The difference between low pass, high pass, low cut and high cut:

First of all, if you want to know the difference between the keywords in audio terminology, you must first understand their definitions . The above four audio terms actually refer to the functions of filters and traps in audio equipment. The following is a brief introduction to the definitions of the above four audio predicates:

Low-pass: refers to the function of a low-pass filter.

Low-pass filter: It is a filter that allows low-frequency signals to pass and restricts high-frequency signals to pass. The cut-off frequency of the low-pass filter is the frequency of the 3dB drop point in the frequency response curve (ƒLC ), signals with frequencies higher than LC are attenuated, and signals with frequencies lower than LC are not attenuated.

High pass: refers to the function of high pass filter.

High-pass filter: Contrary to the low-pass filter, it allows signals with frequencies higher than its cut-off frequency hc to pass through and attenuates signals with frequencies lower than its cut-off frequency hc.

Bandpass filter: signals with frequencies higher than its high-end cutoff frequency hc and signals with frequencies lower than its low-end cutoff frequency LC are attenuated, allowing frequencies below Signals whose high-side cutoff frequency is hc and which are higher than its low-side cutoff frequency LC pass through.

Low cut: Literally, all signals below its cutoff frequency LC are cut off rather than filtered or attenuated.

High cut: Literal meaning, that is, all signals above its cutoff frequency hc are cut off instead of filtered or attenuated.

The definitions of the above related predicates come from the professional audio tuning and tuning technology series. From the definitions, you can notice a few words: attenuation/cutting. Attenuation is to attenuate, weaken, reduce, etc. the frequency amplitude of the signal. , but its signal still exists, just with some changes. Excision is to eliminate, remove, and destroy the signal so that the signal no longer exists. The two have completely different meanings, that is to say, low-cut and high-pass are not the same thing, and low-pass and high-cut are not the same thing, just like a filter and a notch are not the same thing.

For example: For example, when recruiting students for a certain major in a sports school, the first requirement is a height of 170CM to 185CM. The one with 169cm was cut low, and the one with 186cm was cut high. These two people didn't even have a chance to participate in the election. Even those that reach 170~185CM are not all passed. They need to be filtered and passed according to the set requirements. Within this limit, if it is higher than 170CM, it is high pass, and if it is lower than 185CM, it is low pass. If it is too high, at least there is a chance.

It is more obvious if you observe it on the audio frequency curve: Anyone who has used an audio processor knows that, such as the common x3x5, it can be connected to a computer and use software to observe the audio curve. When the music curve is played normally, When the computer board uses low-cut 120HZ, you will see that all the curves below 120HZ disappear. When using high-pass 120HZ, the audio curve below 120HZ still exists, but it is filtered by a filter in the circuit and blocked. It's just outside the door but it still exists. When using high-cut 10.5KHZ, the same audio curve above 10.5KHZ disappears. When using the low-pass 10.5KHZ, anything higher than 10.5KHZ is blocked out, but it still exists.

When the audio curve adopts low or high cut, a problem arises, that is, the audio curve becomes not gentle and smooth, but suddenly stops or appears like a cliff. On the sound curve, it is vertical. of. Therefore, this method is used in extreme places. For example, when a male singer uses a microphone, he will turn on the low cut of the microphone to prevent frequencies below 100HZ from entering, such as the sound of enunciation, external low-frequency interference, and his own bass. Defects etc. This removal is cleaner and more effective, because external low-frequency interference, jet sound, and own bass defects have no meaning for the components you want to display. Naturally, there is no need to use attenuation filtering, which is of course for singing. If it is a piece of music, a high-pass method should be used to attenuate and filter unnecessary components, so that there will be no "cliff" on the audio curve and the curve will become smoother. This is the difference between low pass, high pass, low cut, and high cut.

In short, the difference is just two words: attenuation and resection.