How Real Is Your Center?
Try real hard to think back to the days of stereo, and remember how we got a center image. "Gee, there was no speaker in the middle, yet I heard sounds in the middle, between the two speakers."

The way we got a center image in stereo was to put exactly the same sound in both speakers. This created a "phantom" center or "virtual" center. It worked fairly well, although the image in the center was always big and never tightly focused.

Now, with 5.1 Surround, we actually have a real speaker in the front center. If we place a sound in this speaker, and this speaker alone, we will have a sharply focused sound from the front center of the soundfield. So we have a new option for placing sound that didn't exist in stereo. But we also still have the option of creating a virtual center, also.

Mx51 lets you choose between real center and virtual center, with a shutter on the Surround panner. Just grab the edge of the shutter with the mouse, and pull it in or out.



You can not only select between real center and virtual center, but you can in fact make a blend of the two. This way you can adjust the size of the image for sounds panned to the front center of the soundstage.

Bass Management
Warning: This is the most highly debated topic in Surround mixing.

With 5.1 Surround, we are now surrounded with 5 full-range speakers, and we also have a subwoofer. Do we send all the bass to the subwoofer? Do we ignore the subwoofer and send all the bass to the full-range speakers? Do we send bass to both the full-range speaker AND the subwoofer?

Actually, different recording engineers try doing different things with the bass. More than anything, though, what is determining the direction of this debate is the playback equipment that is going into home theater systems.

Here is how home theater Surround decoders and receivers work:

They send any information from the subwoofer channel of the recording (called the LFE channel, for "Low Frequency Enhancement") directly to the subwoofer. It also filters the low bass out of the other 5 channels, and sends it to the subwoofer also.

Some decoders and receivers use a fixed crossover frequency for filtering the low bass. Others allow the user to tell it if your system has "big" speakers or "small" speakers, and they adjust the bass crossover frequency by guessing how low your 5 full-range speakers can go.

So, as a recording engineer, you have to pay close attention to where you send the bass.

In Mx51, you can drop a SubBass crossover onto any input channel. The SubBass crossover component is on the component toolbox, labeled "sub".



When you drop this on a channel, it gives you a "SubBass" button. When you click on the button, you can adjust the crossover parameters.



With the SubBass crossover, you can extract the low bass from any input channel and send it to the LFE channel, for playback on the subwoofer. You can also send the low bass out to the full-range speakers if you want (by selecting "Thru" under "Surround channels") or you can remove the low bass from the full-range speakers (by selecting "High Pass").

For some really high-power low frequencies, try sending the low bass out to all channels, and let the home decoder/receiver filter it out of the 5 full-range channels and send it to the subwoofer along with your LFE bass. You can rock the house!

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Jeff Wilson works for Minnetonka Audio Software, maker of software for professional sound recording and editing. He can be reached at jeff@minnetonkasoftware.com.