Equalization of Sound Equipment

Ilustrated with 5 Graphics, at the end


Equalization, is an English word which means the Sound Leveling, according to frequencies.


Equalization is essential for sounds being heard well on the Sound Equipments. Most modern sound equipments, include a complicated equalization system by frequencies. But the generalized problem is that most people who have enough money to purchase such sophisticated equipments, do not have enough knowledge as to comprehend about frequencies of equalization. It is for this reason that they equalize wrongly their equipments, and the results are insatisfactory. The voices of some people, are almost not heard, or there are extremely low sounds, or extremely high or screaming. A bad equalization is often a cause of harmy feedback, whether strident screaming, or grave hums, which can be prevented through a good equalization.


The Most Generalized Error, is to set the equalization levers in the shape of a curve with the inverted vertice like this . See Graphic 1: INCORRECT EQ. When using this type of equalization, almost all human voice frequencies are been elliminated, which may range from 100 Hz up to 3 Khz. See curve on Graphic 1. Normal people have a voice range from 260 Hz up to 660 Hz. Abnormal negative and positive people may cover a wide range from 169 Hz up to 1 Khz. A 7 and a half octave piano, covers a range from 32.70 Hz. up to 4.186 Khz. Then, according to curve on Graphic 1, an equalization with an inverted vertice like this , is TOTALLY WRONG, even if it is the most popular among least knowledged people.


Plain Equalización: Some technitians prefer a plain equalization.  This means that that all equalization levers are set in the middle. This method allows reproducing music and conversation such as they are, without any type of selection. This type of equalization is good, but it produces less volume, which sometimes is unsufficient. See Graphic 2: PLAIN EQ.


Correct Equalization: See curve on Graphic 3: RECOMENDED EQ. Taking into consideration what has been mantioned on point one, that normal people hold a voice range from 260 Hz up to 660 Hz, that normal negative and positive people may cover a wide range from 169 Hz up to 1 Khz, and that a 7 and a half octave piano covers a range from 32.70 Hz. up to 4.186 Khz. Then, according to curve on Graphic 3: RECOMENDED EQ, the best way to equalize, is that on which one sets the equalization levers on a reverted curve, that is, with the central vertice uplead on this way . As one can see on Graphic 3: RECOMENDED EQ, in this way it is rasing up volume to the corresponding frequencies of human voice and musical instruments, which are those who should be listened best. So, equalization shown on Graphic 3, is the best for normal use in a public presentation with songs or speaches.


What Is Recommended for Quartets: See Graphic 4: RECOMMENDED FOR QUARTETS. In the case of men's quartets, they sing two intermediate voices, one acute voice and one very low. This situation makes necessary that the two intermediate voices may be heard well, and also the high and low pitch voices. Then, the intermediate frequencies from 300 Hz up to 1 Khz should have a good volume, but the same with the high frequencies between 3 Khz to 6 Khz, and the low frequencies from 60 to 200 Hz. This way, all voices on a quartet will be heard in a well balanced way.


Selective Equalization: In Sound Laboratories it is necessary many times to correct deficcient recordings, in order to improve their quality. The sound technitian can select the good frequencies and eliminate or minimize those which disturb the recording. In some cases, especially on the old recordings, they used to contain a medium level of hum. Hum can be eliminated of minimized putting down the lower frequency levers. A hizz, or "ssss" sound, can be eliminated or minimized putting down the highest frequency levers. There are some noises of scratching, especially on those recordings which were orginally recorded on magnetic tapes or acetate disks. Whenever there are diverse noises, the sound operator can localized the frequencies of the same by putting down and up equalization levers. Once they have been localized, such levers can be set down.  It is very important not to lose useful frequencies, in order not to lessen quality of the recordings or reporduction. In the case of "pops", "cracks" and other purturbant sounds, for recordings, it is better to elliminate them manually using a special program, such as Sound Forge or any other. People's voices vary also one from another, due to a different tone color or voice pitch. The sound operator should grade frequencies according to the voice of the speaker, so that he may be heard with the best sound.


Examples of Wrong Equalization:


1. This author was teaching diverse courses on a South American country. As he was presenting a discourse on Psychology of Music, he was supposed to use some recorded demonstrations on a cassette. He delivered the cassete to the sound operator, who attempted to play it on a very sophisticated sound equipment, and said to him: "The cassette has nothing recorded on". This author replied immediately: "Of course, it is recorded." He didn't tell him that he didn't know how to operate his sophisticated equipment correctly, to avoid offending him, but rather, he asked them to bring a simple cassette player. They did not have a simple cassette player, so they went and bought one. When the sound operator played the cassette on that simple cassette player, without any equalizer, the cassette sounded perfectly. ¿What was the problem? The sophisticated equipment was equalized incorrectly, such as it was demonstrated on Graphic 1 with the curve downwards, this way . Such an equalization was elliminating all audible frequencies of the cassette.


2. A weding was taking place and, before the act, a girl went up to sing a special wedding hymn. But, no body could hear what she was singing, and the sound operator didn't seem to care about the problem. But, this author was uneasy for the situation. When the girl was about one half of the song, without any listening at all, this author couldn't resist the situation any more, and got up to see what was going on. Equalization was thoroughly wrong, such as it was shown on Graphic 1, with the curve downwards,  this way  . It hapened that, on the previous day, a visitor quartet had sung and totally discontrolled the equalization. This author corrected the equalization immediately, setting the levers on the inverted way, like this  and, immediately, the beautiful voice of that singing girl started to be heard nicely.


However, what a difficult task it is to convince sound operators about the right way of equalizing their sound equipments, for they argue that the "incorrect way" is the best "because their ancestors taught them so".


We hope you covert yuourself into a GOOD SOUND OPERATOR. We have here delivered you the best tools.


Dr. Édgar Amílcar Madrid

University Graduate in Music and Techitian on Electronics.



See the 5 corresponding graphics here below.