The D3 Pro includes a low-cut filter, in fact, you have two settings. You can roll-off frequencies below 75Hz or frequencies below 150Hz. When the mic is on and you press the low-cut button once you’ll see the 75 LED lights up and now you have a low-cut of 75 Hertz. If you press the button a second time the 150 LED lights up and the low-cut roll-off is now 150Hz. When both low-cut filter status LEDs are off the low-cut filter is disabled. Having two levels of a low-cut filter is a handy feature to have since in some circumstances you may not need to filter out frequencies below 150Hz. Ideally, you don’t want to lose any of the sounds you are recording. But you might want to turn on the low-cut filter if you are recording somewhere that has a lot of low-frequency rumbles. That might be traffic rumble from a nearby street, roadworks, fans, and AC units. The other occasion when you might consider using the low-cut filter is when recording outdoors in light wind. The foam windshield will not stop anything but the lightest of wind blasts but activating the low-cut filter can remove some of that wind noise. However, getting a dead cat for your microphone would be a better option when shooting outdoors. Note that although the 150Hz low cut filter will remove more wind noise than the 75Hz filter, it will cut into the lower range of the human voice. This will be more apparent in male voices since they tend to be lower than female voices.