Obviously, everyone's understanding of the concepts of "mono" and "stereo" is different, which is affected by people's individual experiences and expectations. Translating one's experience with home audio systems or professional recording studios to large venues, such as churches or theaters, always requires some conceptual adjustment, so we should prepare for mono, stereo, and two-channel sound. Systematic discussion provides a point of reference. Let's start with a mono system.
Description of a mono system: All audio signals are mixed together and sent through a single audio channel. A mono system can have multiple speakers, even multiple speakers widely spaced apart. The key is that the signal does not carry any information that reproduces or simulates the original direction of the sound, such as differences in signal levels, arrival time/phase information, etc.
Common types of mono systems include:
1/Mono center speaker group
2/Mono split speaker group system
p>3/Distributed speaker system (with or without delay speakers)
Although it is mono, the system can still provide full-range response, high fidelity, and can effectively respond to speech and music amplification. The great advantage of mono is that everyone hears the same signal and, in a properly designed system, all listeners hear essentially the same system sound pressure level. This makes mono systems ideal for speech reinforcement, as they can more easily deliver excellent speech intelligibility.
A true stereo system has at least two independent audio signal channels. The replayed signals have specific sound pressure levels and phase relationships with each other. When the audio source is played through the replay system, it will be the original Distinctive reproduction of the sound source. Stereo is used when it is necessary to reproduce the sense of auditory orientation and the position of instruments on the stage or podium, which is a common requirement in art performance venues.
This also means that a mono signal that is only panned between two channels does not have the necessary phase information for stereo, and is therefore not a true stereo signal; although there may be sound between the two channels. The difference in pressure level can simulate the difference in position, but this is just a simulation. A discussion on this point would probably take several pages.
Another requirement for a stereo playback system is that the entire listening area must be equally covered by the left and right channels, with essentially the same sound pressure level. For this reason, in a home stereo system, there is a better listening position ("Emperor's Position") between the two speakers, where the difference in sound pressure level and arrival time of the left and right channel sounds is small enough to maintain the stereo quality. Panning and sound source location.
The best listening position is in a fairly small area between the two speakers. When the listener is outside this area, the sound image is lost and only the sound of one or the other channel can be heard. The sweet spot in a living room may not be a problem because the sofa can be placed there; but in a larger venue, such as a church or theater auditorium, the sweet spot may only include a third of the auditorium. The other two-thirds of the audience will wonder why they can only hear half the source.
Additionally, a stereo playback system must have correct phase response from input to output on both channels. This means that if the system input is a positive pressure waveform signal, then the system output must also be a positive pressure waveform signal.
Therefore, taking the drum as an example, when hitting the drum causes the pickup microphone to generate a positive pressure waveform signal, a positive pressure waveform should also be generated in the listening room. If you don't believe this makes a huge difference, try reversing the polarity of your hi-fi speakers and listening to a source with a strong central image, such as a solo vocal. When the polarity is flipped incorrectly, you won't get a stable center channel image, it will wander away from the center and you can hear both speaker positions.
Many people misunderstand this as a stereo system because there are two channels and a "stereo" mixer is connected in front of the system, with stereo amplifiers and equalizers used throughout the system.
However, what these systems lack is uniform coverage of the entire listening area, and each channel covers the listening area with minimal differences in sound pressure level and phase response.
We might call this type of system a partition overlay system. To obtain suitable sound coverage to reproduce stereo sound images in large venues, it is necessary to have a sound system that can provide the signal of each channel with the ability to evenly cover the entire listening area while maintaining a sense of sound direction. Such systems sometimes require more budget, or the listening area is too wide to achieve smooth overlapping coverage.
If a two-channel system plays a stereo signal and cannot provide smooth sound overlap coverage, then half of the people in the listening area can only hear half of the audio program content, which makes the two-channel system useless for music. A poor choice for sound reinforcement. Most listeners hear a completely different mix of music than everyone else.
This is an all too common oversight in music and entertainment venues, even high-quality venues that should have better system designs. It is a common misconception among people who come from a touring or live sound system background to think that a two-channel system is the same as a stereo system.
?When using a two-channel system to amplify a mono voice microphone, a seat in the center line of the room, just between the two channels, will also experience the same frequency response and coverage Large changes in uniformity are the result of acoustic interference and signal cancellation caused by the same signal arriving at the listening position from the two channels at different times. This is the most important thing to pay attention to when using a two-channel system in voice amplification applications.
Sound systems described as left/center/right (LCR) configurations have specific applications. It combines the best of both systems; it is important when using an LCR system that the mix engineer understands which signal must be sent to which loudspeaker, and which signal lines can cause problems. Additionally, LCR systems are not suitable for all room shapes or listening area layouts.
LCR systems are common in theaters and large churches where monophonic speech reinforcement is required, as well as music or surround sound effects or mixed in a special sense of orientation, with stereo or stereo-like sound picture. Each channel of this three-channel system should provide coverage of the entire seating area while maintaining consistent sound pressure levels and sound directionality, just like the mono and stereo systems described previously. There are methods a system designer can use to extend the stereo coverage of the listening area that involve the use of fill speakers.
Fill speakers
Fill speakers are used to provide coverage for floor areas that are difficult to reach from where the left or right channel speaker sets are installed.
In the above example, the left/right fill speakers are independent from the center speaker group and fed through a signal delay; thus for those on the right side of the room Well, the signal from the left fill speaker and the signal from the left speaker group will arrive at the same time, if the signal from the left speaker group can get here.
For someone sitting near the front right, they will still hear the program coming from the left channel to get the full program content, although the stereo image will be different from that of a listener sitting in the center of the room. The perceived sound image is somewhat skewed, but the final stereo effect is quite satisfying.
The choice of speaker model, as well as the sound pressure level and delay settings of the speakers, are very critical to the successful integration of fill speakers; if the sound is too loud, the delay is too long or too short , fill speakers will detract from the sound image heard by other listeners. If you want to try studying the Haas effect at home, it is recommended that you prioritize setting up sound pressure levels and delays, as well as learning how to use a time domain measurement system. ?
It is also possible to use some speakers of the center speaker group as fill speakers, especially as DSP matrix systems become cheaper and cheaper, and it becomes extremely difficult to set up separate delay processing for each speaker. Simple. This method is particularly effective when the center channel speaker group has similar speakers to the left/right channel speaker group.
Which sound system is better?
Like many questions about sound systems, this one has no right answer.
A properly designed mono system will satisfy more people than a poorly designed or incomplete two-channel system.
The important thing to remember is that the best sound system design for a facility is one that works effectively within the constraints of the program source, room architecture, and acoustic conditions. This means (to paraphrase the Rolling Stones): "You can't always get the system you want, but you'll find sometimes you get the system you need."
If the design of the venue (or the budget) cannot support an efficient stereo playback or PA system, then it is important that the sound system design be as efficient as possible, even if this means giving up the ideal need for stereo sound required by the program source.