Floor-standing Speakers

MartinLogan Purity Floor-standing Electrostatic Hybrid Speakers

ARTICLE INDEX

Introduction

MartinLogan (ML) is a name that all audiophiles know, but the average consumer does not. There are two reasons for this. One is that ML is a high-end speaker brand, and so will not likely be found in most hifi supermarkets (maybe an occasional Best Buy). Secondly, their speakers are all electrostatic (ESL) in design, and ESLs are a specialty product, only sought after by a certain type of user.

The odd thing is that ESLs have been around as long as cone speakers, but they didn't "take off", because they had to be very big in order to produce sound at all frequencies. ESLs use a thin membrane suspended between perforated plates, and the membrane cannot move very far, so it has to be big in order to move enough air for the bass. Cones on the other hand, could be much smaller and still reproduce the bass. So, cones it was, for many decades.

In the 1950's, ELS did begin to "take off" on their own, and in the early 1960's, the KLH Model 9 was introduced. It was a full range ESL, about the size of a door. I was in high school at the time, and my father and I went down to Seattle Stereo to get some speakers. I remember seeing the Model 9s being driven by McIntosh power amplifiers. The sound was to die for, as far as I was concerned, and I would have loved to see them in my home. They still needed to be big, and in fact, the setup included a pair on each side. I think they were something like $1,500/pair. My father was not an audiophile (although I was one, I wasn't even aware of that word), so he opted for some Jensen monitor speakers instead, at $150/pair.

Fast forward to 1980 or so. I was living in Baltimore, Maryland, and drove over to a high end store near my home. There, on the showroom floor, were a pair of MartinLogan ESLs. They were larger than the KLH Model 9s. Can't remember what they wanted for them, but I will never forget the sound. Classical guitar was right in my lap. The detail, the transparency, and plenty of bass. Even though I still could not afford them, I decided right then and there that, someday, I would own ESLs. When I looked at hifi magazines, I always dwelled on the advertising pages for MartinLogan.

Specifications

  • Design: ESL Hybrid
  • ESL Panel: 200 in2
  • Woofers: Two 6.5" Cone; Bass Reflex Enclosure
  • Amplifier Power: 200 Watts RMS (Drives ESL Panel and Woofers)
  • MFR: 41 Hz - 23 kHz ± 3 dB
  • Sensitivity: 93 dB/2.83 Volts/Meter
  • Dispersion: 300 Horizontal
  • Dimensions: 52.3" H x 9.7" W x 14.7" D
  • Weight: 51 Pounds/Each
  • MSRP: $2,995/Pair USA

Now, two more decades have passed, and I am editor of a hifi magazine myself. I have three listening rooms, and I have ESLs in one, planar-magnetic speakers in the second, and ribbon speakers in the third. All three of these types of speakers are "planar", meaning that the drivers are flat, and so are the speakers themselves. ELSs use electrostatic fields to move the driver (a thin plastic membrane), while the other two use permanent magnets to move a membrane through which the power amplifier current is passed. All three have similar characteristics, namely fantastic detail and transparency.

The reason for the detail is that the "driver", being very, very light, responds quickly to the amplifier. The reason for the transparency is that there is no enclosure. The membrane or ribbon is suspended in open air, front to back. And, this front to back open placement results in the speaker being a dipole. This means the sound comes out the front as much as it does the rear. When the sound is moving out of the front, it is moving into the rear, and visa versa. Since sound is coming out the rear, placement is crucial. Also, you have to put them near an AC outlet, since ESLs have a power supply to produce the electrostatic charge on the plastic membrane.

The irony is that none of the planar speakers I own are MartinLogans. No particular reason for that, I just ended up with other brands that came my way in the review process.

But finally, MLs have arrived for me to try out, to listen to, to test, and to enjoy. This model is called Purity.

The Design

The Purity is a new type of design for ML. While they have marketed hybrid models (ESL panel plus cone woofer) in the past, this one has a 200 watt Class D (switching - ICEPowerASC200) power amplifier that drives the ESL panel and the woofers. You can connect the power amplifier outputs of your receiver to the speaker binding posts, or the line-level outputs of your SSP or TV to the RCA inputs. As I mentioned, full range ESLs have to be big, but a lot of people don't want large speakers in their living rooms. So, in order to reach that market, ESLs were designed that had smaller panels, but a cone woofer to handle the low frequencies.

The Purity is only a little more than four feet high. The panel is just 10" wide, and there is a woofer enclosure at the base. So, the active area of the ESL panel is small. However, regardless of the size, you still get the detail and transparency. The tradeoff is that the woofer has to handle everything below 450 Hz, which includes part of the range of the human voice. Well, OK, it is not a full range ESL, but it also is not the size of a door. That is its market: the person who wants the incredible ESL sound, but doesn't have the room for the big one or just does not want a big one. The base of the Purity is adjustable by rotating it so that the speaker will point either straight out at the conventional seated listening position, or slightly upward, if your seats are on raised platforms as in some home theaters.

martin-logan-purity-speakers-rear-panel.jpg

On the other hand, for that full sized ESL, you need a big amplifier because ESLs are difficult to drive (impedance) and are not very sensitive. MartinLogan has addressed that in the Purity by adding a built-in 200 watt RMS power amplifier that drives both the ESL panel and the woofers. So, you give away something due to the small size, but you get something back in having the powered drivers. That's the Purity.

On the rear panel (photo shown above), you can see the single set of binding posts, an RCA line-level input for the amplifier that powers the entire speaker, and a bass level toggle. Normally, you just connect your power amplifier output to the binding posts, and the signal is routed to the built-in amplifier. Otherwise, you can, if you want, connect a line-level output from your processor or receiver to the RCA line-level input, which then drives the amplifier directly. The toggle lets you adjust the bass output depending on how close the speaker is to a wall (walls and corners produce bass loading).