A3D Support

I talked at length about 3D audio basics in my MX300 review. However, let me summarize by saying that if you don't have a PCI 3D audio card, you are cheating yourself out of some amazingly immersive sound in today's best games.

As I've been living with my Vortex 2-powered MX300 for the last few months, a few issues have emerged that I want to discuss, then I'll get right to the ratings.

1. CPU usage
If you've been following the 3D audio "war" between Creative Labs' EAX and Aureal's A3D as I have, one factor that has emerged as a point of differentiation is CPU usage. While both the Live! and the Vortex 2 perform all of their 3D sound functions on the sound card's processor instead of your computer's CPU, they differ significantly in how they handle environmental modeling.

In a nutshell, EAX uses a set of canned presets (e.g., "small room", "large canyon", "water", "stadium", etc), where A3D 2.x dynamically calculates how things should sound based on the actual level geometry-an approach they call wavetracing. There are certainly pros and cons to both approaches, but the most significant negative to wavetracing in A3D 2.x is CPU usage. Although all the actual calculations are done in the Vortex 2 hardware, there is still the unavoidable overhead of sending the level geometry information to the card's driver in the first place, and the API has to pass that information back to the hardware in real time.

Allow me to illustrate. Here's me running the blowout.dem Half-Life demo at 640x480 on a P2-400 with 128mb of RAM:

Impact of A3D Wavetracing
A3D 2.0 (s_geometry 1) - 3D sound + wavetracing	25 fps
A3d 1.x (s_geometry 0) - 3D sound	27 fps
A3D Disabled - Stereo sound	29 fps

For further consideration, here's demo1 from Motorhead at 640x480 on a P2-450 with 256mb of RAM:

Motorhead: Wavetracing Overhead
A3D 2.0 (s_geometry 1) - 3D sound + wavetracing	39.3 fps
A3d 1.x (s_geometry 0) - 3D sound	42.4 fps
DirectSound3D 3D sound	35.6 fps
A3D Disabled - Stereo sound	43.7 fps
Sound disabled - no sound	46.5 fps

That's a complete set of benchmarks from every single currently shipping A3D 2.0 title. I look forward to benchmarking the Heretic II A3D 2.0 support when the Heretic II Expansion Pack is finally available.

As you can see, there is overhead associated with 3D sound, and additional overhead associated with geometry-based wavetracing on top of that. If the percentages here hold, that overhead is about 7 percent for 3D sound, and another 7 percent for wavetracing. Aureal has stated that they are working on reducing the overhead in their A3D API to make it more efficient. I have tried the latest 2.04b update, but there is no benchmarkable change in the Half-Life results.

As with all things sound related, I urge you to hear the difference yourself, as the numbers do not tell the whole story-as far as I'm concerned, the additional immersiveness of both 3D sound and wavetracing far outweigh the small frame rate hit.