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PSB Alpha A/V loudspeaker Measurements

Sidebar 3: Measurements

Despite its diminutive size, the Alpha A/V was quite sensitive, my B-weighted estimate coming in at 88.5dB/2.83V/1m. It is also a kind load for an amplifier or receiver to drive, its impedance (fig.1) dropping below 6 ohms only in the lower midrange and at the port-tuning frequency of 45Hz.

Fig.1 PSB Alpha A/V, electrical impedance (solid) and phase (dashed). (2 ohms/vertical div.)

The small wrinkles visible in the impedance plots at 200Hz and between 400 and 500Hz imply the presence of some kind of resonant behavior at these frequencies.…

PSB Alpha A/V loudspeaker Measurements part 2

But when you look at the curves more closely, there are other differences. The 1999 sample's upper-midrange peak is a little lower in frequency, which ties in with both the slight nasality and the forward upper mids I noted in my auditioning. The 1992 sample has a slight peak at 2.1kHz; in the newer version, this has moved up in frequency to 3.2kHz.

Fig.5 shows how the Alpha's response varies to the sides of the tweeter axis. (Just the differences are shown in this graph, which means that the on-axis response appears to be a straight line.) As very often is the case, the speaker's…

PSB Alpha A/V loudspeaker Measurements part 3

Nevertheless, when you look at the plot of the Alpha's spatially averaged in-room response (fig.7), lacks of energy can still be seen in the middle of the midrange and between 1.25kHz and 3kHz. In my auditioning, I picked up on this as an upper-midrange forwardness.

Fig.7 PSB Alpha A/V, spatially averaged, 1/3-octave, free-field response in JA's listening room.

In the time domain, the step response (fig.8) indicates that the Alpha's drive-units are connected with the same positive acoustic polarity, with the HF unit leading the woofer slightly in time. The discontinuity…

Fine Tunes #35

"J-10, tweakoman," began the e-mail from one of Stereophile's Web mavens and a contributor to "Industry Update," the estimable Barry Willis, "hockey pucks are the cure for what ails you."

I wondered where he wanted me to put 'em.

"Yes, plain old generic black-rubber hockey pucks. Forget the spiked feet under the speakers. Take 'em off and slip three or four hockey pucks under them instead. Haven't tried 'em as footers under other gear, but their density and vibration-damping qualities seem equal to or better than most expensive tweako materials. My local discount sporting-goods…

Prima Luna Prologue One integrated amplifier

My first reaction to the Prima Luna Prologue One was based solely on looks: For $1095, I might not have been disappointed had it sounded no better than a Bose Wave Radio. Its casework straddles the breach between vintage and modern in a way that little else does, at any price. The dark gray-blue finish, hand-rubbed to a tactile gloss, wouldn't look out of place on an Alfa GTV (the new one, which resembles a drop of oil). And for the first time in my experience, a high-end audio manufacturer has figured out a way to make a protective tube cage easy to remove and replace: with banana plugs and…

Prima Luna Prologue One integrated amplifier Specifications

Sidebar 1: Specifications

Description: Single-box line-level tube preamplifier and push-pull tube power amplifier. Tube complement: two each 12AX7A, 12AU7, EL34. Inputs: 4 single-ended. Output power: 35Wpc into 8 ohms (15.4dBW). Voltage gain: 20dB. Output impedance: 4 or 8 ohms. Frequency response: 20Hz–30kHz, ±0.5dB. Input impedance: 100k ohms. Input sensitivity: 300mV.
Dimensions: 11.5" W by 7.7" H by 15" D. Weight: 36 lbs.
Serial number of unit reviewed: 04031452.
Price: $1095. Approximate number of dealers: 1 (sold direct).
US distributor: Upscale Audio, 2504 Spring…

Prima Luna Prologue One integrated amplifier Associated Equipment

Sidebar 2: Associated Equipment

Analog sources: Linn LP12 turntable with Naim Armageddon power supply, Naim Aro tonearm; Rega Planar 9 turntable; Supex 900 Super, Linn Akiva, Lyra Helikon Mono cartridges; Audio Note AN-S2 step-up transformer.
Digital source: Sony SCD-777ES and dCS La Scala-Delius SACD/CD players.
Preamplifiers: Fi, DNM 3C Primus.
Power amplifiers: EAR 890, Lamm ML2.1s, First Watt F1.
Loudspeakers: Quad ESL-989, Lowther PM2A in modified Medallion horns.
Cables: Digital: various dCS. Interconnect: Audio Note AN-Vx, Nordost Valhalla, homemades. Speaker:…

Prima Luna Prologue One integrated amplifier Measurements

Sidebar 2: Measurements

I ran the Prologue One at one-third power into 8 ohms from the 8 ohm tap for 60 minutes—not so much to thermally stress it, as I do with solid-state designs, but to make sure it was up to its working temperature. (I didn't notice the pleasant smell, Art!) I performed a complete set of tests from both its 8 ohm and 4 ohm output transformer taps, but have described the results for both here only when relevant.

The input impedance was usefully high, at 95k ohms at 20Hz and 1kHz, this dropping inconsequentially to 76k ohms at 20kHz. The amplifier preserved…

Wilson Audio Specialties Sophia loudspeaker

Of the small number of times I have been totally swept away by listening to recorded music, a significant proportion have involved loudspeakers from Wilson Audio Specialties. It was my experience of their X-1/Grand SLAMM in the listening rooms of reviewer Martin Colloms, then-retailer Peter McGrath, designer Dan D'Agostino of Krell, and manufacturer Madrigal Audio Labs, that led me to name it my "Editor's Choice" for 1995 and join my vote with those of the Stereophile scribes to make it the magazine's "Loudspeaker of the Year." I wrote in my December 2001 "As We See It" about how a cross-…

Wilson Audio Specialties Sophia loudspeaker Page 2

The crossover is said to use high-quality parts and is encapsulated to minimize vibrational effects. Electrical connection is via a single pair of brass binding posts. Finishing the speaker off are four multi-part spikes, which both set the correct listening height and couple the speaker optimally to the floor.

Setup
Peter McGrath, now with Wilson Audio Specialties, set the Sophias up in my listening room. If you're concerned that this means a reviewer is being given special treatment, I'm told that the dealer from whom you purchase a pair of Sophias will provide this service as a…