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MartinLogan Theos Overview & Build Quality


Although it might be easy to just claim that MartinLogan uses black magic to conjure up sound from a 4 foot tall transparent panel, there is a slightly more helpful answer. A thin diaphragm/membrane is stretched tight and sandwiched in between two perforated metal grills, or stators. The diaphragm is only 12 microns thick (that’s 1/8 the thickness of a human hair) and is made of a special material that MartinLogan developed with 3M. The diaphragm is given a constant positive charge while the charge on the stators is reversed thousands of times per second.  By changing the charge on the stators from positive to negative and back again, the diaphragm is pushed and pulled back and forth. As the diaphragm moves back and forth thousands of times per second it rarefies and compresses the air (it “creates” sound). This is arguably an over-simplification as there are a number of special components and complex processes that are involved in production. Luckily, MartinLogan has a great YouTube channel that can help fill you in on some of the gaps.

The Theos’ panel is 44” high by 9.2” wide, the same height as their $14,999/pr Summit X. The tall panel allows for a larger listening area vertically, higher output, and a lower crossover frequency. The Theos’ panel plays down to 425Hz, below which a front-firing 8” aluminum driver with cast basket takes over. On the bottom of the cabinet is a tuned port that is flared on both sides. A low crossover of 425Hz means that the entire 44” panel plays all of the high and mids, avoiding a crossover in the critical midrange. Once I got the speakers setup properly I found the panel and 8” driver to blend nicely, something that has been an issue with older models.

Every MartinLogan ESL has a 30 degree curve, which is intended to allow for a wider listening area while maintaining controlled dispersion. The hallmark 30 degree curve is known as CLS, or Curvilinear Line Source. One of the advantages of controlled dispersion is that the room does not affect the sound of the speaker as much as it would if the speaker had a wider dispersion. The downside to controlled dispersion is that the sweet spot can be very small. According to MartinLogan a 30 degree curve is a perfect balance to allow for a wide listening window and big soundstage, while still minimizing room interaction. On the flip side, the Theos (and all their other ESL speakers) are di-polar, so proximity to walls will dramatically affect the sound.

The Theos are rated at 6 ohms (they dip lower at high frequencies), with a sensitivity of 90dB. One of the big concerns many people have about ESL’s is that they require a big amplifier. MartinLogan claims that their speakers will work fine with most receivers, even if the receiver isn’t rated to handle a 4 or 6 ohm load.  I hooked them up to a number of amplifiers, from a bottom-of-the-line $100 amp to $4k monoblocks and had no trouble. I tried different volume levels and source material and was never able to make an amp go into protection or clipping. You can actually throw a ton of power at these speakers and it's likely the 8” driver will give out way before the panel (though we experienced neither).  With that said, they sonically benefit from high quality amplification.

Build Quality

We know that the Theos look good, but beauty is only skin deep, right? Apparently nobody at MartinLogan is familiar with that statement because obvious care was taken in designing these speakers.

Internal Picture of Theos from Bottom - CORRECT SIZE

Internal shot of Theos from bottom opening

The air core inductors and poly caps for critical circuit paths are high quality and the resistors are mounted on stand offs for better heat dissipation. It’s rare to see this level of detail employed in a loudspeaker crossover but it’s welcomed. 

The 8” aluminum bass driver has a bumped back plate to prevent driver bottoming and is vented for heat dissipation. The cabling is twisted pair to minimize interference and wrapped in insulation to prevent them from slapping around inside the cabinet. One side of the cabinet has a piece of batting glued in place.

Theos circuitry and bass driver

          Theos circuitry and bass driver

Theos Port Tube - CORRECT SIZE

Theos port tube

The bottom firing flared port is about 3” in diameter and flared on both ends. Many companies cut costs and only flare the side you see. Flaring reduces port noise and placing the port on the bottom of the cabinet and angling it allows for a longer tube than would otherwise not be possible in such a small enclosure. You might notice there is no internal bracing, but it isn’t necessary in an enclosure this size since the panel lengths are significantly smaller than wavelengths of operation of the woofer.

The Theos come with both spikes and rubber feet. Both options are oversized, which makes height (rake) adjustment easier than with most speakers.

I only have two complaints. The speakers came with a 220v European power supply on accident. Luckily, I was able to drive over to MartinLogan and pick up the proper power adapters. Secondly, the wood veneer looks nice, but has rough patches when you run your finger over it. Each cabinet is buffed by hand, so it seems this particular set of speakers must have been produced on a Friday afternoon.


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Recent Forum Posts:

jeffreynoah posts on December 25, 2012 07:55
Martin Logan Theos Speakers Test Report

My musical taste is classical, primarily Renaissance, Baroque and Impressionist. On my ML Vistas, choirs sound like many individual singers and seem to float in space, across and deep within the sound stage. Previously shrill recordings now sound delightful. Drums, which previously sounded like thunder, now offer individual definition, from synthetic or skin impacts. Triangles sparkle and xylophones shimmer. Applause sounds not like rain, but hands clapping. Singers and soloists seem to perform in the room.

According to a reviewer, “finesse and transparency … unbelievable dynamics, speed, transient attack and force … simply glorious front-to-back depth … clear and uncluttered, never losing their ‘space’, while blending seamlessly. Probably the most outstanding characteristic is the way the speakers simply disappear – a familiar MartinLogan trait – allied to simply glorious front-to-back depth. With live recordings of a ‘known’ stage or hall signature, the effect is nothing short of transcendent.”

My standard for sound reproduction is accuracy, from years of listening to electrostatic headphones. My entire CD collection now sounds new, and filled with discoveries.

I am also impressed with the protective cardboard shipping cabinet, including two layers of gowns and foam buttresses, which protect M-L speakers in transit.

Bravo, Martin – Logan for an exciting performance, every time.
alenmics posts on December 16, 2012 09:47
nice infroatmon and ai like it
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