Regardless of amplifier or speaker, the objective parameter that has the greatest impact on sound quality is the amplitude-frequency response, which is usually called frequency response. There are two main requirements for frequency response. One is to have a sufficiently wide frequency range, with low frequencies being lower and high frequencies being higher. Second, the amplitude change in the frequency range should be as small as possible, that is, as uniform as possible. Otherwise, it will directly affect the tone balance of the entire frequency band. In fact, many words of subjective sound quality, such as bright, harsh, and muddy, are all related to frequency response.
As far as the frequency range of the speaker is concerned, the high frequency is now easily above 20kHz, which basically covers the upper limit frequency of the human ear. The difficulty is low frequency playback. For Hi-Fi playback requirements, it should reach the lower limit of human hearing 20Hz, and it should have a sufficiently high sound pressure level.
Otherwise, because the human ear has low hearing sensitivity to low frequency, it is unable to perceive it. Unfortunately, most of the current household Hi-Fi speakers cannot meet the above requirements, and as far as CD records are concerned, for most people, including many audiophiles, they have not yet listened to them in the home. The sound of 20Hz has been reached. If you use ordinary bookshelf speakers, not to mention, I am afraid it is impossible to even listen to 40Hz sound.
The best solution to extend the low frequency on the existing stereo playback system is undoubtedly to add one (of course, you can also use two) subwoofers. Because it has the advantages of the well-known "two-wire" connection, "bi-amp" drive and "pre-stage electronic crossover", it not only expands the low frequency, but also reduces the distortion of the original system and improves its dynamics. .
However, pure audiophiles often don't like this. They believe that the subwoofer is a "home theater" thing, and "Hi-Fi" is a two-way car. This is not the case. We might as well think about it, when you use a DVD to enjoy a concert program, don't you want its sound to be Hi-Fi?
Think about it again, the sound included in the sound of a DVD movie, whether in terms of frequency or intensity range, is far broader than music. The various sounds that human ears can hear in nature and the artificial audio that does not exist in nature are almost all possible and have appeared in DVD. Therefore, as long as your requirements for sound reproduction are the requirements of the Hi-Fi audio system. It can be said that a real home theater system in the sense of Hi-Fi should be able to meet the playback requirements of a Hi-Fi audio system. On the contrary, it may not be necessary to do that.
Some enthusiasts also believe that the Hi-Fi system should not use subwoofers, or even think that large speakers with low playback frequency should not be used in small rooms, otherwise, the overall sound quality will be affected. It should be said that this is based on certain facts. But it should also be noted that this is not entirely the case.
In fact, there are two main reasons why the overall sound quality declines after using the subwoofer. One is the improper sound conditions in the room. For example, the low-frequency standing wave is not effectively suppressed, and the low-frequency reverberation time is too long. The second is the poor quality of the subwoofer itself. Therefore, in order to hear good bass, you must first have a good subwoofer, otherwise it will be "no rice cooking." Then comes the cooperation of the room. Good cooperation will benefit each other. If you don't cooperate well, it can only be counterproductive. So, how can we choose a good subwoofer?
For the purchase of speakers, some enthusiasts believe that performance cannot explain the sound quality, and the performance data is too professional for general readers to grasp. Therefore, the purchase of speakers should be based on listening, and "receive goods by ears." Unless you can't see any data, there is no reason for this statement. It is even more misleading to recommend to general readers.
We believe that there should be no "primary and secondary" between subjective listening* price and objective performance testing, but rather "sequentially". In other words, before purchasing a subwoofer, "look" and then "listen". First collect and understand the price, appearance and performance specifications of similar products, and then select 2-3 "target" products for key audition. This is also the most reasonable procedure for purchasing other audio products, and it has the effect of "doubling the effort with half the effort".
Before deciding to buy a subwoofer, one thing needs to be explained. It is quite difficult to replay a speaker Hi-Fi to 20 Hz and have a sufficient sound pressure level (up and down 100dB). Although the bass of many high-end speakers sounds very satisfying, strictly speaking, they still can't meet the basic requirements of Hi-Fi playback well. In other words, for the Hi-Fi playback of bass, most people still find it difficult to get it right in one step. But this does not mean that we do nothing about it. This is because many speakers we are actually using have the possibility of further expanding the low frequency and reducing distortion to improve the sound quality. Generally speaking, the frequency band to be considered for improvement is 60Hz-100Hz for bookshelf speakers, 40Hz-60Hz for medium-sized floor speakers, and frequency bands below 40Hz for large speakers.
For a subwoofer, we have three requirements for its frequency response. One is that the replay frequency should be as low as possible. Second, the frequency response should be as uniform as possible. Third, the sound pressure level in the audio frequency range should be as high as possible. But it is very difficult to comprehensively meet the requirements of Hi-Fi playback from these three aspects. Even if these requirements are met, the size and price of the speakers are not acceptable to most audiophiles. Therefore, many subwoofer speakers with different performance, form and price grades have appeared on the market to meet various needs of users.
Although, when selecting, you must first choose a subwoofer with a high and uniform output sound pressure level in the low frequency band that you need to expand according to your existing system conditions and actual needs. It is important to note that only speakers with a high and uniform output sound pressure level can achieve lower sound reproduction distortion, which is the key to ensuring the sound quality of the system.