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Nelson-Reed 8-04/B loudspeaker How to Calculate Maximum SPL

Sidebar 3: How to Calculate Maximum SPL

If you have a scientific calculator (or a slide rule, or a set of log tables), it is easy to calculate, from a loudspeaker's sensitivity rating, how much Sound Pressure Level it will put out with a given amount of available amplifier power.

Since a sensitivity rating is a statement of SPL of acoustic output with 1W of signal input (at 400 or 1000Hz), it will be increased according to the difference in deciBels between the amplifier's rated maximum output and that 1W reference level. To calculate this, take the amplifier's rated output,…

Nelson-Reed 8-04/B loudspeaker Specifications

Sidebar 4: Specifications

Description: Floor-standing, three-way, dynamic loudspeaker reflex woofer loading (system Q = 0.7, optimal damping). Drive-units: two 8" cone woofers, one 3" doped-linen dome midrange, one ¾" soft-dome tweeter (B), 1" metal-dome tweeter (CM). Crossover frequencies: 300Hz, 6kHz (B); 320Hz, 4.2kHz (CM). Nominal impedance: 8 ohms, 6 minimum. Frequency response: 32Hz–20kHz ±3dB, . Sensitivity: 92dB. Maximum acoustic output: 120dB SPL at 500W RMS in. Linear continuous output (3dB compression): 114dB at 320W RMS. THD at 1kHz: 0.15% at 100dB, 0.35% at 110dB SPL.
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Jadis Eurythmie II loudspeaker

The Jadis Eurythmie speakers ($37,000/pair) arrived in a multitude of oversized boxes. Importer Northstar Leading the Way's Frank Garbie dragged them into our downstairs lobby and broke them open, elevatoring the individual modules up to our door. This happened on one of my office days, but Kathleen pushed me out the door in the morning with a "Don't worry cherie, I can handle it..." She phoned in periodic updates on Garbie's progress. Remember that old Stan Freberg routine? "I got it, I got it...I don't got it!" I arrived home just in time to hook up the amps.

Frank had set down the…

Jadis Eurythmie II loudspeaker Page 2

"A horn speaker's design is based upon calculations that determine the correct shape to amplify a certain range of frequencies. Hence our optimized four-driver system: Bass, Mid-Low, Mid-High, and Treble." See, it's Franglais, but it gets the point across. "With the Eurythmies, the bass crossover frequency of 180Hz allows a maximum of fundamental tones to be reproduced by the horn transducers—the pitch, the treble clef, and the bass clef are present in frequencies from 180 to 800Hz. We have therefore prioritized this range and kept the advantages of a drum..." (that's a dynamic moving-coil…

Jadis Eurythmie II loudspeaker Page 3

The lobe of sound the Eurythmies threw seemed pear-shaped, with the bulbous end acoustically circumambient to the listener. I know about pear-shaped—that's what Kathleen says I am! That may account for the sense that I was sitting a few aisles removed to the middle of the concert hall when taking the rear seat. In fact, you're at the rear of the lobe, looking into, rather than being immersed by, the energy of the soundfield.

While pear-shaped is what I've used to describe the lobe of sound, it should be understood that sitting within that fruity lobe, the apparent soundstage for the…

Jadis Eurythmie II loudspeaker Measurements

Sidebar 1: Measurements

My apologies but there are no measurements of this intriguing speaker's performance. Logistical problems, a winter storm, and sheer lack of time to make the trip to Durango, CO, prevented me from measuring the Eurythmie II in time to accompany this review. However, the horn speaker had a even-balanced power response, based on my experience at J-10's, where it sounded less-colored/more-neutral the farther away I listened to it.—John Atkinson

Jadis Eurythmie II loudspeaker Specifications

Sidebar 2: Specifications

Description: 4-way hybrid horn/dynamic-driver loudspeaker system. Crossover frequencies: 180Hz, 700Hz, 7kHz. Peak power handling: 70W. Sensitivity: 103dB/W/m with bi-amplification, above 180Hz, 96dB/W/m with mono-amplification.
Dimensions: 59" (1500mm) H by 27.5" (700mm) W by 27.5" (700mm) D. Weight: 176 lbs (80kg).
Price: $37,000/pair (1996); no longer available (2012).
Manufacturer: Jadis S.A.R.L., Villedubert, France. US Distributor: Northstar Leading the Way, Durango, CO 81302 (1996); Bluebird Music Ltd., 310 Rosewell Avenue, Toronto, Ontario M4R…

Follow-Up, July 1988

JGH wrote again about the Hafler XL-280 in July 1988 (Vol.11 No.7):

This budget-priced ($650) power amplifier has been the center of some controversy over the validity of a nulling test that Hafler devised, wherein an amplifier's output is fed, in reversed phase with its input, to yield an overall signal cancellation. Hafler contended that any amplifier that gave a perfect null must, by definition, be a perfect amplifier, and that, since the Hafler XL-280 gave by far the most nearly perfect nulling, it must be the most nearly perfect amplifier in existence.

The argument sounded…

Follow-Up, July 1988

JGH wrote again about the Threshold SA-1 in July 1988 (Vol.11 No.7):

The original version of this has been my reference amplifier since I reviewed a pair of them two years ago (Vol.9 No.1), and although it has since seen a number of small but significant changes, I felt I couldn't part with mine for long enough to get them upgraded. Finally, when I saw that I was going to be out of town for a week, I sent them back.

What I got in return was, for all intents and purposes, a pair of different amplifiers. On first listen, right out of the box, they sounded quite bad—harsh, rough, and…

Manufacturer's Comment

Editor: Since J. Gordon Holt's description of the SWDT (straight wire differential test), there have been many comments and inquiries directed both to Stereophile and directly to me concerning this test. I will try to answer most of these in this catchall commentary.

The starting point is that it is very difficult to compare amplifier A with amplifier B to make a quality assessment. The conventional A/B test, or any comparison, may indicate that the amplifiers are different, but how can one determine which is "best"? "Best" is a matter of judgment, and even…