05 April, 2010

HiFi Letter from NYC 2010 (2): Magnepan MMG growing-up pains

HiFi Letter from New York 2010 (2): Magnepan MMG growing-up pains

This time I recovered from jetlag surprisingly quickly, and had little use of the second system after a few days. I concentrated on my main system, The first thing I did was to improve its performance. Current main system:

Digital: Linn Karik/Numerik (Linn RCA cable to preamp); Meridian 500/563 (Gotham GAC-3 XLR to preamp)
Turntables: Linn LP12/Ittok/Denon 304, Lingo power supply; AT PL1200/Grado Gold
Phono preamps: PS Audio GCPH; WE 285L (step-up trans) into BAT P5 (Gotham GAC-3 XLR to preamp)
Preamp: BAT VK3i (Filotex RG58 coaxial thru adaptor to amp) Amp: McIntosh 2200 (4-ohm tap)zzd

Placement
The day after I set up my main system, after not such heavy use, the system was already surprisingly in reasonable form. There was not that much I could do in positioning, but within a 2 sq ft area I experimented and obtained a small improvement. My room is ~12.5 ft in width and 20 ft in length (to the kitchen partition; 26 ft counting the corridor on the right). The speakers are placed ~10-11 ft from my listening seats, and are 6 ft apart (inner edge to inner edge). With those measurements, the manual was correct in saying having the panels upright resulted in better sound (but the opposite would be true for shorter listening distances). Here, I must add that I feel the larger Maggies with non-adjustable upright stands are NOT meant to be used in rooms too small, which would result in an over-bright sound. Take in only what you can swallow, that applies to hifi too. Unfortunately, audiophiles in HK most often ignore this, a result of the pitiable general situation of having money but not space. Blame the real estate tycoons, and the government.

Left or right, game of the mirror image
Some say the Maggies MUST have the tweeters inside. This is too dogmatic, and presumptive by not taking individual environments into account. While the Maggie MMG manual advices at one point to place the tweeters inside, somewhere else it encourages the user to switch the 2 panels and experiment, a good attitude that's there for a reason. In my space placing the tweeters on the outside reaped big rewards: a larger and deeper soundstage, more easeful climaxes and better gradation of dynamics, all at little cost. Okay, with solo instruments there is a slight shift in the position of the images, which also softens just perceptively, but I'd regard the gains far outweigh the slight imaging compromise (haven't you ever noticed even the best Maggies tighten up when the going gets rough?). Most importantly, on big pieces there was just more atmosphere. I surmise the improvements are due to 2 reasons: (1) the increase in distance between the tweeters by more than 1 ft yielded a better ratio, although mine is within the rough Maggie ballpark of 60%; and (2) moving the bass panels a little less close to the sidewalls cleans up the bass a little.

Here I must ponder what people mean by "holographic". Most people link it with imaging, and that's not true at all. Sometimes over-emphasis on imaging reduces the sense of holography, snifling out the real hall sound by creating an artificial soundfield (I'd refrain from using the term "soundstage" as it has no bearing to the real "stage" on which the musicians perform). By having the tweeters on the outside, presumably reducing imaging exactitude (though I hardly noticed), my sound definitely became more holographic and provided more ambient information and sptial clues on the performance venue. By the way, that was not the first time I felt like this; it had happened often (but not always) before with mirror image pairs, from vintage JBLs (4312A and Century Gold) to Proac (original Response 2). All I can say is, experiment.

(Click on pics to enlarge)

Cable Talk

Using the records shown I proceeded to determine which of the 3 pairs of speaker cables I had on hand was best suited to the task. I started with the Belden 9497 (twisted 2-conductor; TPC). The sound was, as usual, undeniably right, and transparent, showcasing all the concertante and solo moments. However, due to its relatively small gauge (for driving the current-hungry Maggies) its sound at big clmaxes was held in with a little restraint. This was particularly evident with the opening of Solti's CSO Mahler Sixth (London), which was less threatening than desired. A swtich to an old pair of Cable Talk Model 3 (thick stranded Cu-parallel conductors) immediately brought more gravitas, but then the sound was just slightly dark (not so bad for Maggies) and more importantly the inner details were audibly compromised. The violin and viola of Grumiaux and Pellicia in Mozart's Sinfonia Concertante (Philips) lacked sparkle and rosin and the highlighted viola sounded a little too close to the cello for comfort. I finally settled on Acrotec 6N-1010 Cu, a finely balanced cable that sounded more like the Belden, but with a little more weight due to its moderately heavier guage. This settled, my attention wandered to other perhaps equally important things.

Again, what a difference an inch makes
The MMG is spec'ed at 50-26k Hz +/- 3db. If you guess from the figure that the speakers, without port and enclosure, are prone to sound lean in the bass and with a certain prominence in the treble, you're largely right (otherwise tweeter-attenuation resistors would not have been supplied). In my well-damped living room, and with a tube preamp and the McIntosh, the treble, though a shade pale (like most Maggies), did not however sound over-bright. In an attempt to improve details in the inner spaces I substituted the original tweeter attenuation jumper (a solid block of metal) with a piece of wire (16 AWG vintage silver-plated Cu I have on hand) and I was gratified that opened the sound up a bit while exacting no compromise.

How low, and how much?
I have waited long enough to come to the million dollar question. What about a subwoofer to fill out the bottom? Note that almost all serious Western Maggie users use a subwoofer, and that includes HP of TAS, surely the person who had put Magnepan on the map. Despite this, I have yet to see a Maggie user in HK use a sub, ostensibly for fear of compromising the "purity" of the speakers. Is the fear rational?

Good as the sound of the MMG is, it DOES sound lean in the bass in my 250 sq ft+ room, which could actually accomodate a pair of MG1.7, but that's for later, if ever. As holographic and airy as they are, the MMGs just do not flesh out like the Martin Logan Source, and I don't expect them to. Robbed of the lowest fundamentals, maybe that bass is just not as rhythmic as you'd like, but with vocals and jazz it perhaps would not be so important. But big orchestral music simply demands reinforcement. Enter the subwoofer.

The experiment was conducted with a very modest AR powered subwoofer borrowed from a friend. It cannot have more than an 8" driver inside. From the start I did not expect it to plumb great depths, but to "fill in" a little. This old sub did not have high-level inputs, so I had to use the second pair of my preamp out. Using the same recordings I judged the adjustable crossover was best at or below 65 Hz; further up the band some compromise in mid-bass clarity was audible. The volume took a while to set, but it was just a notch or two above barely audible.

What's the difference? I say, not so subtle. While tonality remained much as it was, the bass fleshed out. It is important you feel it in the atmosphere, not in your pants. Solti's Mahler 6th became more subjectively threatening. The best way to tune the subwoofer I found is by using a well-recorded piano piece that has slow left-hand rumblings. This was more than amply provided by the Jorge Bolet's Liszt album, particularly on Reminiscenes of Don Juan. You want to hear the bass rumbling, but you also want not to lose the articulation, or for the faint bass notes to smear into one. You have to listen hard.

The "subwoofer" I don't think really extended the bass of the MMGs by much, maybe 10 Hz, but I feel it filled out the leaness in the bass without robbing the panel bass of its tunefulness. Unless your Maggies are big enough for your room you should investigate adding a subwoofer. Also, the type of music you listen to makes a difference too. Light vocal and jazz lovers are more likely not mindful of the bass leanness, but lovers of big orchestral works (me) would definitely feel otherwise.

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