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Audio 101, a primer -a very long post!

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modelmaker:
 -As mentioned in anther thread (Sound Quality Battles), I spent 30 years as a Tech-Rep in the audio/video buisness. It was my hobby starting in 1967 and getting a degree in elctronics became my profession in 1974.(I also had my fist experience with a computer in 1970: an IBM 360 - it was as big as a house! and you could only talk to it in fortran and cobalt and some other obscure computer languages).

For you experienced audiofiles the following are some of my thoughts and experiences and meant as general information and opinion and a basis for discussion.

For the audio novices a little audio history/info/opinion to get the ball rolling:

>The  Goal: Reproducing music (live and studio) acurately.

>the source: the vinyl LP/45 read by a stylus(needle) following a squiggely grove(a mechanical representation of the anolog signal). This is converted to an electronic analog signal then amplified and passed on to the speakers. With a high quality stylus/cartridge the LP was capable of reproducing a frequency response range far exceeding the audible range of the human ear (+/- 50Hz-16KHz), typically 5Hz to 45kHz and more. However, we don't just HEAR sound we also FEEL sound. Frequency response also affects the tonal quality of the sound we do hear. The wider the freq. response, the more harmonics are reprodused and the more accurate the signal is that is delivered to the speakers. LPs disadvantages: wear and tear due to dust and repeated playings.

The source: The CD. Due the technological limitations of the time (mid to late '70s) frequ
ency response was set at 20 - 20kHz with a sample rate of 44 100 sam/sec. This limitation in frequency response and hence the limitatation of reproducable harmonics is the reason many of us "old timers" still prefer the sound of LPs. Most people that have had the opportunity to do A/B comparisons between LPs and CDs thru a high end system agree that the LP has a more full and lifelike sound and the CD (a flat/a more lifeless sound).There are some CDs produced at double the standard sampling rate that overcome this - double the sampling rate and you double the frequency response and you decrease the harmonic distortion.
The CD of course has other distinct advantages: much wider dynamic range(the difference between quietest point and the loundest point) which in turn gives you a better signal to noise ratio, most scratches are in-audible(error corrected), they don't wear out - older LPs were recut every time the diamond stylus passed thru the groove, later vinyl compounds were more flexible and would deform and recover to a certain extent.

>This is one of the most important rules in audio: Your audio system is only as good as the weakest link.

>The Weakest Link , The Speakers. Theoretically the ideal sound source is a single point source. Only a few speaker manufactures have ever come close to this ideal: two  Brit comanies, Tanoy produced the original true co-axial speaker, Quad with their ELS electrostatic speakers and in the US Magnaplaner's 6ft plus elctrostatics also come to mind.There are others. Today's satalite speaker systems come close to the ideal, but due to their size have other limitations,  suwoofers overcome some of them. Full range/ full size systems compensate for the lack of being single source  in other ways. One thing all speaker systems have in common; distortion. levels vary from 2 -3% (high end / audiophile) to 10 - 15 %(middle/low end/large paper woofers).The smaller and stiffer the woofer the lower the distortion. Multiple 8" or 10" woofers are generally better, tighter and lower in distortion than one big 15".Larger voice coils with flat wound wire increase your power handling capability and lower the frequency range the woofer has to reproduce - no sense in making a woofer reproduce midrange when it doesn't need to.

And then there's the human factor! Very few humans have a flat frequency response curve and our ears can be very fickle. They have no memory. Our brains store an impression of what sounds good to us. There are a lot of factors that go into finding your ideal speakers, showroom environment vs your environment, musical taste, etc...

Environments are a crucial facter. Live classical music as performed in a concert hall has cold or hard surfaces surrounding the performers on 3 sides and open to the audience on the 4th. this promotes reflectivity and makes the sound more lively. Bose speakers using the direct/reflect principle emulated this by rear firing some speakers & forward firing one or more. The result: you get the direct sound and milliseconds later you get the reflected sound as in the concert hall environment, assuming the listening room is built the way the concert hall is with hard surfaces surounding the speakers.

Older audiophiles will be rolling their eyes as they remember the top of the line Bose 901 which fired eight 4"  drivers to the rear and 1-4" driver in the front. In order to get full range sound tho you had to use their equalizer which to the purist added an additional device and inherent noise and distortion to the signal path.

Rock music generally tends to overpower it''s envirronment, lliteraly and therefore can live in a wider range of home environments.

Jazz is usually somewhere in between, some jazz lovers prefer the concert hall (loose/lively)others prefer a small club type sound (tight/warmer).

>What I'm trying to show about speakers is that it's the most SUBJECTIVE component of an audio system.There is no "best" or they're all the"best", it's your choice.

Here's a few shopping tips: Speakers should be 1/3 to 1/2 of your total system budget. Pick 4 or 5 speakers to audition but compare only 2 at a time , ex: A/B, A/C, A/D etc,then B/A, B/C, B/D etc. If you try A/B/C/D/E, once you get to E your ear/brain can't remember A. Start eliminating a speaker at a time. Bring your music with you -  at least 4 or 5 selections. Don't bring a friend! They tend to influnce you to buy what they like, they don't have to live with them - you do.

That's it for this chapter. I hope didn't drone on and  bore you all too much, I jumped around a bit too. If this was of interest, I'll drone on about amplifiers and other stuff in "audio 102".Feel free to chime in - maybe we should start a new thread for discussion? Also feel free to eml directly with any specific question.

Charlemagne 8:
Will there be more? Today?

CVIII

Wobbley:
Yes, yes please share more of your knowledge.  I'd love for you, if and when you have time, to explain as much as you know about all of this...be as technical as you'd like...

Wobbley

Charlemagne 8:

--- Quote ---Will there be more? Today?

CVIII
--- End quote ---



7/07/03

Thanks. More please.

nameless:
Speaker-selection advice is very welcome.  I've always detested the task.  Listening in a showroom?  I'm too self conscious and just plain nervous to feel comfortable enough to not rush.  But right now, someone else has asked me to help they choose a set of speakers.  Oh, please!  I know not where to start.  (I loved the "compare A/B, not A/B/C/D/E" advice.  Goofballs like me need obvious tips like that.)

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