In last month's review of the venerable LS3/5a loudspeaker (Vol.11 No.2, p.115), you will remember that I had intended to compare an 11-year-old pair of these BBC-designed monitor speakers against a brand-new pair. As explained in the review, this turned out not to be possible before the review deadline, due to the new pair getting lost in shipping. (As Murphy's Law would have it, they finally arrived just after the February issue had been put to bed.) The new version of the LS3/5a differs in detail from those manufactured before 1987,…
search
John Atkinson's review of the Harbeth version of the BBC LS3/5a appeared in the December 1993 Stereophile (Vol.16 No.12):
The Rogers version of the BBC -designed LS3/5a appeared in 1975 and remained in production until early 1993. Other licensees have included Audiomaster (whose designer, Robin Marshall, went on to found Epos), Chartwell, RAM, Goodmans, Spendor, and Harbeth; the last two still manufacture the speaker.
In all that time, the design has been revised just twice. In 1988, the woofer's surround was changed from a springy Neoprene rubber to a more lossy vinyl compound…
Sidebar 1: 1993 Review context
Power amplifiers were either a pair of Mark Levinson No.20.6 monoblocks or a YBA 2, while the preamplifier was either the Melos SHA-1 headphone amplifier used as a line-stage, the YBA 2, or the Audio Research LS2B. A Mod Squad Phono Drive EPS amplified LP signals from a Linn Sondek/Cirkus/Trampolin/Lingo/Ekos/Arkiv setup sitting on an ArchiDee table. Digital source was variously a Theta DS Pro Generation III, a Counterpoint DA-10 with UltraAnalog DAC module, a Mark Levinson No.35, or the new Sonic Frontiers SFD-2, all driven by a Mark Levinson No.31…
Sidebar 2: Harbeth Measurements
The LS3/5a's impedance magnitude and phase are shown in fig.1. Dropping to 6 ohms only in the top treble octave, it shouldn't give the partnering amplifier any hernias. The sealed box is tuned to 76Hz, the impedance reaching 31.2 ohms at that frequency. There is a very slight wrinkle in the impedance trace at 350Hz, probably not visible at the printed scale of the graph, which coincides with the frequency of the main cabinet resonant mode (see later). The speaker's sensitivity is low at around 82.5dB/W/m; it won't accept high power inputs without the…
The Harbeth's impulse response on the tweeter axis, measured with the DRA Labs MLSSA system and a B&K 4006 microphone calibrated to be flat on-axis, is shown in fig.7. The multiple-humped shape betrays the presence of the high-order crossover, while the step response (fig.8) reveals the tweeter to be connected with positive polarity (the sharp up-down spike at 3.5ms), and the midrange/woofer with the opposite polarity (the slower negative-going hump peaking at 3.9ms). The two are obviously not time-coherent. The cumulative spectral-decay, or waterfall, plot (fig.9) reveals an initially…
John Atkinson wrote about the Stirling LS3/5a V2 in April 2007 (Vol.30 No.4):
Back in the early 1970s, the British Broadcasting Corporation needed a physically unobtrusive, nearfield monitor loudspeaker for use in remote-broadcast trucks. A team led by T. Sommerville and D.E. Shorter, of the BBC's Research Department, developed the two-way, sealed-box LS3/5, based on a small monitor they'd designed for experiments in acoustic scaling. That monitor used a B110 woofer with a doped Bextrene 5" cone and a T27 SP1032 1" Mylar-dome tweeter, both sourced from British manufacturer KEF. The only…
Sidebar: Stirling Measurements
You can find the measurements of my 1978 samples of the LS3/5a here, and a comparison of their measurements with those of a 1996 KEF sample here. The Stirling LS3/5a V2 offered the same low sensitivity as the original, 82.5dB(B)/2.83V/m, but its impedance (fig.1) is closer to the final KEF version than the original. The peak of 34.8 ohms at 81Hz reveals the tuning frequency of the sealed enclosure, and implies only modest LF extension. Other than dips to 7.5 ohms at 171Hz and 9.7 ohms at 20kHz, the Stirling's impedance stays well above 10 ohms at all audio…
Sidebar: JA's 2007 Associated Equipment
Digital Sources: Classé cdp-202 DVD/CD player, Ayre C-5xe universal player; Mark Levinson No.30.6, Benchmark DAC 1 D/A processors; Slim Devices Squeezebox WiFi music processor with Apple Mac mini running OSX for media storage.
Preamplifiers: Mark Levinson No.326S, Audio Research Reference 3, Ayre K-5xe.
Power Amplifiers: Mark Levinson No.33H monoblocks, Halcro dm38.Loudspeakers: Revel Ultima Studio, Era Design 4, Harbeth HL-P3ES2, PSB Alpha B1, Rogers LS3/5a (1978 samples).
Cables: Digital: Kimber Illuminations Orchid AES/EBU, AudioQuest…
Sidebar 3: BBC LS3/5a Specifications
Description: Two-way, sealed-box, stand-mounted loudspeaker. Drive-units: 0.75" (25mm) Mylar-dome tweeter, 4.5" (110mm) Bextrene-cone woofer. Crossover frequency: 3kHz. Crossover slopes: not specified. Frequency response: 80Hz-20kHz ±3dB at 1m with grilles on. Sensitivity: 82dB/W/m. Nominal impedance: 16 ohms (1977-1984); 10 ohms (1989 onward). Amplifier requirements: 50W maximum.
Dimensions: 12" H by 7.5" W by 6.25" D. Enclosure volume: 5 liters. Weight: 11.7 lbs each.
Serial numbers of review samples: S0429 & #S0430 (1976 pair), none noted…
This must be the month I drew the right straw to review "loudspeakers with three-letter initials." Elsewhere in this issue I describe my experiences with pair of JBLs. Everyone knows that JBL stands for "James B. Lansing," founder of that company. You do, don't you? But PSB? If you've been paying attention here, you probably remember that JGH reviewed one of their loudspeakers back in May 1988. If you haven't, well, listen up. PSB is named after Paul Barton and his wife Sue, who formed Canada-based PSB in 1971. (Paul is still their chief designer.) The company was unknown in the US until just…