1. Qtc: The total Q value of the speaker system,
Second, the loss Q value of the cabinet:
Ql-Leakage loss Q value. It is caused by leakage caused by poor sealing of the cabinet and unit. Usually this has a greater impact on the inverter box. The general value is 5-20, which is difficult to predict. 5 means that the seal is very good! Usually the default value is 10.
Qa-Absorption loss Q value, which is produced by the absorption of sound waves by the box, and the filling material in the box will greatly enhance the absorption. The inner wall of a dry, smooth, rigid box is usually about Qa=30-100, and it will reach 3-5 when it is filled in a large amount.
Qp－Inverter tube loss, which is generated by the inverter tube. Due to the friction of the tube wall when air passes through, the inverter tube will have some damping. In fact, if you set this Q value very small (meaning that the damping is very Big), the inverted box will become a closed box, ha ha.
A digression, about the understanding of Q value: (Q value is generally literally translated into quality factor, this name is a bit confusing to rookies...)
The Q value is a mathematical quantity that describes the resonance situation. It is always introduced to everyone with the concept of damping (in a resonance system), or some people equate it with the damping value to introduce it. For a resonant system, the greater the damping, the more the resonance of the system is clamped, resulting in a low-Q resonance curve. When the damping is small, the situation is reversed, the resonance is intense, and a high-Q curve is formed.
Generally speaking, for a speaker system, the appropriate Q value is between 0.5-1.5. When it is lower than 0.5, the damping is too strong, and no resonance occurs at this time. Therefore, some people call the value of 0.5Q as critical damping, and even the smallest Q value is called over-damping. Conversely, if Q is greater than 1.5, it can be called underdamped.
On the frequency-amplitude curve of the resonant system, we can intuitively see the curves represented by different Q values and the meaning of different Q values.
Qes is the electrical Q value of the horn, which reflects the resonance capability of the unit under electromagnetic control during Fo. The lower the value, the stronger the damping and the smaller the system resonance.
Qms is the mechanical Q value of the horn. It reflects the resonance capability of the unit in terms of mechanical structure when Fo, the lower the value, the stronger the damping, and the smaller the system resonance.
Qts is the total Q value of the speaker (coupling Qms and Qes in parallel). It reflects the resonance capability of the unit at Fo. The lower the value, the stronger the damping.
Q value of the system
The whole system refers to the output terminal of the power amplifier, the speaker cable, and the speaker. This is the actual Q value at work. Compared with the box Q value Qtc, the factor of damping coefficient is added here.
The influence of the damping coefficient includes the output damping coefficient of the power amplifier, the damping coefficient of the speaker cable, the damping coefficient of the serially connected speakers (if any), and the damping coefficient of the frequency divider.
Therefore, in order to ensure that the Q value design of the original box is not affected, the general power amplifier requires the damping coefficient to be as small as possible, at least 10 or more, but generally more than 100. The frequency divider is mainly the influence of the resistance of the inductance, which is generally more than 20. The wire should also be as small as possible.
For serially connected speakers, the damping coefficient is inevitably above 1, so the general design is for parallel speakers.
Damping and Q value both describe the working condition of the unit near the resonance point, that is, the change of sound production near the resonance point, and has basically no effect on the frequency response of other frequency regions.
Of course, there is some in-depth study, depending on the specific unit.