Magnepan 2.7i

What is common to both Magnepan 2.7i & 2.7x:

The Magnepan 2.7 loudspeaker is a full-range, planar magnetic speaker that is designed to deliver exceptional sound quality with a wide range of music genres. The speaker features a 1.75-inch thick panel that measures 22 inches wide by 72 inches tall, with a thin-film planar magnetic driver. It weighs 48-52 lbs depending on configuration. The 2.7 has a frequency response of 40-30 kHz with 86 dB efficiency and a 4 Ohm load. The speaker is also bi-wireable, allowing users to connect separate cables to the low and high frequency drivers for optimal performance.

Like all Magnepans, the exceptional transparency, detail, and imaging of its dipole design creates a spacious, natural sound that is free from the coloration and distortion often associated with traditional box speakers.

The 2.7 is a three-way loudspeaker which means its (three-way) crossover splits the music into bass, midrange, and treble then sends those parts of the music signal to three different drivers: the bass goes to a bass quasi-ribbon panel, the midrange to a midrange quasi-ribbon panel, and treble to a true-ribbon driver. 

By comparison, the 1.7 is a two-way. The 1.7's (two-way) crossover splits the music into bass and treble, then sends those parts to two different drivers: the bass goes to a bass quasi-ribbon panel, and the treble to a treble quasi-ribbon panel.  

From a design perspective, the 2.7 is more a downsized 3.7: Both are 3-way, and both have true ribbon tweeters.  
From a room size perspective, the 2.7 is more of an upsized 1.7.  You can fit both speakers into midsize rooms. 
From a visual in-room presence perspective, the 2.7 is closer to a 1.7.

The 2.7 speaker requires a good deal of room space to perform at its best, and it is recommended to be placed at least 3-4 feet from the back wall and several feet from the side walls. Overall, the Magnepan 2.7i loudspeaker is a standout product that offers excellent sound quality, a unique listening experience, and a great value for its price point for audiophiles and music lovers.

What is unique to the Magnepan 2.7x vs 2.7i

The gneral idea of the Magnepan X program is to take th existing design of a given speaker (a Magnepan i series speaker),  and simply, almost one-fo-one, replace all of the components leading up to the driver, with superior ones.  This yields a noticeable, graphable, and awing improvement.  There are certain model-specific features, but the X upgrade at its core is characterized by the following:

Better Capacitors: All capacitors that aren't already, are replaced with high quality, copper-rich, polyproylene capacitors [banks].  Each capacitor [and bank] used is individually tested to the hundredth such that left and right crossovers capacitances are within five thousandths.  With the increased level of testing and tighter tolerance, minor value tweaks are employed in some models resulting in fewer capacitors used and a smoother response overall. 

Better Coils (inductors): All coils that aren't already, are replaced with high-guage, copper wire, air-core, bobbin wound coils [arrays]. Each coil [array] used is individually tested to the tenth such that left and right crossovers' inductances are within five hundredths.  Model dependent: with the above capacitance changes in mind, some values are minorly adjusted for smoother response overeall. 

Better Wiring: All wiring (asside from the green(+) and yellow (-) wires for True Ribbon Tweeters) is replaced with 15gn or higher solid copper wire. Excess wire (for ease of assembly, for instance) is completely removed. Careful attention is paid to design, layout, and pathing of the crossover components such that wire lengths are short and the overeall wire-mass is significantly reduced.  Left and right crossover and nameplate impedances are ensured to be equivalent for ideal balance. 

Better Connections: All connections within the circuit, from the solder lug attached to the terminal screw on the nameplate, to the crossover board, to the driver terminal block, and back are soldered connections. Besides the terminal screw, solder lug, and jam nut connection on the nameplate, there are no mechanical connections used.

Better Inputs: All nameplate components are gold rather than nickel. 

Appearance: The appearance of an X Upgrade is not intended to be visually really any difference from that of its non-X counterpart (aside from teh gold nameplate components in situations wher ethat wouldn't already be gold).  The crossover of some models may be visible, such as with the MG 1.7x, and as such that will be noticeably different in a side-by-side test, from the back of the speaker. The nameplate will also have a small X after the model to denote that it is part of the X Upgrade program.