DC-2

Posted by Andre Yew on October 05, 1998 at 11:07:46:

In Reply to: DC-2 posted by carl on October 02, 1998 at 11:51:16:

While this scheme sounds like an interesting idea on paper, in reality, it is much more difficult to achieve good results because of:

1. Mic position (wavelengths at 3 kHz
are on the order of 4 inches, and sound can vary greatly over that much space).

2. Mic off-axis response. You cannot precompensate for off-axis response problems, and this will affect other channels, and reflected sound.

3. Non-minimum phase reflections. Unless you have a system like the SigTech, it is impossible to correct (even with stuff like the Z-Systems devices) for reflections with a minimum phase equalizer (what every EQ in the world is). If you're hoping to correct room modes due to bass, this is the most important point.

4. Size of sweet spot. As mentioned above, the wavelength of 3kHz is 4 inches, so you depending on how high in frequency you want to take the correction, the sweet spot narrows linearly with increasing frequency.

5. Huge computational overhead. I've seen a SigTech (lots of Motorola DSP56000s in one box) being calibrated for one room with a very high-end and linear B&K omni mic, and it couldn't smooth all of the bumps out, especially in the bass. The more you want to smooth things out, the more computational power, and more importantly, the more latency through the system (latency translates to the audio falling behind the video). It gets very expensive.

Given how difficult it is for a human to place one mic and calibrate the room with a system whose only purpose is to correct the room, I think that the mic auto measurement thing is a gimmick, and money would be best spent elsewhere on more effective measures.

--Andre

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