Those of you that are familiar with the M will know that it has an FG microphone, with a sampling rate of 312.5 kHz. The M2, however, has a SiSonic microphone with sampling rates of 312.5, 384, and 500 kHz. These microphones are discussed further below.
In terms of sensors, the M can record temperatures, whilst the M2 does this and also has sensors for humidity and brightness. Finally, the M2 uses a USB-C to charge and transfer data.
The main features of the M and the M2
The Microphones - FG vs SiSonic
Both the FG and the SiSonic microphones have integrated preamplifiers and are omnidirectional. The FG is an Electret Condenser and has a frequency range of 10-150 kHz, whilst the SiSonic is MEMS with a frequency range of 10-192 kHz.
MEMs (Micro Electro-Mechanical Systems) offer high SNR, low power consumption, and good sensitivity. MEMS uses an acoustic sensor that has a perforated fixed backplate and a moveable membrane that flexes under the pressure of sound waves. As this happens an electrical current is generated.