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Upgrading for Xtreme Fidelity
Although the X-Fi supports 24-bit/96kHz multi-channel output, most audio is only 16-bit/44.1kHz in stereo. The X-Fi has no problem faithfully reproducing 16-bit/44.1kHz stereo audio, and it can even do so without any sample rate conversions by bypassing the SRC, but that leaves much of the X-Fi's potential untapped. Instead of being content with simple reproduction, Creative has also endowed the X-Fi with the ability to upgrade a 16-bit/44.1kHz stereo audio stream to multi-channel, 24-bit/96kHz sound. The philosophy behind this upgrade to "Xtreme Fidelity" is that a sound card should strive to create the best listening experience possible rather than simply defaulting to bit-accurate playback. This philosophy works in reverse, too, optimizing playback of multi-channel content through headphones or two-speaker setups.

Creative's Xtreme Fidelity initiative has two components: 24-bit Crystalizer and CMSS-3D. The first tackles upsampling, while second expands and contracts audio streams over multiple channels to optimize playback for a listener's speaker configuration.

24-bit Crystalizer
With claims that it "enhances MP3s and movies to sound better than they do on their original CD or DVD," the 24-bit Crystalizer is easily the X-Fi's most-hyped feature. Creative certainly has a history of hyperbole, but the audio world in general seems rife with wild claims. 128kbps MP3s that offer CD-quality audio are one of my personal favorites.

If you don't buy into the hype, the 24-bit Crystalizer is easy to enable and disable within the X-Fi driver control panel. When enabled, audio streams are run through the X-Fi's sample rate converter and upsampled to 24-bit and 96kHz. From there, the Crystalizer attempts to simulate how a sound engineer would go about remastering the audio stream. It's common for studio engineers to compress the dynamic range of instruments to fit into a 16-bit/44.1kHz recording, and the Crystalizer tries to restore some of that lost dynamic range.

Creative says that the Crystalizer is able to extract crisper high frequencies, punchier mid-range percussion, and stronger kick bass hits from lower bitrate recordings, a claim we'll examine in our listening tests. First, though, we thought it would be interesting to examine the Crystalizer's impact on RightMark Audio Analyzer. We fired up RMAA and ran the X-Fi at 16-bit/44.1kHz with the Crystalizer disabled, at its 50% default, and at 75% and 100%. Only a couple of RMAA's tests were affected by the Crystalizer, with the most dramatic difference observed in the frequency response test.

Notice how the Crystalizer pumps up high and low frequency sounds, but has poorer frequency response in the middle of the spectrum. In general, the Crystalizer's impact is consistent across all three percentages, but the same can't be said for its influence on intermodulation distortion.

Intermodulation distortion occurs when a sound card can't accurately reproduce two sounds at the same time. With Crystalizer percentages above 50%, the X-Fi definitely struggles. Perhaps that's why 50% is the default.

Although it's hard to imagine that the 24-bit Crystalizer can divine enough information from an MP3 to make it sound better than the original CD, the technology may have merit, particularly with low bitrate recordings. Our listening tests will shed some light on just how useful the Crystalizer is in the real world.

CMSS-3D
While the 24-bit Crystalizer upsamples low bitrate recordings in an attempt to recover detail lost in the compression process, CMSS-3D expands and contracts stereo and multi-channel recordings to best match a user's speaker configuration. CMSS-3D aims to make playback more immersive while still preserving the intent and quality of the original recording. This technology comes in 3DHeadphone, 3DVirtual, and 3DSurround flavors, each of which is optimized for a different speaker configuration.

As its name implies, CMSS-3DHeadphone optimizes playback for headphone listening. Headphones generally give listeners the impression that sound is arcing through their heads, but 3DHeadphone creates the illusion that playback is occurring through a pair of virtual stereo speakers. Creative says this effect can lessen the listening fatigue that some experience with headphones, although some listeners may prefer that the voices stay inside their head.

In addition to creating the illusion of stereo speakers, CMSS-3DHeadphone can also virtualize multi-channel speaker configurations for 3D audio playback. Various techniques are used to trick the ear into thinking that sounds are coming from imaginary speakers that surround the listener. It's a neat effect, and although I'm in no rush to trade in my six-channel speaker setup for a set of headphones, CMSS-3DHeadphone worked better than I expected.

CMSS-3DVirtual is actually quite similar to 3DHeadphone. Both can virtualize multi-channel audio for stereo playback devices, but instead of concentrating on headphone playback, 3DVirtual is designed for stereo speaker configurations. The same battery of tricks is used to fool the listener's ears, and since users have more freedom to place stereo speakers than they do headphones, 3DVirtual can be calibrated to take into account the distance between a user and his speakers.

CMSS-3DHeadphone and 3DVirtual both translate multi-channel recordings for stereo output, but CMSS-3DSurround works in the opposite direction, upmixing stereo content for multi-channel playback. 3DSurround doesn't arbitrarily assign the voices and instruments from a stereo recording to surround speakers, though. Instead, it taps the surround channels to deepen listener immersion and uses the center channel to expand the sweet spot between the front left and right speakers. To achieve immersion without disrupting a stereo recording's original intent, CMSS-3DSurround extracts ambient sounds from the original recording and routes them to surround channels. Then, it expands the front channel sweet spot by directing center-panned sounds to the center channel. This method keeps the primary image in front of the listener while surrounding him with the ambient noise of the recording. As far as preserving the intent of the original recording goes, that's a pretty good compromise.