The 3.3 ohm amplifier output resistance test
One of the problems for someone auditioning a good SE amplifier for the first time is that all audiophiles have a psychological need to hear a difference. Some audio differences, while important, are quite subtle. Their analysis requires fine equipment, good circumstances, and, in some cases, extended listening. However, when compared with a conventional, solid-state, or push-pull low-impedance tube amplifier, a single-ended tube amplifier will always sound substantially different. This is due to the complex interaction of an SE design with…
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Test 1, WATT V: The Watt V is nominally a 5-6 ohm loudspeaker. The calibrated loss in loudness due to the simulated source resistance was therefore a substantial 3.6dB. (Note that with an even-lower-impedance speaker, the output impedance of a tube SE amplifier will result in an even greater loss in loudness.) No sense could be made of the comparison, so I raised the volume by 4dB to match the subjective loudnesses.
What a fascinating result! The resistor feed dramatically shifted the tonal balance of the Wilson WATT, with the general view that it now sounded more like a free-field-…
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These anecdotal tests only go to show the remarkable complexity of sound-quality changes that can result from using an amplifier with a significant source impedance. Even experienced critics—sorry, I do place myself in this category—find it very difficult, if not impossible, to separate these physical and acoustic interactions from the overall perception of sound quality. We have to accept that moderate tone-control effects—unfamiliar response changes over limited sections of the overall frequency range, allied to changes in level—can significantly alter perceived sound quality…
These anecdotal tests only go to show the remarkable complexity of sound-quality changes that can result from using an amplifier with a significant source impedance. Even experienced critics—sorry, I do place myself in this category—find it very difficult, if not impossible, to separate these physical and acoustic interactions from the overall perception of sound quality. We have to accept that moderate tone-control effects—unfamiliar response changes over limited sections of the overall frequency range, allied to changes in level—can significantly alter perceived sound quality…
Sidebar: Sonic Speaker Tailoring
It's not readily appreciated that a loudspeaker's treble balance exercises a powerful control over perceived clarity, right into the midrange. The perception of a loudspeaker's quality hinges strongly on the balance the designer has achieved between the midrange and treble levels—both in the on-axis frequency response and in the acoustic power delivered to the room.
It's not readily appreciated that a loudspeaker's treble balance exercises a powerful control over perceived clarity, right into the midrange. The perception of a loudspeaker's quality hinges strongly on the balance the designer has achieved between the midrange and treble levels—both in the on-axis frequency response and in the acoustic power delivered to the room.
This is very critical, and if a speaker system lacks sufficient clarity, the designer may be led, intuitively or deliberately, to lift the treble power to improve things. It is amazing…
It was 20 years ago that I began audio reviewing as a second career. It was also 20 years ago that I made my first very expensive audio purchase: a pair of Infinity RS-1b speakers. The RS-1b was a landmark speaker in its day, and very costly for the time at $5500/pair. (I think my dentist has just spent more than that on a TV.) In retrospect, the RS-1b was an extraordinary value. With four large towers, more than 30 drivers, and a servo network and a passive crossover, the Infinity RS-1b resolved a significant amount of detail, was capable of large dynamic swings, had pinpoint image…
The bass performance of the little Primus 150 excited me. On "Feel No Pain," from Sade's Love Deluxe (CD, Epic EK 53178), although the synth bass drum lacked bottom-end extension, the synth bass lines were natural, fast, and clean, with great authority, dynamics, and clarity. On rock recordings such as Gary Wilson's "When You Walk Into My Dreams," from You Think You Really Know Me (CD, Motel MRCD 007), Fender basses were quick, natural, and forceful. Ray Brown's double-bass solo on "I'm an Old Cowhand," from Sonny Rollins' Way Out West (CD, JVC VICJ-60088), was so natural and vibrant that I…
Sidebar 1: Specifications
Description: Two-way, reflex-loaded, magnetically shielded, stand-mounted loudspeaker. Drive-units: ¾" "Metal Matrix"-dome tweeter, 5¼" "Metal Matrix"-cone woofer. Crossover frequency: 3.3kHz. Crossover slopes: 24dB/octave. Frequency response: 58Hz-20kHz, ±3dB. Sensitivity: 88dB/2.83V/m. Nominal impedance: 8 ohms. Recommended amplification: 10-100W.
Dimensions: 123/4" H by 73/8" W by 101/2" D. Weight: 13.5 lbs (6kg).
Finish: Black ash.
Serial numbers of units reviewed: ME0678-06400/01064.
Price: $198/pair. Approximate number of dealers: 100.
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Sidebar 2: Associated Equipment
Analog sources: VPI TNT IV turntable, Immedia RPM tonearm, Koetsu Urushi cartridge; Rega Planar 3 turntable, Syrinx PU-3 tonearm, Clearaudio Virtuoso Wood, Aurum Beta S cartridges.
Digital sources: California Audio Labs Icon Mk.II Power Boss, Creek CD53 Mk.II CD players; Pioneer DV-333 DVD-Video player.
Preamplification: Vendetta Research SCP-2D phono stage, Audio Valve Eklipse line stage.
Power amplifier: Audio Research VT100 Mk.II.
Integrated amplifier: Creek 5350SE.
Loudspeakers: NHT SB3, Paradigm Atom, Polk RT25i.
Cables: Interconnect…
Sidebar 3: Measurements
A fundamental choice faces every designer of small speakers: extend the low-frequency performance but accept a low sensitivity, or maximize sensitivity and live with the curtailed bass response? The Primus 150's designer has chosen the latter course; while Bob Reina noted its lightweight bass in his auditioning, the speaker offers above-average sensitivity, at an estimated 89.5dB(B)/2.83V/m. In addition, its impedance is also fairly amplifier-friendly, remaining above 5 ohms for most of the bass, mid, and treble ranges (fig.1). The impedance magnitude does drop to…
This morning, John Atkinson passed along to me an e-mail he received from one of our most attentive correspondents—a reviewer, in fact, for an erstwhile competitor. We know that this particular writer ranks among our closest readers because an issue seldom comes out but that he writes an analysis of it, including, and down to, what he considers our excessive political correctness in choice of pronouns.
Today's missive included his comments concerning our latest CD, Rhapsody (see June 1997, pp.70-81). He hasn't yet heard it, but regards its main work, George Gershwin's Rhapsody in Blue,…