MartinLogan Sequel II loudspeaker Page 2
The evening of the third day witnessed my next attempt at serious listening. The lower midrange had acquired a little more flesh, but the sound was far from meaty. This was with the woofer control set to "0dB"; switching it to "3dB" exacerbated the problem. Worried, I checked the overall system frequency response, measured at the speaker terminals. With the Line Drive's volume controls set to 12 noon, the bass was very slightly lightweight, shelving down by 1dB at 20Hz. Obviously, the Tempest's output stage was not quite up to the task of driving cables, Line-Drive, and Krell input impedance. This would not be enough to explain my reaction, however: though taking the Line Drive out of circuit and connecting the Tempest to the C-J Premier Seven did bring up the low bass a tad, the sound still lacked body in the lower midrange.
Since Richard Lehnert and I endured, sorry, enjoyedno, I was right the first timethe nine-hour epic about Richard Wagner's life starring Richard Burton, the beginning of Die Walküure, nervously scrubbing strings over chugging double-bass quarter notes that seemed to burst from the soundtrack every time the story line lagged, has become engrained in my brain. Yet via the Sequels driven by the Krell (the Solti recording on London 414-105-2, of course, Richard), the bass line that is so essential to the music's setting the stage for the drama to unfold was dramatically undernourished, the rosiny leading edges to the sound being unsupported by the body of the tone.
This was when I decided to move the speakers closer to the rear wall. This usefully fleshed out the sound, but at the expense of that wonderful image specificity. I had to face the fact that a) the speaker had some kind of problem in the lower midrange, b) the Krell/Sequel combination was incompatible, or c) both of these. I hadn't yet done any measuring, so I thought I would take another rest from serious listening and carry out a basic set of measurements. I was confident that I had enough of a handle on the Sequel's sound, at least from 100Hz down and 400Hz up, that I would not be swayed by any measured revelations. (It is distressingly all too easy to hear what you think you should be hearing.)
With the CD player buffered by the Premier Seven, the drive to the speakers was just 0.2dB down at 20Hz. While testing with pink noise, however, I was disturbed by the fact that the Krell KSA-50's protection activated. Repeating things showed that five minutes of pink noise at an RMS level of 6V (equivalent to 23V peak as measured on the 'scope), which was raising an acoustic spl of approximately 96dB in-room, would shut the Krell down. I couldn't repeat this phenomenon the next day, however, which was significantly cooler, and prolonged high-level rock music didn't trigger the amplifier's protection, so I can only assume that it is a sign that the Sequel II makes large simultaneous voltage and current demands on a power amplifier.
In addition, when playing piano recordings at high but not unreasonable levels, there were moments when the sound became momentarily congested. The obvious explanation was that the Krell was being driven into clipping, but there was always the possibility that the input transformer was saturating. To check the cause, I looked at the actual waveform at the speaker terminals while playing the track where it was most apparent, Jorge Bolet performing Liszt's Reminiscences de Don Juan (London 417 523-2). The unweighted peak spl in my room was between 96dB and 98dB, and the peak voltage being swung by the Krell was +39, 32V. This is equivalent to more than 80W RMS into an 8-ohm loadnot bad for a nominally 50W amplifier! Although it couldn't be clearly seen on the 'scope screen, the amp must definitely be into clipping at this point, indicating that an amplifier capable of swinging more volts was necessary to drive the Sequels to sensible levels.
When choosing a matching power amplifier, therefore, all the indications suggest that wimps need not apply. While the Krell is most definitely not a wimp, I decided that something a little more burstproof would be in order for the bulk of the auditioning. Accordingly, I liberated the $11,500 pair of Mark Levinson No.20.5 amplifiers from Larry Archibald's listening room. (Don't worry, LA had just bought a pair of Quicksilver monos, so my action didn't leave him bereft of musiche is my boss, after all!)
Now things started to cook, the Levinsons, ahem, really being able to kick, er, well, you know what portion of the anatomy usually gets kicked. The sound acquired enough midrange weight that, desirous of some more of that great imaging, I moved the speakers back to where they had been originally. A quick check with the Solti Walküure confirmed that the soundstaging was both dramatic and precise: thus I continued with the rest of my listening, both formal (notebook in hand) and informal (a cold beer in the other).
Although you never listen to music by dismembering it into bite-sized, audiophile-ready chunksthis is the treble, this the midrange, these are the lows, that is the soundstagereviewers often structure their reviews in such a manner, it being perhaps the most effective way to convey a product's strengths and weaknesses. I shall not be an exception: I will first discuss the Sequel's sound sector by sector, before discussing its performance as a whole.
First, when driven with a powerful amplifier, the Sequel has astonishing dynamics for an electrostatic design. The pair driven by the Mark Levinsons would easily reach 100dB average levels before any sense of strain set in. Some five years ago now, I was lucky to be given the opportunity to record Elgar's The Dream of Gerontius in England's Ely Cathedral. With a 200-strong choir, a full orchestra, and one of the more thundering of the UK's pipe organs, the music's live dynamic contrasts are extreme. (I used my Revox running at 15ips with dbx II noise reduction to squeeze them on to tape, and I must say that I have yet to hear a recording of this work on CD that gets anywhere near this work's real-life dynamics or those of this tape.) Near the end of the work's second part, rehearsal mark 120, an orchestral climax is itself climaxed by a monstrous fffz blow on the bass drum. (The score actually says " 'For one moment' must every instrument [sic] exert its fullest force.") While not quite achieving the cataclysmic effect that this recording produces on Infinity IRS Betas, the Sequels still almost managed to knock LA out of his chair! Celestions or Quads just don't even begin to get close.