Audyssey Pro EQ Calibration and Acoustic Bubble

Before an installer begins his first installation he will have been asked to register himself and his serial numbered kit on the Audyssey website. Doing this will establish a personalized folder of the various installs that the Installer has performed. This in-house data base will allow Audyssey and the custom installer's company to have a full time access to all his installations.

NOTE: Since I knew that Audyssey Sound Equalizer should now be capable of approximately 1/24th octave data gathering in the two low bass octaves I switched out the on-board R.A.B.O.S. parametric equalization on both Infinity subwoofers. Now that I had two separate bass channels I figured the Sound Equalizer should easily be capable of doing this most band-critical phase and frequency equalization.

Once past the initial Audyssey welcome screen here are the screen sequences that follow:

• Product selection : Audyssey Sound Equalizer (or Audyssey OEM's product and model numbers later on)

• Options : Serial numbered microphone matched to CD s/n is listed.

• Zone Configuration : How channels in each zone are assigned. For instance Zone 1 could be a 5.1 system set up in the home theater room and Zone 2 could be a stereo set-up in another room. For my combination living room/home theater set-up I chose to do a 6.2 system because I needed two separate bass channels. (This is due to my non-symmetrical layout of the subwoofers in our living room.) This meant that I had to place the left-rear and right rear surround channels in series instead of operating them independently as I'd done when only the Denon AVR-3806 receiver was being used. Two notations:

• a) This 6.2 configuration leaves one channel of the Outlaw Audio amp unused.
  
  b) There are only 6.1 channels (maximum) of information discretely recorded on a Dolby Digital EX or DTS Neo 6 release.
  
  The 6.1 to 7.1 split that takes place in most receivers uses matrixing to derive the seventh rear surround channel.

• Select a Zone : If you have more than one Zone this screen comes up.

• Room Dimensions : Enter Length, Width and Height and the Room area comes up. I would have thought room cubic volume to be more helpful information but Mike Thuresson tells me that this screen's information is not tied into any type of calculation relating to the selection of high frequency roll-off curves which is seen on a later screen.

• Rather, this Room Dimension screen meant to be used as a guide to the installer/technician who is running the software. This screen aids the technician and his client in selecting the curve that would be most appropriate for his client's room and taste in sound balance. Thus, at a later date the installer can;
• Have a record of the room's square footage.
• Use this screen's information to inform the client of the possible future need for recalibration if, for instance, the client moves his listening position furniture around.
• Additionally, Audyssey uses this data for R & D purposes to create better algorithims.

• Equipment Info : Spaces are given for Primary Source Component, Preamp/Processor, Amplifier(s), Main speakers, Center Speaker, Subwoofer(s), Surround Speakers and Back Speakers. I filled in all relevant manufacturers, model numbers and in the case of speakers, a short description. i.e. 5.25" two-way.

• Measurement: At Last! The most important placement of the microphone is the first. Start at the position that, in theory, should give the best "sweet spot" flat-frequency response. i.e. Place the microphone at the seat height which would put your ears and eyes directly in line with your video display and center channel speaker .

• In our situation the center of our sofa is exactly 9.1 feet from the video display and our center channel speaker. The center channel Beta 10 speaker is mounted over the Sony HDTV and pointed (with the aid of a flat sided, red laser pointer), angling down toward where a 6' listener's head-center would be. The left and right front speakers are also toed in and angled (via laser pointer) to the exact center-of-sofa spot. In our set-up. The left and right speakers are 6' apart. This gives my set-up a slightly less than ideal ±20° spacing from the 0° center channel centerline. (Minimum recommended left-right spread is ±22.5°)

Note that neither my wife nor I usually sit in the center of the sofa. I sit on the left side of the sofa and my wife sits or even lays down on the right. The goal is to calibrate for optimal flat response performance within the acoustic bubble. The optimum acoustic bubble shape will be determined by the seating arrangement in the room.

Note: If you as an installer have already followed due diligence with respect to the THX/ITU775 speaker layout (from Part I of this review), building your acoustic bubble space from the center sweet spot outward will allow MultEQ Pro to work in optimal acoustic and psychoacoustic fashion.

Good data in = awesome performance out .

Once MultEQ Pro went through its first sequence to determine that all satellites were in proper absolute phase (or in phase with positive polarity) the actual measurement sequence could begin. Our room/satellite/subwoofer layout from the center-of-sofa, sweet spot microphone position is as follows: (Microphone at 35" height just above, inside sofa back.)

• Left Front; -20°, 35" H to midpoint between tweeter/woofer, 9.1' to mic
• Center; 0°, 53 舡 H to midpoint between t/w, angled downward, 9.1' to mic
• Right Front; +20°, 35" to midpoint between t/w, 9.1' to mic
• Right Surrounds; +90°, 96" to midpoints, woofers on top, 12.5' to mic
• Rear Surrounds; +200°, -160°, 85" to midpoints, woofers on top, 14.5' to mic
• Left Surrounds; -90°, 85" to midpoints, woofers on top, 15.5' to mic
• Subwoofer, Front; 0°, 10.1' to mic
• Subwoofer, Rear; +200°, -160°, 6' to mic. Sub faces forward toward listening position.

When I first ran through my planned ten mic position, twelve sample iteration sequence it didn't occur to me until I got to the Detection Results screen that I'd have two different subwoofer trim settings to deal with. And the Denon AVR-3806 only has one subwoofer trim adjustment. Hmmm...

The answer is simple. I shortened the full system calibration sequence to only three microphone positions. Left, center and right, at head height across the sofa. That got me to the Detection Results screen quickly.

Once I could see the two different subwoofer gain results I readjusted each sub's gain controls accordingly to bring the trim figures more in line with each other. As would be expected the more powerful, corner mounted 12" front subwoofer needed to be dialed back a bit while the non-wall augmented 10" sub at the rear had to be driven harder.

I had to go through this sequence twice, re-adjusting each sub's gain controls until both showed that they needed the same amount of trim (in dB). Now I could go back and run the full ten microphone position, twelve-sample iteration sequence (to be explained) for all six satellites and both subwoofers. Note: individual subwoofer distances to the first sweet spot calibration position were added then divided in two to get a single averaged distance for the AVR- 3806 as pre-pro.

The Audyssey system's true brilliance lies in its ability to overcome the most powerful of psychoacoustic phenomena, the precedence or Haas Effect, in enclosed spaces. In greatly expanding the acoustic bubble from a small sweet spot to a much larger area, Audyssey's room/speaker correction solution cheats longtime audiophiles - most deeply ingrained stereo dictum which states, "To hear the best reproduction of a recorded event one needs to sit at the tip of an equilateral triangle in the so-called sweet spot."

As it turns out, if you can hold the full bandwidth power response, especially with the L/C/Rs, as flat as possible over a very wide listening area your ear/brain mechanism perceives all sound sources with greater clarity. That is, at far-off-the-ideal-sweet-spot locations, i.e. say the outer right fringe of the Audyssey acoustic bubble, the left front and left surround speakers will still sound remarkably well balanced.

Said another way, with Audyssey engaged, sitting to the right of the sweet spot allows you to still hear the left front and left surround speaker clearly. Stay in that same right-of-sweet-spot position and turn Audyssey off. The acoustic bubble collapses and left front and left surround speakers become very difficult to hear. The Haas effect, closer right front and right surround speakers, takes prominence and the total surround envelopment effect is lost.

In my centralized-corner home theater the measured left surround-to-right surround diagonal span is 27". The width across my couch (for my data acquisition) is 8'. Our front-to-back-of-theater diagonal is 23.6'. And the depth of our elliptical acoustic bubble measure from in front of to behind our sofa is 5' .

With the above in mind here are the ten microphone positions (with twelve sets of data) that were used to "form" the optimized acoustic bubble listening area.