What Are the Different Types of Ported Subwoofer Enclosures?

The current "portable" audio products mainly include two types of portable signal sources (CD / MP3) and portable speakers. In addition, many portable speakers also have USB \ SD playback functions to carry out "portable" to the end; while portable audio sources are paired with headphones. The system appeared earlier, from the earliest cassette player products to later portable CDs and MP3 players. With the development of technology, the functionality of "portable" audio products has gradually increased, and the volume has become smaller and smaller. Although the sound quality is limited by volume, the sound quality of today's portable speakers is better than ever.

Portable audio

The current "portable" audio products mainly include two types of portable signal sources (CD / MP3) and portable speakers. In addition, many portable speakers also have USB \ SD playback functions to carry out "portable" to the end; while portable audio sources are paired with headphones. The system appeared earlier, from the earliest cassette player products to later portable CDs and

"Portable" audio sources on the market

Portable audio player

In the 1980s, although the CD (Compact Disc) format jointly developed by Sony and PHILIPS has perfect sound quality, as a portable audio device, the size of CD Walkman discs is large and unacceptable. Writing, portability, and user's choice of audio source are not ideal.

Sony, the ancestor of the Walkman, realized these problems and began to explore a new audio technology that is more suitable for carrying around. In 1986, Sony successfully developed a write-once optical disc, WO (Write Once Disc). In 1988, on the basis of WO, Sony invented the magneto-optical disc (MO), which can be rewritable multiple times. MO (Magneto Optical Disc). The successful development of MO technology has pointed out the direction for Sony. The storage medium is repeatedly transcribed, and the volume of the storage medium can be further reduced. In 1989, a research and development group led by Kemin Tsushima of Sony's Audio Technology Department demonstrated a recordable CD prototype product at the audio exhibition of the year. This disc uses the same technology as MO, which was later developed by the MD (MiniDisc The birth of) laid a solid technical foundation.

In May 1991, a brand new storage medium, MD (MiniDisc), was announced. The size of the disc was customized to 64mm in diameter and the recording time was 74min. Compared with a CD, the area is only 1 / 4. In addition, ATRAC digital audio compression technology also came into being. In order to ensure the portability of the final product and reduce the vibration caused by vibration during carrying, a shock-resistant memory technology based on semiconductor media was also developed. These technological breakthroughs enable future MDs to combine the recordability of tapes, the high sound quality of CDs, high-speed random playback, and fast search. At the same time, Sony clearly defines the differences between CDs and MD Walkmans. CDs are used for leisure music Enjoy, and MD is to enjoy high-quality music anytime, anywhere.

In 2000, under the aggressive momentum of MP3 players, Sony introduced ATRAC3 encoding technology, named MDLP (MiniDisc Long Play). This improved encoding technology increases the compression rate on the basis of the original ATRAC encoding, and greatly reduces the space occupied by ATRAC format files at the expense of a certain sound quality, so that the original MD discs can be accommodated according to different compression rates. 2 to 4 times the music. Its birth has injected new vitality into the MD Walkman market. As for the sacrifice of sound quality, ordinary users can't distinguish it at all. It is very successful to use this loss of sound quality in exchange for the benefits of use.

In June 2001, Sony released the NET MD technology, which is a solution for rapid production of MD discs. The MD Walkman with NET MD technology can download ATRAC or ATRAC3 format files directly from the personal computer to the MD discs. The MD recording method has changed from a true recording to a MP3-like file download through a USB interface Transfer, greatly reducing the time it takes to make MD discs. NET MD technology is undoubtedly another important achievement in the history of MD development. 2. Many domestic manufacturers of CDs and CD / MP3 Walkmans choose laser heads from Japan's Sanyo and Sony, not only because of their reasonable price, but also because of their strong ability to read and correct discs, and their quality and technical support are guaranteed. In order to reduce the thickness of the CD Walkman, in addition to the need to choose a thin bald head, the choice of electronic components is also very particular. Electrolytic capacitors need to be small in size. The chip can only use multifunctional circuits with a large integrated scale to cooperate with peripheral components. With SMD material, the printed circuit board is designed to be double-sided, so that the thickness of the fuselage can be made between 24-26mm. Another feature of CDs and CD / MP3 Walkmans is the addition of an "electronic anti-vibration" function, because during the normal reading process of the CD optical head, if it is subject to a certain degree of vibration, it will directly affect the focus and tracking of the optical head, thereby deviating from the audio track. To make the music playing intermittent. After the anti-vibration function is added, the anti-vibration system first stores the read-in signal into a memory temporarily, and then takes out the signal from the memory for processing as required for playback. When the body is shaken, the optical head cannot deviate from the audio track. The moment the signal is normally read, the signal that has been stored in the memory can still be taken out for processing, so that the optical head has enough time to resume reading, thereby solving the "jumping" phenomenon caused by the shock. The length of the "electronic shock resistance" time depends on the capacity of the memory used. Commonly, there are 10 seconds, 40 seconds, and longer shock resistance time, which depends on the market demand for the product.

Portable audio player

The difference between CD and CD / MP3 Walkman is the decoding chip of both. The decoding chip of CD and CD / MP3 Walkman must not only recognize the CD signal and decode it, but also be able to identify and decode MP3. Format data signals; CD / MP3 / VCD portable players have added video signal identification and decoding functions, and have a video output interface; because the working current when playing VCD discs is larger than when playing CD discs, it is recommended Use the supplied external power adapter when playing VCD discs. Jinye's CMV320 series Walkman is a new product that integrates CD / MP3 / VCD playback functions, with infrared remote control, 9-screen browsing and playback. With the rapid development of digital information technology, more new functions will appear in portable audio products, and more types will enter the market. The "portable" signal sources mentioned above include both audio and video. They belong to earlier products, and today there are a variety of portable signal sources. MP4, portable DVD and other products have become newcomers in the market.

Portable audio speakers

Portable speakers are also commonly referred to as portable small speakers. Most of them use SD / U disk, Line in three audio source input methods, and many will be equipped with FM radio, remote control and other functions. According to users' mobile performance requirements, large Some choose a passive design, which is equipped with a lithium battery or a replaceable battery. With the development of integrated chips and speaker and speaker units, portable speakers are becoming smaller and smaller, and battery life is gradually increasing. Domestic small speakers like to use BL-5C as a power supply solution, and extend the development of FM one-click search Channel, lyrics synchronous display, touch screen, voice song and other rich features, and there are already mature voice song song speakers on the market, high accuracy of Mandarin song songs, but also supports a few dialect song songs. For the design of the cabinet, starting from ergonomics, most small speakers use a flat and long bar configuration, which is easy to hold. From the perspective of cost and ease of processing, most use ABS engineering plastic casings, and a few high-end products use metal casings.