Article Index
Martin Logan Summit X
page 2
page 3
page 4, Sound quality
page 5, Conclusion
page 6, Measured Performance
All Pages

Apart from these unusual practical issues that surround electrostatics – which also influence performance in the tropics as we’ve been told by Hi-Fi World readers – our measurements clearly show the XStat panel smoothly covers the audio band, like no other loudspeaker.Having no crossover at 3kHz it also lacks phase anomalies and character changes between bass/midrange unit and tweeter that afflict conventional box loudspeakers. This consistency contributes much to their exceptional imaging and, for example, gives violin in particular a sense of being a one-piece physical instrument rather than a mellifluous representation.
    But I must not keep talking about the XStat panel, or even electrostatics.For the Summit X also has a compact bass cabinet and progressive phase cancellation toward higher frequencies that, Martin Logan say, makes the bass transition from monopole to dipole radiation at the crossover frequency.
    Put more simply, this means the panel which fires sound forward and backward (dipole), out of phase, better matches the bass bin (monopole) where no such forward/backward cancellation occurs.
    I did once use a true bass dipole, the Celestion SL-6000, to match an electrostatic dipole, Quad ESL-63s, but it was a horribly complicated arrangement and viciously demanding of bass amplifier drive power. I did get ultra-low, near-perfect bass – but what a hassle! Which is why Martin Logan’s less complex blending approach on the Summit X struck a chord with me.

There is just one set of loudspeaker terminals, so bi-wiring is out. The terminals fitted accept 4mm banana plugs or bare wires. Above them are three control knobs, controlling very low bass at 25Hz – subsonics really – and deep bass at 50Hz. These interact with room modes, controlling room boom in effect. The idea is to avoid boomy bass, but alternatively bass power can be increased to add extra oomph, according to taste.Alongside the two bass level controls, that provide both lift and cut, is another rotary switch that controls three lights, to give seven settings for them, including a down light, no less. Response shaping is digital: the signal passes through an ADC, is processed, and is then converted back to analogue for the bass power amplifiers.
    One bass unit moves slowly out of phase with the other as frequency increases to smooth the transition from monopole to dipole and our response graph does show a shallow dip in output above 100Hz due to this effect.
    At the other end of the frequency scale, because the big panel runs flat to 20kHz, our measurements show, it puts out a lot of acoustic power at high frequencies and tilting back using the adjustable feet will lessen this a little. I also used an Audiolab M-DAC with optimised time-domain filtering for CD, to roll down treble smoothly.
    I used acoustic absorption panels against the rear wall, a few feet behind each Summit X, to absorb rear radiation. An obvious partnering amplifier is the solid-state Quad QMP Elite monoblocks I used, or Quad II-eighty valve power amplifiers. Generally, a good valve amplifier with 4 Ohm tap is a fine match for an electrostatic and I used my own WAD 300B amplifiers. Beware of powerful transistor amps having bright treble: the big XStat panel reveals their limitations and this isn’t a match made in heaven.

Comments (2)
summit x noise
2Friday, 24 October 2014 14:52
I really enjoy the sound quality the Summit delivers, but has anyone recognised the noise both of the digital amps produce?
Summit X
1Thursday, 13 February 2014 21:46
Bruce Low
Very interesting review re the above especially in the context of Noel's love of dipole bass. As a former Quad 57 and 63 listener but current martin logan Spire owner I was particularly struck by Noel's far more positive comments re Summit X bass, (and indeed overall performance) in contrast to his comments on the Montis bass performance. Did I pick you up right? Should I upgrade to Summit X if that is the case. Did Noel find any difference in the xStat performance in Montis compared with Summit X eg soundstage .... Or was this essentially identical given same panel. If it had gains here that would also interest me in terms of potential upgrade. With the Spires I find the slightly soggy and texturally undifferentiated bass (by the highest standards) its only real weakness. It is so good I have hesitated to make any upgrade move up until now,

Yes, the Summit X does have better bass than the Montis, although it isn't perfect perhaps. There is less disparity between panel and box, they seemingly integrate better. That "textural" lack of differentiation remains, but it is less apparent. The Summit X seems to have lighter and drier bass, although it goes very low and subsonics are obvious.
I heard no difference in the XStat panel, and its imaging remains superb.
The Summit X is a step up on the other models and bass is improved. It has become more academically correct, as it were. Big bass form a small box will forever raise problems DSP cannot eradicate. The big issue is internal energy emerging through the cone time delayed (overhang). There's little that can be done about this, other than Isobarik loading. NK

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