MCACC Multi-Channel Acoustic Calibration System

What MCACC is

MCACC is Pioneer's room calibration system for its AV receivers. Pioneer's support documentation describes it simply: place the supplied microphone at the listening position, and the unit measures the test tones from the speakers and automatically sets the optimum volume level for each speaker, the crossover frequencies, and the distance from the listening position. It also reduces the effect of standing waves according to the listening environment, adjusts the equalizers for the speakers, and corrects distortion caused by the room's acoustics. The acronym stands for Multi-Channel Acoustic Calibration System, a name Pioneer's own 2003 press release uses in full.

How a Full Auto MCACC run works

Full Auto MCACC is the one-button path. The user selects the speaker configuration, places the microphone at the seat and connects it to the SETUP MIC jack, and confirms that the subwoofer is producing a test tone. The receiver then sends tones to each speaker and measures the connected speakers and the noise in the room, shows the detection results, and plays tones again to set volume level, crossover frequency and the other values. Pioneer says calibration takes between 3 and 12 minutes, that the subwoofer level should be set to more than half, and that the test tones are loud. After the first measurement it is possible to add 8 more listening positions, for 9 in all, by selecting Next; selecting Finish (Calculate) ends the process. If the receiver shuts off suddenly, Pioneer says a speaker wire has touched the rear panel or another wire and the protection circuit has engaged.

Manual MCACC and MCACC Pro (EQ)

After the automatic run, the Manual MCACC and MCACC Pro menus expose the numbers. The documented ranges for the Pioneer VSX-LX805 are specific. Fine Channel Level trims each speaker from -12.0 dB to +12.0 dB in 0.5 dB steps, and the subwoofer from -15.0 dB to +12.0 dB. Fine Speaker Distance adjusts from 0.1 to 30 feet in 0.1 foot steps, or 0.03 to 9.00 m in 0.03 m steps. The Standing Wave function offers three filters each for the main speakers, the center and the subwoofer; each filter has a center frequency of 63 to 250 Hz, a bandwidth setting from 2.0 to 9.8 in 0.2 steps and attenuation from 0.0 to 12.0 dB in 0.5 dB steps. EQ Adjust provides up to 9 bands for each speaker, from 63 Hz to 16 kHz, and 4 bands for the subwoofer, from 31 to 250 Hz, each adjustable by plus or minus 12.0 dB; the 63 Hz band is available only when the speaker is set to Large in the crossover setup. "OVER!" on the display means a band or the combined boost is too high.

The third part is EQ Professional. It measures the reverberation characteristics of the room, displays them in Reverb View per speaker and frequency, then lets the user choose the Time Position to calibrate. The default is 30 to 50 msec, selectable from 0 to 20 msec up to 60 to 80 msec in 10 msec intervals. Pioneer recommends 30 to 50 msec when reverberation differs by frequency or channel, and 60 to 80 msec when it is similar across the board. The default EQ type is Symmetry. Standing Wave Multi Position, off by default, can be set to 2 through 9 positions so that standing wave calibration is run at several seats, with the main seat calibrated last.

A short history

A Pioneer press release from June 26, 2003 introduced the VSX-55TXi and VSX-53TX with a "refined" MCACC and an "advanced" MCACC. The system checked ambient noise, the microphone and speaker level, confirmed speaker size and distance, ran a surround analysis, then played pink noise and timing pulses that fed a nine-band digital equalizer for final calibration of up to seven channels, with 96 kHz and 24-bit analog-to-digital conversion on all channels. Pioneer's naming has shifted: the 2003 release says "advanced MCACC," and the current VSX-LX805 menu is titled MCACC Pro (EQ). The tiers also show in the menus. The entry-level VSX-535 documents only Full Auto MCACC and an MCACC Data Check that lists speaker settings, channel levels and distances, while the VSX-LX805 adds Manual MCACC and the Pro (EQ) pages described above.

MCACC alongside Dirac Live

Current Pioneer Elite receivers can run either system. The VSX-LX505 and VSX-LX805 support documents both include MCACC and Dirac Live, and they carry a warning: if Full Auto MCACC has been executed, the speaker calibration made with Dirac Live is disabled, and when measurements are made with Dirac Live, the Manual MCACC and MCACC Data Check functions cannot be set. So the choice is one or the other at a time. For a subwoofer-heavy room the comparison is with Dirac Live Bass Control, and the Anthem equivalent is ARC Genesis. The Audyssey family, MultEQ XT32, is a different system on other brands.

Which receivers and what it cannot do

Pioneer's support site carries MCACC articles for the Elite VSX-LX305, VSX-LX505 and VSX-LX805, and the VSX-LX305 troubleshooting page lists Dirac Live as a related article too. Treat the results as a starting point. The VSX-LX305 page says Full Auto MCACC can report speaker distances that differ from the real ones, in which case you set them by hand under System Setup, and that a subwoofer level reported at the lower limit means you should lower the subwoofer's own volume and measure again. The calibration helps with standing waves only at the measured positions, and Standing Wave Multi Position lets it cover up to 9 seats. It also cannot add bass a speaker cannot produce, and the Standing Wave filters reach no lower than 63 Hz, so deep sub-bass problems below that band are handled by subwoofer placement, bass traps and the subwoofer's own 31 Hz EQ band. For the physics behind the 63 to 250 Hz window, see the Schroeder frequency.