Decided to to downsize quite a bit from my last build. Still staying away from the cooler radios for the time being and building a portable dual 4” bluetooth speaker box. Here are the details.

Sorry if the links are dead after a while, just google the description and you’ll find the part.



TPA3116D2 50Wx2 Official Version Finished Stereo Digital Power Amplifier Board

Battery and Charger

Super Power 12V 6800mAh Rechargeable Li-po Battery for CCTV Cam Safe Package DF

12V to 5V Adapter for Bluetooth Receiver

DC-DC 9V/12V/24V to 5V USB Step Down Power Module 2A Precise Vehicle Charger

USB Powered Bluetooth Receiver

USB Bluetooth Wireless 3.5mm Stereo Audio Music Receiver Adapter Dongle AUX A2DP

Voltage Meter for Charge Indication

Mini DC 2.5-30V LED Display 3-Digital Panel Volt Voltage Meter Voltmeter Black

4” Speakers

Rockford Fosgate R14X2 Prime 4-Inch Full Range Coaxial Speaker - Set of 2


Wood box peices made from 0.5” thick, 6” wide common board (spruce/pine/fur), which can be obtained at HomeDepot for less than $1/ft.

The speaker location with grills and speakers

Most of the other components, exlcuding the amplifier

The handle, switch, and voltage display

Box with cutouts

Pre-wired amplifier, battery, and speakers. Bluetooth module powered from wall outlet, have some noise issues but will figure it out


Final updates…!!

Noise issues: since there is a need for 5V via USB to power the WiFi audio receiver a DCDC step-down converter is necessary. The converter and the amplifier are connected to the same battery power source and the amplifier is connected via an audio cable to the WiFi audio receiver. This can cause unwanted ground loop current through the audio cable = horrific noise from the speakers. Two possible solutions are 1) an isolated DCDC converter or 2) an audio ground loop isolater. Off the shelf isolated DCDC converters are rather costly so I elected to go the audio ground loop isolater route. Both methods use transformers to mitigate DC current in the audio cable. The audio ground loop isolator uses two 1:1 transformers with some filtering/DC blocking capacitors.

Decided to change from the bluetooth receiver to a AirPlay/DNLA WiFi audio receiver to improve audio quality and range. They range from $20-25 for cheap ones but they work very well!

The first few coats of paint are truck bed liner then the final coats will be standard teal latex house paint.


WiFi Audio Reciever AirPlay/DNLA

SABRENT Wi-Fi Audio Receiver for Home Stereo, Portable Speakers (WF-RADU)

Audio Ground Loop Isolator

PAC SNI-1/3.5 3.5-mm Ground Loop Noise Isolator Works with iPod/Zune/iRiver and Others

New 12V to 5V Adapter (easier to mount)

Kimdrox 3A/15W Dual Power Adapter 12V to 5V Double USB Cable Connector Car Charger For IPhone/iPad/Nokia/HTC


WiFi Audio Receiver, uses AirPlay or DNLA, much longer range than bluetooth

DCDC converter, WiFi audio receiver, and ground loop isolator installed

Preliminary wiring

Testing of final wiring before screwing the box together

A peek into hole #1

A peek into hole #2

A peek into hole #2

Box finally screwed together

First coat of truck bed liner for rigidity

Of course I had to move it inside, it was chilly in the garage!

Finally finished off Baby Mr Meeseeks. Put a coat of teal latex paint and then sealed it with 5 coats of polyurethane. I’m fairly satisfied with the final product.

Final product


From left to right, USB port for charging devices, on/off switch, battery volt meter, and battery charging port