HiFi headphone speakers/acoustics top ten common misunderstandings

The recording studio is the anechoic room"
This is a very common misunderstanding, especially for some people in the recording industry who think that the rooms with certain acoustic treatment such as recording studios/mixing rooms they usually use are anechoic rooms. But in fact, although the common recording studio has acoustic treatment, it only partially absorbs and diffuses the reflected sound, or just treats some reflected sound that is not conducive to the working position, especially the part of the early reflected sound that may cause sound staining.

However, in a real anechoic room, sound-absorbing materials are placed anywhere in the room, and any reflected sound is minimized to simulate the free field (if it is a semi-anechoic room, there are sound-absorbing materials on 5 sides). Moreover, the actual sound absorption coefficient and effect of the sound-absorbing materials used in the anechoic room, such as the common wedge, are also different from those used in the recording studio or listening room. And even in a fully anechoic room, there is a low-frequency cut-off frequency.
 
Therefore, there is still a certain amount of reflected sound in common recording studios, and there is also a certain amount of late reflection sound that is reverberation. Therefore, there is no playback type similar to the reflection of the speaker system in the playback process of headphones, and even the restoration of reverberation is incomplete.
 
 "People have two ears, so the stereo is more HiFi"
This is basically a false statement that can be seen everywhere.

Humans have two ears, so only one person can sing in a band + a total of two sound sources for an instrument to listen to? People have two eyes, so two screens are needed to watch TV? Only two people can play in the game? Humans have ten fingers, so the phone should have ten buttons?

This is actually something irrelevant.

In fact, if you want to play back a band consisting of 1 singer + 4 instruments, it is better to use 5 speakers, each speaker is placed at the position and height of the corresponding instrument and musician, and 5 sound sources can be simulated to get Better sound field effect.

In addition, the high-quality multi-channel system has the real sound image brought by the center channel, and the sky channel effectively restores the sound source and reflected sound in the three-dimensional space. Although the stereo sound system can achieve the sound image close to the real sound image through recording and speaker positioning, the sound image drift, sound image positioning change, and sound image focus caused by the dynamic factors of the human head are the congenital defects of the stereo speaker system. In other words, it is difficult to make up. The center speaker can effectively and better restore the human voice and image, with accurate positioning and no drift in sound.

As for the sky channel, the restoration of the three-dimensional sound field of medium and large buildings such as concert halls and theaters can be achieved through algorithms or pre-mixing. Compared with a stereo system, it is a dimensionality reduction blow.

As for the timbre, if other conditions are determined, as long as the speakers of the multi-channel system and the stereo are the same, the timbre is roughly the same. Many enthusiasts think that the sound quality of a home theater system in a multi-channel system is not as good as HiFi. In many cases, it is because two sets of HiFi speaker systems at the same price are compared with a home theater system. In layman's terms, if you compare 20,000 pairs of HiFi speakers with a set of 70 to 100,000 sets of multi-channel speakers, there will be no idea that the sound quality of a multi-channel system is not HiFi.

To put it more vividly, if you bought a Jie Shi home theater for 50,000 yuan, you may feel that the sound quality is not as good as the JBL 4367 that you also bought for more than 50,000 yuan. But if you use 7 4367s to make a set of 7 in 7.2.4 of the home theater (not considering other factors such as power amplifier sound source), then you will not feel that the sound quality of these 7 4367s is not as good as your original two 4367s, because they They are all exactly the same 4367. . .

"Subwoofer is not HiFi"
When many people think of subwoofers, they think of "moving times hitting times" and "earth hey". Indeed, there are many subwoofers on the market that give a sense of volume and sound quality. There are also some subwoofers designed specifically for home theaters that focus on high rated power, rather than the performance of heavy bass distortion and sensitivity. But there are subwoofers that can be used for HiFi/monitoring. They often have a certain degree of sensitivity, lower distortion, and performances such as transient dynamics and other HiFi speakers with lower dive. It is a very one-sided view to simply think that as long as there is a system with a subwoofer, it is not HiFi.

On the contrary, due to the inherent properties of the room mode, as well as the influence of room reflections and direct sound angles within the geometric sound field on the perception of space impression, in order to obtain better bass performance and sound field performance at the same time, in theory, the woofer should not be the same as the mid- and high-frequency unit. In the same location. The 2.2 system is theoretically better than the 2.0 system.

"The room curve/headphone curve is flat and straight is HiFi"
The frequency response curve of the speaker should be as straight as possible in the axial and off-axis to be HiFi. (For the frequency band where the direct sound is dominant, the axial and the auditory window can be maintained)

 About HiFi science and art, opinions and facts. The sound reproduction-Dr. Floyd Toole. Everything you need to know about HiFi.
  
But if the speakers are in the room, the room curve should usually have a certain gain at low frequencies and a certain attenuation at high frequencies. This is due to the different absorption of sound at different frequencies in the room and the different directivity of common speakers at different frequencies. If the room does not change the frequency response of the speakers at all, that is, the curve of the flat speakers in the room is still straight, then such a room is usually the anechoic room mentioned above. The ideal listening environment should never be without any reflections, just go to the anechoic room and listen to the music.

For headphones, a basic logic is that if a speaker + room system has a good sound performance, then the sound of the headphones (sound quality and tone) should also have a good performance. The bass belongs to the wave acoustic area, and the sound power of the speaker plays a major role. Therefore, the bass of the earphone and the steady-state curve of the speaker in the room should show a similar trend, so the low frequency of the earphone should have a certain gain relatively speaking. In addition, there is another explanation that the low-frequency frequency response of the pressure field of the earphone should be equivalent to +6B in the free field of the speaker.


Why is the frequency response curve of headphones not straight?

This is an overly basic question. As for why there should be bulges around 3kHz, I really don't want to waste my tongue. I will only talk about why the earphone frequency response curve should also have gain at low frequencies. 1. Let's start with one of the most common examples. We all know that the frequency response curve of speakers should tend to be flat, yes. But this is the frequency response of the speaker in the anechoic room, that is, the frequency response of the speaker itself should be flat. In the actual listening environment, we basically belong to the so-called reverberation field, not the free field simulated by the anechoic room. In our actual listening environment, the energy in the high frequency part is easily absorbed by the walls, carpets, sofas, curtains, etc. of the absorption room, which means that the reflected sound in the high frequency part is less; while the energy in the low frequency part is not. Completely lost, also
 

Whether it is the room steady-state curve of the speaker system or the headphone curve, the low-frequency part should not be flat. Therefore, neither the old Etymotic curve nor the energy in the low frequency part of the previous Zenith room calibration kit is wrong. In contrast, Dirac's low frequency calibration is closer to correct. Regarding the above, the assumption that the energy of the low frequency part of the Harman curve is higher than the green curve part is subjective preference correction. The actual hearing is really so much more low frequency, basically revealing two problems:

Lack of basic listening ability. It is impossible to judge by hearing how much the low frequency of actual acoustic products is higher than the standard sound.

Lack of basic acoustics and psychoacoustic common sense, do not have a correct understanding of the meaning of common forms of curves.

"Adjust the room acoustic treatment and positioning through the frequency response curve in the room"
This only applies to the wave acoustic area below the transition band. The key to understanding this problem in essence is to understand that there are two sound fields in a room. For wave acoustics. You can use the RTA curve to represent the actual sound you hear, usually the low-frequency Sound Power.


However, for the area of transition bandwidth and geometric acoustics, the actual subjective sense of hearing of the speaker system also depends on factors such as the relationship between the direct sound and the reflected sound, and the angle of the connection between the speaker and the listener. Even in the measurement in the room, it is necessary to consider the RTA or FFT, as well as the timing window and window function of the FFT, in order to correspond to the room steady-state curve problem mentioned above.

Dr. Floyd Toole gave an example. The speaker in a room is placed in the corner, the listening position is in the other corner, and the speaker and listening position in the room are both in the middle of the room. We can adjust the curves in the two rooms to be roughly the same through EQ, but the sounds we hear are different. For another example, we can face the speakers in different angles and directions at the same location, and still adjust the room curve to be roughly the same through EQ, but the actual listening experience is also different. Unless you also measure the binaural cross-correlation transfer function IACC and the early lateral sound energy ratio LF and the like. But this only represents the tone and sound field that the speaker itself may produce, but for some multi-channel speaker systems, algorithms and mixing logic must also be considered. This is a problem with the speaker system. I can also give a more extreme example. For example, two speakers and the listening position are placed in an equilateral triangle in one room and pointing to the listening position, while in another room, the two speakers are placed next to each other in the listening position. Right in front of the bit, obviously the former will get a good sound field performance, while the latter will almost turn stereo into mono.

This is different from the correspondence between headphones and headphone curves, which is essentially the difference between free field/reverberation field (speakers) and pressure field (headphones).

For the pressure field, the sound pressure is the same everywhere in the space, and there is no direct sound and reflected sound from the actual sound source in the headset. But for the speaker system, although the steady-state curves of high-quality speakers in a room with good acoustic decoration and placement are convergent, it cannot be reversed.

"Good speakers don't need to be placed/can ignore room effects"
This is utter nonsense. Any speaker needs to be placed. The room mode is the inherent acoustic property of the room, and it is not dependent on the will of the person and the quality of the speaker.

Of course, a good speaker can have a certain effect even in a poor room. But the room and placement will always restrict the final performance of the speaker system. More precisely, Dr. Floyd Toole's research found that different room environments do not affect the relative order of sound quality between different speakers, or even in a poor room, the sound of good speakers is still better than poor speakers. Well, it won't be the other way around because the rooms are different. For example, the scores of three speakers ABC in one room are 567 points, and the scores in another room may be 678 points. The room will not change the order of good or bad, but it will change the ceiling, which can be roughly understood. Different locations in the same room will cause differences. This is another problem.

I have seen someone put a 15-inch speaker in a small room with no acoustic treatment, and there is a problem with the placement, but the owner of the speaker claims that the bass of this speaker is "soft", so the small room is not placed. You can also make a good voice. As mentioned above, the room does not care whether your speakers are "soft or not", let alone whether you have a fever or not. The problem is always there. And I think the reason why he thinks it is soft is because the standing wave of the room and the marginal critical effect have greatly weakened the energy of some low frequency bands.

This is true for low frequencies, as are the effects of room reflection and positioning on the soundstage and image.
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