People who play audio often ask: Is this pair of speakers difficult to push? In fact, for speakers with a general efficiency greater than 85db, they should all be able to push, but some speakers are super hard to push. Some of these speakers call them "fading" speakers. Some of these hard-to-push speakers are inefficient and expensive bookshelf. Speakers (known as difficult to push), they have high requirements for amplifiers, not only require a large output power, but also require a large enough output current, and good damping characteristics, otherwise the effect is often not as good as the average speaker, this is everyone Be fully aware. Sometimes in order to control these speakers, the money spent on the amplifier is often several times that of the speaker, so some people simply replace the speaker. But there are also enthusiasts who are obsessed with their unique sounds, and spend more money to find the right amplifier, the most typical is Rogers' LS3/5A. In fact, due to the current technological advancement, there are still many bookshelf speakers with good sounds and good sound.
Reasons why the speaker is not good:
I often hear enthusiasts say: A lot of speakers with excellent sound quality, using a general amplifier, the sound quality is not good. That means the speaker is difficult to drive. The difficulty of driving the horn is inseparable from the trend of the impedance curve, the sensitivity, the phase angle shift, and the strength of the counter electromotive force.
First, the impedance curve
In the description of the speaker specifications, we often see the record of the horn impedance of 8 ohms or 4 ohms. In fact, the number of 8 or 4 ohms is only a rough figure, because there is no impedance curve of any horn, it can maintain the position of 8 ohms from the frequency range of 20Hz to 20KHz of audio, it will The impedance value is changed as the frequency changes. Sometimes it is as high as tens of ohms, and sometimes as low as 1 ohm.
What is the relationship between the change in the impedance curve of the horn and the rear stage of the amplifier? Don't forget that the power output of the rear stage is determined by the load impedance of the horn. If a rear stage claims to have a 100 watt output at 8 ohms, then there may be only 50 watts left at 16 ohms. Under OM, there is only 25 watts of output. Conversely, when it is 4 ohms, the output may be as large as 200 watts, and when it is 2 ohms, it is more likely to be as large as 400 watts. When the horn impedance becomes high, the output of the rear stage is only getting smaller. However, when the horn impedance becomes lower, the output of the rear stage is not as large as it is. When the output of the rear stage becomes larger, the first problem that will be encountered is, can the power supply provide such a large output power? If not, it would not be possible to reach 200 watts at 4 ohms, not to mention 400 watts at 2 ohms. If the power supply has such a large margin and can supply enough power of 400 watts, then another problem must be considered. Can the power transistor withstand such a large voltage or current?
Although the demand voltage of 4 ohm speakers is lower than 8 ohms, the demand current is relatively high. Take 4W output as an example. 8 ohm speakers are 0.7A, while 4 ohm speakers have 1A current, so everyone says, Low-impedance speakers are harder to push. Because the low-impedance speaker "eats" the current, the latter stage forms a large current design. As long as the load current is sufficient, the output power of the amplifier will increase as the impedance of the speaker decreases.
The impedance curve of the horn is one of the important factors that determine whether the speaker can be pushed well. Dynaudio speakers are hard to find, the biggest factor is that its aluminum coil causes the impedance of the speaker unit itself to change too much (from 3 to 30 ohms), so the amplifier itself does not have high voltage, high current output ( This is almost something that is needed for the high-powered monsters.) It is difficult to launch a comprehensive good sound. If you use a megaphone with insufficient power and output current to push it, the most obvious is that the sound becomes thinner, the sense and extension of the low frequency are worse, the sound field is narrowed, and the depth is not available. If the thrust of the amplifier is sufficient, all aspects will have excellent performance.
Second, the sensitivity of the speaker
On the surface, a 90db sensitivity speaker may be better than the 86db sensitivity. The problem is that the sensitivity test tests only the sound pressure that can be emitted by the entire speaker, rather than the sound pressure that can be emitted by each speaker unit. Therefore, when 100 watts of power is simultaneously input to the high, medium, and low-range units of the speaker (assuming the horn is a three-way design), the first crossover will be encountered, and the crossover will eat some power and then leave the remaining The power is delivered to the top of the three speaker units. At this time, the three units will react differently to the input power because of their different efficiency and impedance curves; in other words, the volume of the high, medium, and low-range units will be different. Usually, if we find that there is very little sense of low frequency, we will say that it is difficult to push the speaker. No matter how high its efficiency is in the specification, it is very difficult to push. This kind of difficult-to-push speaker is often accompanied by another problem, that is, the tweeter is very good to push. Under the condition that the woofer is difficult to push and the tweeter is pushed, what can you imagine? That is the bitterness that many people have tasted. The low frequency is not full, but the high frequency is harsh.
The sensitivity is too low and requires enough power to make a good sound, such as the famous LS3 / 5A speaker. Its impedance is as high as 11 ~ 15Ω, and its efficiency is as low as 82db. This high impedance combined with low efficiency is one of the main reasons why LS3 / 5A is difficult to serve. Some people use the big POWER to push it, but the 3/5A can't eat a big POWER. When the power is too high, it is easy to push its bass to the bottom, which makes its KEF woofer not dynamic.
Third, the phase angle shift
The phase angle offset is actually a complex change of the speaker's capacitive reactance, inductive reactance, impedance forward or backward. Since the horn is not only related to the electronic reaction (passive crossover), but also related to the mechanical reaction (cell structure), and more related to the air volume, they will have complex reactions with each other. That is to say, the latter stage is always fighting with complex speaker resistance, impedance, and inductive resistance, which is one of the reasons why the speaker is difficult to push.
Fourth, the counter electromotive force
We can think of the composition of the speaker unit as a generator with coils and magnets. When the current input of the amplifier drives the diaphragm to move the pistons before and after, the speaker unit will generate an induced current, and this current will be returned. In the class amplifier, we call this phenomenon a counter electromotive force. The larger the back electromotive force, the harder it is to push the speaker. The latter stage is more susceptible to back EMF due to its direct coupling to the horn.
Five, the sound circuit is complicated, resulting in high energy consumption
In order to make the high, medium and low sounds detailed, some speakers use a lot of large-capacity capacitors, resistors and inductors on the sound-splitting circuit. Although the overall high, medium and low-pitched sounds are well divided, they are also input. The energy is consumed, so you have to input more power in order to drive it.
The reason why the speaker unit is not pushed well
The diaphragm supporting structure of the speaker unit is relatively soft. Such a unit is easy to generate free vibration which is not controlled by the driving current, and the sound quality is deteriorated, and the performance is that the bass is loud and unsound, difficult to control, and the tailing is serious. A megaphone with a large damping factor should be used. Only in this way can the free vibration of such a loudspeaker be effectively suppressed.
The diaphragm supporting structure of the speaker unit is relatively hard. When driven by a general low-power amplifier, it is felt that the low-frequency of such a speaker is small, and the sound is biased to medium and high-pitched sounds, which is relatively dry and hard. This kind of speaker needs to be driven by a megaphone with a large dynamic and large peak output current, in order to introduce the sense of low frequency and the balance of high, medium and low. We call this kind of horn like to "eat" dynamic current.
Some speakers have more than two conditions, which are more difficult to control. The support structure is soft and the sensitivity is low. It is really not easy to push it.
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