If the speaker of your Echo Dot 3rd Generation sounds muffled or is distorted in any way, the speaker may need to be replaced. Follow this
Echo Dot 3rd Generation Speaker Replacement - iFixit Repair
Echo Dot 3 Mic/LEDs/Button Replacement - iFixit Repair Guide
Echo Dot 3rd Gen Disassembly - iFixit Repair Guide
Echo Dot 3rd Gen Disassembly - iFixit Repair Guide
Echo Show 10 3rd Gen Woofer Replacement - iFixit Repair Guide
Over 100 Million Alexa-Enabled Devices Have Been Sold
Seeing inside: What's 's fourth-generation echo dot got? - EDN
Echo Dot Speaker Replacement
Echo Dot 5th Generation Speaker Replacement - iFixit Repair
Echo Dot (3rd Gen) - Speaker Disassembly
Echo Dot 3rd Generation Speaker Replacement - iFixit Repair
The second-gen HomePod may be easier to repair than the first
Echo Dot 2nd Generation Speaker Replacement - iFixit Repair