1. A speech recognition system comprising: a first speech signal preprocessor to receive first input data representing a speech input signal and having first speech input signal preclassifying output data; a second speech signal preprocessor to receive second input data representing the speech input signal and having second speech input signal preclassifying output data; a mixer to receive the first and second speech input signal preclassifying output data and having output data represented by a selected mix of the first and second speech input signal preclassifying output data; a selection control circuit coupled to the mixer to determine the selected mix of the first and second speech input signal preclassifying output data by determining an appropriate balance between speech recognition accuracy of the speech recognition system and a speech recognition processing speed of the speech recognition system; and a speech classifier to receive the selected mix and having output data to classify the speech input signal as recognized speech.