1. Adjustment method of equalizer: subwoofer: 2Hz-4Hz, with strong sound when appropriate. Can control thunder, bass drum, organ and bass. Excessive ascension will make the music cloudy. Bass: 4Hz-15Hz, which is the basic part of sound, and its energy accounts for 7% of the whole audio energy, and it is an important component of expressing music style. When appropriate, the bass is relaxed properly, and the sound is full and soft. When it is insufficient, the sound is thin, 15Hz. When it is raised excessively, it will make the sound dull, the brightness will decrease, and the nasal sound will be enhanced. Bass: 15Hz-5Hz, which is the structural part of the sound. The human voice is located in this position. When it is insufficient, the singing sound will be drowned by the music, and the sound will be soft and weak. When it is properly lifted, it will feel powerful and improve the strength and loudness of the sound. Excessive lifting will make the bass stiff, and excessive lifting at 3Hz will be 3-6dB. If reverberation is added, the clarity of sound will be seriously affected. Midrange: 5Hz-2KHz, including the lower harmonics and overtones of most instruments, is the characteristic sound of snare drum and percussion instruments. When appropriate, the sound is clear and bright, and when it is insufficient, the sound is hazy. Excessive lifting will produce a sound similar to a telephone. Tenor: 2KHz-5KHz, which is the characteristic sound of strings (the rubbing sound of the bow and string when pulling strings, and the sound of fingers touching strings when playing music). When it is insufficient, the penetration of sound will decrease, and when it is too strong, it will mask the recognition of language syllables. Treble: 7KHz-8KHz, which is the frequency that affects the sound layering. Excessive promotion will make piccolo and flute sound prominent, the tooth sound of language will be aggravated and the timbre will be hairy. Extremely high sound: When 8KHz-1KHz is suitable, the metal permeability of triangle iron and vertical fork is high, and the rhythm of sand clock is clear and recognizable. Excessive lifting will make the sound unnatural and easily burn high-frequency units. 2. A balanced and pleasant sound should be: below 15Hz (bass) should be plump, soft and elastic; 15Hz-5Hz (mid-bass) should be vigorous and powerful; 5Hz-5KHz (medium and high notes) should be bright and thorough without being stiff; Above 5KHz (treble) should be slender, round and not sharp. When the whole frequency response is flat: the sound is naturally full and elastic, and the level is clear, round and pleasant. When the frequency response is multi-peak-valley, the sound is rough and turbid, the high-pitched sound is harsh and hairy, and the sound reinforcement without layering is prone to feedback howling. 3. Sound sense characteristics of frequency: 3~6Hz is dull, and it is difficult for human ears to feel it without considerable loudness. 6~1Hz heavy around 8Hz can produce a strong "heavy feeling" effect, and high loudness will not give people a comfortable feeling, which can give people a strong stimulus. 1~2Hz fullness 2~5Hz force is easy to cause buzzing boredom. If it is increased by 1dB near 5~1KHz and 8Hz, it will obviously produce a sense of noise and narrowness. 1K~2KHz is transparent, and the brightness is the most important near 28Kz. 2K~4Kz sharp 68Hz forms a shrill and sharp feeling. 4K~8Kz crisp 34Hz is easy to cause hearing fatigue. 8K~16Kz is slender > ＞7.5KHz is clear and slender.