Zhao Yi: Thinking and Practice on Multi-channel Setup in Home Theater

In the next year, over the flower, playing video and audio for nearly 30 years, starting from the combination of audio and video recorders, the equipment used has been updated several times. With the concept of multi-channel home theater, it will be gradual. As long as the media reports have new technical equipment, we will find ways to purchase at the first time (limited to the middle and low price of financial resources), so we will endlessly repeat investment, resulting in Self-use equipment has been frequently eliminated.

Hume's original "home theater" (beautiful name), video source is just video tape, LD, VCD, video display device is more shabby: 18-inch TV. The audio device is a Dolby Pro Logic decoder with a three-channel power amplifier. The original combination audio is used as the front main channel, and a mid-range and two surround small speakers are separately purchased. Entering the Dolby Digital and DTS era, the matching method is still a decoder with a three-channel power amplifier plus a two-channel device (only the equipment has been replaced to a better one, and a subwoofer has been added). The collocation method is more feverish. In fact, the drawbacks are obvious. In addition to the unsatisfactory sounds of different grades, the difference in tone color caused by different equipments, especially different models or even different brands of speakers, also has a negative impact. 5.1 channel is followed by 6.1, 7.1 Dolby-EX, DTS-ES (and Dolby Pro-Logic II, IIx, DTS 96/24, DTS Neo: 6 and other extended formats), the channel of the amplifier is increased, the speaker is also It will increase.

Moved to a new house 12 years ago, the living room has 33 square meters (after the entrance hall, balcony, the actual use area of ​​the audio-visual room is 28 square meters), I was determined to make a decent home theater. In addition to sound treatment, sound absorption, sound insulation and other acoustic treatment and light isolation, pattern modification, equipment placement, lighting control and other related settings and processing, it is very important that the wiring (multiple types of lines, only speaker lines here), before Set, the middle of the three-way line, the rest of the dark line is not just buried two surround channel lines as simple as I have buried a total of 9 routes, namely: side surround, rear surround each two, and The two sides of the side surround, this is due to the use of the Tianlong AVR-3803 amplifier has this requirement, it is said to listen to multi-channel music with A group surround or side surround, watching movies with Group B surround is placed in the corner of the room Two channels. In addition to the main channel and the center channel, the other two channels are also close to the corner of the ceiling. It is derived from the "effect channel" recommended by Yamaha's high-end power amplifier, and the other is the center channel. The centering position above the screen is intended to enhance the sounding point of the center channel placed under the screen for more accurate vocal dialogue positioning. The most ideal solution for center channel positioning is of course the use of a sound-transmitting screen. But when this precondition is lacking, I think that using dual center is a good solution - although there are few precedents in this regard.

Now it seems that these embedding settings I had a decade ago are still somewhat foreseen. At that time, it was also considered to reserve 2 to 4 channels of buried wires in the middle of the roof to make the front and back sound fields of the rectangular audio-visual room connect. However, after hesitating to give up, the main reason is that there will be no signal source suitable for top positioning. Some regrets now, if I did this at the time, it would correspond to the current Dolby Atmos. Of course, when you need to increase it, it is very difficult to take the dark line.

A few years ago, Dolby TrueHD and DTS-HD high-definition audio became the basic configuration of mid-to-high-end AV amplifiers. So I purchased the Tianlong AVR-A100 with 9-channel power output and 11.2 channels. The surround sound output was set to be added to the front-end widening. The Dolby Pro-Logic IIz and Audyssey DSX modes of the front-increasing channel, the 9-channel power output adds the front widening channel in addition to the original main, middle, side, and rear rings, due to the proximity of the two speakers. Left and right walls or diffused bookshelves, so the route is better solved. The other 5 channels are the front-mounted, upper-center, and side-surround channels, which are handed over to a 6-channel input amplifier (the specific model is Tianjin BOG-DH999). The signal is taken from the preamplifier of the AVR-A100. Output.

The 14 full-range channels have 12 speakers that are also available in the Klipsch Judge Reference II series. Main speaker: RB-81II×2, center speaker: RC-62II×1, upper center speaker: RC-52II×1, front booster channel: RB-41II×2, front widening channel: RB -51II×2, left and right surround speakers: RS-42II×2, rear surround speakers: RB-51II×2, only the side surround speakers are temporarily replaced by other brands. One of the two subwoofers is the 10-inch unit of the Wolfdale Diamond 10MX-SUB, the other is the dual 15-inch speaker of the US EPIK (Emperor) EMPIRE (64kg body weight, Class D 600W average power, low frequency can dive to 15Hz, in fact, it is enough to have one opening sound).

Regarding the upper center channel, it was not used in the previous years after the reservation. To tell the truth, the effect was unrecognizable. Later, it was tested in a long time, and the conclusion was positive. First, it was indeed high. The center channel positioning (the positioning is higher and lower, depending on the loudness ratio of the upper and lower speakers and the height of the listener's head), and the second is the image of the sound positioning is basically accurate, rather than the fuzzy that is worried beforehand. In one piece. As for positioning, as long as the sound is still clear, solid, and not scattered, I don't think it is necessary to locate at a certain point, because the screen is huge, and the specific vocalization points in the screen, such as the dialogue in the drama, whether single or multi-person, The position of the mouth is not fixed at all, so it is not necessary to focus on a small position in the center. Most devices put the center channel on or under the screen. The reason why it is widely accepted is that it is not demanding. It is considered that the theater, especially the home theater, looks at the picture effect and even appreciates the plot is the first. And as long as the sound is synchronized with the picture, it will naturally give the audience a feeling of sound and picture. Compared with the single center, the double center sound is more open, clear, full and heavy, not only the sound pressure becomes stronger, but also the density increases. With this practice test, I began to officially activate the upper center channel.

Later, several situations have caused me to be troubled for a long time:

The first is the signal from each channel of the AVR-A100 preamp output, the level is extremely weak, which has nothing to do with the downstream equipment used as the post-stage, because I use three AV amplifiers including the Denon AVR-3803. As such, the signal level is estimated to be as low as -40 to -50 dB, and only the potentiometer of the downstream power amplifier is turned on to a substantial size to substantially match. I have checked the manual several times and adjusted the output level to a large extent (because the 11.2 channel is set, only the front booster channel and the subwoofer channel that require an external amplifier are true preamp signals. The rest is actually adjusting the synchronous power output level). If the original setting of the machine is only a pure signal output when the pre-stage is pure, then the front-end increase (or the front-end widening, both can be taken The setting of one) is unreasonable. I am puzzled by this question, and I can't find the answer (because there are very few people who use it to expand and use it like me. I am grateful if there is expert advice.) Although the post-level is adjusted to be large enough to achieve the goal, it is always unsatisfactory and psychologically uncomfortable.

Looking for a workaround: find a Dolby Digital and DTS fiber decoder (CAV DC-2000) that has been dust-sealed for many years. Input digital audio from each audio-visual equipment, and then give the decoded analog signal to the sub-level. The problem of volume is solved, but a prominent problem has arisen: the sound coming out of this decoder is out of sync with the sound of the A100, and the difference (advance) is about half a second. I don’t know if the audio and video equipment is on the principle of setting the fiber. The output time of coaxial and HDMI digital audio is different, or whether this decoder is different from the digital audio processing of A100 (if the latter, it means that the sound processing of A100 has a delay), because it is the sound of the decoder. First, the decoder is adjusted for sound delay, but when the maximum value is adjusted, the two are still out of sync, so the scheme is abandoned.

Looking for a solution again: online purchase of a simple digital-to-analog conversion device with HDMI input to 5.1 analog output, the source is also the HDMI output, there is no time difference in this link (for audio and video source devices with only one set of HDMI output interfaces, plus One HDMI one-two device can be), but another problem has appeared in the experiment. This converter only supports RAW source compression audio input. For uncompressed LPCM source audio, only 2 channel analog signals can be output and cannot be output. 5.1, I naturally can not sacrifice LPCM, although there are other conversion devices that support uncompressed source code, but I did not continue to buy, because from the grade of sound quality processing, this is obviously not an ideal solution (the actual experience gap is obvious).

Do the experiment again: replace the Tianjin BOG-DH999 without the digital-to-analog conversion function with the lion dragon QG-500AVR (Chinese version RD-8105), and set the two Blu-ray players, one HD player and one cable set-top box respectively. Coaxial, fiber-optic access QG-500AVR (also connected to the front-end output of the A100 and the 5-channel input of the unit), the worry after the boot did not happen, the two amplifiers are completely synchronized, and the sound quality and tone Close (this connection, the original pre-adjustment channel is actually the front main channel signal). At this point, my 14.2 channel cinema sound has a good display, the only cumbersome is that the volume of the two amplifiers needs to be adjusted separately (when the downstream power amplifier is switched to 5.1 input, just place the potentiometer in a one-time fixed fixed Position, you can control the volume synchronously by the “main power amplifier”; when switching to the optical fiber and coaxial single device audio output mode, even if the sound pressure ratio of the two is adjusted during a certain viewing, as long as the “main power amplifier” increases or decreases the volume "Sub-amplifiers" should be increased or decreased as appropriate, especially the two audio amplifiers have completely different sound control display modes. The 500AVR is a simple digital increase and decrease method. The larger the number, the louder the sound, and the A100 is a strict dB sound pressure indicator. In the -dB state, the smaller the number, the greater the gain, so the two cannot be numerically mapped. From this point of view, I may have to put the AVR-3803 in this position). Watching movies by yourself or your family usually only starts with 9.1 channels. When a visitor visits, it is natural to "open the fire." If you only listen to multi-channel music, in addition to the channel selection of 9.2 and 14.2, you can also select only the 5 channels of the upper sound field (plus .1 channels), and occasionally listen to this somewhat different way. Background music and casual music are also a new feeling.
In the audio-visual room of only about 28 square meters, watch the action blockbuster open to 14.2 channels (even if there are several channels that are expanded rather than independent channels, but the speaker position is different), the sense of envelop can be quite Strong, I thought it was a very luxurious enjoyment. At present, although there is no Dolby panoramic sound, as many as nine upper speakers have a strong coverage effect on the sound. In the future, when possible, you may join the real Dolby Atmos immersive home theater with ceiling ceiling speakers.

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