Description: Belt-drive turntable with outboard motor controller.
Dimensions: 19" W by 6" H by 15" D. Weight: 65 lbs.
Serial number of unit reviewed: None found.
Price: $4995 with acrylic motor mount, $5995 with aluminum motor mount (1997); not currently available (2005). Approximate number of dealers: 10.
Manufacturer: Immedia, 1101 Eighth Street, Suite 210, Berkeley, CA 94710. Tel: (510) 559-2050. Fax: (510) 559-1855. Web: www.immediasound.com.
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Sidebar 1: Specifications
Sidebar 2: Associated Equipment
LP Playback: Linn LP12 with Naim Armageddon Power Supply, Naim ARO tonearm, van den Hul Frog cartridge; VPI TNT Mk.III with Immedia RPM-2 arm, Lyra Clavis D cartridge.
Preamplifiers: Conrad-Johnson Premier Fourteen linestage, Premier Fifteen phono section; Ayre K-1.
Power Amplifiers: Krell FPB 600, VTL MB750 monoblocks.
Loudspeakers: Aerial 10T, EgglestonWorks Andra.
Cables: Kimber KCAG interconnects, Kimber Black Pearl speaker cables.
Accessories: Audio Power Industries Power Wedge 112; MIT Z-series power cables; Highwire Audio Power Wrap…
This series of articles was initially written (in slightly different form), as a paper presented at the 103rd Audio Engineering Society Convention, New York, September 1997. The preprint, "Loudspeakers: What Measurements Can Tell Us—And What They Can't Tell Us!," AES Preprint 4608, is available from the AES, 60 East 42nd Street, Room 2520, New York, NY 10165-0075. The AES internet site, offers a secure transaction page for credit-card orders.
What's the point of measuring the performance of an audio component if what owners do is listen to it? Of the 20 or so regularly published…
Subjective loudspeaker performance is thus a multidimensional phenomenon. However, to make objective measurements that are both meaningful and practicable involves a subjective choice about what parameter to plot against one, or at most two, other parameters. All other parameters have then to be held constant. If you plot, say, a loudspeaker's sound-pressure level against frequency for a given input voltage, the result is the typical amplitude or "frequency" response. But this measured response will only be valid on the chosen axis in an anechoic chamber at the chosen sound-pressure level at…
Voltage Sensitivity
A loudspeaker's sensitivity appears to be universally confused with its efficiency. Efficiency is strictly defined [6, 7] as how much acoustic power the loudspeaker puts out for how much electrical power it is being driven with. If you feed a loudspeaker with 100 electrical watts, how many acoustic watts of sound does it produce? The answer is "not many," a typical moving-coil loudspeaker being about 1% efficient.
A loudspeaker's sensitivity appears to be universally confused with its efficiency. Efficiency is strictly defined [6, 7] as how much acoustic power the loudspeaker puts out for how much electrical power it is being driven with. If you feed a loudspeaker with 100 electrical watts, how many acoustic watts of sound does it produce? The answer is "not many," a typical moving-coil loudspeaker being about 1% efficient.
Efficiency, or more correctly sensitivity, is usually expressed in the form of a sound-pressure level produced by a speaker at a specific distance, 1m…
In 1990 Ronald Aarts of Philips [9] carried out a study of the effect of loudspeaker response on perceived loudness. He concluded that weighting the spectral balance with the popular noise A-weighting curve gave limited correlation with subjective loudness, instead calculating the loudness in phons based on critical-band analysis (ISO932B). Critical-band analyzers not being easy to come by, at Stereophile, I feed the loudspeaker with 20kHz-bandwidth noise at a standard level, capture the output waveform with the DRA Labs MLSSA system used in its storage-oscilloscope mode [10], and apply B-…
Then there is the fact that the first method drives the speaker-under-test with a wide-band noise signal while the second drives it with one frequency at a time. Some engineers conjecture that speakers will behave differently to the two stimuli. Having used both methods, I have only found minor differences between the results, if at all. However, for practical reasons, I use the second method, using an Audio Precision System One to drive the loudspeaker in 240 frequency steps from 10Hz to 50kHz with 6V via a series 600 ohm resistor (actually the unit's source impedance). While a true plot of…
The impedance measurement is a major diagnostic tool. It is possible to find out a lot about how a loudspeaker is going to behave just from looking at its electrical impedance. Without even seeing the speaker, the number of "ways" will almost always be apparent from the impedance plot, as will whether it is a sealed-box design (one hump in the bass), a reflex or a transmission line (two humps in the bass), or a horn of some kind (a series of regularly spaced peaks). The approximate low-frequency extension will be apparent from the shape of the plots in the bass, as will its Q. The "saddle"…
REFERENCES
[1] M. Colloms, High Performance Loudspeakers, Fourth Edition, pp.391-395 (John Wiley & Sons, 1991).
[1] M. Colloms, High Performance Loudspeakers, Fourth Edition, pp.391-395 (John Wiley & Sons, 1991).
[2] F.E. Toole, "Listening Tests—Turning Opinion into Fact," presented at the 69th Convention of the Audio Engineering Society (1981 May). Preprint 1766. J. Aud. Eng. Soc. Vol.33, pp.439-440 (1982 June).
[3] F.E. Toole, "Subjective Measurements of Loudspeaker Sound Quality and Listener Performance," J. Aud. Eng. Soc. Vol.33, pp.9-12 (1985 January/February).
[4] Perception of Reproduced Sound 1987, Symposium Proceedings edited by S. Bech & O. Juhl…
Chances are you've never seen an amplifier quite like the Mark Levinson No.33H. That's because there's only one other amp that's anything like it: the Mark Levinson No.33, upon which it's based. Both amps are more tall than broad, looking almost as though they're resting on their ends; heatsinks cluster around their side-panels. In the city of the High End, the No.33 and No.33H are skyscrapers standing tall above the warehouses.
When Madrigal first unveiled the No.33, they were drawing a line in the sand. "This is everything we know about building amplifiers," they said. But they weren'…