The relationship and principle of series and parallel connection of speakers

Speakers can be connected in series or in parallel. They can also be connected in series and then in parallel. The purpose of connecting speakers in series and in parallel is to get the required impedance and power output. Let's talk about the theory first.

First, let’s review the series and parallel connection of resistors in junior high school.

Series connection: R=R1+R2+………Rn.

Parallel connection: 1/R = 1/R1 + 1/R2 + ... 1/Rn

When connecting speakers in series or in parallel, we require that the power and impedance are exactly the same, preferably speakers of the same brand and model. So the above formula is simplified to:

Series: R=NR1
Parallel: R= R1/N

Note: In the above formula, R represents the total impedance, R1 represents the impedance of a single speaker, and N represents the number of speakers.

When connecting speakers in series or in parallel, we usually group them in pairs. So for example, when two speakers are connected in series, the total impedance is equal to the impedance of a single speaker multiplied by 2, and when two speakers are connected in parallel, the total impedance is equal to the impedance of a single speaker divided by the number of speakers.

So what about the power consumption of the speakers?

According to the electric power calculation formula P=U2/R

Let's look at the series connection first. Since the rated power of the speakers will not change, the rated power of the two speakers in series is the rated power of a single speaker multiplied by 2. The power consumption will not increase after the speakers are connected in series, but will decrease instead. This is because the impedance of the two speakers is the same, so they share the voltage output by the amplifier equally, that is:

The power of a single speaker is P1 = (U/2)2/R, which means that each speaker in series consumes only 1/4 of the power before the series connection, and the total power consumed by the two speakers in series is only half of the power consumed by the single speaker not in series. So the sound will become smaller, but this also shows that the speaker group in series has great power potential.

Let’s look at the parallel connection

Because the two speakers are connected in parallel, the voltage acting on the two speakers does not change and is the same, so the power consumed by a single speaker remains unchanged, and the total power consumed is equal to the power of a single speaker multiplied by 2 - this is a test for your amplifier. The most common practice in reality is to connect speakers in parallel.

So what about connecting in series and then in parallel?

The four speakers are connected in series first and then in parallel, and the total rated power is (P1+P1)x2, which can also be understood as the sum of the rated power of the four speakers.

Because the two speakers are connected in series and then in parallel, the voltage on each speaker is still only 1/2 of the original, so the actual power consumption of these four speakers is only 1/4 of their rated power. In order to truly drive the speaker group composed of these 4 speakers connected in series and then in parallel, not only the overall impedance and power of the power amplifier must match the sound group, but the power amplifier also needs to have huge current output.

Theoretically, the rated power of an amplifier is 400W (4Ω), and the rated power of four speakers is 100W (4Ω). These four speakers are connected in series first and then in parallel, and the total impedance is still 4Ω, but their total rated power can reach 400W (4Ω).

From the perspective of impedance matching, connecting speakers in parallel or in series can save the number of amplifiers and money. However, if we return to reality, the above theory may not work. Because live sound reinforcement is not about doing various tests with speakers. It is best to follow the manufacturer's instructions.

Generally speaking, we most often use the parallel connection of speakers. However, it should be noted that although some amplifiers can apparently work under the impedance after parallel connection, they may already be at the end of their strength. We need to understand the current output capacity of the amplifier before using it, otherwise the amplifier and the speaker system may be burned. For example, for an amplifier with an impedance of 8 ohms, the average maximum output voltage of the amplifier is 100V, and the maximum output current is 12A, which is equivalent to an output power of 1200w. If a second speaker system is connected in parallel, the impedance drops to 4 ohms, and the amplifier should provide twice the current (24A). But this is impossible because the current exceeds its limit.

Some amplifiers have a "load matching system", such as LAB.GRUPPEN's MLSTM technology. If it is found that it cannot provide such a strong current, it can be converted from 100V X 12A mode to 80V X 15A or 55V X 22A mode. In this way, it can continue to work.

Speakers are not just connected in series, they are all connected in series and parallel. When there are many speakers, they are connected in series to 16 ohms and then in parallel to 8 ohms, 4 ohms or even 2 ohms. The more speakers there are, the higher the power, and the higher the power of your amplifier. This "principle" connection method can be used for low-power speakers of the same model, but it is not advisable for speakers of high power and different models. In a series circuit, if the impedance of the two speakers deviates (there are no two speakers with exactly the same impedance), the relative power of the one with a larger impedance is greater than that of the one with a slightly smaller impedance. Moreover, if the series connection is connected and then connected in parallel, once a burnout failure occurs in the series-connected unit, or the voice coil is short-circuited, the subsequent speakers may also be implicated and damaged.

Therefore, it can be said that the stability and reliability of the speaker system with speakers in parallel or in series-parallel combination is poor. You must be very careful when debugging, and make fine adjustments bit by bit, and avoid making drastic changes.

Of course, if you encounter a bunch of speakers and amplifiers that do not match them, and you must combine them yourself, you must be cautious and calculate carefully. Before combining, confirm the rated power and impedance of each amplifier; as well as the rated power and impedance of each speaker. Secondly, you must strictly abide by the matching rules of speakers and amplifiers. For example: two 8-ohm, 350W speakers, after parallel connection, the impedance becomes 4 ohms, the total power is 700W, and can be driven by a 4-ohm 1000W amplifier. For example, if there are 8 100W 8-ohm speakers and an 800-watt amplifier per channel (4 ohms), you can use 4 speakers per channel, first in series and then in parallel.

Personally, I think: it is best if the resistance values ​​are the same, and the power of the power amplifier is 1.5 times that of the speaker; if the impedance cannot be equalized, the impedance of the speaker must not be smaller than the impedance of the power amplifier. The impedance of the speaker can be slightly larger than the impedance of the power amplifier, but the difference between the two cannot exceed 4 ohms.

Generally speaking, speakers with built-in frequency division cannot be connected in series. Otherwise, the following may happen: the positive speaker is relatively normal, while the negative speaker has a weaker frequency than the positive speaker. When the volume is turned down, the volume of the positive speaker will feel louder than the negative speaker. Speakers with professional external electronic frequency division can be connected in series. Also, please remember that speakers with different nominal impedances cannot be connected in parallel.

Parallel connection of professional speakers is commonly used in engineering projects, but it requires the same power and preferably the same model. Only 2 8-ohm speakers can be connected in parallel, and 3 12-ohm speakers can be connected in parallel. If the resistance after parallel connection is lower than 4 ohms, the power amplifier will be easily protected, the heat will increase significantly, and the sound quality will be very noisy, because the power amplifier circuit is mostly designed for 4-16 ohm values.

Some imported speakers in the world have 16 ohm mid and high frequencies. This depends on the situation. Generally, manufacturers will provide professional guidance in the manual.

Ohm's law states that the current in a conductor is directly proportional to the voltage across it and inversely proportional to its resistance. This is Ohm's law. Let I represent the current passing through the conductor, U represent the voltage across the conductor, and R represent the resistance of the conductor. Ohm's law can be written as a formula:

I=U/R. Power calculation formula: P=UI; P=U2/R; P=I2R