Music in the Round #44 Page 3

I used HDMI for audio and video connection to the Oppo BDP-83 and my cable box. I connected the audio-only Sony XA-5400ES SACD/CD player with HDMI and balanced XLR, and, just for kicks, the Oppo with six RCA cables to the 707's multichannel analog inputs. Analog inputs can be used as a pure analog path, the Krell contributing only the volume control and output stage; but these inputs can also be digitized, affording use of bass management and other processing. At the output, I connected my Bryston 9B-SST five-channel power amplifier to the RCA outputs, and later via the balanced XLRs. Since I had two Paradigm subs, a Sub-15 fore and a Servo-15 aft, it was great to be able to set them up as "Front+LFE" and "Back+LFE," as this preserved the orientation of the (presumably) nondirectional bass.

I spent a few days listening to CDs and stereo SACDs with the 707 before delving into EQ. Via the Sony XA-5400ES and a direct analog path, the sound was positively glorious. It had been some time since I listened to two-channel recordings in this room, and the sound had a seductive clarity and depth, particularly with solo piano, cello, and guitar. With recordings of larger ensembles, I did miss the envelopment that multichannel affords. In addition, the degree of intrusion of the room's acoustics varied with the recording. Of course, that's no criticism of the 707, which was remarkably transparent and detailed and, in my opinion, should satisfy even the most demanding listener. By comparison, when I digitized the two-channel input, there was a slight loss of detail in background sounds, but not in the direct sounds of the performers.

The tradeoff was an opening up of harmonic detail below 250Hz as I invoked the EQ and bass management. I had similar reactions with the 5.1-channel analog input, but unfortunately heard that the BDP-83's D/A and analog stages added an unnecessary sheen all too ruthlessly revealed by the Krell's lucid, grain-free treble.

Automatic Setup/EQ: I could wait no longer. I mounted the Krell microphone on the boom of my mike stand, positioned it midway between where my ears are usually situated in my sofa, and plugged in the generously long cable. I navigated to the 707's room-EQ page to choose among Auto, None, or Manual 1–4. The last circumvents Auto EQ but lets the user store a manual parametric EQ in any of four memory slots (footnote 2) I chose Auto, and then could select between Full Range or EQ only below 250, 125, 80, or 63Hz. I experimented with both Full Range and <250Hz. Following that choice are options for the EQ curve: Flat, Music, and Movie. Flat sounded a bit bright, and Movie added a weight to the bass that I didn't care for; Music was the one for me. Finally, you choose Run Auto-Setup With EQ or Run Auto-EQ Only. The latter keeps the current settings for the speakers and calibration (levels and distance). I began by going for the whole enchilada.

The procedure sweeps the speakers several times each with different test tones to identify, locate, calibrate, and finally equalize each speaker. I particularly noted the reiterated alternating testing of the front left and right speakers and the surround left and right speakers, in what seemed an effort to optimize the pairs' timbral balances. The subwoofers were pulsed individually and together. With little pause for calculation and with only one mike position permitted, all this was done amazingly fast. Krell's system determined that all my main speakers were full-range, differed by only 1dB or so in level, and were closer to the mike than they actually were. For example, the three fronts were 9.5' from the mike; the Krell said they were only 5' away. Remarkably, the differences in distance among the five speakers were dead-on, so delay settings should be correct anyway. Consequently, I set both subs as LFE devices only.

More remarkably, the Krell's measurements of the subs' distances from the listening position and each other were similar to what I've measured with other electronic tools, even though the measure is a composite of physical distance and processing latency.

I didn't much like the resulting sound. While the soundstage was large and spacious, with excellent integration of the outputs of all speakers and subs, the main performers' voices and instruments seemed recessed, and the upper bass (80–200Hz) was too prominent. The lower bass was hard to assess in that context, but it was a little anemic by my measurements.

Still, there were many options left to pursue, and I tried to impose some manual constraints on Krell's AutoEQ process. One was to bass-manage the speakers, crossing the fronts (Paradigm Studio/60s) over at 45Hz and the surrounds (corner-mounted Paradigm Studio/20s) at 60Hz. Another was to set the front sub to be Front+LFE and the rear sub to be Back+LFE. Finally, I tried various frequency limitations for the EQ, and liked <250Hz best.

Well, with Krell's help, I did get it right. First, limiting the EQ to <250Hz in an effort to restrict it to fixing only those room effects below the "critical" frequency was not optimal with these speakers in this room. The Paradigms seemed a bit too forward and bright unless I let the 707 run a Full Range EQ. On the other hand, the results of Full Range EQ with my bass-management settings and the reconfiguration of the subwoofers sounded just dandy. Tests with the XTZ measurement system showed that the Krell's Auto-EQ effectively smoothed the frequency response in each channel, but did little to correct the extended decay of the room's modes. Those considering the Evolution 707 for a custom setup, for which it seems intended, should consider getting the services of an acoustically skilled installer who can use the processor's room EQ and its even more formidable parametric tools.

Britten's Orchestra, the first multichannel SACD from Reference Recordings, with Michael Stern conducting the Kansas City Symphony (Reference RR-120SACD), was absolutely spectacular for both its dramatic and detailed depiction of the orchestra and the absolute solidity of the bass. And bass there is a-plenty on this disc, to the point that some have criticized it for excess. I can understand that, but, damn, it is delicious, and through the Krell 707 the bass drum was devastatingly big and tight, and easily distinguished from the timpani in timbre and position. Perhaps that had to do with the way my two subs were set up and fed. Even bigger stuff, like the opening of Act 3 of Wagner's Die Walküre, with Zubin Mehta and the Valencia Community Orchestra (BD, C Major 700804), with the brass choirs and the flying Valkyries, was thoroughly transporting and nearly overwhelming. As I watched the Valkyries swooping and singing, everything matched—there was no "out-of-body" localization of their voices.

Roy Orbison's Black and White Night (Image Entertainment ID4954OBBD), one of my favorite Blu-rays, was just a bit more close-up and lively than I'd experienced it before, as was Willie Nelson's Night and Day (DVD-A, Surrounded By SBE-1001-9), although it was just as immersive as ever.

In transparency and impact, Krell's Evolution 707 Reference was at least the equal of any other processor I've used. Its sound was somewhat more forward and detailed, where others offer a soundstage that's a bit more tiered and spatially balanced with regard to depth. This character will, of course, depend on both the source and the room, but the Krell was absolutely convincing with dts-HD Master Audio soundtracks. It would garner an overall high recommendation from me but for its cost ($30,000) and size. Those issues aside, the Krell Evolution 707 is a comprehensive and completely competent preamplifier-processor. It is the only pre-pro I have used that proved completely immune to audio interruptions caused by the power recycling of a connected display. Moreover, it is as great-sounding a digital processor as it is as an analog preamp . . . and vice versa.

Footnote 2: The Evolution 707's manual EQ is described as a 1/3-octave digital parametric equalizer. On one hand it's superbly sophisticated, with low-pass filters, high and low shelf filters, and peaking and notch filters with useful amplitude ranges. However, its 1/3-octave limitation in frequency resolution makes it somewhat less useful in the low-frequency range than many DSP-based equalizers. I tried to use it to implement correction filters that have proved effective in my room, but was briefly frustrated by Krell's use of their own Shape parameter for the peaking/notch filters rather than the more common Q. I converted my filters using the formula Q=SQR 2N/ (2N-1), where N is the bandwidth in octaves (Krell's Shape parameter), but the results were suboptimal: the 1/3-octave spacing prevented me from setting the filters at the exact frequencies specified. I admit that I'm not skilled enough at math or acoustics to make good use of Krell's EQ, but I think a professional installer would find it more powerful and more useful than the 707's Auto-EQ.
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