- Written by Chris Heinonen
- Published on 31 October 2011
Design and Setup of the Martin Logan Theos Electrostatic Speakers
Martin Logan made their name designing and building electrostatic speakers (ESL). An ESL speaker works by combining a thin diaphragm that is coated with conductive material between two electrically conductive grids (MicroPerf Stators, in this case). The movement of electricity over the grids causes the diaphragm to move, creating sound. The use of this technology has many benefits, including no crossover, very fast response due to the short transfer distance, and very low distortion. The potential downsides compared to a standard loudspeaker are that a panel isn't as good at low bass frequencies, and the bidirectional nature of the panel can make setup and placement tricky, as well as provide a smaller sweet spot for the audience.
Knowing these limitations, Martin Logan has been addressing them for years. With one exception, all of their ESL speakers also include a conventional cone woofer to handle the lower bass frequencies. The Theos has an 8" woofer that is crossed over with the panel at 425 Hz. This lets the panel handle all midrange and high frequencies while still providing frequency response down to 43 Hz in a standard tower speaker. Martin Logan has also designed their Curvilinear Line Source (CLS) panels to be curved and help to provide a larger sweet spot for listeners.
One surprise to people might be that both speakers have their own AC adapter. This is necessary to provide power to the MicroPerf Stators and helps to keep the sensitivity of the speakers higher than other panel technologies. The Theos also has two sets of binding posts on the back in case you wish to bi-wire your Theos, and nickel-plated jumpers are included if you don't wish to. Adjustable feet that can be replaced with included spikes round out the features on the speaker that the user will interact with. After removing the Theos from their well-packaged boxes, I hooked them up to my Anthem Integrated 225 using a shotgun bi-wire pair of Wireworld Eclipse speaker cables terminated with spades. The binding posts on the Theos were very easy to tighten and took the spades easily, though they will also accept bare wire or banana plugs.
I initially setup the Theos with very little regard to position, as I wanted to get going as fast as possible. The initial reaction was that the sound stage seemed to come from a spot around 7' high on the wall behind them, above even the speakers themselves. While the soundstage was also reasonably wide and deep, the very high nature of it was a bit odd. I also found that if I was standing up, my ears were high enough that I lost lots of the treble and midrange but the bass stayed strong. That narrower sweet spot was coming into play, though dome tweeters also have better horizontal than vertical dispersion as well.
After a couple of days, I finally had some more time to work on the placement of the speakers relative to my listening chair. I started by moving them further apart, and having the panel around 3' away from all side and rear walls. I also toed them in so I could just see the panels themselves and the rear of the woofer was hidden behind it. After doing this, the soundstage came back to resemble what I had heard at CEDIA. No longer were voices coming from a couple of feet above the speaker but were anchored between the two panels. Instruments would extend beyond the edges of the panels, though not quite as far back as it has been in the smaller room in Atlanta.
Now that the speakers were better positioned in the room, I was ready to start playing a stack of records I had been accumulating waiting for these to arrive.