Passive Audio Monitor

A 3D printable handheld enclosure for a battery-powered audio recorder that stores recordings locally on an SD card — no cloud, no WiFi, no accounts.

Designed for a high-quality MEMS microphone, long battery life, and simple physical controls, this enclosure supports a compact, privacy-focused voice recorder suitable for meetings, lectures, or personal voice notes.

👉 Full build (parts, wiring, firmware, and assembly):
https://modo.is/b/audio-recorder

Description

This model is a portable enclosure for a passive audio recording device built around a MEMS microphone and local SD card storage. The design prioritizes privacy, battery life, and simplicity, avoiding any cloud or streaming features.

Key features supported by the enclosure:

• Handheld form factor

• Internal mounting for MCU, microphone, SD card, and power circuitry

• USB-C charging port cutout

• Power switch opening for true offline operation

• Status LED visibility

• Space for a high-capacity 18650 battery

The enclosure is intended for local-only recording, with timestamped audio files saved directly to removable storage.

The full project includes:

• Validated bill of materials (real components)

• Wiring diagrams

• Firmware scaffolding

• Step-by-step assembly instructions

Those resources are maintained on the linked build page.

Printing Notes

• Material: PETG or ABS recommended

• Layer height: 0.2mm

• Infill: 15–20%

• Supports: Not required

• Orientation: Print main body flat

PLA can be used for prototyping, but PETG or ABS is recommended for durability in a handheld device.

Assembly Notes

This Printables listing contains only the enclosure STL files.

For the complete build — including parts list, wiring, firmware, and assembly steps — see the full build page:

https://modo.is/b/audio-recorder

Files Included

• Main enclosure body

• Rear or battery cover (if applicable)

Tags

audio
recorder
privacy
sd-card
electronics
portable
handheld
enclosure