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PC Audio Systems
Computer sound systems have become sophisticated enough to turn more than a few stereos into dust collectors. Is your computer taking full advantage of the latest audio options?
Awesome audio isn't for everyone. If you're adding basic workstations to a corporate office, for example, don't bother with more than the most basic audio system. If, however, you're looking for a desktop that can really make some noise, read on as we examine the two main ingredients in a PC sound system: the sound card and the speakers. Each has various considerations that affect purchase price and, ultimately, your enjoyment of the audio experience.
Sound Cards
The sound card, or audio adapter, is where the PC audio experience begins. Most audio adapters are installed as PCI sound cards that can be removed and replaced, while others are audio chipsets integrated onto the motherboard to keep production costs low. Whichever the case, the audio adapter works the same way, except that to add a new sound card to a system with integrated audio, you have to disable the audio chipset in the BIOS setup or move a jumper or two on the motherboard.
In the early days of PC audio, people had to choose between 8- or 16-bit cards, with the latter approximating the quality of CDs. There were also mono and stereo models. Today, all sound cards offer at least 16-bit stereo and all of them are able to sample audio at a frequency of 44.1 kHz, the same frequency used to make audio CDs.
This doesn't mean, however, that all sound cards will sound the same. A card has to handle two types of audio, digital and MIDI (Musical Instrument Digital Interface), and the way it does each varies as greatly as the prices of computers. To play back digital audio, such as CDs, WAVs, or MP3s, the sound card uses a digital-to-analog converter (DAC). Unfortunately, just paying $1,500 or more for a computer does not ensure a good DAC will be used in its sound card.
Cards with cheap DACs are noisy, and some of the better ones are made noisy when the designer fails to shield them properly or places them next to "dirty" circuit components that generate a lot of interference.
Another big difference between types of audio circuitry lies in the method used to generate notes when recreating a MIDI file. These files are nothing more than numbers representing pitches, voices, and the duration of musical notes, and are the most efficient way to store audio in a digital format. MIDI files can't contain voices or actual samples, but when you can do without these, MIDI can save a lot of disk space. For example, a minute of instrumental CD-quality digital audio could take up about 12MB while its MIDI equivalent could be about 12K. Most music in games is stored in this space-saving format.
There are two methods used to turn the numbers in MIDI files into music: FM synthesis and wavetable synthesis. The former was available first. Through frequency modulation (FM), a synthesizer circuit can simulate a variety of instrument sounds. The results vary from so-so to poor. Remember the audio tracks in early video games with bass notes that sounded like rubber-band strings and drums that sounded like tiny firecrackers?
The best form of synthesis is, without a doubt, wavetable, wherein the sound card has a bank of real instrument sounds sampled and stored in RAM or ROM. Whenever a MIDI note is presented to the sound circuitry, the instrument sound called for is brought up and used to generate the tone. Depending on the quality of the circuitry and samples, certain musical passages can sound like real WAV files.
Sound cards based on wavetable synthesis are obviously of a higher quality and tend to have good-sounding DACs, too. There's no way to prove the latter, but the vast majority of machines conform to this rule. It's likely that this is so because wavetable audio represents better attention to an audio card on the part of the designer.
A final circuitry concern is whether the card supports full-duplex audio. That is, does the card let you listen to and input audio at the same time? If you plan on doing any kind of videoconferencing or plan on using Internet telephony, look for a full-duplex rather than a half-duplex unit. Whether a sound card features this is not always mentioned in ads, so you'll want to ask when you're ready to buy.
We mentioned earlier that all sound cards are now capable of 16-bit audio. Some new sound cards go even higher--to 18 or 20 bits. Some high-end cards, like the Sound Blaster Audigy, add fancy recording features like digital output for use with a digital audio tape (DAT) deck.
If you plan to do a lot of gaming, consider a sound card with surround-sound capabilities. There's no doubt that 3D positional audio adds to the life of a game, but if you're more concerned with music, you can do without it. Actually, 3D makes most music sound odd. Disable it for best results when playing a CD.
A final item to check when choosing a sound card is its I/O capabilities. Keep the differences in mind. Only a headphone jack can drive headphones sufficiently, while a line-out jack sends out a line-level signal, suitable only for connecting to amplified speakers or line-level audio equipment. The same type of difference applies to inputs. You can't use a mic jack for a line-in or vice versa. Most cards come with these four basic jacks.
Speakers
Let's say you've found a computer with a cutting-edge sound card. Now you have to consider how the audio from that fine card will be delivered to you. Dozens of amplified desktop speakers on the market could make you perfectly happy, as long as they're accompanied by a subwoofer.
We can't stress this enough. Nothing sounds worse than music coming out of a pair of small speakers that shouldn't be doing anything more than providing treble or "tweeter" signals. Practically all music is designed to have bass, mid-range, and treble registers. Tiny desktop speakers try to cram all those signals into transducers that can't reproduce the individual frequencies involved.
With a speaker system that comes with a subwoofer, better-quality sound is almost guaranteed. In such an arrangement, the signal usually goes first to the subwoofer. A crossover circuit then "keeps" the bass frequencies in the subwoofer and sends the higher frequencies to the satellite speakers. This is currently the best way to reproduce audio on a desktop.
Gamers and others who appreciate a true 3D audio experience should consider a five-piece speaker system, which consists of a subwoofer and four satellite speakers. With such a set, two speakers are placed in front of the user, with one off to the right and the other to the left, and two more are behind the user, off to each side. Five-piece speaker systems work best with a sound card, like the Creative Labs Sound Blaster Audigy, designed with front- and rear-channel audio outputs. The Audigy can actually handle a six-piece speaker system with two front and two rear satellites, a subwoofer, and center channel speaker. This center channel can really make DVD movies come to life.
A poorly made speaker system will sound bad, so stay away from computer dealers who don't tell you the brand name of the included speakers--these can end up being two tinny-sounding speakers with the acoustics of a pair of cans. With these considerations met, your next PC's sound system should provide you a wonderful dimension of entertainment. It might even inspire you to dust off the stereo.
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