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More important, though, is the aural break-in often required by the listener with this class of speaker. Without the room masking and excess bass many audiophiles have become conditioned to, you'll hear both a lot more and a lot less than you're accustomed to hearing from favorite recordings: less coloration and more musical detail, particularly in the lower midrange and bass. My experience was that, as I listened to an ever-greater variety of music running the gamut of recording quality from poor to awesome, the deeper my appreciation grew for the "rightness" of the Beethoven's performance…
Sidebar 1: Specifications
Description: Four-way, bi-amplified dipole system consisting of two dynamic main panels, two subwoofers, a pair of passive crossovers, and a unity-gain, noninverting, balanced, active (line-level) crossover. Drive-units: one 1" soft-dome tweeter, two 8" Kevlar-cone midrange drivers, two doped paper-cone 10" woofers (main panel); four 12" cone woofers (subwoofer). Crossover frequencies: 200Hz, 2kHz (main panel); 100Hz (subwoofer). Frequency response: 20Hz-25kHz, ±2.5dB (complete system); 40Hz-25kHz (main panels used without subwoofers); 100Hz-25kHz (main panels…
Sidebar 2: Associated Equipment
Analog Source: Immedia RPM-2 turntable and improved RPM-2 unipivot arm; Sounds of Silence Crown Jewel and Lyra DaCapo phono cartridges.
Digital Sources: Muse Model 5 with I2S interface, Theta Data Basic 2, Sonic Frontiers SFT-1 transports; Wadia 16 CD player; Muse Model Two-Plus with I2S interface, Theta Gen.Va, Sonic Frontiers SFD-2 Mk.II processors.
Preamplifiers: Jeff Rowland Design Group Coherence-Cadence battery-powered line/phono combo, Muse Model 3, Sonic Frontiers SFL-2, Audio Research LS22, BAT VK-3i.
Power Amplifiers: Jeff Rowland Design…
Sidebar 3: Measurements
The Beethoven is quite sensitive, 2.83V of B-weighted noise generating an spl of 88.5dB at 1m on the tweeter axis. The impedance of the panel, however, (fig.1) drops significantly below 4 ohms between 45Hz and 210Hz, and to 4 ohms in the mid-treble. A good solid-state power amplifier would best drive this speaker, as suggested by Audio Artistry themselves. The impedance peak at 22Hz I assume is due to the free-air resonance of the twin woofers.
Fig.1 Audio Artistry Beethoven panel, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div…
To the right of fig.3 are shown the crossover's complementary high-pass responses for the drive to the Beethoven panel, with the woofers turned on and off. A small degree of tonal shaping can be seen between 200Hz and 1kHz. Without the subwoofers, the crossover adds a modest amount of boost below 150Hz to flatten and extend the panel's output, with then a steep rolloff below 40Hz. When the subwoofers are used, the crossover gently rolls out the panel woofers below 100Hz. The crossover's input impedance was a high 86k ohms (balanced), while its output impedance was a low 450 ohms. The…
In the time domain, the Beethoven's step response (fig.9) is not coherent. The tweeter and midrange units appear to be connected with inverted acoustic polarity, the woofer with positive polarity. Fig.10 shows the cumulative spectral decay plot calculated from the Beethoven's impulse response. It is superbly clean throughout the treble, but there is some hash present in the low treble, which I suspect is due to early reflections from the speaker's structure. However, as SD had nothing but praise for the Beethoven's sound, I assume this is benign.
Fig.9 Audio Artistry Beethoven,…
I've long been a fan of Naim electronic gear, and have used it for many years. I also have admiration and respect for the company's uncompromisingly consistent and determinedly individualistic approach to the various tasks and problems of loudspeaker design. But my enthusiasm for Naim speakers has long been tempered by a feeling that mechanical aspects of the design are given priority over acoustics and styling.
Naim's new NBL loudspeaker has been wowing plenty of hi-fi show visitors recently, and is unquestionably the most attractive-looking speaker the company has yet produced. The…
While the bass drivers will normally be acoustically coupled to wall and floor, the cabinet's depth not only ensures excellent stability (to some extent unnecessary in view of the mechanical decoupling and horizontally opposed bass drivers), but also places the mid and treble drivers sufficiently far from the wall to avoid the most serious effects of reflection coloration. The main enclosure and its substantial, neatly styled, cast-alloy plinth is the "virtual mechanical earth" for this speaker system. Its lower 23" act as the main, 2.1ft3 (60-liter) bass cavity, but above that the cabinet…
The first time I heard the NBLs in my room, I was reminded of the wall-mounted drive-units by Tannoy (15" alnico-magnet dual-concentrics) I sometimes use. These drivers, flush-mounted in a structural wall and left unobstructed to their rears operate as true boxless infinite baffles, and are regular reminders of the limitations of normal loudspeaker enclosures. While the NBL doesn't share the same tonal balance of these wall-mounted Tannoys by any means, it does have something of the same "boxless" sound quality. This would seem to confirm the efficacy of that complex enclosure decoupling.…
I discussed the NBL's tonal balance with Phil Ward, who said that the speaker had existed in active form for some months before the passive version was finalized, and that the control settings arrived at under active drive provided a "target function" for the speaker's passive balance. It's my suspicion that an active system can get away with being more "forward" than its passive equivalent, simply because the absence of passive crossover components invariably makes the sound inherently cleaner. A slightly more restrained balance might be more acceptable in the marketplace.
Stereo…