The Song Meter SM4 and Song Meter SM Mini recorders use the same microphone elements for their audible-range recordings, and in many recording scenarios, they will produce recordings of very similar quality. That said, the more expensive SM4 uses more advanced recording circuitry that gives it an edge above the SM Mini in a few different ways:
The analog-to-digital conversion circuitry in the SM4 maintains a consistent signal-to-noise ratio regardless of sample rate, with 16 effective bits of recording depth. The SM Mini’s effective bit depth is still 16 bits when recording on a single channel at a sample rate of 16 kHz or lower, but at higher sample rates, the effective bit depth is reduced. For example, when recording on two channels at 24 kHz or one channel at 48 kHz, the effective bit depth is reduced to 15. This means that when using higher sample rates or recording on both channels at a time, there will be a slight increase in the background noise level. Depending on the noise level of your environment, this electronic noise may or may not be significant when compared to the surrounding acoustic noise.
The SM4 has a very steep anti-aliasing filter. This filter sharply cuts off any sound that is higher in frequency than the SM4 is able to accurately record based on its selected sample rate. Any frequency up to half of the sample rate is passed with next to no alteration. Any higher frequency that would cause aliasing in the finished recording is almost completely eliminated. In comparison, the Mini’s anti-aliasing filter is less steep and less flat. This means that the recorder’s sensitivity will be reduced between ¼ and ½ of the sample rate as the anti-aliasing filter starts to gradually kick in. Additionally, if there is strong noise present in the environment just above half of the selected sample rate, some of that noise will show up in the final recording as aliasing artifacts. In essence, this means that the Mini recordings will tend to exhibit more background noise towards the top of the recording frequency range when compared to an SM4.
For a typical use case of recording animal vocalizations in order to identify species, these differences may not be significant. However, for applications involving measurement of noise levels or where getting the largest possible signal-to-noise ratio is a concern, the SM4’s advantages are more worth considering despite the higher price.