Correcting the Room
The Pioneer VSX-49TXi ($4,500) and VSC-45TX ($1,400) receivers come with what Pioneer calls a Multi-Channel Acoustic Calibration Circuit (MCACC). A microphone plugs into the receiver. The process automatically checks ambient noise levels, speaker size and several other things before performing its surround analysis with pink noise and timing pulses. A seven-channel, nine-band EQ does the correction, however, it does not affect the sub. The user can manually override the automatic process with his own settings. Pioneer's lower-priced VSX-43TX ($1,200) offers a manual-only version of MCACC.
Even Bose has reacted to the room-correction trend with its Lifestyle 35 ($2,999) and Lifestyle 28 ($2,499) — all-in-one systems that include speakers, amplification and a DVD-Video drive. The user wears a headset outfitted with mics, thus identifying acoustic conditions to the system, which takes about 10 minutes to make adjustments. Earlier versions of the two systems don't have the room correction process, which is called ADAPTiQ, but a DVD-based software upgrade is available. While these Bose systems don't require an installer, they illustrate how mainstream room correction has become.
THERE ARE LIMITS
Before you get excited about the prospect of using room correction as a panacea to fix all kinds of problems, be advised that at least one manufacturer has made a credible claim that room EQ has some pitfalls of its own. According to a Meridian white paper, "The Gentle Art of Room Correction," one obvious problem is that the EQ itself might introduce ringing and phase errors. The paper goes onto discourage anyone from using an EQ to simply invert frequency response because that brings a number of other problems.
For instance: "To change a non-minimum phase response into a linear phase response requires that [the] signal starts to emerge from the filter before the sound has arrived at its input. This requires the filter to know what is going to happen in the future." If the filter did have such predictive powers, it would also introduce pre-echoes, and the time needed for the signal to pass through the system might lead to video sync problems.