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So, how to examine the HeadRoom's response shaping and crossfeed? In its bypass mode, the amplifier was flat in response up to the mid-treble, with then a gentle ultrasonic rolloff. This can be seen in both the rounding of a 10kHz squarewave's leading edges (fig.5) and in the amplitude response (fig.6). The -3dB point lies at 27kHz, meaning that audio-band response is down 2.2dB at 20kHz. This will be audible as a slight softening of the overall sound—not a bad idea with headphones! The effect of the filter is also shown in fig.6; it can be seen to shelve up the mid-treble by a mild 3dB.…
Wes Phillips wrote about the Supreme in July 1996 (Vol.19 No.7):
HeadRoom's $399 HeadRoom Supreme headphone amplifier seemed the logical comparison to the Audio Alchemy HPA v1.0/PS3. The portable HeadRoom can run off either a small wall-wart, or an external four-D-cell power pack. I prefer its sound with the battery pack, so I used that for my comparisons.
They were both very good, but the Audio Alchemy sounded just a shade coarser, with a bit of grit in the upper octaves. On "Third Uncle," from Brian Eno's Taking Tiger Mountain (by Strategy), remastered and Super-Bit-Mapped on…
Someday we may speak wistfully to our grandchildren about the "golden age" of digital audio when consumer formats (CD and DAT) contained a bitstream that was an exact bit-for-bit duplicate of the original studio master recording—not a digitally compressed, filtered, copy-resistant version whose sound is "close enough" to the original. Digitally compressed formats such as DCC and MiniDisc represent, in effect, a return to the pre-CD era when consumer-release formats were always understood to be imperfect copies of the studio original. Even the most ardent audiophile accepted the fact that LPs…
For still more efficient coding, linear PCM can be replaced by a "floating-point" code in which leading zeros are eliminated by repetitive division. (The linear PCM codes in a single CD contain more than a billion leading zeros, in small signals and wherever a large waveform crosses the zero-voltage axis.) A small number such as 0.00000001 in decimal arithmetic becomes "1E-8" in floating-point form; the number after the E tells the decoder how many places the decimal point was moved to the left.
With typical program material, lossless coding can cut the bit-rate by at least a factor of…
As with PASC, most of the complexity (and cost) in the AC-2 system resides in the encoder. An AC-2 decoder can be produced as a single under-$20 IC and can be designed to work with either fixed-filter AC-2 codes or the improved sound provided by dynamic-filter AC-2A coding.
Dolby AC-3
Two of the five proposals for high-definition TV currently being tested by the FCC employ AC-2 coding for stereo sound. At the NAB convention, Tom Holman of Lucasfilm went a step farther. He reviewed the psychoacoustic factors that affect the perception of timbre and imaging, concluding that the…
"Ah, I see what the problem is. Your ear canals are larger in diameter than normal."
Size does matter, I guess. I was talking to Shure staffers at their booth at Home Entertainment 2003 last June. I had always had a problem with such in-ear headphones as the industry-standard Etymotics, and was explaining that I was getting on no better with the review samples of Shure's then-new, $499 E5c in-ear cans. With what I now knew to be my wider-than-normal ear canals, I had not been able to get the supplied sleeves, foam or soft plastic, to seal properly. The result was sound that seriously…
Sidebar: Specifications
Description: Lightweight, sound-isolating, in-ear headphones, with foam or soft flex sleeves and 1/8", gold-plated 3.5mm stereo plug. Impedance (at 1kHz): 26 ohms. Sensitivity (at 1kHz): 115dB/mW. Supplied accessories: Personal Fit Kit with three sizes of flex and ultra-soft flex sleeves, one pair of foam sleeves; nylon carrying case.
Dimensions: Weight: 0.9oz (28gm). Cable length: 60" (1.52m).
Serial number of unit reviewed: N/A.
Price: $179. Extra foam sleeves, $21.20/20; extra flex sleeves, $12.60/10. Approximate number of dealers: sold direct. Warranty…
Michael Fremer wrote about the Shure E5c in December 2004 (Vol.27 No.12):
My current headphone of choice is Shure's E5c in-ear model. Sure, the Shures are expensive at $500, but after a year's listening, I'm convinced they're worth it. They can be surprisingly comfortable, once you've chosen the correct in-ear plug size. Their isolation rivals that of any of the electronic noise-canceling models I've heard—and whether it has to do with the Shures' lack of electronics, two drive-units per channel, or something else, they sound much, much better. Plus, the E5cs are tiny, unobtrusive,…
I visited the Revel room on the last day of the January 1999 CES, expecting another dynamic demo of their Ultima line. Instead, I found a pair of floorstanding Performa F30s connected to a rack full of the best Mark Levinson electronics. Deeply impressed by the dynamics and clarity of this first model in the new Performa line, I called Revel's Kevin Voecks as soon as I got back to New York City, but was told that another Stereophile reviewer had already got first dibs on the F30. Would I be interested in one of the other Revels? Well, yes, sure, but...
A pair of Revel's Ultima Studios…
Setup
However, the initial results I obtained were what I had feared from the wide-dispersion specs. The speaker end of my room is fairly hard, with large windows and mostly nonabsorbent surfaces, which added some glare to the presentation. In addition, the large, reflective yew-wood credenza immediately to the left of the left speaker, and the absorbent sofa to the right of the right speaker, created a significant tonal imbalance. If I toed the F30s in so much that the left speaker aimed away from the credenza, then the right one was aimed at it. Either way, the glare was not entirely…
However, the initial results I obtained were what I had feared from the wide-dispersion specs. The speaker end of my room is fairly hard, with large windows and mostly nonabsorbent surfaces, which added some glare to the presentation. In addition, the large, reflective yew-wood credenza immediately to the left of the left speaker, and the absorbent sofa to the right of the right speaker, created a significant tonal imbalance. If I toed the F30s in so much that the left speaker aimed away from the credenza, then the right one was aimed at it. Either way, the glare was not entirely…