The relationship between capacitors and sound

As we all know, capacitors (C) and inductors (L) form an LC network (NETWORK) on the sound circuit for frequency division. When the output integrated signal of the power amplifier (POWER AMPLIFIER) passes through this LC network, the high and low frequencies will be separated and sent to different speakers (such as TWEETER, MID-RANGE, WOFFER, SUB-WOOFER, etc.) according to the designed frequency division point and sound path.
The LC network is designed by engineers of each factory, ranging from the simplest two-way (2 WAY) high/bass, the common three-way (3 WAY) high/middle/bass, the advanced four-way (4 WAY) high/middle/low/sub-bass or super high/high/middle/bass, to the top five-way (5 WAY) super high/high/middle/low/sub-bass, and even more sound paths.
The circuit of the LC network is also designed by the engineers of each factory. Each audio circuit has from the most basic 1 capacitor and 1 inductor, 2 capacitors and 2 inductors, to several capacitors and several inductors.
Because the phase of the signal goes back 90 degrees when passing through the capacitor (if the capacitor is lossless - in fact, this is impossible), and the phase of the signal goes forward 90 degrees when passing through the inductor, so in order to restore the signal phase to the original phase, usually each audio circuit of the complete crossover circuit must use the same number of capacitors and inductors. (Of course, some people insist on using different numbers as the signal phase difference)
Because all sounds from the power amplifier to the speaker must pass through the LC network (unless it is a simple type), the importance of these two components to the sound cannot be ignored. It is not an exaggeration to say that their importance is the same as that of a single speaker or speaker box.

The relationship between capacitors and sound:

the precise crossover point and capacitors
As mentioned before, the capacitor and inductor form an LC network as a crossover circuit, and its formula is
F (crossover frequency) = 2π√( L x C )
Therefore, the frequency division of the classification point must be accurate, and the capacitance value of the capacitor must also be relatively accurate. Therefore, the error value of the capacitor used in the frequency division circuit is relatively accurate, such as ±20% ±10% ±5% or even ±2% ±1%.


Signal (SIGNAL) and capacitor polarity (POLARITY):
Because the power amplifier outputs signal voltage (also known as alternating current), the capacitor used in the frequency division circuit must be "non-polarized" (NON-POLARIZED)


Signal (SIGNAL) and capacitor withstand voltage (WV):
In order to carry the signal voltage output by the power amplifier, the withstand voltage value of the capacitor used in the frequency division circuit must be higher than the output signal voltage PP (PEAK-PEAK) value designed by the power amplifier, which is generally 30%-40% higher as a safety value (there is no need to require an excessively high withstand voltage value to avoid increasing unnecessary costs) The signal voltage output by most power amplifiers does not exceed 30VAC, so a withstand voltage value of 50V is sufficient. Of course, a withstand voltage value of 100V is safer

** Carrying power The size of (POWER) has no effect on the withstand voltage of the capacitor, but is related to the ripple current (RIPPLE CURRENT) that the capacitor can carry, that is, the loss angle value (DISSPATION FACTOR) ·


Signal power (POWER) and the loss angle of the capacitor:
As mentioned above, the power carrying capacity of the capacitor is related to the loss angle value. The lower the loss angle value, the greater the carrying power, and the higher the loss angle value, the smaller the carrying power ·
What is the loss angle (DISSPATION FACTOR-also referred to as DF)? The angle between the phase angle of the signal passing through the capacitor and -90 degrees is called the loss angle (DISSPATION FACTOR-also referred to as DF) ·The phase angle of the standard capacitor is negative 90 degrees (Loss angle is zero, ESR impedance value is also zero), and the lower the DF value, the lower the ESR impedance value.
For example, the phase angle of the signal through the standard capacitor is negative 90 degrees, so the closer the capacitor phase angle is to -90 degrees, the lower the loss angle value, and therefore the greater the carrying power. If there is a standard capacitor, because its phase is -90 degrees, that is to say, the loss angle value is zero, and the ESR impedance value is also zero, so it can carry infinite power.


Sound quality (TONE) and the loss angle of the capacitor:
The loss angle value is proportional to the grade of the capacitor series internal resistance value (ESR). The lower the loss angle value, the lower the internal resistance value, and the higher the loss angle value, the higher the internal resistance value. Therefore, the quality of sound is inversely proportional to the loss angle value. The lower the loss angle value, the lower the internal resistance value, so the better the sound quality, and the higher the loss angle value, the higher the internal resistance value, so the worse the sound quality.


Frequency response (FREQUENCY RESPONSE) The loss angle of the capacitor:
The same capacitor works at different frequencies, and its loss value and capacitance value are different. Generally speaking, the higher the working frequency, the larger the loss angle value (the smaller the capacitance value). The size of the change rate is proportional to the height of the loss angle value of the capacitance. The lower the loss angle value, the smaller the change rate, and the higher the loss angle value, the greater the change rate. Therefore, the frequency response and the loss angle value of the capacitance are closely related. The capacitor with a lower loss angle value has a smaller change rate of its loss angle value and capacitance value when it works at various frequencies, so the frequency response will be flatter (it can pass a wider frequency), and the opposite is true for a high loss angle value.
** Most of the capacitors for frequency division can specify the maximum allowable loss angle value (for example, 10% 5% 4% 3% 1%...) at a test frequency of 120HZ or 1KHZ. However, in order to make the frequency response flatter and perfect (generally, the high frequency, that is, the treble curve, should not be pulled down), the capacitor can also be required to specify its test frequency at a higher frequency (for example, at 3KHZ 6KHZ 10KHZ or even 20KHZ, preferably the same frequency as the set crossover point) Set the highest allowable loss angle value and rated capacitance value - Regarding this point, professional audio capacitor manufacturers can cooperate to meet this requirement.


Speed ​​of sound transmission (SPEEDY OF TRANSMISION) and the loss angle of the capacitor:
As mentioned above, the loss angle value is proportional to the grade of the capacitor and the series internal resistance value (ESR). Therefore, in addition to the quality of sound and the loss angle value, the sound transmission speed is also closely related to the loss angle value. The lower the loss angle value, the lower the internal resistance value, and therefore the faster the transmission speed. The higher the loss angle value, the worse it is.
From the above, we can understand that the quality of the capacitor and the audio speaker (whether it is for home or car use) have a very important relationship. The capacitor is like the artery of the audio. A good audio crossover circuit must have a good capacitor - that is, the error value of the capacitor must be accurate, the withstand voltage must be sufficient, and the loss angle must be low.

A brief description of the capacitors used in various crossover circuits:
capacitor types and
its highest DF value @1KHZ
general capacity range and
tolerance value
Features
PP plastic film
0.04% ━ 0.10%
0.01μF ~ 47μF
± 1% ~ ± 10%
Lowest loss angle Fastest speed Highest frequency
Clearest sound Highest cost
Applicable to: UHF High frequency High power Top grade

PE plastic film
0.4% ━ 1.00%
0.1μF ~ 100μF
± 1% ~ ± 10%
low loss angle, fast speed, high frequency
bright sound, high cost
applicable to: high frequency, medium and high power, high-end products

low loss NP electrolytic
2% 3% 4%
5% 6% 10%
1μF ~ 300μF
± 2% ~ ± 10%
low loss angle, acceptable speed, medium and high frequency
soft sound, moderate cost
applicable to: medium and high frequency, medium and high power, high-end products

general NP electrolytic
10% 12% 15%
1μF ~ 1000μF
± 10% ~ ± 20%
high loss angle, slow speed, medium and low frequency
fuzzy sound, lowest cost
applicable to: low power, general-grade products