Horn speakers are still widely used in some fairs in rural areas and cities. Once the sound film of horn speakers is lost, it is necessary to ensure the correct installation of the sound film position. The following introduces a method that can easily solve this problem. The installation can be carried out in two steps.
The first step is to select paper of appropriate thickness and cut two loose ~ 10mm paper strips with a length of 20mm larger than the diameter of the center piece. Then put the two pieces of paper perpendicular to each other on the center piece (take the middle position). To prevent them from moving, stick them with a little paste.
Insert both ends of the paper strip into the magnetic gap. Align the voice coil on the voice film with the magnetic gap and press it down gently. Due to the existence of the note, the position of the voice coil is just in the middle of the magnetic gap without deflection. Apply all-purpose adhesive on the edge of the sound film and cover the upper cover of the sound head.
Align the screw hole and tighten the screw. And note the relative position of the upper cover and the sound head at the appropriate position. Place it for 8 hours. After the all-purpose adhesive is completely dry, unscrew the screws and remove the upper cover. At this time, the sound film has been stuck to the upper cover.
The second step is to weld the lead on the terminal. Take down two pieces of paper, then cover the upper cover back, and pay attention to align with the original marks. A multimeter R can be used at this time × Block or 1.5V dry battery, while constantly touching the two terminals to make a "click" sound, tap the upper cover until the "click" sound reaches the maximum and there is no friction sound, you can gradually tighten the fixing screws.
When screwing the screws, the ground shall be tightened in turn, instead of tightening the second screw after one screw is tightened very tightly.
technical parameter
Speaker parameters refer to the specific performance parameter values of speakers tested by a special speaker test system. Its common parameters mainly include: Z, fo, η 0, SPL, QTS, QMS, QES, VAS, MMS, CMS, SD, BL, xmax, gap Gauss. The following are the physical meanings of these parameters.
Z：
It refers to the impedance value of loudspeaker, including rated inductive reactance and DC resistance（ Unit: ohm / Ohm), usually refers to the rated impedance.
Rated impedance Z of loudspeaker: that is, the minimum impedance modulus after the first maximum of impedance curve, that is, the impedance value corresponding to point B in Figure 1.
It is the benchmark for calculating the electric power of loudspeaker.
DC resistance DCR: refers to the impedance value measured by DC signal when the voice coil is stationary. We usually say 4 Ω or 8 Ω refers to the rated impedance（ ACR AC impedance: the resistance value measured under the dynamic condition of voice coil)
Fo (lowest resonance frequency): refers to the frequency corresponding to the first maximum value of speaker impedance curve. Unit: Hertz (Hz) impedance curve of loudspeaker is the curve of loudspeaker impedance modulus measured by constant current method or constant voltage method with frequency under normal working conditions.
η 0 (speaker efficiency): refers to the ratio of speaker output sound power to input electric power.
SPL (sound pressure level): refers to when the horn is connected with the voltage of electric power with rated impedance of 1W. At a point 1m from the horn on the reference axis. Unit: sound pressure generated in decibels (DB).
QTS: total quality factor value of loudspeaker.
QMS: mechanical quality factor value of loudspeaker.
QES: power quality factor value of loudspeaker.
VAS (effective volume of loudspeaker): refers to the volume when the sound flow of air enclosed in rigid container is equal to that of loudspeaker unit.
MMS (vibration mass): refers to the total mass of all parts of the loudspeaker participating in vibration during movement, including paper drum, voice coil and elastic wave. Unit: gram. And the air quality involved in vibration.
CMS (force compliance): refers to the compliance of the supporting parts of the loudspeaker vibration system. The larger the value, the softer the whole vibration system of the speaker. Unit: mm / Newton (mm / N)
SD (vibration area): refers to the effective vibration area of paper drum / diaphragm during the vibration of loudspeaker. Unit: square meter (M2).
BL (magnetic force): the product of gap magnetic induction intensity and effective voice coil line length. Unit: (t * m).
Xmax: linear stroke of voice coil during vibration. Unit: mm.
Gap gaps: gap magnetic induction value. Unit: Tesla.
Fault handling
Open circuit fault: the resistance between the two pins is infinite, which is silent in the circuit, and there is no sound in the speaker.
Paper basin rupture fault: this fault can be found by direct inspection, and the faulty loudspeaker should be replaced.
Poor sound quality fault: This is a soft fault of the loudspeaker. Usually, no obvious fault features can be found, but the sound is not pleasant. The faulty loudspeaker should be replaced.
Under amateur conditions, only audition inspection method and multimeter detection method can be used to detect speakers.
The audition inspection method is to connect the speaker to the output of the power amplifier and subjectively evaluate its quality by listening to the sound.
Using a multimeter to detect the speaker is also rough.
Measure the DC resistance: measure the DC resistance between the two pins of the loudspeaker with gear R * 1, which shall be slightly smaller than the impedance of the nameplate loudspeaker under normal conditions. For example, the resistance measured by an 8 ohm speaker is normally about 7 ohms. If the measured resistance is infinite or much greater than its nominal impedance value, it indicates that the speaker has been damaged.
Listen to rattle: when measuring the DC resistance, disconnect one watch rod intermittently from the pin, and you should be able to hear the rattle of the speaker. The louder the sound, the better. No such sound indicates that the voice coil of the speaker is stuck.
Visual inspection: check whether the loudspeaker has broken paper basin.
Check magnetism: use a screwdriver to test the magnetism of the magnet. The stronger the magnetism, the better.