Mid-July 2007

Audiolics Anonymous Chapter 94
Optimizing The Old Lexicon MC-12 By Using The New
Article By Bill Gaw

  Welcome to another meeting of insatiable audiophiles. This is mid-June as I write and we are into our second heat wave of the year. Now you have to understand that a heat wave in New Hampshire is not the equivalent of one in Arizona, as we consider hot to be anything over 90 degrees Fahrenheit for more than a few hours. But here, it is accompanied by high humidity and for those of us used to below zero weather in the winter it is HOT!! Especially when running 5 pairs of 300 B tubes with their drivers, tube preamps, projector televisions, etc. Thank God I put in Central Air two years ago.

I can still remember days back in the 1980's when I was running behemoth tube amps with multiple 6550's how hot and uncomfortable the room would become. Of course, opening the window would have helped, but unhappily, my closest neighbor over 200 yards away would complain about the noise. Its amazing what an audiophile will put up with for discomfort to get his fix of music.

There were also those sessions at The Listening Studio, run by Clark Johnsen in an old mill building's top floor in downtown Boston, also without cooling. We'd evaluate equipment in the super-heated space as long as possible, then open the windows and put on a large fan to blow in at least a modicum of cooler air, then close them and shut off the fan so as not to disturb the sound evaluation. There, the winter weather was almost as bad, as the heating system consisted of a large ceiling-hung hot water heating system with a very noisy blower fan that also had to be turned off for listening. Without insulation in the brick walls, the room would get cold fairly fast. My media room at the time didn't have any heating system, but relied on heat circulated in from the house. Unhappily, the door had to be open for the heat to circulate, which produced difficulties with the non-audiophile family members. Of course, the tube amps significantly helped that problem. When I went over to solid state for a while, it ameliorated the summer heat problem, but did little for the winter cold. Such were the times. Obviously we were artists suffering for our art.

Anyway, these problems were solved in the Gaw Media Room when we installed a groundwater heat pump heating-cooling system with circulation into the listening space. The main reason the system was put in was to "benefit my wife's allergies", but it certainly didn't hurt my listening sessions; that is, until last week, when one of the cooling system's coils sprung a leak and the replacement part was unavailable. Of course, this had to occur during this mini heat wave, which brought these fond remembrances back to mind. So I'm back to 1980's underwear-only listening sessions until the cooling system's functioning again. That's a horrible image for you to ponder.

Lexicon MC-12 Music & Cinema Processor

As you know from reading my previous columns, I have what some would call an eclectic system, mixing the best of the old and new. While I'm into 1930's horn loudspeakers, and 300B tube amplifiers for the stereo and center channels, my music system is also my video system, consisting of an up to date 8.1 surround sound setup using solid state amplification for the rear, side and ceiling speakers. While the projector is a 1990's Electrohome 9500LC 9" CRT unit for a picture still superior to the solid-state units out there, the sources vary from ancient but still great vinyl (even 1900's Edison Diamond Discs) to SACD, DVD-Audio, and the newest high definition satellite audio and video. Although open reel tapes have disappeared from my system, the new HD-DVD and Blu-Ray have not found a place here, and won't until they finally produce a machine that will play back the high definition Dolby and DTS audio (which may or may not be as good as SACD and DVD-Audio, which seem to have been abandoned by the majors equipment producers, even Sony).

I mention the above to show that I'll use what I consider to be the best equipment available; whether the latest or the oldest, that will produce the best picture and sound available. In addition, all my purchase decisions are predicated not only on quality, but also on cost, as befits my Scot heritage. While I'll spend the arm to get a better product, the leg will remain attached. I confess I go for the deal every time possible. While this meant years ago going from audio salon to audio salon seeking out specials and used products, various web sites have made the task of purchasing gently used products infinitely easier. On the other hand, it does improve your chances on being ripped of, so buyers beware. This has produced a problem for the audiophile; purchasing and evaluating new equipment has become harder as audio salons have closed right and left over the past few years as the web and big box companies have competed, and people like me have moved away from using them. "My Bad" as the younger generation says.

So what's the point of the above? Simply that with the changeover that is occurring on the home theater side with the introduction of the HDMI digital link between equipment, many stratospherically priced high end preamp-processors, using classical RCA, XLR or BNC analog and digital connections, are coming out on the used market at unheard of low prices. There are always first responders out there who have to have the latest and greatest, and I was one in the past. Likewise, there will always be individuals, like myself at present, who are willing to wait until a new technology matures before buying the latest and greatest, and are willing to snap up the great, but not the newest, discards at fire sale prices.

Thus, three months ago, Lexicon announced that they were coming out with an update to their MC-12 music and cinema processor, the MC-12HD, with no plans to upgrade the original MC-12's to HDMI status. Immediately, and for the succeeding weeks, many of the original MC-12's have been seen on different auction sites. To own one of the Lexicon  units has been an ambition of mine for several years but just couldn't see spending north of $13,000 for one. A Revision 4 balanced unit came on the auction block, and luckily, I had the winning bid of, I kid you not, $4000. What a steal, especially since no one is certain that the HDMI connection will carry the audio digital signal to high-end standards.

For the past 10 years I've owned and admired several iterations of the pre-pro's from Enlightened Audio Design, or EAD, called Theatermasters, but the company went out of business a while ago and there were no further updates forthcoming. While the unit was superb, and its sonics were such that several reviewers, including two from Stereophile, had them, the unit was a dead-end, and there was only one place accepting them for repairs. Plus, I had always wanted to try DSP for room and speaker correction, with the Lexicon unit being one of, or possibly the best unit for this. Happily the EAD was auctioned off to an individual from France who admired the EAD equipment, for almost the same amount of money paid for the Lexicon.

Lexicon, originally a pro company making reverb and digital signal processing units for the recording industry, has been producing pre-pro's for about 10 years, with the MC-12 being manufactured for about 6. During that time, the chassis and hardware hasn't changed much with everything being controlled by software, which was easily upgradeable but only by their factory authorized stores. There are two models, the regular single ended RCA audio output and the MC-12B, which has balanced circuitry and XLR outputs.

There have also been 5 changes in software, called "Levels" by the company, each time adding new digital signal processing either for new audio codecs, or for room correction. The latest, Level Five differs only from Level Four in allowing stereo subwoofers, Dolby Pro Logic IIx decoding and the ability to use microphones with room correction software to allow live music presentations in your room to have the feel of being in a concert hall, called LIVE for "Lexicon Intelligent Variable Environment." Steve Stone, fellow reviewer for this rag, has told me that it works exceedingly well at this task. But for those content with a single subwoofer channel and are not considering holding live concerts in their rooms, that the Level Four Software is great. What made the deal even better was that the unit also included a four microphone $1000 add-on by Lexicon that is used to do the room correction. Such a Deal.

While all of the 8 analog stereo (or 3 stereo and one 5.1) inputs are single ended, the audio output circuitry on the B unit is completely balanced with 10 main room outputs and a pair for Zone Two and two unbalanced Recorder outputs, each Zone being independent in connection and  control of inputs. For instance, if someone produces an HD-DVD player that outputs 7.1 analog channels, one could connect two of them to one of the stereo inputs and route it to the Zone Two outputs attached to the added amplifier and speakers. Thus, theoretically, one could set up the unit to actually control 12 different sets of speakers in the same room if one needed the channels. My room is set up for 8.1 with two rear and one overhead channel for those few Telarc SACD's which have an overhead channel, so this feature may be a boon in the future.

There are 6 coax and 6 optical digital inputs with rates from 16 to 24 bits, 44 to 96 kHz. On the video side, there are 5 composite, 8 s-video and 4 component video inputs with a separate video amplification and processing for the component video inputs and 4 composite, 4 s-video and one component output for those who will use the unit as their video switcher. As I have a Calibre Vantage video switcher processor, none of the video signals go through the MC-12 unit normally. I did try plugging in several video sources to check for audio distortion with video RF floating around the chassis and didn't hear any degradation in the audio processing, so the isolation between the audio and video systems must be very good. On the other hand, one of the few weaknesses of the unit is a slight noise in the audio signal when the front LCD panel is on. Therefore its best to set the unit to turn it off when music is playing. For the setup of the room correction there are four mini phono plugs for the needed microphones.

So you may ask, why, if I had one of the best sounding pre-pro's that has ever been made, did I switch to the Lexicon? First, because Lexicon has been around a long time, have regularly updated their products, and have not gone out of business. But, more importantly, they are the leaders in the field of digital signal processing, especially for room correction and codec decoding. At this point with my system and the lack of need for HDMI and video processing, as there is still no ability to do decoding of the new high definition audio standards, the MC-12B Level Four was the perfect pick, especially at its fire sale pricing.

First, the unit is built like the proverbial "brick outhouse", weighing 45 pounds or more than most of my amplifiers. Parts, including four DSP engines, are some of the best available. The instruction book while very long at 200 plus pages is extremely well written and informative, but several of the sections had to be read two or three times for full comprehension by this reviewer, but then I'm not an engineer. The backlit remote, is well-configured, and while intricate, with each button having two to three functions, is well thought-out and fairly intuitive to use once one masters it.

Second, while I was afraid that the unit would not sound as superb as the EAD, in its non-DSP mode, allowing the signal to pass straight through without processing, it sounded great, just different. While the EAD was a little towards the romantic of neutral, the Lexicon drifted toward the slightly analytical, sounding slightly more open and clean on the top end with firmer deeper bass. While the Dolby and DTS processing were superb, maybe even better than the EAD, their Logic 7 processing takes DTS and Dolby digital to a new level. Even their simple reverberation constructs for concert halls, church, jazz hall, etc. are the best I've heard, and on some 2 channel CD's the concert hall effect actually sounded better than any other surround mode, and far superior to any others I've encountered.

Then there's the room correction. Through a simple four step process that takes approximately 30 minutes, with the use of its four microphones, speaker distances, volume, subwoofer crossover, and, most importantly, room correction for response peaks and trough anomalies can be corrected for all of the speakers individually. Since each speaker is done independently, not only will standing waves be smoothed out, but also problems with the speaker's frequency and time response. If one bunches the microphones at the sweet spot, it will be optimally corrected, but one can also spread the four microphones out to the various listening positions to get an averaging for all of the listening area. Which to do will depend on whether you're a typical audiophile who wants optimal sound in the sweet spot, or the family type person who wants everyone to have decent sound. One can even set up the unit for a sweet spot, then reconfigure the unit for a wide area before inviting friends over, by redoing the setup, as it only takes 20 minutes. This is an advantage of the Lexicon, as other units require a technician with a computer to redo it every time one changes equipment.

One can then turn the room correction on and off while music is playing to hear the difference, and with a program such as Dr. Jordan's Audio Realtime Analyzer, , a superb product by the way that can be used with any computer and a decent microphone, hear and see the difference.

As 90 percent of the time I'm the only one in the room, I set all four microphones at my normal listening position and set the unit to automatically go through its program. After about 20 minutes of frequency sweeps and pings, the unit had evaluated each individual speaker for distance, volume, and room correction, an in the process will correct for anomalies in the speaker's output. Interestingly, my chair, although it looked as though it was perfectly centered, was actually 1 foot closer to the rear speakers and the center speaker measured 1/2 foot closer than the fronts. As most of the speakers couldn't be moved, my listening chair position was changed, the center channel speaker was pushed back, and the process was repeated. This time the time alignment was right on.

Looking at the various speaker curves both before and after room correction on the Realtime Analyzer was very informative, and allowed me to make some adjustments in speaker assignment, placement and crossover corrections before final setup. This allowed the maximization of the speakers' potentials before using the Lexicon for it's digital room and speaker correction. Using both the Audio Analyzer and the Lexicon's room correction made this task much simpler than either alone.

While "statistics lie," speaker curves, depending on how they're manipulated, can be made to show almost anything you want depending on how the variables are adjusted. For instance, if one sets the width of frequencies to one octave steps, one can get a curve that makes the speaker look as flat as a plane, whereas if its set to 1/32 octave, all sorts of horrible anomalies of both the room and the speakers show up with huge 10dB to 16dB. spikes. To me, the ideal measurement setup was at 1/12th octave steps.

On the other hand the one octave measurement did show that all of my speakers had been tuned subconsciously by your truly to have about a 1dB per octave decrease from about 100Hz to 20kHz, with a 2dB per octave increase from 100Hz to 20 Hz. This probably goes along with my preference for the lush sound of Boston's Symphony Hall and New York's Carnegie compared to the newer halls such as Atlanta's and Avery Fischer. Whether this would affect my judgment when reviewing equipment, you'll have to decide, but that's the way I like it and that's the way it will stay.

Second, using a 1/12 step octave sweep and a 20Hz to 20kHz ping, I did find an anomaly in the four side and rear and center speakers with a hole at the 360Hz crossover between the woofers and mid-range drivers, due both to a time alignment problem and a drop-off in the output of the mid-driver. This was easily corrected by an adjustment of about four inches to the mid horn backward, and adjusting the Behringer active crossover's frequency crossover and volume. Interestingly, the front left and right main speakers using Alan Wright's Vacuum State preamps with built-in crossovers had almost perfect crossover points. Go figure. The center's subwoofer, a Carver unit, also needed a little tweaking on its crossover point and volume to better match the front left and right speakers.

Interestingly, there was no such anomaly between the mid and tweeter crossover point in the frequency sweep, even though there's almost a foot discrepancy on their time alignment, although it did show up in the impulse and step response graphs. Whether that's due to the very short wavelengths or the test equipment's inaccuracies at the 10kHz crossover point, I have no idea, but if indeed it's not a problem, then this would certainly negate the necessity for mid to tweeter time alignment that some loudspeakers proclaim as being necessary to fractions of an inch.

Third, my original setup had one pair of subwoofers for the subwoofer channel, with a separate subwoofer for each of the surround and main speakers, thus running all of the speakers full range with their own assigned subwoofer. When run in this fashion, each subwoofer showed 6dB to 10dB spikes and drop-offs, but because each is at a different point in the room, the anomalies were at different frequencies, so tended to even out somewhat even though they had different signals.

Then I got the bright idea of just leaving the front speakers as "large" with their own subwoofers, and making the four side and rear speakers "small", with their lower frequencies and the subwoofer channels mixed, thus allowing all their energy to be shared. The crossover was at 80Hz, 24dB per octave, which theoretically should be below where one can pinpoint the source. As each sub woofer-amplifier combination had varied sensitivities, I did have to add a balanced distribution amplifier with volume pots, and then run low frequency sweeps to adjust their individual volumes. The frequency sweep with all subs tied together then showed only 3dB to 6dB spikes and dips in only four places between 20Hz and 100Hz, significantly better than previously.

Once all of the speakers had been adjusted and balanced optimally, the Lexicon was once more put through its program for speaker and room correction. With the Lexicon's digital processing not needing to make up for some of the speaker's anomalies, the curves for each speaker were even flatter than before all of the mechanical correction, but with the slight 1 dB downward slope still in place. The unit was then set up so that each source could be heard either flat or with the room correction by using one button on the remote. Although the switching took about two seconds, so was not seamless, and so-called true ABX testing could not be performed, the changes were significant enough so that anybody with two ears and a brain between should have been able to hear the difference.

First, the Bass. On a frequency sweep, in the main listening position, using a Radio Shack meter and my ears, the rapid volume swings between 20 and 200 Hz. endemic to most audio systems due to room standing waves were almost completely gone. Music became much less boomy, with added weight and tightness.

On stereo recordings, the soundstage was cleaner, wider and deeper, with much more ambiance effect. On those recordings done in Kingsway Hall in England, not only were the subway trains clearer, but also one could almost make out which way the different lines were running. I'd never been able to hear this before on my system. Now some of you may wonder why listening to subway noises on a recording is floating my boat? Because it tells me that bass energy with its overtones, if properly reproduced, is indeed directional, and the Lexicon in the system will improve it.

Using the different Logic 7 processing for both two channel and DD and DTS recordings significantly improved on the ambiance recovery. Previous gaps in the soundfield between the speakers, especially between the front and side speakers, were narrowed. With the overhead speakers turned on with the few Telarc recordings that I have which matrix the overhead with the subwoofer channel, the soundspace was almost seamless, and far better than anything I've heard in my room previously.

The biggest surprise was listening to two channel symphonic CD recordings using the  concert hall setting. Basically, while the other codecs use ambiance recovery, this is just a reverberation program that takes the front channel information and adds reverberation to the rear and side speakers based on measurements gleaned from concert halls. In addition, while the Logic 7 and DTS Neo-6 programs which also reconstructs a center channel, this seems to muddy somewhat the soundstage compared to just using the left and right speakers, although it can solidify the center of an orchestra on those stereo recordings where there is a central gap between the strings. Lexicon, if I remember correctly, actually started out years ago as a developer of these programs in the two-channel era, and it certainly shows.

Now you may ask, what's the effect on analog signals. Vinylphiles, including yours truly, detest having to take their signal through the A/D and D/A process, but in this case the advantages far outweigh the disadvantages. Running the signal from my Walker Proscenium Gold turntable with Kondo IO cartridge straight through the unit without processing gave no discernible difference over running it through just my VacuumState preamps, and allowed me to use the remote control for analog volume adjustment.

When the DSP was switched in, there was actually an increased clarity to the soundstage. Also, for some reason, the subwoofers didn't go as crazy with record warp subsonic information. In addition, the MC-12 has separate controls for bass and treble, and has a tilt control which allows adjustment of bass in relation to treble across the frequency band. Judicious use of these can significantly improve the sound of those many vinyl recordings which were injudiciously jimmied with by the recording engineers, especially those Columbia's and Dynagrooves with their screwed up sound. In addition, with the best of the minimally mic'ed vinyl having hall ambiance information, its recovery and placement in the surround channels significantly improves the image.

Since I've only had the EAD pre-pro for the past several years, and have only heard other room correction- signal processing units at shows where the sound is always less than ideal, and I haven't heard the latest that Lexicon is offering, I can't comment on how the MC-12B compares to other units, especially the Audyssey, which did sound wonderful at the last CEDIA. What I can say is that using the newest digital signal processing to make corrections for the weaknesses of horn loudspeakers and tube amplifiers has added significantly to my enjoyment of my system.

Loudspeaker manufacturers have caught on to the advantages of DSP processing to replace passive and active crossovers, and several at the New York Stereophile show demonstrated new speakers using this method either in addition to or replacing crossover components. While this does require separate amplifiers for each driver, using the proper processor, computer, and brain, it should be possible to construct better and more accurate loudspeakers that will be adjustable for every room and taste. In the meantime, at least for me, the advantages certainly outweigh the minor disadvantages.

Lexicon is not the only company that will be updating in the next couple of years to the HDMI interface so I expect several other company's units will also go on sale. I even saw an advertisement today for an MC-12 Level 4 single ended unit for $3200. As an infamous audio dealer from New York used to advertise "These prices are insane!"