Audyssey MultEQ Pro Sound Equalizer Review

In our living room/home theater layout I run an acoustic suspension Infinity Intermezzo 1.2 1", 850-watt sub in the front corner of our living room. The sub sits just behind the equipment rack that will hold our 56" Samsung LED DLP video display. Using Infinity's R.A.B.O.S. CD measurement system, in-room response of the 1.2 measures -1 dB @ 20 Hz with ±1.5dB frequency response up to 80Hz. Back at the center-of-couch listening position the 1.2 can hit 108dB without breaking a sweat.

Listening area; left surrounds at top left above fan blade. Listening sofa at bottome left. Three Beta 10 LCRs and Infinity Intermezzo 1.2 tucked behind equipment rack in corner. On right, close-up of Intermezzo 1.2 in front corner behind equipment rack.

A second sub, an acoustic suspension Infinity CSW-10 was one of my designs and originally part of the Infinity Beta series. The CSW-10 is a 25 lb. magnet structure, 10", 650-watter, also with an on-board R.A.B.O.S. single-band parametric equalizer. The CSW-10 is only 6' behind our sofa but 8' away from the two rear walls because a 90°- bend, two-section staircase to our downstairs is built into that corner. That leaves the CSW-10 working much harder then the Intermezzo 1.2 because the smaller 10-incher doesn't have the luxury of free sidewall or corner bass augmentation. (And yes, for those who may be wondering, the still available Revel SP12 is essentially the same subwoofer.)

If I calibrate the Infinity CSW-10's R.A.B.O.S. parametric in it's open floor position six feet behind our sofa, the sub will chart down to -3dB @ 27Hz and -6dB @ 24Hz, (at 105dB and ±1.5dB to 80 Hz). These are exactly the lower roll-off points and max SPL I had measured in Harman's large 4 pi anechoic chamber when I was designing it. (In the chamber the frequency response was much flatter at ±0.5dB.)

Now plug the two subs together by using a Y-connector from the receiver's subwoofer output and bingo, 6dB more headroom than with a single subwoofer and smoother in-room response, right? Well, not so fast. Once I plugged the two subs together using the Y-connector to the Denon AVR-3806's single subwoofer output I re-plotted the two subwoofers' frequency response to see how the two subs reacted together at the listening position. Horrors! The interaction of the two subs together raised the 3dB down point to 33Hz and the frequency response variation envelope expanded to ±2.5dB up to 80Hz.

The reason for this problem was that the Infinity subs only have 0° or -180° phase controls. And the CSW-10's position, back 75% into our room would require its compatible (at the listening position) phase setting ( relative to the Intermezzo 1.2) somewhere in between the 0° and 180° choices. When trying to use the Denon AVR-3806's internal MultEQ XT along with the Infinity subs' 1/20th octave frequency dial-in capability the phase differential problem could not be resolved with enough accuracy. Thus, to apply a sufficiently accurate frequency-phase data package for each sub, as measured from the listening position, requires two completely separate packages. (The Denon AVR-3806 can't measure the subs separately as it has only one dedicated and assigned subwoofer channel.)

This interaction of two different, but very capable subwoofers points out just how absolutely intertwined, because of wavelength, half-wavelength and every portion of wavelength in between both the room and asymmetrically placed subwoofers become. At the listening position each mono, electrically correlated bass note will arrive in a slightly differing positive or negative phase, ready for a fight. Remember the rest of Forest Gump's "Life is like a box of chocolates" line?

The upfront corner mounted Intermezzo 1.2, for instance, would generally be assumed to be at 0° starting phase because of its position in the front system corner. This sub is almost in line physically and therefore should be pretty close phase-wise with the front 5.25" two-way L/C/R-s. Plus the L/C/Rs' close proximity to the corner walls augment their low bass performance. Thus when read by the mic at the primary listening position the Beta10s might appear to be able to go down past 80Hz (-6dB) with ease. My thinking then was that the often tough 80Hz subwoofer-to-satellites splice should be a pretty easy blend for either the Audyssey MultEQ XT or MultEQ Pro programs.

The problem comes when the second CSW-10 is added into the mix. If you're talking about any room over 2000 cubic feet of enclosed volume, the potential ~6dB extra SPL headroom gained with a second subwoofer will always be needed to get to realistic SPL on low bass program peaks. The larger your room and the lower you want to go into the first 20Hz to 40Hz bass octave the more headroom (subwoofers) will be required. The Robinson and Dadson equal loudness curves below illustrate this.

To attain a rather loud 85dB at 1kHz you'll see that to match the subs to the satellites you need 27dB of subwoofer gain at 31.5Hz! Since the auto set-up routines for Dolby Digital EX and DTS Neo 6 already boost sub levels +10dB we still need 17dB of below-80Hz gain just to get to "equal loudness". That's one reason why two subs is always so much better a solution than a single larger or more powerful sub. And since we're talking about achieving the smoothest, widest bandwidth possible over the largest acoustic bubble listening area I would consider two high quality/high acoustic output capability subwoofers the absolute minimum to wring out the best bass performance from Audyssey's Sound Equalizer and most listening environments.

The Audyssey technologies are computer programs which must depend on the skill of the System Designer and the Electronics Tech to chose proper equipment and install, position and calibrate the room/components as a unified system. Even the seats are part of the system so do yourself and your clients a favor and stay away from the high backed models that block the ears' ability to hear direct surround information.

The current L/C/Rs for our home system are three Infinity Beta10 s; rear ported, 5.25" two-ways with a 1" metal-composite dome tweeter, ($150ea. SRP). Before you turn up your nose take at look at Dr. Floyd Toole's CEDIA class outline which is available online.

Check out the performance graphs. At the bottom of page 19, the $300pr. of anonymous speakers; that's the Beta 10s. And that's the type of performance envelope specifications that even non-golden eared people will favor time after time after listening double-blind versus similarly priced competitors' speakers.

Audyssey Sound Equalizer at lower left on top shelf in rack. Infinity Beta 10 L/C/Rs. Beta 10s aligned to 34" H @ midpoint on sofa. Sony 32" XBR LCD is temporary.

Surrounds consist of three pairs of JBL SP5 s; 5.25" two- way in-walls with 1" metal-dome tweeters, ($175/pair SRP). The SP5's have swiveling tweeters but I set them straight forward. I like keep the horizontal and vertical axis of woofers and tweeters the same, especially for surrounds. Speakers that are designed to a flat response with smooth but continual high frequency attenuation when moving off axis have been proven to provide a superior performance envelope. So why mess with success? Tilting a tweeter toward the listening area destroys the performance envelope with which it was designed. It also calls far off-axis attention, very high frequencies only, to an area which is supposed to be invisible, for envelopment.

For the eight stereo pairs of interconnects required going into and coming out of the Audyssey Sound Equalizer's eight inputs and eight outputs I went with seven and a half 3' pairs of Impact Audio's SonicWave interconnect. The single long-run interconnect going to the rear subwoofer is a no-name that I made up from cable I had on hand. The required Y-connector from the single subwoofer out on the Denon AVR-3806 to the two subs was also an Impact Audio SonicWave interconnect.

Each of our three pairs of surround speakers (right, rear & left) is wired in series which presents a very easy-to-drive 12 ohm load back at the amplifier (6 ohms + 6 ohms for each JBL SP5). Note from the pictures that each of the monopole surround speaker pairs points at 90° perpendicular angles to each other and toward a different wall (for reflection generation). All surrounds point away from the "acoustic bubble listening area".

I can't refer you to a set of performance graphs for the SP5's but I can tell you that all Harman (monopole) speakers are designed to the same criteria; flat on-axis frequency response with smooth and continual high frequency attenuation when moving off axis.

Looking across sofa back. Dual JBL SP5 5.25" two-way right surrounds. Dual JBL SP5 5.25" two-way left surrounds.

Wire runs from the surround speakers are 14 gauge, twisted two-conductor, off-the-roll Monster. The longest wire runs to the left and right surround rears is ~45'. For the short runs to the L/C/Rs I've used the same DH Labs Silver Sonic T-14 (twisted-pair, 14-gauge) for many years.

Terminations to the in-wall SP5s with push in spring terminals are 3/8" bare copper wire; simply twist wire ends (tin lightly if you like) and insert. Wire terminations to the L/C/Rs are gold-plated and silver-soldered spade connectors which give a tight connection when the gold-plated barrel + and - terminals of the Beta 10s are tightly snugged down. Terminations to the Outlaw Audio 7075 amp are self expanding, gold plated, spring-steel and copper alloy banana plugs which are again silver-soldered to stripped wire ends.

The power amplifier. In the days of stereo receivers many of the higher quality units had true pre-amp out, power amp in jumpers. With today's multi-channel receivers that particular feature is almost non-existent. So when I started thinking about a low-cost, well-built multi-channel power amplifier I turned to long time industry colleague Peter Tribeman of Outlaw Audio and Atlantic Technology. Back in the eighties Peter was one of the founders of NAD, a brand always known for tremendous audio performance for the dollar. A quick perusal of the Outlaw Audio 7075's specs indicated this $599, 7-channel amp looked to be out of the same low dollar, high performance mold.

The Outlaw amp's 75 watts/channel x 7, , looked to be exactly the choice to replace the 7-channel amp section in the Denon AVR-3806. The 7075 is built like a pro product. Heavy gauge steel chassis with beautifully rounded front-to-back edges, a just-under 0.5" (!) thick black anodized front panel, 12V amp-to-pre-pro trigger, and five-way binding posts on the rear. This little bad boy is only 4" H x 15.5" D x 17.2" W yet it weighs 41 lbs (due to a beefy toroidal transformer), more than the entire Denon AVR-3806 receiver.

I knew I was going to high pass all the satellite (loudspeakers set to "small") at 80Hz so the 7075's power supply section would be loafing along even when driving all "small" loudspeakers to their limits. What really sealed the deal though was a damping factor greater than 400 from 10Hz to 400Hz and a slew rate of 50V/microsecond. The 12-ohm surround speaker pairs would be extremely well controlled at their 80Hz high-pass crossover frequency. (Given the lack of an engineered back enclosure for most in-wall speakers, electronic control in the form of electronic damping applied to the speakers - voice coils aids bass damping and control at the in-walls - applied 80Hz low frequency cut-off.)

For the eight stereo pairs of interconnects required going into and coming out of the Audyssey Sound Equalizer's eight inputs and eight outputs I went with seven and a half 3' pairs of Impact Audio's SonicWave interconnect. The single long-run interconnect going to the rear subwoofer is a no-name that I made up from cable I had on hand. The required Y-connector from the single subwoofer out on the Denon AVR-3806 to the two subs was also an Impact Audio SonicWave interconnect.

With the Audyssey Sound Controller between the Outlaw Audio amp and the Denon AVR-3806, the receiver now became a preamp-processor. In preparation for putting the system through its paces immediately after running the MultEQ Pro routine I went into the Denon's menu and configured it as follows:

• Room EQ (Audyssey, Front and Flat) > Off
• Tone Defeat > In
• Left, Center, Right, Left/Right Surround > Small
• Speaker B > None
• Speakers Surround Back > 1 Speaker
• Subwoofer > LFE
• Crossovers > Subwoofers and all Satellites > 80Hz
• Important! Set "3. Input Function Level" on the AVR-3806 to +9 to +10dB for all inputs. i.e. Tuner, Phono, CD, Tape, DVD, VDP, etc. The MultEQ Pro's equalization algorithms can add a maximum of +9dB boost at selected frequencies. So inserting the Audyssey Sound Equalizer between pre-pro and amp attenuates all signals by -9dB to self-assure adequate headroom. Thus when contemplating the use of another model or brand of "pre-pro" it is imperative that the unit's pre-amp section has a true 3 to 4 VRMS gain stage to ensure adequate headroom and protection against input signal overload.

Now the Denon AVR-3806, configured as a pre-pro, can be turned off. It can remain off during the whole Audyssey Sound Equalizer set-up and calibration routine.

The final pieces of audio gear for our home theater is the main A/V source DVD player and a UPS. The DVD player is an $80 Toshiba SD-K860. That's right, a Costco special. How can you beat a player that comes with its own HDMI cable included? Simply amazing value.

One last piece of gear is a Tripp-Lite Omni (aka Smart) 1000 LCD 1000VA UPS with battery backup. Also from Costco and another bargain at $100. This unit is a basic surge and spike protector but with a beefy 1000VA transformer. Neither the subs nor the Outlaw amp is currently plugged into this unit but the amp probably could be without any current limiting. So it's adequate protection until I substitute an APC H-15 with voltage regulation, at which time I will also plug in the Outlaw Audio 7075 satellite amplifier. The two subs each are plugged into their own dedicated 15 amp circuits.

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.

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...

When I saw the very low recommended crossover frequencies for the L/C/Rs and all the surrounds it seemed fairly obvious that the microphone, back at the listening position, was reading the combined low frequency energy of the speakers and the close-proximity walls.

Well, I'm being facetious here, but it's not really possible to equalize walls. And a reality of speaker design is that most 5.25" mid-woofers have a free air resonance around 65Hz to 70Hz. A third factor in the mix is that it is not known what type of target equalization, if any, the MultEQ Pro software might be trying to apply within this range of subwoofer-to-satellite splicing frequencies.

So in my opinion it is best to stick to a crossover frequency with which we are well assured both subwoofer and satellite can function optimally and within their mechanical and electrical design limitations. My favored target crossover frequency, 80Hz is virtually ubiquitous in the movie business since both Dolby Digital encoders and DTS encoders use 80Hz. (Dolby decoders are variable from 80Hz to 120Hz whereas DTS decoders are at a fixed 80Hz.)

"What if - you say - I've got a huge room dip at 72Hz so I can't bring the subwoofers up to 80Hz."

My first suggestion would be to change the location of the subwoofer if you're still using only one sub. A better plan would be to use two subs in the first place, symmetrically located so they can be coaxed to naturally smooth out their two octave frequency response at the listening position within a particular room. If you have two subs and you're still having problems try four subs. The room you're working with is probably huge. It needs four subwoofers.

"Why not just bring the satellites down to 60Hz or 70Hz"

You probably could bring the 5.25" satellites down below 80Hz but be aware that the maximum excursion capability of satellites would become the weakest link in the entire system. A 6.5 舡 mid-woofer in all satellites or at least in the three front L/C/Rs would be the wiser choice here.

Okay, back to the Detection Results Page.

Evaluating the Home Theater Experience with the Audyssey Sound Equalizer

Epilogue