Obviously bought a good power amplifier and speakers, why the sound quality is still so bad? Are you still worrying about the power amplifier connecting to the speaker debugging? When planning and installing a sound system, you will always encounter questions about the connection between the power amplifier and the speakers. In terms of timbre, after all, the whole set of equipment should be restored to a neutral tone. This is only from an artistic perspective. From a technical perspective, the elements of the power amplifier and speakers are:
In order to meet the needs of high-fidelity listening, the additional power should be determined based on the sound pressure of the better listening. We all have such experience: low volume, weak sound, thinness, lack of dynamics, dullness, significant lack of low frequency, and fullness Poor, the sound can't come out as if shrinking inside; the volume is right, the sound is natural, clear, round, soft and full, powerful, and dynamic; when the volume is too high, the sound is hard, not soft, rough, and has a feeling of rooting in the ears. Therefore, the replay sound pressure level has a greater relationship with the sound quality. The sound pressure level of the regular listening area is better than 80-85dB (A-weighted), which can be the interval from the listening area to the speaker and the characteristic activity of the speaker To calculate the extra power of the speaker and the extra power of the amplifier.
Power reserve matching
In order to enable the speaker to burst with the impact of strong pulses in the program signal without being damaged or distorted, here is an experience worth referring to: the nominal additional power of the selected speaker should be three times the power calculated by theory. Compared with the power amplifier, the required power storage is different. Here, because the overload curve of the tube power amplifier is relatively flat. For the high quality of the overloaded music signal, the tube power amplifier does not have a significant skinning appearance, only the high quality of the peak Rounding; this is what is often referred to as a soft peak. However, after the transistor power is placed at the overload point, nonlinear distortion is added quickly, and severe clipping occurs on the signal. It does not round the peak, but flattens it. From this, Regarding the storage capacity of transistor power amplifiers, the choices are: high-fidelity power amplifiers are 10 times; high-quality power amplifiers are 6-7 times; mid-range power amplifiers are 3-4 times; public broadcasting systems and tube power amplifiers can be much smaller than the above ratio. How much margin should be left for the average sound pressure level and the larger sound pressure level of the system depends on the content of the broadcast and the operating environment. This redundancy is lower than 10dB. For modern pop music, bungee music, etc., you need to leave There is 20-25dB redundancy.
It refers to the additional output impedance of the power amplifier, which should be consistent with the additional impedance of the speaker. At this moment, the power amplifier is in a well-planned load line condition, so it can give greater undistorted power. If the additional impedance of the speaker is greater than the additional output impedance of the power amplifier , The actual output power of the power amplifier will be less than the additional output power. If the additional impedance of the speaker is less than the additional output impedance of the power amplifier, the audio system can work, but the power amplifier has the risk of overload, and the power amplifier needs to have complete overcurrent protection measures to deal with it. In terms of power amplifiers, impedance matching requirements are becoming more stringent.
The matching of damping coefficient (this is the most difficult to understand)
The damping coefficient KD is defined as: KD = additional output impedance of the power amplifier (equal to the additional impedance of the speaker) / internal resistance of the power amplifier output. Since the power amplifier and output internal resistance have become the resistance of the speaker in practice, the KD value determines the sound of the speaker The resistance value. The larger the KD value, the heavier the resistance value. The KD value of the power amplifier is not the larger the better. Too much KD value will make the speaker resistance too heavy, so that the pulse front will be established and the public address system will be increased at all times, and the transient response will be reduced. Goal. Therefore, when choosing a power amplifier, you should not pursue a large KD value one-sidedly. As a home high-fidelity power amplifier, there is an experience value for the damping system for reference; the KD value of the transistor power amplifier is greater than or equal to 40, and the KD value of the tube power amplifier is greater than or equal to 6. The basic conditions for ensuring the steady-state characteristics and excellent transient characteristics of playback, should pay attention to the cooperation of the equivalent mechanical quality factor (Qm) of the speaker and the damping coefficient (KD) of the amplifier. This cooperation requires the speaker's feeder to be used as the sound system. Think of it as a part of the whole. The power loss of the speaker feeder is as small as 0.5dB (about 12%) to achieve this kind of cooperation.