Floor Loudspeaker Reviews

Dick Olsher reviewed the Sequel II loudspeaker in October 1989 (Vol.12 No.10):

It was in early August, on a Sunday afternoon, that I got my first listen to the MartinLogan Sequels. Remarkable transparency, lightening-quick transients, and lots of low-level detail, were some of my immediate observations. You should know that the venue was JA's listening room, and the occasion was the Stereophile writers confab, where we compiled the "Recommended Components" listing that appears in this issue. There was a significant slice of the magazine's writers on hand, including guru J. Gordon Holt (in whose ears we trust).

To a man, a consensus developed that there was something terribly wrong with the Sequel's lower registers. A common complaint was the lack of instrumental body, the range affected, as reported by JA in his review in the August issue, being from the lower mids through the upper bass. The resultant tonal balance was strange indeed. Keep in mind that the mid- and deep-bass registers, at least in the range from 40–80Hz, were quite strong. The floor was being energized easily, for example, with organ music. This combination of deep- and midbass energy, together with a suckout in the upper bass and lower mids, gave the bass registers a hollow or disembodied feeling.

When JA offered me the Sequels for a listen, I quickly accepted because I wanted to try an experiment. JA had already speculated about the possibility that the drivers were incorrectly phased. He had found the woofer and electrostat panel wired in-phase, which runs counter to the common practice of connecting second-order (12dB/octave) high- and low-pass sections out of phase. At the crossover point, such complementary filters produce responses that are 180° out of phase, so that an in-phase connection of the drivers will produce a suckout around the crossover frequency. Simply put, I wanted to reverse the phasing of the drivers and compare the sound of the in-phase connection to that of the out-of-phase (footnote 1). This is easy to accomplish because of the bi-wire provision. The first step, and an important one, is to remove the jumpers from the two pairs of binding posts. Parallel two "go" legs and two "return" legs of speaker cable at each amp output. Connect the stat panel while observing the correct polarity. Now reverse the polarity at the woofer inputs, so that "red" connects to "black," and vice versa. This will assure that the stat panel and woofer will be connected out-of-phase.

The first order of business, however, was to clarify MartinLogan's intentions in this matter. I discussed this whole subject with Gayle Sanders over a number of phone conversations. According to Gayle, the drivers are to be connected in phase; the speakers are QC-checked in this regard. I was sent a wiring diagram for the drivers. Sure enough, both the stat panel and the woofer were connected per factory specifications. I also checked the woofer polarity using a battery. The woofer pushed and sucked in concert with the proper polarity. At this point, there could be no doubt left that the review pair were wired in-phase, as intended by MartinLogan.

The big surprise was just how big an improvement was brought about with the out-of-phase woofer connection; clearly a night-and-day difference! The tonal balance was much more satisfying. The whole bass character still sounded distinctly lean. But most importantly, the big suckout—an octave on either side of the crossover frequency—vanished. I spent a couple of hours convincing myself that the lower mids and upper bass were reasonably acceptable now. The integration between the drivers was that much better, although again the Sequels still lacked soul-satisfying body. Double-bass was obviously being reproduced with a noticeable degree of anemia, but timbrally much more naturally than before.

Next, I undertook a series of measurements in an attempt to shed some more light on the problem at hand. It turned out that the interference pattern between the drivers was a sensitive function of vertical height off the floor and, of course, room location. Take a look at figs.1 and 2. These measurements were taken at 1 meter on-axis at a height of 30" off the floor. As you can see, the in-phase connection actually measures to have more upper-bass energy. However, as the microphone approaches typical listening heights, the situation changes. At a height of 43" off the floor, still at 1 meter on-axis, figs.3 and 4 show a dramatic difference between the two connections. Note the large suckout obtained with the in-phase connection (fig.3) between about 125 and 300Hz. Near the listening seat (about 8' away and slightly off axis) and 38" off the floor (figs.5 and 6), the difference between the two connections is not that dramatic, but still clearly in favor of the out-of-phase connection.

Fig.1 MartinLogan Sequel II, in-room response at 1m, 30" from floor, woofer in-phase.

Fig.2 MartinLogan Sequel II, in-room response at 1m, 30" from floor, woofer out-of-phase.

Fig.3 MartinLogan Sequel II, in-room response at 1m, 43" from floor, woofer in-phase.

Fig.4 MartinLogan Sequel II, in-room response at 1m, 43" from floor, woofer out-of-phase.

Fig.5 MartinLogan Sequel II, in-room response at 1m, 38" from floor, woofer in-phase.

Fig.6 MartinLogan Sequel II, in-room response at 1m, 38" from floor, woofer out-of-phase.

MartinLogan's measurements at about 3 meters away and 42" off the floor in a fairly reverberant room actually show, according to Gayle, a 2dB reduction in output in the range from 100–400Hz with the out-of-phase connection. The key to this puzzle may lie in the type of listening seat and room the Sequels are used with. For near-field listening or even in a far-field listening environment in a well-damped room, the out-of-phase connection appears to be the best bet. In a reverberant room and far-field listening conditions, where the sound energy at the listening seat is at least 50% indirect, the in-phase connection may be preferred.

The bottom line is that you should let your ears be the final arbiters in the matter, and not be afraid to experiment. Why go to this much trouble? Because above about 500Hz, the Sequel's level of performance is nothing short of Class A. Its levels of transparency, spatial cohesiveness and resolution, and transient control are simply astonishing. I have not lived with these speakers very long, but they just swept me away—quickly and decisively. I'd have to go back to the Alan Hill helium plasma tweeter to find a driver that bettered the Sequel in terms of treble performance.

Let it be known that in my opinion, with the proviso of an out-of-phase connection and the understanding that one needs to be tolerant of bass anemia, and that the driving amp must be capable of handling the 1.5 ohm or so impedances in the treble, the $2500/pair Sequel II is a strong Class B contender. I would opt for the Sequel over most of the mini-monitors out there—even over the venerable Quad US Monitors.

I write this after having spent some time at LA's house listening to the Infinity IRS Betas. These tweaked Betas sounded as good as I've ever heard Betas sound, and in many respects their sound was impressive, highlighted by an effortless feel and an authoritative quality. Yet, for me, the Betas failed to break the transcendental barrier—they failed to give me a satisfying illusion of live music. The Sequels are not as tonally accurate, but they sure as hell weave a better illusion.—Dick Olsher

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Footnote 1: Readers may feel that I missed a trick in my review by not investigating the sound with the woofer polarity reversed. In fact, the instant I discovered the in-phase connection of the drivers, the idea did occur to me but I abandoned it when I was reassured that this was how the Sequel was meant to sound. I don't regard redesign of a product, even if it features what the reviewer regards as a serious design anomaly, as a primary part of his or her responsibility. Note that, regarding the implications of Dick's conclusions, my listening room is reasonably small—20' by 15'—and at the listening seat, the direct sound from the speakers predominates.—John Atkinson