Another review, another RMAA version, this time to 6.0.6.  The X-Audio was measured using the loopback test, with it recording itself.  If you'll remember that the Audigy sound card used an APU that worked in 48KHz mode.  I know people read guru3d.com just for the pictures, but try to remember.  This information is important later. 

First up is the complete run of modes, from 16-bit/44.1 KHz to 24-bit/96 KHz.  Have a look-see:

These are very good numbers, especially the Stereo crosstalk, which is an indication of how accurate the sound field will be.  The Noise and Dynamic range are also very good, but not exceptional.  The THD is very good.  What is interesting is the progression of the Intermodulation Distortion, which is distortion produced when two sounds are added together (real music is just that: lots of instruments added together).  Here's a graph:

Above is the 16-bit/44.1 KHz sample rate graph.  It's quite noisy with SRC errors.  And again at 16-bit and 48 KHz:

Now that is much better!  The original Audigy and Audigy 2 had this same issue, where the APU is working at 48 KHz and the signal asks to play at 44.1 KHz (a CD or WAV for example).  In order to play the file, the APU must convert from 44.1 KHz to 48 KHz, but the SRC in the Audigy was not of high quality and introduces a lot of spikes in the graph (this is the noise I mention earlier).  What is so nice about the true X-Fi is that it doesn't matter what you throw at it, it will always do nearly perfect sample rate conversion.

Let's take a look at the X-Audio's frequency response:

I was not successful at getting the X-Audio to extend its frequency response all the way to 48 KHz (96 KHz sampling frequency).  It liked it here.  But the response is fairly flat, but not the best I've seen.  Here's the graph for frequency response, mixed in with some competition:

There's a little squigly-ness there for the X-Audio (the white line), which is the classic sign of feedback.  The monitoring was off, so some processing effects might still have been active.  The green line is the Auzentech X-Prelude, and the purple line is the XtremeMusic.

In comparison to the X-Meridian, X-Prelude, the XtremeMusic, at 24-bit/96 KHz the X-Audio is about where you expect it to be, just behind the other cards. 

One thing I cannot make fun of Creative for is that they do know how to engineer a sound card.  All these cards are very high performance, no doubt about it.  If it weren't for the SRC issues, I'd have no problem recommending the X-Audio.  I'd certainly recommend the X-Audio if you're on a budget and running Vista.