While I have strong positive reactions to the basic Audyssey EQ/NAD EQ system, I have somewhat mixed reactions to Audyssey’s Dynamic EQ and Dynamic Volume functions, and I recommend approaching both with some caution. While the Audyssey Dynamic EQ function offers potentially worthwhile benefits for those who listen at low-to-moderate volume levels, adjusting EQ curves in keeping with the volume settings you’ve chosen, I personally find that the Dynamic EQ function seems to undercut clarity a bit (which the basic Audyssey EQ/NAD EQ system does not). My basic complaint is that the Dynamic EQ system seems to impart an ever-so-slightly bass-heavy sound. The Audyssey Dynamic Volume function, in turn, can be very useful for those listening in apartments—especially in terms of managing volume levels late at night—but seems to undercut clarity further still. My suggestion, then, would be to try both functions for yourself and make your own judgment as to whether their benefits outweigh potential drawbacks.
As I mentioned above, the T 775 offers not only the standard “Audyssey EQ” response curve, but also a special “NAD EQ” curve, which raises an important question: what’s the difference between the two? I posed this question to Greg Stidsen, NAD’s Director of Product Development, who offered a great deal of useful background information.
First, Stidsen explained that it was a natural choice for NAD to explore digital room correction solutions in general, and to collaborate with Audyssey in particular. This is partly because of NAD’s long association with TacT’s Peter Lyngdorf, Stidsen observed, who “had sold his interest in NAD to pursue the development of the TacT room correction (system) along with V. Bosovik many years ago.” But apart from its familiarity with the Lyngdorf and TacT’s efforts in the room correction field, NAD also had a great deal of prior experience in working with Audyssey co-founder Tomlinson Holman (of THX fame), since “NAD developed the first THX product, the 208THX amplifier.” Putting these two factors together, it was perhaps inevitable that NAD would want to incorporate Audyssey features in its receivers, and indeed NAD worked closely with Audyssey as it developed successive iterations of its systems, including the MultEQ XT system incorporated in the T 775.
But, says Stidsen, the key issue for any room correction involves the fact that “all of these adaptive correction systems base their correction on a measurement of the existing acoustic 'fingerprint' of the speakers and their interaction with the room. The system doesn't know what the overall 'correct' or 'target' response should be; this needs to be programmed into the system. There are several theories about what the target response should be…”
Expanding on this point, Stidsen explains that, “in a nutshell, most speakers are designed for 'flat' response in an anechoic chamber. When that flat responding speaker is placed into a typical room, the bass response is elevated due to 'room gain' and the high frequencies are absorbed by walls and furnishings. The resulting response in the room is very different from the response in the anechoic chamber, which mimics a 'free space' response. All recording engineers use a speaker in a room to monitor their recordings, and the acoustic balance of all recordings reflect this reality. If you make a speaker/room combination 'flat' (an option on the T775) it will sound 'thin' and 'bright' with too much treble energy and not enough bass. The Audyssey setting compensates for this by increasing the bass and decreasing the treble”—a setting that Stidsen and others at NAD perceived as sounding good, but also a little “like a ‘loudness control’ had been applied.”
While acknowledging that many listeners like the effect of the standard Audyssey EQ setting, the NAD team felt that with some extra time and effort it might be possible to produce an even more natural sounding alternate EQ curve—one that would potentially hold even greater appeal for critical audiophiles. Accordingly, NAD worked out an arrangement with Audyssey where, as Stidsen put it, “Audyssey allowed us to include our own target (EQ curve) as long as we also included theirs.”
According to Stidsen, the NAD EQ curve “was developed in the NAD Lab with help from our sister company PSB Speakers. Steve Wilkins from NAD (developer of EARS) and Paul Barton (of PSB) did most of the acoustical measurement and analysis.” The NAD team felt the standard Audyssey EQ curve added “a little too much energy in both the bass and treble (regions),” so that NAD’s strategy was to try for an EQ approach that was “a bit more sophisticated and uses a couple of 'shelving filters' in the treble response and a bit less emphasis in the bass region. Our goal was to leave intact the character of the loudspeaker as it would be heard in a room with favorable acoustics.” Stidsen observes that, “if you have your front stereo speakers well placed and you have a good room, the NAD target curve will sound very similar.”