Sidebar 3: Measurements
JA measured the Vandersteen 3A and provided me with the results after I completed my listening tests and wrote up the results. The Vandersteen's sensitivity measured lower than specification at an estimated 85dB/W/m (B-weighted). Its impedance is shown in fig.1. The magnitude remains below 6 ohms for much of the range, and dips to a minimum of 2.8 ohms at 35Hz—this, I assume, the tuning of the active acoustic (bass) coupler. This is a moderately demanding load, though the phase angle is low, except in the low bass. The moderate changes due to the various…
The general trend of the midrange and tweeter response is quite linear, though some clearly visible response ripples—particularly from 1kHz to just above 2kHz—would appear to be due to reflections from the cabinet top and its support rods (footnote 2). The sharp peak at about 26kHz is the ultrasonic tweeter resonance. Fig.3 shows the overall response of the Model 3A averaged across a 30 degree horizontal window (again, measured at 39" from the bottom of the cabinet, 50" away). The bass is down by 6dB at 23Hz, and very flat up to about 500Hz—both excellent results. There is a mild suckout…
The horizontal response family of the Vandersteen 3A, with any on-axis response deviations subtracted out so that the on-axis response appears as flat, is shown in fig.6. That response notch at just below 1kHz deepens at extreme off-axis angles. The overall dispersion through the midrange and top end—making allowances for the small ripples caused by cabinet reflections—is otherwise excellent. The vertical-response family (fig.7) indicates that listeners are better off slightly below the optimum axis than they are above it. Translated, that means that it would be better to err on the side of…
The impulse response on the tweeter axis, shown in fig.8, is very good, with a time-coherent shape and a small amount of damped ultrasonic tweeter ringing. The time-coherence of the 3A is even clearer from the step response (fig.9), which reveals a very good step shape. The small plot wrinkles just below and above the 6 millisecond mark in fig.9 are probably reflections from the cabinet structure, and are also visible—though less obviously so—in fig.8. Fig.8 Vandersteen 3A, impulse response on optimal axis at 50" (5ms time window, 30kHz bandwidth).
Fig.9 Vandersteen…
Sidebar 4: Manufacturers' Comments
Editor: Thank you for this opportunity to comment on the review of our Model 3A loudspeaker. The distorted, fluttery sound heard on the introductory drumstrokes of the Jurassic Park soundtrack was the active acoustic coupler reaching its excursion limits and hitting the rubberized stops built into the driver. These excursion stops prevent bottoming and greatly reduce the chance of the driver being damaged. We have found very few pieces of recorded music with bass levels capable of pushing the driver to its limits. To safely and properly reproduce the…
The High End is a tidily ordered world. There are CD players, transports, and processors used to play stereo recordings and drive stereo preamplifiers. There are stereo or mono amplifiers used to drive a pair of speakers. And then there is the British high-end company Meridian, run by one J. Robert Stuart, one of audio's deeper thinkers and a Fellow of the Audio Engineering Society. Meridian does it their way. They put their amplifiers inside their speakers. Heck, Meridian even puts their D/A processors inside their speakers when they can. And two speakers to play back stereo recordings?…
Before I discuss the results of my auditioning, I'll present the measured results. These were all taken in the digital domain using an Audio Precision System One fitted with the DSP option. The Meridian 518 was fed a data signal from the AP's AES/EBU output, set to a 20-bit word length. The 518's AES/EBU data output was looped back to the AP's digital input. In the digital domain, the data word length is inexorably tied to the ultimate level of the noise floor. The longer the word, the lower the noise, with an approximate increase of 6dB in the system S/N ratio every time the word length…
The Meridian offers seven different noise-shaping algorithms, shown in Table 1. The spectral effects of each on the noise floor, hence the ultimate resolution, are shown in figs.8 through 14. (All of these were made using our old friend, the 1kHz tone at -90.31dB.) Which will be optimum depends on the nature of the original signal, the playback situation, and individual taste. For example, I ended up using Shape A on the Concert CD, which was originally recorded on analog tape. For Festival, for which I used a Nagra D 20-bit digital recorder, I used Shape C. And the late recording engineer…
Glitches: Any recording engineer using A/D converters with better than 16-bit resolution but storage media restricted to 16 bits—CD, CD-R, DAT, etc.—owes it to their sound-quality-conscious customers to use a Meridian 518. However, I did have one operational problem using the 518 in that I could not get my Panasonic 3700 professional DAT recorder to lock to its output, even with the channel bit set to "P" for "Professional." For the Festival project, I used a Meridian CDR as an interim storage medium (footnote 1), as this would lock onto the 518's data output with the channel bit set to "C"…
Sidebar 1: Description Specifications: Digital processor, with infra-red remote control, capable of operating in three modes: "Type 0," Digital Control Center with digital source selection and digital volume control (1dB step size); "Type 1," Digital Resolution-Enhancement Device with user-selectable input/output data-word lengths, gain, and dither/noise-shaping (five algorithms available); "Type 2," Digital Mastering/Multimedia Processor. Digital inputs: three electrical S/PDIF (RCA); one S/PDIF optical (TosLink); one AES/EBU (XLR). Digital outputs: one AES/EBU (XLR); one S/PDIF (RCA).…
