Hello guys, the first topic we are going to learn is filters. But before that, let's start by learning something very important for understanding equalization. That is frequency and frequency ranges. Frequency means how fast an object vibrates, this object could be a string and or column, a membrane, etc. If it vibrates really fast, we say it has high frequency and it will have a high pitch. On the other hand, if it vibrating slowly, then it has low frequency and a low pitch.

Frequency is measured in hertz. There's also the kilo hertz, one kilo hertz equals 1000 hertz. With filters on equalizers, we may hear the word octave very often, an octave is the double or half the frequency. For example, let's hear note a three which equals 220 hertz Okay, now the note a4, which is the same note, but it's an octave above it is 440 hertz. And if we go one octave above of that, then we have the note a five, which is 880 hertz. So that's the octave the difference between the same note it's the double or have the frequency.

Now maybe you notice that these three notes sounded with different loudness, right? Let's see why is that humans can only hear sound in certain frequency range. That is between 20 and 20 kilohertz. This is only a theoretical range. But let's keep that it is very important to understand then that we cannot hear all frequencies equally loud. The graphic shows that we need more energy to hear bass and treble sounds and less energy for mid frequencies.

And that changes with volume too. So our ear is not linear at all, which makes something complicated to use equalizers without proper ear training. So if we want to learn how to equalize, then we need to educate our ear to recognize some frequency ranges first. The first one is the very low frequency range. We don't manipulate so much this range, actually, we usually filter this one. Let's hear an example.

Now we're going to hear a fragment of music. And I'm going to emphasize this range with an equalizer. So hopefully you will hear the difference. Maybe this range is going to be a little hard to perceive because it's very low. But let's try it So it's hard to hear, right? Because there's little musical content, just a few bass notes.

For most loudspeakers, we cannot hear this range. It's mainly used only for FX sounds like earthquakes or explosions in movies or music. It doesn't make so much sense. So let's check the next one. The next range is around an octave above. And this is the low frequency range.

We have the bunch of sound it's very important for kick drum or bass. This range is reproduced mainly Buy subwoofers so if you don't have a subwoofer right now, maybe you won't hear a lot, but for many older systems, you may hear some difference. Let's hear it. Probably you've heard some kind of what we call punch. This is very important for for music, and mainly for kick drum and bass. Okay, now the next range is another octave above.

It's called a opera bass range. And this may have what we call a boomy sounds, or MADI, you know, and it is are important for many instruments like trombone, cello, guitar, piano, most instruments work with this range and also the male vocals. Let's hear it. Okay, there are more range left, but we will deal with them in the next lesson.