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Meridian DSP8000 digital active loudspeaker Measurements

Sidebar 3: Measurements

Performing acoustic measurements on a speaker that has only a digital input posed some problems, as the DRA Labs MLSSA system I use for all of my loudspeaker tests outputs only an analog signal. I therefore digitized the MLSSA stimulus at 24 bits/88.2kHz with a dCS 904 A/D converter, and converted the AES/EBU datastream to S/PDIF using a Z-Systems rdp-1, this set to do nothing but convert formats. The peak level of the digital signal, measured with a Dorrough digital-domain meter, was -6dBFS.

The second problem involved the sheer bulk of the DSP8000—it was…

Meridian DSP8000 digital active loudspeaker Measurements part 2

But before you jump to any conclusion about the subjective effects of this behavior, look again at fig.1: The midrange unit narrows its dispersion in the exact region where the on-axis response is a little "hot." Similarly, the tweeter's lower-octave flare occurs where the on-axis response begins to plateau down. In a typical listening room, the '8000's on- and off-axis behaviors will tend to balance each other, resulting in a neutral perceived balance.

However, the use of a short horn surrounding the tweeter dome does increase that drive-unit's directivity above 11kHz or so. In all but…

Audio Physic Rhea powered subwoofer

"You can't get deep bass in your room," a reviewer from another magazine who'd never visited my room insisted recently on the phone. "Do you know how long a 20Hz bass wave is? It's 40 feet long, and your room is tiny."

"Then I guess headphones can't reproduce any frequency longer than the length of the ear canal, which, of course, is absurd." I responded. "That would mean headphones can't reproduce midrange—not to mention bass. And we all know they can."

The problem with small rooms isn't that they can't do deep bass, it's that below the frequency of the smallest standing wave (a…

Audio Physic Rhea powered subwoofer Page 2

The Rhea includes two controls to deal with "room gain." One adjusts for the amount of increase in level below the standing-wave mode, and the other compensates for the frequency at which the pressurization occurs in the room. In other words, the first deals with "room stiffness," the second with room size. The "stiffer" the room—ie, the less the walls flex—the greater will be the amplitude rise below the pressurization frequency. The more the walls flex, the more "leakage" of low bass into the outside world. The smaller the room, the higher the frequency at which pressurization occurs.…

Audio Physic Rhea powered subwoofer Specifications

Sidebar 1: Specifications

Description: Powered subwoofer. Drive-units: two 101/2" Vifa coated-paper-cone woofers. Amplifier: 300W, with velocity feedback circuit. Frequency response: 10Hz-80kHz +/-3dB, restrictable to 35Hz, 46Hz, and 61Hz. Maximum SPL: 98dB at 10Hz, >110dB from 30Hz up. Input impedance: 600 ohms. Suggested room size: 125-1050 sq. ft. with average ceiling height (around 2400 cubic feet).
Dimensions: 29" H by 18.5" W by 18.5" D. Weight: 88 lbs.
Finishes: Cherry, white, black ash, or custom.
Serial number of unit reviewed: 059.
Price: $5995. Approximate…

Audio Physic Rhea powered subwoofer Associated Equipment

Sidebar 2: Associated Equipment

Analog sources: Lyra Parnassus D.C.t and Koetsu Urushi phono cartridges, VPI TNT Mk.IV turntable, Graham 2.0 tonearm; Simon Yorke Series 7 turntable/arm, Immedia RPM arm.
CD players: Bow Technologies ZZ-Eight and Naim CDX CD players.
Preamplification: Ayre K-3, Jadis JP 80 Mk.2, Stax SRM-T1W passive line section.
Power amplifiers: VTL MB-450 and Conrad-Johnson Premier Twelve tube monoblocks.
Loudspeakers: Sonus Faber Concerto Grand Piano, NHT Super One, Audio Physic Virgo.
Cables: Yamamura Millennium 6000, Cardas Golden Cross, and Electra-…

TacT Audio RCS 2.0 digital equalizer/preamplifier

I anticipated the installation of the TacT Audio RCS 2.0 room-correction processor with mixed emotions—I already liked my system and room, and such a device threatened to make all my studied efforts trivial. What if one might use any decent amps and speakers, cables that were merely conductive, and no room treatment at all? And what if, on top of that, you could just put them wherever your significant other thought they looked right? What if all the magic you needed was contained in this box? Scary.

The TacT RCS (Room Correction System) 2.0 is an up-to-date manifestation of a…

TacT Audio RCS 2.0 digital equalizer/preamplifier Page 2

How to listen?
Assessing the overall performance of the TacT RCS required me to distinguish the RCS's DSP/room-correction capabilities from its other capabilities. I began by evaluating the RCS's own DAC by running digital lines from the TacT to the Perpetual Technologies P-3A and Mark Levinson No.360 DACs, and coaxial analog lines from the TacT, PT, and ML to my Sonic Frontiers Line-3 preamp. All three inputs were gain-adjusted at the preamp to give equal output. A/B/C comparisons revealed that each DAC sounded so subtly different as to leave me unable to express a strong preference.…

TacT Audio RCS 2.0 digital equalizer/preamplifier Page 3

I had intermittent problems switching between correction filter modes on the RCS. Selecting a particular correction from the remote or the keypad on the front panel sometimes muted the output and sometimes made a clearly spurious correction. There were also times, when switching among inputs, when the RCS failed to access the new input. In both situations, switching to Bypass and/or to another input and back successfully recovered the desired function.

What did it sound like?
Objectively, as measured by the ETF and the Sencore analyzers, the RCS accomplished three things. First, it…

TacT Audio RCS 2.0 digital equalizer/preamplifier Page 4

Hoary old platitudes
The walls melted away. I was transported to the performance. The speakers disappeared. A veil was lifted. Yadda yadda yadda.

Well, excuse me! These clichés accurately describe the RCS's removal of my listening room's superimposed character. It permitted me to hear the low-level ambience cues of the original performance sites. This information was already on the recordings, but now I was simply hearing more of it, and better. The rain during Ivor Humphreys' flute solo on an old Hi-Fi News & Record Review test CD, and the various activities, acoustic and…