A loudspeaker is a transducer, converting applied electrical energy into acoustic energy, and when it comes to evaluating a transducer, perhaps no single component can affect that conversion, and ultimately, the loudspeaker’s performance, more than the power amplifier that drives it. Loudspeakers present complex and sometimes difficult demands on amplifiers, due to many factors, such as input-impedance and crossover anomalies. To evaluate the impact the 60XT’s nominal 4-ohm input impedance on different amplifiers, I listened to it with several power amplifiers of various construction, quality, and output power.
I first replaced my reference (solid-state) Sunfire amplifier with a Bob Carver Silver Seven 700 tube amplifier (current production, not to be confused with the legacy Carver model with a similar name). While certainly not requiring the massive power (700Wpc) that this tour-de-force, four-chassis tube amplifier can produce, especially in light of the 60XT’s 94dB/2.83V/1m (91dB/1W/1m) sensitivity, the MartinLogan nonetheless responded beautifully to the amplifier’s sonic character, excellent dynamic range, and low noise floor.
The Silver Seven 700 has dedicated output taps for 8, 4, and 2-ohm loads. Given the Motion 60XT’s nominal 4-ohm input impedance, I initially connected the speakers to the amplifiers’ 4-ohm taps. Listening again to the Stone Poneys’ A Different Drum, I found Linda Ronstadt’s vocals sounding easy and lifelike. When I switched to the amplifier’s 8-ohm tap and replayed the same song, the performance seemed thin and lacking in dynamics. Repeating the sequence once more, this time with the 2-ohm taps, resulted in a dull sound and a muddy performance. I used the 4-ohm tap for the remainder of my listening session.
With the prerequisites out of the way, I began assessing the combined performance of the Silver Seven 700 amplifier and the Motion 60XT. Though the speakers already sounded exceptional driven by the Sunfire amp, it didn’t take long to hear differences in the presentation with the Silver Seven. The ESL-like delicacy of the treble that, when using the Sunfire, sometimes became slightly edgy when played loud, was softened, remaining light and delicate even at higher volumes, until the AMT tweeter output finally began to beam a bit. The bass, already well presented with the Sunfire, took on a character and depth previously unheard, with 3-D spatiality perhaps the most improved sonic characteristics I noted. Although the Sunfire amplifier had previously raised the bar for Fleetwood Mac’s “Woman of a Thousand Years” from Future Games [CD, Warner] to the highest level in my experience, the Silver Seven 700 revealed a never-before-experienced depth and dreaminess in the recording.
The manufacturer specifies that the 60XTs are “compatible with 4-, 6-, or 8-ohm rated amplifiers.” To test that claim, I replaced the Silver Seven 700 in my system with an available Kenwood KM-209 stereo power amplifier (150Wpc into 8 ohms)—a mass-market model from a few years back—using the previously described bi-wire connections. It became readily apparent that the necessary drive current for the 60XT’s 4-ohm load was not available from this amplifier, which sounded weak and flat no matter the source material. Given the speaker’s efficiency, a suitable amplifier need not be exceptionally powerful, but must be able to provide adequate drive current into lower-impedance loads, and have a slew rate fast enough to satisfy the transient-response characteristics of its AMT tweeter. If one has any concerns about an amplifier’s ability to satisfy such demands with this or any other loudspeaker, it is a good idea to arrange a demo using the amplifier in question prior to purchase.
Finally, returning to the Sunfire amplifier, I integrated my Sunfire TSEQ-10 subwoofer into the system, adjusting it to complement the 60XT’s response. On the 1812 Overture, this time with the subwoofer connected, the cannon fire left me blown away! Listening to “Flight of the Cosmic Hippo” from Bela Fleck’s album of the same name [CD, Warner Bros.], Victor Wooten’s low, low bass was amazingly matched, both tonally and in output, with Fleck’s electric banjo, sounding almost as if they were in my listening room. Rounding (or perhaps I should say, bottoming) out the already superb sound of the speakers with an appropriate subwoofer makes these speakers outstanding performers overall, regardless of cost.
The Motion 60XT does many things not only right, but magnificently, provided a suitable amplifier is used to drive them. I can’t remember when I enjoyed listening to a speaker as much as I did these. As they were designed in Lawrence, Kansas, by the same team that creates the company’s electrostatic models, it should be no surprise that the upper midrange and treble are similarly voiced to ML’s ESL models, though with slightly less finesse in the upper frequencies. Vocals are lifelike, engaging, and captivating, whether you’re listening to the silky sound of your favorite chanteuse or the gravelly voice of a screaming rock star. An added benefit of the excellent driver and crossover matching is the realistic lower-midrange/upper-bass performance, further enhanced by the woofers’ vertical location in the cabinet. The 60XT produces a broad soundstage that exceeds the width of the loudspeakers’ placement, with pinpoint imaging and amazing, three-dimensional depth, even when the source material is of average sonic quality. The twin 8" woofers produce bass extension that will satisfy all but hard-core pipe organ and electric-bass aficionados (or lovers of the 1812 Overture’s artillery fire). If these heavyweight genres of music are your thing, the addition of a subwoofer of your choice (MartinLogan offers several) can easily satisfy you, too.
To enjoy the full performance that these speakers can produce, you have to be patient; the 60XT appears to require every bit of the specified 72-hour break-in period to really sing. Nevertheless, the wait is well worthwhile, rewarding the listener with sonic performance that is nothing short of unbelievably realistic compared with other speakers in this price range, as well as more expensive models.
At the outset, my expectations for a “conventional” loudspeaker designed and produced by a manufacturer whose products have historically been electrostatic designs were undefined. After living with these speakers, however, I no longer have any doubts; the 60XTs are so impressive I could easily adopt them as my reference. Listening to the them was tantamount to a physical addiction for me! They are a “must audition” for anyone interested in natural and realistic sound that will continue to satisfy and impress for a very long time. Highly recommended.
SPECS & PRICING
Type: Four-way, dynamic, floorstanding loudspeaker
Drivers: Folded Motion XT tweeter, 6.5" aluminum-cone midrange, two 8" aluminum-cone woofers
Frequency response: 35Hz–25kHz +/–3dB
Sensitivity: 94dB/2.83 volts/meter (91dB/1W/meter)
Impedance: 4 ohms
Crossover frequencies: 400Hz, 2.2kHz
Recommended amplifier power: 20–400W
Dimensions: 11.4" x 48" x 14.4"
Weight: 66 lbs.
Price: $2999 (piano black); $3299 (black cherrywood)
Rega P5 Turntable with TT-PSU upgrade, RB700 tonearm, Shure V15VxMR cartridge; Rotel RCD-1072 CD player; Sunfire Vacuum Tube Control Console; Sunfire 300~two amplifier; Sunfire TS-EQ10 True Subwoofer; Sunfire CRM-2 Cinema Ribbon loudspeakers; Kenwood KM-209 stereo power amplifier; Bob Carver Silver Seven 700 amplifier (manufacturer loan)
2101 Delaware St.
Lawrence, KS 66046