Magnepan MG-20 loudspeaker

Magnepan founder Jim Winey could be considered the patriarch of planar loudspeakers. His innovative leadership of and commitment to the technology over the past 20 years have propelled Magnepan to a position of preeminence in the speaker business. You won't find any hybrids rolling off the production line at Magnepan's corporate headquarters in White Bear Lake, Minnesota. The entire Magnepan line is devoted strictly to planars that use ribbon tweeters and quasi-ribbon midranges and woofers—not a stray dynamic woofer in the lot!

Magnepan's status in the marketplace is supported by sound value for the dollar. With models ranging from the affordable SMGc ($690/pair) to the popular MG-3.5 ($3150/pair) and the new and exciting MG-2.7 ($1995/pair), it's evident that good planar sound doesn't have to cost you an arm and a leg. Even the top-of-the-line MG-20 retails for under $10k/pair. In this day of $5k minimonitors, that's genuine value.

Why are they so BIG?
At 79" high and 29" wide, this question is exactly the sort of comment the MG-20s are likely to elicit from your non-audiophile spouse. Note that I've avoided the term Wife Acceptance Factor (WAF), as I find it extremely patronizing. It presumes that the wife's sole criterion in judging a loudspeaker is equivalent to interior decorating. I've known couples who have willingly accepted a baby grand piano into the confines of an already crowded living room—their love for music overcame other practical considerations.

The proper response is that planar speakers have to be so big for the same reason a piano has to be as big as it is: No one in his or her right mind would accept a piano the size of a violin. For the same reason, no one should take a planar the size of a toy piano seriously.

Whether it is to produce or reproduce bass frequencies, bigger is better. Efficient coupling to the impedance of air demands a large radiating area. A piano string cuts through the air with little acoustic-energy transfer—most of the acoustic power emanates from the piano's body and soundboard. Similarly, a 15" woofer is inherently more efficient than an 8" woofer in the deep bass, precisely because of its greater area—it's able to couple mechanical energy more efficiently to air. In the same way, a planar speaker's power finds full expression when it's allowed to assume realistic proportions.

Technical details
The MG-20 is a three-way design with a built-in passive crossover for the tweeter/midrange interface, and the optional XO-20 external passive network ($695/pair) for the midrange/woofer interface. Introduced in 1994, the XO-20 allows either single-amp operation or bi-amping without an active crossover. Previously, the MG-20 could only be bi-amped, with the help of two stereo amps and an electronic crossover.

Like all planars, the MG-20 combines a low-mass diaphragm with drive that's arranged to be uniform over its radiating area. All things being equal, low mass confers the advantage of high acceleration. The ability to start and stop quickly, relatively unhampered by inertia, translates into excellent transient response—the diaphragm is able to faithfully execute the requirements of the drive signal. The major advantage of uniform drive, or force-over-area, is the resultant excellent acoustic phase coherence; the wave launch of the drive-units is from a common plane.

The tweeter is a patented ribbon design driven directly without transformer coupling. A 0.3" by 60" by 2.5µ-thick aluminum ribbon is suspended in the magnetic field of two long, permanent bar magnets. This long, narrow ribbon provides excellent dispersion in the horizontal plane, and acts as a line source in the vertical plane. (By this I mean that the diaphragm is sufficiently tall compared with the height of the room that the interaction between the diaphragm and the floor and ceiling results in a cylindrical wavefront.) The ribbon has a very low moving mass, so take special care in handling. For example, never attempt to use a vacuum to clean the tweeter channel—you'll suck the life right out of it. For shipping, the ribbon is protected by a cover.

The midrange and bass drivers are traditional Magneplanar drive-units. The midrange driver uses a large but very thin—13&181;;—Mylar diaphragm to which are bonded rows of long conductive strips. The 137in2 diaphragm is suspended in front of vertical rows of bar magnets so that the strips are centered in the magnets' fringe field. The similarly constructed 786in2 bass driver uses aluminum wires instead of the strips. In all cases, it's the interaction of the current flowing through the ribbons or wires with the magnetic field of the bar magnets that provides the impulse force for the ribbon and diaphragms.

Setting up a planar is no more difficult than setting up a conventional loudspeaker—provided one has control over the listening environment. As with any dipole radiator, it's imperative to allow adequate "breathing room" behind the speaker—at least 36" from the rear wall is a good starting point. Some absorption and diffusion behind the speaker are appropriate to partly attenuate and disperse the backwave.

Listening distance is another critical parameter. Slowly move the listening seat on the central axis until you settle on a suitable tonal balance. For me, that distance was 9', with the panels toed-in toward the listening seat. I also experimented with the position of the tweeter ribbons. Because the ribbons are mirror-imaged on the left and right front baffles, it's possible to position the MG-20s so that the tweeters are either on the outside or inside edges of the speakers. The inside position worked best for me, in that it yielded the most cohesive soundstage.

When all was said and done, the MG-20s ended up in roughly the same location as the Sound-Lab A-1s, but with the listening seat a couple of feet closer. The MG-20s' resultant soundstage, however, was quite a bit more spectacular than the Sound-Labs'. The A-1's greater radiation angle produces more side-wall reflections (at least in a moderately sized room), and hence a less convincing panoramic view. In contrast, the Magneplanars flooded the front third of my room with a seamless soundstage in which I was able to turn my head from left to right without missing a beat. In audiophile jargon, the speakers seemed to disappear, leaving in their place a living, breathing spatial framework.

Image outlines were remarkably life-sized—in the best tradition of planar speakers. Listening to a closely miked double-bass or piano proved a humbling experience. Rather than looking out at a parcel of space that even a child could wrap its arms around, the breadth and height perspectives projected by the MG-20s were totally believable.

Speaker cable of choice was TARA Labs Rectangular Solid Core Master Generation 2. As TARA Labs' Matthew Bond provided me with 18" sections of cable terminated with pin connectors, I was also able to cover the signal path from the passive network to the speaker inputs with RSC Master cable. For greatest soundstage transparency, I settled on a bi-wire configuration between the amp and the external passive network. Most of my listening was conducted with Acrotec's fabulous 8-Nines Stress-Free interconnects, whose praise I shall sing at a later date. And as for amplifiers—read on!

Sound: single-amping
My samples of the MG-20s were delivered with the external passive network, so that's how I initially deployed the speakers. Only much later did I turn to bi-amping.

My first order of business was to investigate the speaker/amplifier interface. After auditioning both the Air Tight ATM-3 and the Manley 175 tube monoblocks, it became clear that I would have to investigate solid-state amplification. Although both the Air Tights and the Manleys painted a warm and palpably exciting soundstage—lovely stuff—they failed to deliver satisfactory performance in two areas. First, dynamic headroom was constrained—the Air Tight more so, but even the Manley labored when navigating very loud passages. Second, there was a lack of punch and crunch through the lower registers, a loss of bass definition and transient power that robbed the music of impact and drama.

The MG-20 is a true 4 ohm nominal load, maintaining a 4 ohm minimum into the deep bass, and only falling to about 3 ohms in the treble. On this basis, it qualifies as a moderately difficult load. Together with a low sensitivity specification, this suggests the advisability of transistor drive. It was still surprising to discover that only solid-state amps capable of swinging several hundred watts into 4 ohms seemed capable of satisfying the MG-20's appetite for current.

The Classé M-700 solid-state monoblocks that I reviewed last month may not be alone in their ability to dish out a kilowatt into 4 ohms, but no other high-powered amp I've heard to date can do so as smoothly and as musically. The Classé excelled at both ends of the spectrum, dealing with tasks that could be broadly characterized as brawn and finesse. Bass punch and definition were exemplary, the M-700 fleshing out the MG-20's full potential in this regard. On the other hand, the manner in which the Classé caressed the bloom of harmonic textures earned it the respect of even Toob Man himself.

The Bryston 7B monoblocks proved another synergistic coupling. In fact, my first serious listen to the MG-20s was at Peter McGrath's (Mr. Sound Components) Miami home, where they were tri-amped with a stack of Bryston 7Bs. (Snell THX subwoofers were used on the bottom.) Program material at the time was Peter's own master tapes feeding an Audio Research LS5 line preamp. I still can recall the astonishing clarity and transparency of that particular setup; yet, even with a single pair of 7Bs, I was treated to a command performance. Although not as texturally smooth as the Classé, the 7B's main attraction was its remarkable level of midrange clarity and transparency.

1645 Ninth Street
White Bear Lake
MN 55110
(612) 426-1645

yooperaudio's picture

A TWENTY-FOUR year old article is posted here, with some kind of assumption that it will be valued? Jesus god - get a grip.

John Atkinson's picture
yooperaudio wrote:
A TWENTY-FOUR year old article is posted here, with some kind of assumption that it will be valued?

This review is of what was at that time Magnepan's flagship loudspeaker and will be of interest to many. When we launched our website, our plan was to post every review that had been published in Stereophile to our on-line archives and we are well on the way to achieving that goal.

John Atkinson
Technical Editor, Stereophile

Bogolu Haranath's picture

The latest version is 20.7 .......May be Stereophile could review them? :-) .........

Bogolu Haranath's picture

"Get a Grip" ......... Aerosmith :-) ........

JRT's picture

I thank you and/or others responsible for posting this interesting content.

My comment here is intended as counterbalance to complaints about posting older articles.


prerich45's picture

Bravo!!!!!! I enjoy reading blast from the past!!!! Especially the Infinity Composition Prelude PFR and the MTS reviews!!!!

Jim Austin's picture

We respect tradition, and history, and our elders.

Plus, whatever you might think, these historic articles are widely and enthusiastically read.

Jim Austin, Editor

yooperaudio's picture

Oh please. What a load of BS. Elders? Fuck your pomposity and your lawn.

Jim Austin's picture

You cannot make him drink.

I'm thinking our site is a poor match for you. Do you agree?

Jim Austin, Editor

yooperaudio's picture

Happily, yes. Carry on with your self-aggrandizing myth-making. You’re grand!

Jim Austin's picture

Excellent. I'm glad we agree. Goodbye.

Jim Austin, Editor

scottsol's picture

Unlike printed magazines where editorial page count is limited by ad revenues, posting old reviews has no effect on the number of posts with new information.

Moreover, in the many years that Stereophile has been posting old material they have typically received more reader comments than new material.

So, your comment was not only of no possible significance, but completely wrongheaded in its premise.

Bogolu Haranath's picture

DO's description of 'Planar Imaging', with JA1's comments, are an interesting read :-) .........

gcvanwinkle's picture

The $650 LRS OWNS the older Model 20 in terms of time coherent performance:

The use of a first-order crossover pays off - along with a little care in speaker placement. Now test a newer 3-way Magnepan and see if they can do the same trick with a more complex design.

And thanks for the look back in time!

Joppe Peelen's picture

haha yeah sure, nice all the hype on the LRS. witch still is the normal basic magnepan. foil and conductors in this case being foil. ribbon speaker is a missleading name. And im pretty sure the 20.7 would rock the world of an LRS , as it should. far more surface area true ribbon not a normal planar, and push pull mid... what else do you want to improve over the LRS? the first order filter? yes i personally go for first order on my planars if i can. but time aligned ? NO. the tweeter and the mid/bass use the same foil and are toed in, besides that the midrange/bass is rather big so perfect time alignment is not doable. not that it matters much either. since the frequencies they are crossed are lower then usual, then with a dome tweeter. as for the 20.7 that would even improve since its a 3 way.

volvic's picture

Back in 1989 I auditioned what I thought was going to be my final turntable purchase, it was between the Linn LP-12 and Roksan Xerxes. The speakers used were the large Maggies, I believe they may have been the 20's or at the very least the precursors to the 20's reviewed above. The speakers and Bryston electronics were revealing enough to let me make my decision. I can still remember the addictive sound they had and if I had space in my Manhattan apt I would have swapped my Kans for a pair of Maggies. Love that Stereophile releases these old reviews. Takes me back to a time when physical media was king and when retail hi-fi stores were more plentiful.

BDP24's picture

yooperaudio's comments certainly mirror the unnecessary nastiness I see in so much social interaction these days. Dick Olsher has long been amongst my two or three favorite hi-fi critics of all time, and much of what he had to say about the MG20 is timeless, and still relevant today. I happen to own a pair of Tympani T-IVa, which can be viewed as the basic blueprint for the current Maggie flagship, the MG30.7. Thanks for the reprint, though I still have my copy of the issue it appeared in. A Stereophile subscriber since 1972!

Big eugene's picture

Re: yooperaudio. Wow....what an absolutely pathological, colossal, jerk. No real arguments, just pejoratives.
If this is what passes for civility these days, we're finished as a society.

David Harper's picture

another interesting read would be a review of the original Acoustat monitor, the one that resembled the black monolith in "2001". My friend had a pair of these and they sounded amazing.

scottsol's picture

The Acoustat model that most closely resembled the 2001 monolith was the 2+2 which arrived five years after the first Acoustat. Ironically, they bore a far greater resemblance to that monolith than the first Martin Logan speaker, the Monolith.

David Harper's picture

maybe those were the ones my friend had. I just ordered the new maggie LRS.