Deep Decora Electrical Box (Oversized Devices)

A deep, installer-grade double-Decora back box designed for oversized 70V stereo volume controls. Provides 105 mm internal depth, recessed cover support, hidden device mounting, rear mounting holes, and a reinforced top conduit cutout. Includes STL, STEP, and Bambu Studio 3MF with custom supports. Built for real-world AV installs where standard boxes fall short.

This enclosure was created to solve a real installation problem: fitting a large, high-power (200W class) stereo 70V Decora volume control with dual transformers that simply will not fit in standard wall boxes.

The device itself measures roughly 93 mm deep from faceplate to rear terminals, leaving no room for wiring in conventional enclosures. This custom box provides proper depth, cable clearance, and a clean Decora finish while still installing like a standard wall plate.

The device mounts directly to the box using heat-set inserts, then the recessed double-Decora cover installs normally — just like a traditional Decora setup.

Designed for professional AV environments but shared here in case it helps others facing the same challenge.

Internal Dimensions:

Depth: 105 mm

Height: 113 mm

Width: 103 mm

Wall thickness (all sides): 3.5 mm

Rear mounting holes:

Modeled at ¼″ equivalent (metric)

60 mm on-center spacing

Design Features:

Standard double-Decora openings

Recessed inner cover to accommodate thick device faceplates

Hidden internal device mounting for clean exterior appearance

M3 heat-set insert mounting for the device

Cover plate installs afterward using standard Decora screws

Rear molded mounting holes (¼″ equivalent, 60 mm O.C.)

Internal shelves to support the device during installation and alignment

Top Rear Conduit Cutout:

The top rear of the enclosure includes a predefined knock-out area for wide, flat surface-mount conduit (Panduit-style or similar):

Exterior engraving labeled “CUTOUT” for easy field identification

Thin coupon is approximately 1.2 mm thick for clean cutting

Inside perimeter is reinforced with a 2 mm structural brim, so after cutting you still have material to enlarge or fine-tune the opening if needed

This allows clean surface-mount cable entry while maintaining enclosure strength.

Recommended Bambu Studio Settings:

Filament: Bambu PETG-HF (validated with Bambu PETG HF White)

Nozzle: 0.4 mm (0.6 mm optional)

Wall generator: Classic

Walls: 5

Infill: 20% Gyroid

Top layers: 5

Bottom layers: 5

Supports: use included custom supports from 3MF

Heat-set inserts: M3

Custom supports are embedded in the 3MF:

If you change filament in Bambu Studio, simply change both the model filament and support filament to match.

Assembly Steps:

Print box and cover using included 3MF.

Remove supports.

Install M3 heat-set inserts.

Mount volume control directly to the box.

Route and terminate wiring.

Cut top rear conduit opening if needed.

Align device using slotted holes.

Install recessed cover plate with standard Decora screws.

Installs just like a normal Decora assembly — but with proper depth.

Use Case:

Oversized 70V stereo volume controls

High-power Decora devices with rear transformers

Commercial AV installs

Conference rooms, hospitality, retail, distributed audio

Anywhere standard wall boxes are too shallow

Disclaimer & Material Guidance:

This model is provided as-is for personal and professional use.

Always verify fitment with your specific device before installation.

Ensure compliance with all local electrical and building codes.

This is a 3D-printed enclosure and is not UL-listed or certified.

Installer assumes full responsibility for wiring practices, safety, and final application.

Material Notes:

This enclosure was printed and validated using Bambu PETG because it’s practical, affordable, and appropriate for housings like this.

You may print this enclosure using any filament supported by your Bambu printer and Bambu Studio — simply select the corresponding support material to match your chosen filament.

Choose material based on environment, application, and applicable code requirements.

This is not a magic box: improper installation, poor wiring practices, or ignoring electrical codes can create safety hazards. Use common sense.