Arduino. Arduino. Arduino - HomePage. Dayton Audio RS75-4 3" Reference Full-Range Driver 4 Ohm 295-380. HiWave HIAX25C07-8/SP 25mm SoundPAX Exciter 8 Ohms 297-220. Dayton Audio BCT-2 45 x 17mm Bone Conducting Transducer 240-612. Unlike conventional transducers that use moving air to produce sound around you, Dayton Audio BCT-2s (bone conducting transducers) convert the electrical signal into mechanical vibrations so clean, that the brain interprets the vibrating stimulus as excellent sound.
Listener's ears are left free to remain aware of their surroundings, increasing personal safety. When used against materials such as cardboard, wood, steel, and plastics, the BCT-2 operates much like a surface exciter and is capable of moving mass to produce robust sound output; much like an invisible speaker! 2x100W @ 4 Ohm TK2050 Class-D Audio Amplifier Board 320-300. The first 2 options would help a lot.
The 3rd might also help, but probably not as much as the first 2. As I'm guessing you know, the amount of power that this amp can put out is dependent on the power supply's voltage: the higher the voltage, the higher the power output. With your current setup of a 12V power supply and 8 ohm speakers, this amp is only capable of putting out about 9W/channel. This is a very small amount of power, especially in an outdoor environment, so it makes sense you're getting clipping: to get the volume output you need, you always have to be running near its maximum output of 9W, and when those transients hit (from piano chords, etc) you will get sudden, short clipping because the amp simply cannot output a voltage as high as what's demanded from it.