Thx for your explanation.That gives then a noise floor of 34 dBa, if that were the true figure. They are just quoting the capsule's specification. They don't add in the preamp noise. In reality the best results they get are a noise floor of 40 dBa. As a conversation in a quiet location is around 65 to 68 dBa and although you would like a 20 dB signal to noise ratio, 10 dB is often enough. That leaves about a 15 dB path length loss to pick up a conversation. So even their claim of 25 feet is a bit of a stretch. The microphones are spaced every 50 to 100 feet apart. That is why I go for 74 dB S/N. They don't even get close to handling the maximum levels without distortion.
The interesting issue is the performance adjustment controls. As soon as they are touched, no two microphones will sound the same. There is no provision for easy calibration. Another problem is the output level switch is not suitable for the actual signal levels. It will become noisy.
Most of the microphones sold for the purpose are just capsules on a cord. No additional electronics. Also not premium capsules.