Audyssey MultEQ Pro Sound EQ Overview

Ultimate audio performance within the listening area starts with the loudspeakers and the room. How the Installer gets the loudspeaker system to integrate within the listening space is what can make or break even the best assembled audio systems. In our article Better Sound Through Active Room Correction (recommended reading before reading this review) the important metrics of loudspeaker placement and selection, room acoustics, and how to best integrate all of these variables using the new Audyssey Pro MultEQ enabled processor for the ultimate theatrical experience in the comforts of your home was discussed. We now expand upon this with a formal review of the Audyssey MultEQ Pro sound equalization processor.

Audyssey comes to the table with a proprietary phase and frequency measurement technology. Co-founder and Chief Scientist, Tom Holman, in my December 2004 interview with he and cofounder and CTO Chris Kyriakakis states "While real-time analysis is 'time-blind' (so you have to know something about the time domain before you use it) nevertheless, if you clean it up, it has some advantages over the FFT-based analyzers. The THX R2 (from the eighties) was readily able to do spatial averaging and temporal averaging and we realized if we made an extension of it using a laptop with an add-on spectrum analyzer peripheral that we could send signals across dynamically from the analyzer and do a lot of mathematics to it and therefore clean up the signal."

To gather the precise phase and frequency data requires another capability; extremely accurate (claimed to within 0.25" !) speaker-to-microphone distance information. When an installer begins to go through the Audyssey Sound Equalizer measurement routine the first packet of data he feeds into the MultEQ Pro's memory is the speaker task-name such a left-front, center, etc. (The installer will have already defined the size of the room [length, width and height] on a previous screen within MultEQ Pro). While it is taking distance information MultEQ Pro will also take the first 200 milliseconds of phase and frequency data and place the information into the i.e. "left-front" folder. Repeat the operation with the microphone stationary at this first "sweet spot" eight times (for the Sound Equalizer's 8 channels) for all satellites and subs in the room. MultEQ Pro will now have a very precise map of how the speakers are arranged in the room.

Online comments from Audyssey CTO Chris Kyriakakis indicates that in the low bass region the Sound Equalizer running the new MultEQ Pro software is eight times (!) more precise than the original (low bass) Dynamic Frequency Allocation Algorithm built into the MultEQ XT receiver-based version. That would give both 20Hz-40Hz and 40Hz-80Hz low bass octaves 1/24th octave precision or better than 1Hz and 2Hz respectively for the lowest two octaves!! The eight octaves above 80Hz receive a doubling of the amount of taps of the receiver-based XT version.

Also bear in mind the Audyssey system captures and manipulates both frequency and phase information. So as long as a separate channel in the Sound Equalizer is assigned to each subwoofer the subs can be placed in non-symmetrical locations within a room and the "acoustic bubble" area within the listening area will still be very precisely optimized for both flattest bass frequency response and correct phase.

(Note: Careful symmetrical placement of dual subs, such as positioning each sub at 1/3rd distance across the front of a enclosed rectangular home theater can allow the use [via Y-connector] of only one of the Sound Equalizer's channels. Thus, two Sound Equalizer channels could be utilized to run four subwoofers just as long as the symmetry of the woofer positions is maintained relative to the desired "acoustic bubble" sweet spot listening position and the room.)

The promise of this extremely precise bass frequency correction for my non-symmetrically placed front and rear subwoofers was the factor that most intrigued me as I awaited the arrival of the Audyssey Sound Equalizer...