Objective: Learn about speaker design by building one from scrap parts
Goals:
Design a light and compact enclosure
Power Source: rechargeable Li-ion battery
Include both AUX and long range bluetooth connectivity
Clear and loud audio
Offer stereo audio
Include microphone for calls
Enclosure had to use screws for easy disassembly for repair
Clean and minimalistic aesthetic
Low cost
Utilize durable but light enclosure
Used ¼ in MDF
Utilize dual channel and high efficiency IC to deliver clear and loud audio without draining battery
Used Texas Instrument’s LM386 IC
Speaker drivers large enough to offer deep bass while still being compact enough to be portable
Used two 4W, 4 in dia drivers
Include a bluetooth circuit in addition to a direct AUX connection
Used existing bluetooth receiver
Speaker produced a high pitched whine
Implemented a low pass filter to remove very high pitched audio
Battery would drain quickly due to bluetooth receiver drawing current even when idle
Added a secondary switch (in addition to the main power switch) to disconnect power to the bluetooth receiver
Audio from LM386 IC was unclear
Switched to TPA1517
Bluetooth receiver caused loud crackling sound
Used an isolated ground 12V - 5V converter in place of a linear voltage regulator