Tag Archives | audio

New Orleans Bump

Memo to David Simon and Treme: Turn it up!

Turn it the fuck up.

I’m loving more or less every second of the second season of HBO’s tortured love song to New Orleans music, cooking, African-American genius, cultural gumbo, and much else, and the successor to Simon’s transcendent Baltimore epic, The Wire. Among other things it’s the best portrait of jazz and jazz musicians and the glories of musical miscegenation in the history of television. (I bet even David Simon is getting tired of the phrase “in the history of television.”)

My one giant peeve about the show is that whoever’s doing the sound recording and mix is failing miserably when it comes to serving up presence and punch. I’d almost swear that the frequent anemic-sounding musical interludes are set at a lower volume than the spoken dialogue. I’ve got my TV sound running through a receiver and feeding Epos speakers and a big, fat subwoofer, and I watch the entire show gripping the remote in order to drastically crank up the sound during the music, and then instantly tone it down when the dialogue resumes to avoid having the voices blare. Even at high volumes there’s a notable absence of low-end and mid-range muscle when the music’s playing.

There was a recent joke on Glee about “hate-watching” Treme. I’d never go that far, but Treme‘s sound design is (softly) begging for a severe ass-whupping.

October 20, 2012 at 2:43 pm

Bluestem Wolf Howls

Another beautiful field recording — this one of the ethereal howling of the Bluestem Mexican wolf pack, near the west fork of the Black River in the White Mountains of Arizona, on October 7, 2009, by John and Mary Theberge. Despite innumerable setbacks and constant illegal killing of the reintroduced Mexican wolves in New Mexico and Arizona, the Bluestem pack, with five of its members wearing radio collars, was reported to be still traveling through its traditional territory last month with at least four pups.

Image: Canis lupus, circa 1819-22, by Titian Ramsay Peale, National Museum of Wildlife

October 15, 2012 at 2:56 pm

The Sounds of Shangri-La

In October 2000, a reporting team from the NPR-National Geographic program Radio Expeditions traveled to the high mountains of western China, near the Tibetan border, to document the Yunnan Great Rivers Project. NPR engineer Bill McQuay roamed the region for two weeks by car, horseback and on foot, through 12,000-foot passes and forests of giant rhododendron, recording villagers herding yak and cattle, Buddhist pilgrims offering prayers to mountain gods, and musicians performing on traditional instruments.

October 12, 2012 at 2:26 pm

3D Audio at Princeton

I’m standing in the confined space of a custom-built anechoic chamber at Princeton University’s 3-D Audio and Applied Acoustics Lab, bathed in green light and surrounded on all sides by wedges of melamine acoustic foam. I’m facing a pair of Ascend Acoustics speakers set on tall stands about a foot and a half apart. And I’m considering the advice that professor Edgar Choueiri has just offered, in a voice curiously deadened by a total absence of room reflections.

“You may want to close your eyes,” he said. “If you clear out the visual cues, you get even more realism.”

I’m about to hear a demonstration of Choueiri’s Pure Stereo filter, which promises “truly 3-D reproduction of a recorded soundfield.” Only a handful of people have heard his 3-D demo, but it’s already spawned awestruck hype, as well as preemptive rumblings of audiophile skepticism.

Choueiri leaves. A few seconds later, the sound of flowing water fades in and rises in both volume and presence. I have the uncanny sensation of standing neck-deep in a river, with its plashing surface spreading around me. Next, a buzzing fly circles my head. Then an aural nightscape of crickets and the loud croaks of a frog, precisely over there. An excited crowd, children shouting. A train chugs in from the right and comes to a halt across the platform.

Musical selections follow—an a cappella choir in some vast reverberant space, a New Orleans street band, a quartet of classical guitars—featuring shockingly expansive soundstaging, exact source positioning, and vivid ambience. Then Choueiri’s virtual voice is speaking in my left ear, my right ear, behind my head, and lastly he’s simulating giving me a haircut, with scissors snipping sides, top, and back.

Choueiri reappears at the door. “That was absolutely fantastic,” I tell him.

Spatial hearing in three dimensions depends on subtle differences in timing, sound level, and the shape of our heads and ears, among other factors. Binaural and even conventional stereo recording incorporates rich 3-D information. But “crosstalk” collapses the 3-D illusion: during playback, the left ear hears not only sound from the left speaker, but also some of the right-speaker sound, and the right ear likewise hears spillover sound from the left speaker.

A technique called crosstalk cancellation—processing the audio signal so that the left ear hears sound from only the left speaker, and the right, from only the right—can reveal the inherent 3-D sound in stereo. But crosstalk cancellation has always introduced audible spectral coloration. It’s this problem, applied to two-speaker playback, that Choueiri says he’s licked. He wrote a fiendishly abstruse 24-page technical paper explaining his theoretical work, and then spent several years coding and designing his Pure Stereo filter.

Manufacturers and producers sense enormous profits looming in 3-D audio for TV, cinema, and gaming. Compared with 3-D, the sales pitch goes, surround-sound systems are unwieldy and offer crude spatial definition. Princeton is now negotiating with various consumer companies to license Pure Stereo, and Choueiri also hopes to improve on hearing aids, which currently are not very good at pinpointing where sound is coming from.

In a sense, Choueiri’s adventures in audio represent a hobby that’s spun out of control. His real job is teaching applied physics at Princeton and developing plasma rockets for spacecraft propulsion. Visiting Europe to attend a conference in 2003, Choueiri decided on a whim to detour to Amsterdam and crash a meeting of the Audio Engineering Society, where several sessions explored the technical challenges of 3-D audio. “Within a few weeks, I read pretty much every paper in the field,” Choueiri recalls. Funding for his 3-D audio lab came from Project X, an initiative to encourage unconventional engineering research at Princeton.

Later during my visit, Choueiri invites me to his restored 1834 home near campus, where we spend hours sampling his enormous collection of vinyl LPs, reel-to-reel tapes, and high-definition audio files. Choueiri has a Jerry Garcia beard, a high forehead topped with stray tendrils of disorderly hair, and the dark-circled eyes of a nocturnalist. He puffs on a pipe while he roams the shelves.

“The most tiring part of stereo is the fact that the image spatially doesn’t correspond to anything that you ordinarily hear,” Choueiri tells me. “That’s what drove me to create this thing. Your brain is getting the right cues, and you relax. Your brain stops trying to re-create reality.”

[This post originally appeared (as “What Perfection Sounds Like”) in the March 2011 issue of the Atlantic.]

March 1, 2011 at 4:59 pm

Riding the Groove

My all-time favorite explanatory passage from the literature of hi-fi appears in Laura Dearborn’s sadly out-of-print 1987 guide to audio, Good Sound. In it, she contrives to describe what’s happening when a turntable cartridge’s stylus rides an LP groove, and she pulls it off in a way that makes it sound like a marvel akin to a Star Wars jump into Hyperspace. Now and then, when I’m playing a great-sounding record via my trusty Ortofon Kontrapunkt A cartridge I remember Deaborn’s thrilling explication.

So let’s cue up Good Sound:

Visualize the fineness of a record groove, and then consider that it combines two distinct channels of information, each with completely different modulations. Some of the signal modulations in the groove are on the same order of size as a wavelength of light, which means the stylus has to “read” a signal as small as a millionth of an inch…

For the half a mile or so of record groove per LP side, the stylus must precisely trace abrupt changes in the direction of the undulating groove, sometimes traveling at speeds several times the acceleration of gravity, without ever losing contact with either wall or blurring together the modulations.

Groove friction heats the stylus up to 350 degrees Fahrenheit and the groove vinyl momentarily liquefies each time the stylus passes over it. (This is why one should let a record rest for at least 30 minutes before replaying it, and preferably for 24 hours.)

Even though the cartridge tracking weight is commonly set at only about 1.5 grams, the entire weight is supported on the minute edges of the stylus. As a result, the downforce applied to the groove on a per-square-inch basis is several TONS.

Combine these extreme conditions of weight, heat, speed, and need for exquisite maneuverability, then add in the scale of environmental vibrations that interfere with the stylus as it retrieves the music from the groove, and it’s extraordinary that ANY music (as opposed to noise) is heard through an audio system.

For the grand finale of her bravura account of LP playback, Dearborn gets all Brobdingnagian, blowing up the stylus-and-groove action to outsized gynormousness. Technology as minute as an LP record groove is typically measured in microns. One micron equals 0.0039 inch. Dearborn walks us through what would happen if you could convert the micron scale upward to inches, borrowing a thought-experiment originally devised by the Boston Audio Society’s magazine, The Speaker.

Using the inch scale, a stylus is 30 feet long, affixed to a cantilever 50 feet thick and 275 feet long, which extends from a cartridge body 2,000 feet long, sitting 80 feet above the record. The tonearm, 450 feet in diameter, crosses 1,500 feet above the record from its pivot point four miles away… The stylus downforce temporarily deforms the vinyl by as much as an inch (20 times the size of a violin harmonic), leaving a stylus footprint on the groove wall measuring 10 inches long and 4 inches wide. A typical midrange signal demands that the stylus move 16 inches from peak to peak of the wave form. A deep bass note 10 dB louder requires the stylus to move 10 feet 6 inches whereas for a high-frequency harmonic at a very low sound level , the stylus must move only 0.68 inch. Even the simplest piece of music is likely to contain, at any one time, enormous numbers of frequencies at different levels.

The next time you hear someone try to dismiss vinyl as a primitive, antiquarian, and thoroughly Luddite approach to sound reproduction, just remember that analog vinyl sound reproduction is, and always will be, miraculous. Perfect Sound Forever, suckas!

Electron microscope photograph by Chris Supranowitz / Institute of Optics, University of Rochester

October 27, 2010 at 6:56 pm

Heat and Light

A general reader of i-fi journalism and discourse—someone who isn’t an audio engineer, or the equivalent thereof  in scientific expertise—has to push against a stiff headwind of technical terminology, specifications, and jargon. You have to resign yourself to encountering a certain degree of incomprehensible wonkishness, accept that it’s appropriate, and skim past it. Occasionally you’ll suspect that there’s a touch of professional grandstanding, obfuscation, or sheer mumbo-jumbo at work. But once in a while, the hi-fi layman is rewarded with a scientific exegesis that not only makes explanatory sense, but has a kind of poetry. The other day I was listening to an episode of Home Theater Geeks, a weekly TWIT Network podcast hosted by Scott Wilkinson. The guest was Bob Carver, a legendary audio designer, innovator, and all-around idiosyncratic genius who owns a long list of hi-fi patents. Carvers’s finest hour, I’d argue, came in 1985, when he made a bet with the editors of Stereophile that he could modify his $700 Carver Model 1.0 solid-state amplifier, on the spot, to match the sound of any reference (i.e., state of the art) amplifier Stereophile decided to throw at him. The magazine accepted the challenge, and chose the Conrad-Johnson Premier Four, a 100-watt tube amplifier that cost $3,000. When Carver emerged after a couple of days of tinkering in a hotel room, his modified amp was a perfect match for the Conrad-Johnson, and he won the bet. J. Gordon Holt’s rueful, impeccably fair-minded account of Stereophile’s unconditional defeat is an audio-journalism classic and a perennial parable of the danger of audiophile certitude. But back to the podcast. At the end of the hour, Carver was asked for his thoughts on the relative merits of solid-state amplification and tube amplification. The valves-vs.-transistors war has now been going on for decades (Stereophile’s “The Carver Challenge,”of course, was one of its great skirmishes) and it will probably go on forever. I prepared for an answer that would leave my usual mystified state intact. What I heard was something beautiful, lovely, and lucid. First, notwithstanding his 1985 triumph, Carver declined to pick sides in the endless feud:

 I grew up with tubes. I love vacuum tubes. They glow in the dark. I have a wonderful warm feeling when I listen to my music with vacuum tubes. A vacuum-tube amplifier and a solid-state amplifier can be made to sound virtually indistinguishable. That’s the reality of it. However, when I listen to vacuum-tube amplifiers, there’s a magic there that I adore and love, and I’m not about to give it up. I have both amplifiers in my listening room, I have vacuum-tube amplifiers, I have our latest solid-state amplifiers. They both sound stunning to me.

Then Carver outlined the concept of “the feedback signal”:

If we listen to a vacuum-tube amplifier, when it produces a signal, it makes the loudspeaker move. The loudspeaker sends sound waves into the room, the sound waves bounce off the wall, they come back to the loudspeaker, and the sound waves make the loudspeaker move like a microphone. That loudspeaker motion makes a little voltage, just like a microphone would. The voltage is fed around the amplifier’s feedback loop back to its input. All amplifiers have two inputs. One is the audio signal that comes from the [playback source], the other is the audio signal that is the feedback signal. Both of these signals are the same. They’re the same amplitude, the same frequency response, everything.

But then Carver blew my mind:

 What happens in a vacuum-tube amplifier, the amplifier makes another sound that is related to the sound it heard. In other words, the amplifier is able to listen to the room. Because it’s hearing reverberation, echoes, time delays, all of the components associated with the venue. The loudspeaker speaks, and the room speaks back to the loudspeaker. The amplifier hears it, via the signal going back around the feedback loop, and out it comes again. It’s not delayed by much; the real decay is the acoustic delay. That delay makes it sound spacious and big to our ear-brain system. We love sounds that have ambience, and echoes, and stuff like that.

He went on to explain why solid-state amplifiers behave differently:

 The output impedance  of a solid-state amplifier is so low that when it tells the speaker to move, the speaker sends the wave out, it bounces off the walls, comes back, and the solid-state speaker will not allow the speaker to move in response to the sound wave coming back and hitting it. The amplifier shorts the speaker out so that the speaker can’t move on the back wave. The amplifier is said to have a very low output impedance. It shorts the speaker out, basically. A higher output impedance is one of the things we hear when we listen to vacuum-tube amplifiers. It’s one of the things that makes a vacuum-tube amplifier sound so enjoyable and so nice and so spacious.

Needless to say, I have absolutely no way to judge the technical merits of Carver’s explanation. I’ve read that other factors, including things called “soft clipping” and “core saturation,” are said to contribute to the sound of tube amplifiers. The science may be in dispute, Carver’s disquisition an oversimplification. I don’t care. Bob Carver’s the man. He’s made me believe I finally have a fleeting grasp of the meaning of “output impdedance.” What he said, that’s how I’m gonna roll.

[Note: I’ve edited and slightly condensed Carver's recorded comments for the sake of readability.]

Photo by arbyreed

September 6, 2010 at 5:41 pm

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