class-D amplifier module – 1× – hadex.cz

• Speaker Roadstar VO-401 (100 × 50 mm, 4 Ω, 20 W RMS) – 2× – hadex.cz

• GY-PCM5102 I2S DAC – 1× – laskakit.cz

• KY-040 rotary encoder with push button – 1× – laskakit.cz

• BME280 temperature / humidity / pressure sensor – 1× – laskakit.cz

• BH1750 light sensor – 1× – laskakit.cz

• microSD card module – 1× – laskakit.cz

• Tactile switches 12 × 12 mm (set, 3 used) – 1× – laskakit.cz

• Li-ion battery GEB 2×18650 1S2P 3.7 V 6400 mAh (66 × 37 × 20 mm) – 1× – laskakit.cz

• Powerbank charger + 5 V boost module, USB-C + USB-A (25 × 20 mm) – 1× – laskakit.cz

• WS2812B LED strip 144 LED/m, black, 1 m – cut 40 LEDs (≈28 cm) – 1× – laskakit.cz

• Rocker switch for a 13 × 8.4 mm cutout – 1× – any

• Resistor set (10k ×6, 100k ×2, 22k ×2, 4.7k ×2, 330 Ω) – 1× – laskakit.cz

• Ceramic capacitor set (100 nF ×4) – 1× – laskakit.cz

• Electrolytic capacitor set (470 µF 16 V ×2) – 1× – laskakit.cz

• Damping fleece VISATON Damping 20L – 1× – reproobchod.cz

• Heat-set inserts M3 standard (CNC Kitchen), 100 pcs – 46 used – 1× – prusa3d.com

• Silicone wire 0.5 / 0.25 / 0.14 mm², heat-shrink, microSD card (FAT32)

Everything is soldered (no Dupont jumpers). The Wiring Guide shows every connection with ESP32 pin, wire colour and length.

How to build it

Everything you need is in the PDFs – this description is only an overview:

1. ESP32_Soundbar_Assembly_Guide.pdf – printing order, heat-set inserts, joining the body, speakers, holders, front panels, gaskets – every step as a picture with the parts and screws used.

2. ESP32_Soundbar_Wiring_Step_by_Step.pdf – all electrical connections, one per page: which pin goes where, wire type and length, what to check before the next step, plus detail drawings (DAC, audio chain, buttons, battery divider).

3. ESP32_Soundbar_Nextion_Build_Sheet.pdf – how to build the display project in Nextion Editor from the included images and upload it to the display.

Tips

• Print the 00 speaker template first and check that your speakers' holes match.

• Line the speaker chambers with damping fleece (sheets pressed against the walls) and keep the space behind the drivers free. Loose wadding slides onto the cone when the speaker is tilted.

• Insert the microSD card before mounting its holder – it stays inside.

• Seal everything well – every leak in a chamber costs bass.

User manual

Controls

• Rocker switch – I = on, O = power completely off

• Rotary knob – turn = volume, press = play / pause, hold 2 s = sleep

• Three buttons (left to right, seen from the front) – 1 = previous, 2 = play / pause, 3 = next. Radio switches stations, SD card and Bluetooth switch tracks.

• Touch screw on the top – touch to turn the underglow on or off. In the app it can be changed to bass boost or play / pause.

Power on, sleep, power off

1. Power on: switch the rocker to I. The underglow flashes red, green and blue. The speaker continues where it stopped: same source, station or track and volume.

2. Sleep: hold the knob for 2 seconds. Sound, display and lights turn off. Press the knob to wake it up.

3. Auto sleep: after 30 minutes with nothing playing and nobody touching it. The time can be changed in the app.

4. Power off: rocker to O. The knob will not wake it then – switch it back on with the rocker.

Display – the home screen shows the clock, date, temperature, humidity and pressure, what is playing and the battery level in the top right corner.

• Radio – internet radio and player; the list button opens the stations

• SD card – folders and tracks on the card; tap a folder to open it, tap a track to play it

• Bluetooth – speaker for your phone, player with the track name

• Settings – display brightness, underglow on / off and its brightness, network address, firmware version and battery voltage

The player has mute, previous, play / pause, next, list and a volume slider. The arrow in the top left goes back home.

Three sound sources

• Bluetooth – select ESP32 Soundbar on your phone; next time the phone connects by itself. Volume can be changed from the phone too.

• Radio – internet radio, needs WiFi. Switch stations with buttons 1 and 3 or pick one from the list.

• SD card – MP3, AAC and WAV. After a track the next one in the folder plays; after power-on it continues where it stopped.

• Switching between Bluetooth and Radio / SD restarts the speaker (the display shows "Switching to…" for a few seconds). Radio ↔ SD switches instantly. In Bluetooth mode WiFi is off.

What the underglow means

• Red, green, blue – the speaker has just powered on

• Blinking orange – connecting to WiFi or looking for a new firmware version, wait a moment

• Steady red – normal operation; colour, brightness and effect (breathing, rainbow, music, wave) can be changed in the app

• Dimmer – it dims itself in a dark room, and below 20 % battery to save power

• Off – underglow switched off (touch screw, settings) or the speaker is asleep

Battery and charging – charge it with a USB-C cable. The battery level is in the top right corner of the display. Below 10 % "Battery low!" appears; when the battery is empty the speaker goes to sleep by itself.

Automatic adjustments – display and underglow brightness follow the light in the room. At low volume the speaker adds bass so the music does not sound flat.

Firmware updates – do not switch off – in Radio and SD mode the speaker checks for a new version by itself. If there is one, the display shows "Firmware update" and the underglow blinks orange. The download takes about a minute, then it restarts by itself. Do not switch it off during the update.

Messages on the display

• Bluetooth - waiting – waiting for a phone; connect to ESP32 Soundbar on your phone

• Connecting to WiFi... – connecting to WiFi

• WiFi not connected – WiFi is out of range; the speaker tries again in a minute by itself

• WiFi off (Bluetooth mode) – WiFi is off in Bluetooth mode, that is OK

• Buffering... – the radio is loading data, it will start playing in a moment

• Stream not available – the station is not broadcasting right now, try another one

• No stations – the station list is empty, add stations in the app

• No SD card – the card is missing or cannot be read

• Muted – sound is muted; cancel it with the mute button on the player

• Battery low! – the battery is almost empty, connect the charger

Troubleshooting

• The phone cannot find the speaker – select Bluetooth on the display and wait for "Bluetooth - waiting".

• Radio does not connect to WiFi – the network is set directly in the speaker firmware; for a new WiFi the firmware has to be uploaded again.

• No reaction at all – rocker to O, wait a moment and switch it back to I.

Phone control – Android app on the same WiFi, in Radio or SD card mode. The app is still in development and will be published later; everything above works without it, settings that mention the app keep their defaults until then.

Firmware

The full firmware follows the development brief included in the files; the user manual above describes how it behaves. The Android app is in development and will be added to this model when it is ready.

• Source code: github.com/davidvancl/smart-speaker

• Latest firmware release: github.com/davidvancl/smart-speaker/releases/latest

Designed & built by Ing. TULák
More projects & code: github.com/davidvancl

Built one? Share your Make – I'd love to see your soundbar on someone else's desk! Questions or ideas? Ask in the comments.

Thanks for printing – may your bass be deep and your layers clean!