Portable stereo speaker

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1 General

DISCLAIMER: I DO ELECTRONICS AND 3D DESIGN SOLELY AS A HOBBY. THERE -COULD BE ERRORS THAT CAN RESULT IN ALL KINDS OF DAMAGE. USE THESE -DESIGNS AT YOUR OWN RISK. -
This design is released under Creative Commons Zero (CC0) license. -
Author: -
- Svjatoslav Agejenko -
- Homepage: https://svjatoslav.eu -
- Email: svjatoslav@svjatoslav.eu -
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See also: -
- Other physical projects in this repository -
- Other projects hosted at svjatoslav.eu -
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2 Project description

-I had pair of good compact stereo speakers lying uselessly around as -well as secondhand TDA2030 Chinese knockoff audio amplifier chips. -Also I wanted to test modular construction approach: motherboard with -shared bus and functionality realized via pluggable modules. So I -built stereo speaker: -

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-Indicator on the front panel shows available power within the -system. Ideally it should be at the maximum. It drops when batteries -run empty or when consumed power (too loud music) is greater than -onboard power supply or batteries can handle. It has on/off switch and -stereo audio input. Audio input impedance is about 100 ohms. -

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-Idea for the holes on the top and smaller ones on the bottom back is -to enable air flow for passive cooling. -

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-Entire construction is made of parts, no larger than -120x120x120mm. Maximum for my printer. -

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3 Battery holder

-Device is powered by 4 times AA NiMH batteries (1.2V each). -

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-I happened to have AA battery adapters lying around with different -bottom hole configurations. Therefore this weird hole design: -

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-Download: -

FreeCAD file -
STL file -

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-Result: - -

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-Attaches to the back of the body: - mounted%20on%20the%20back.png -

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4 20V up-step module

-Battery pack voltage is routed through main on/off switch on the front -panel, and then it goes to the 20V up-step module. -

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-It uses ready made upstep module, but adds extra voltage filtering via -inductor and capacitors. -

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5 Main board

-Voltage upstep above sits on top of main board (motherboard). It has -uniform central bus that spans all connectors. -

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-First row of the main board is special IO terminal (for connecting -speakers, front panel, etc..) -

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-Remaining rows are for connecting boards: -

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-To provide structural support, main board is attached to frame: -

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-Download: -

FreeCAD file -
STL file -

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-And boards plugged into main board are fixed at the top, using clip: -

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-Download: -

FreeCAD file -
STL file -

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-Result: -

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6 Mono audio amplifier module

-Design uses scavenged secondhand Chinese TDA2030 audio amp -clones. Each chip is mono audio amplifier. Therefore 2 almost -identical audio amp modules had to be built, one for left speaker, one -for right. -

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-I like to build on top of prototype PCBs. Gives results much faster -for one-off projects. Before soldering, I solve component layout on -paper: -

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-Result - front: -

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-Result - back: -

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-Here copper tape is used as improvised heatsink. -

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7 Speakers

-High frequency small speaker and medium frequency bigger speaker are -combined. -

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-Capacitor acts as high-pass filter on top of tiny PCB: -

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-Speaker enclosure: -

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-Download: -

FreeCAD file -
STL file -

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-Speaker enclosure cover: -

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-Download: -

FreeCAD file -
STL file -

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-Result: -

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8 Front panel

-Initial idea was really simple panel: -

on/off switch -
system power indicator -
stereo audio input -

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-But, since I'm using "agile" approach, during load-testing, it become -clear that active fan based cooling would be nice (when playing loud -music). I found tiny cooler fan that needs 5 volts to operate. Also I -need to power backlight for power indicator. For both of these cases, -I decided to add another voltage up-step module (target voltage output -set to 6V). This time directly on the front panel. -

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-Front panel case: -

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-Electronics fits inside: -

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-Front view: -

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-And attaches to the remaining components: -

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9 Extra capacitors

-Another thing that become clear during load-testing: output -power/volume can be further enhanced by adding high power capacitors -to even out load on primary 20V up-step module. -

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-Download: -

FreeCAD project -
STL file -

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-Extra caps are mounted on top of the speaker and electrically attached -to the main board. -

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10 Center box

-Last physical part, to attach it all together: central body. -

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-Front: - -

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-Back: - -

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-Download: -

FreeCAD file -
STL file -

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11 Conclusions / TODO

-These things could be done better: -

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Instead of using undersized heatsinks on the audio amplifiers and -need for active cooling as a consequence, it would be better to try -to mount audio amplifier chip on top of speaker metallic body. It -would provide plenty of cooling and reduces power losses within -cable, since amplifier would be as close to the speaker as possible. -
I used agile design. That is, implemented functionality ad-hoc. If I -had done design in advance, then I could have had smarter connector -layout between main board and front panel. That is: Instead of -multiple smaller cables, one wide (multi connector) cable. -
Screw holes are too close to the edges on the front panel. -
It would be better if screw heads were slightly buried within -construction body. -

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-Overall, it was good learning experience and I was able to test -various ideas on it. Will add cooler later :) -

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-Photo of initial PSU + audio amp test: -

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