Audio Design

It's reduced, but it isn't necessarily eliminated.

If you compare a stereo "phantom center" acoustic signal with one generated by a real sound-source at center-stage, you'll find that they aren't the same. An impulse from a true center-stage sound source will reach each ear only once (neglecting reflections from the room surfaces, of course). An impulse from a pair of stereo speakers, energized with the same signal, will reach each ear *twice*, a few hundred microseconds apart.

Fortunately, our ear/brain system is reasonably good at "ignoring" the second copy of the signal... I gather that it's probably being interpreted by the brain as an "early reflection" from something close to a sound source located at the center-stage position. However, this filter-it-out ability may vary from one person to the next, and may depend on the type of program material... it's not always equally convincing, and can cause the phantom-center image to seem less "solid" and "convincing".

There are also differences between real-center and stereo-phantom-center behavior if you rotate your head, or move from side to side. A phantom-center image will appear to "wander" much more than a real sound source located in the center.

Quite a few ways have been tried to minimize the "blurring" effects in a stereo phantom center. Discrete multichannel is one, of course... stick an extra speaker in the center, and mike/mix signals only into this one channel.

Another method which works surprisingly well (and is fully compatible with normal 2-channel stereo recordings) is the venerable Dynaquad system, which uses three front speakers and one in the rear, wired up in interesting ways to a stereo amplifier.

A third way is to use DSP techniques: delay a copy of the left-channel signal by a few hundred microseconds, invert it, and mix it with the right channel (and vice versa), in an attempt to cancel out the second impulse image. I believe that Carver's "Sonic Holography" system may have used this technique but I'm not sure of the details. It can produce some strikingly effective 3D-like images, but can also introduce some acoustic side effects and may only work convincingly if you're sitting right in the "sweet spot" at equal distances from the speakers.

--
Dave Platt                                    AE6EO
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior
  I do _not_ wish to receive unsolicited commercial email, and I will
     boycott any company which has the gall to send me such ads!

Audio as a hobby is fine. As a career path, it's mostly a dead end. Try to work on some more challenging stuff, too.

Every business has superstars and peons. In audio, engineers are mostly peons. In scientific projects, they are mid-level. In oime things, like aerospace and instrumentation, you have a shot at being a star.

John

You are right, you should not limit yourself to one domain, only.

This depends on the company. E.g. producing high quality audio equipment for broadcasting can be challenging and you'll need motivated long term employees (or freelanceers like me :-) for developing good products.

--
Frank Buss, fb@frank-buss.de
http://www.frank-buss.de, http://www.it4-systems.de

For an undergraduate, audio is a suitable playground. You can learn a lot there: transistor circuit design, stability, noise, achieving bandwidth, mirrors, bandgaps, differential stages, Miller, cascodes, offset servos, biasing, pssr, current hogging, grounding, deblocking, how to measure that all, and and and.

Just look upon it as a step on the ladder and not as the final goal.

And Williams, Pease, Gibert.. _are_ superstars. Maybe not in audio, but in the topics above.

regards, Gerhard

idth,

biasing,

d and and.

Think "signal aprocessing", not audio, if you want to actually be employed. Or you start your own hifi company.

"Dave Platt"

** The central part of a stereo image is a "virtual" image for a centrally located listener - ie if the listener moves their head to the left or right, the central image moves in the opposite direction.

The point is that when listening to stereo speakers, the listener must remain seated and pay attention like a member of an paying audience at a concert would.

** Undetectable on music programme.

** You are making this nonsense up.

( snip rest of fantasy drivel)

** As noted above. ** Once you have experienced well set up stereo you would never bother with any such silly thing.

Shame is so few folk ever have.

..... Phil

Yup. Our products are "audio" but less than 10% of the work really deals with audio circuits. The bulk of the work is in the DSP and processor, with FPGAs coming from behind on the inside rail. ;-)

ASIC and processor development is up there too. Big money can also be made in RF. Audio is all marketeering.

biasing,

and and.

Sell wire, in pretty packages.

bandwidth,

biasing,

and and.

Be sure and use OFHC copper, and recrystallize them with a(an?) LN2 dip. ;-)

Cheers! Rich

biasing,

and and.

It's impressive how many people around here have, at one time or another, worked for Dolby. I hear that they don't pay well. It's like working for ILM, you're supposed to accept second-hand glory in lieu of pay.

John

a

ndwidth,

s, biasing,

and and and.

t

I never worked for them, but got to tour the SF labs. I could see working there being entertaining.

bandwidth,

biasing,

and and.

I got a tour of ILM, with the stepper-motor Millenium Falcon models and such. Pretty cool. We bid on some servos, but they thought $20K was too much for a bunch of engineering and hardware, so got it somewhere else. The guy we worked with showed up in the credits of the Star Wars films - sort of a high-tech roadie - so I assume that was a good piece of his compensation.

My PCB layout guy quit about a year ago to move to LA and take classes to become an audio engineer. The Brat took over board layout. I wish him luck.

John

That explains this... "So You Want to be an Engineer"

from

Thanks,

Michael

...

The Brat, or the PCB layout guy? :D

Michael

bandwidth,

biasing,

and and.

"a" LN2, "an" before word starting with a vowel, except for "u" when it is normally an "a"

HTH!?

Bratinella is doing great, about to finish an 8-layer, 8-channel BGA-studded VME resistance simulator board, then moving on to something really nasty. Who woulda thunk that a softball/psychology/beer-pong major would be good at PCB layout?

No, it's the dream of a job as a sound engineer that's scary. But I have noticed that PCB layout guys tend to burn out after a few years.

John

Well, I was kinda thinking "ell enn two", which starts with a vowel... ;-)

Cheers! Rich

Perzactly, so it gets an "an".

obertB.pdf

Oh, the money squandered on marketing and sales.... and yes, Dilbert is much more than just a cartoon.