HiFi Headphone Speakers/acoustics Top Ten Common Misunderstandings(III)

- Mar 29, 2021-

"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. To be more precise, 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 of different rooms. 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 that 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.