There's also high and low pass filters so you can use it for speakers or subs. (geekwrapped.com)
For more flexibility, you can even control the variable low pass filter to let as many or as little of low sounds through as you want. (geekwrapped.com)
The process of thermal diffusion puts many stages of low pass filtering on the temperature signal (i.e. time resolution gets worse with increasing time in the past). (judithcurry.com)