pmr@drufl.UUCP (Rastocny) (01/10/84)
I am a bit puzzled by some of the comments I've read on the net. Some (not all) of these puzzles are summarized and listed below. > "...distortion specs on CD players are far better than the > ear has the ability to detect..." > "...people could not hear distortion that was artificially > introduced until it reached a level of about 0.5%..." > "...the ear cannot hear phase differences above 10KHz..." > "...digital is emphatically superior to analog..." If all of these statements are true, and since the specs between digital players are too insignificant for the ear to detect (0.05% THD, etc.), then why does a Sony CD player sound different from a Luxman CD player (or a Hitachi, or a Technics, etc.)? Yours for higher fidelity, Phil Rastocny AT&T-ISL ..!drufl!pmr
rfg@hound.UUCP (R.GRANTGES) (01/11/84)
Are you, Mr. Rastocny, saying they do sound different from your own two-eared experience or is this just another rhetorical question designed to provoke the easily provoked. The critical comment I have read to date preponderantly indicates they all do sound alike. When answering you should also indicate if you hear the difference between monster cable and any old 14 gauge wire so we can calibrate on the sensitivity of your hearing. Thanks, Dick Grantges hound!rfg
5121cdd@houxm.UUCP (C.DORY) (01/11/84)
Boys, Boys...are we forgetting all the anolog circuitry in the CD player?
There are about as many unique realizations of these analog circuits
(i.e., anti-aliasing filter, reconstruction filter, line-level circuitry, etc.)
as there are currently available CD players. Not to mention, some
manufacturers utilize over-sampling techniques, both digital and analog
filtering, etc., etc... If, of course, you believe the rave reviews in
Audio, Stereo Review, and High Fidelity, these varying executions of CD
players make no difference whatsoever -- remember, these mags live off the
advertising revenue from audio-equipment manufacturers. The CD has received
the biggest media hype the audio industry has seen. (Has anyone seen a bad
review in one of these mags lately?)
There are other IMPORTANT aspects to audio equipment performance than
simply THD distortion specs and magnitude response (erroneously called
"frequency response") alone. What about time-domain response? We are
attempting (through the recording chain) to recreate musical performances
so that we can enjoy them time and time again. Music is NOT time independent --a bassoon sounds like a bassoon when its frequency and time components
are reproduced accurately. (These are not usubstantiated claims --
much of the recent work of Deane Jensen - Jensen Transformers, John Bau -
Spica Loudspeakers, Mile Nestorovic - Nestorovic Loudspeakers, John Meyer -
Meyer Sound Labs, Patrick Duran - Horus Music, John Curl, (the list goes
on...) is focused on TIME DOMAIN accuracy of their components.
It is very important, also, to note what type of music is listened to in
making subjective judgments in audio equipment. No offense, but there
is little "true stereo" information in current Rock/Pop and most of
the Jazz recordings -- Supertramp - "Crime of the Century" and
Pink Floyd - "Dark Side of the Moon" and "The Wall" are notable exceptions,
however. Most of the Pop/Rock and jazz recordings are made with
the recording console as an integral "instrument" in the compositions
and, therefore, these recordings are multi-mono. True stereo ONLY comes
from simple miking techniques (two and at most three mics with the
best results from coincident techniques).
What I'm getting at, is that unless that your source is of unimpeachable
quality (I know of few), your system is accurate (well?), you have an
excellent listening room (noisy fridge, flimsy walls?) there is no way
you can make many of the subjective judgments that I see made here on the
net and in the mags.
Craig Dory -- AT&T Bell Laboratories
Holmdel, NJpmr@drufl.UUCP (Rastocny) (01/11/84)
Interresting, and I agree. But several engineering types have claimed that time-domain related errors are undetectable by the human ear at higher frequencies (names withheld). (CD systems are uniform at lower freq's and get into trouble usually over 5KHz.) Others say that they all should sound the same since distortion (et. al.) specs are insignificantly different from one CD unit to another. Some, understandably, think that minute differences in loudness sway a person's opinion of superiority regardless of the reference system's quality. You all can't be right, can you? Who is? Before things get too enFLAMEd, I suppose I should explain why I started this. I feel that the current set of specs used by everyone in the top three audio mag's is inadequate in describing sonic differences that are currently described in subjective magazines. Anything that we can hear, we should be able to measure. Can anyone offer opinions as to what specs would more correctly describes these differences? (e.g., why isn't there a plot of the power supply impedance vs. frequency at full load? Or supply ripple at the output devices under full load? Or a time-domain plot?) Yours for higher fidelity, Phil Rastocny AT&T-ISL ..!drufl!pmr
gregr@tekig1.UUCP (Greg Rogers) (01/12/84)
Phil, you seem to want to provoke a debate on the sound of CD's based only on unsupported assertions of their sound quality. Is it correct to assume that you have no knowledge of, or respect for scientific method? I have yet to find a single person who has been able to demonstrate any significant audible difference between CD players under a scientifically controlled double-blind test. If anyone is aware of any such test that supports your assertion will they please provide a reference to the test. This will really be of benefit to those of us who spend a great deal of time discovering the physical, measurable differences between audio components that do contribute to audible differences. It must be stressed EMPHATICALLY that any perception of differences between audio components that is NOT the result of controlled double-blind testing is simply worthless information given the performance levels of todays electronic components. (It is likely that the audibly gross differences between speakers and cartridges makes such rigorous testing unnecessary to merely prove differences exist but continued improvements in these components may make or already have made even this a dangerous exception.) Note carefully the word CONTROLLED above. This implies that all external variables that can influence the sound of the units under test are removed. I believe that we are all aware that when comparing two nearly identically components if the sound levels are not precisely matched (0.2 dB has been documented) that the louder observation will usually sound better and at the least different. Hence I repeat any claims of sound differences between CD players NOT made under controlled double-blind testing is WORTHLESS. But maybe the real question should be, "Given the amazing measured performance levels of even the very first CD players, could they still sound different?" The answer to that is very simple - "Of course they could". It seems unlikely (even contradictory to many controlled tests) that the current set of parametersbeing measured would be responsible. But the possibility exists that we are not measuring some previously unconsidered parameter that does have an effect at an audible level. But it is clearly up to those that claim to hear a difference to prove through proper testing that a difference exists before we need to search for some heretofore unknown parameter. Until that day comes the evidence suggests that even the first of the CD players are capable of reproducing the recorded CD's with no significant degradations or differences. (Ah yes, that word "significant" again, there is no question that measurable differences exist between players, but our previous knowledge maintains that they are not audible.) For anyone not yet bored I should give an example of discovering a new parameter that affected sound quality but proved tough to discover. It was long believed by many (seemed obvious to most critical listeners) that moving magnet input stages of phono preamps sounded different between components. Some "objective" reviewers who based their opinions only on measurements claimed that differences didn't exist. This was due to the fact that they made measurements by driving the input of the preamp from signal generators which didn't accurately simulate the complex interaction between the output impedance of the cartridges and the input loading of the preamp. Hence their measurement technique was faulty. (Their real sin here was not trusting their ears to make them question the measurements). Controlled double-blind testing provided ample evidence that differences did in fact exist.Having proven the existence of differences it was relatively straightforward to isolate the cause and design better measurement techniques and in fact to design better circuits to eliminate the interaction problem. The difference in this example to today is that testing did show audible differences between components. Critics of CD's should not take too much encouragement from this example because the reverse has also proven true. Despite the best efforts of a rather famous amplifier designer he was unable after several attempts to prove his amplifier to sound audibly different than another under such rigorous testing. If anyone would like further information on testing methodology or any example I noted consult the back issues of the Audio Engineering Society Journal. Still working on REAL improvements, Greg Rogers
jj@rabbit.UUCP (01/12/84)
Well, Phil, you say, and I paraphrase: 1) Some people say that time domain behavior doesn't matter above 5kHz or so 2) Some people say that CD distortion is so low that there's no sonic difference 3) Some say (understandibly) that minute differences in playback levels will influence listeners more Then you say, "Well, how can you all be right?" It's a nice debating technique to say that, but it's also TRUE. They are ALL right about what they've said. Why? 1<-->2 Phase distortion ::= Time domain distortion and the people who are (informedly) saying 1 and 2 are saying, in part, the same thing. Furthermore, 1 is simply a subset of 2. The people who claim 3) are pointing out (VERY correctly) that minute <.1dB> differences in playback levels will mask ALL of 1) and 2) when the spec's are at the CD level. I don't understand just WHAT you even intended to say with your article, given the incorrect (but effective in debate) assumtions of the first two paragraphs. <Unless the ONLY point was making debate that is intended only to influence uninformed people.> Another really offensive debating technique you use is to say ...don't get into trouble until above 5kHz... What do you mean getting into trouble? Apparently a distortion that's 40-50dB better than any vinyl ever made, and a phase response that's SMOOTHLY changing, rather than raggedly jumping all over the place like a cutting lathe and mastering deck, is getting into trouble, while the gargantuan CHANGES in group delay (let's use the relevant terms, here) that one gets from a tape deck (not to mention the self-erasure and scrape/flutter noise) aren't trouble at all. I'm confused, Phil, what are you saying, perhaps that analog recordings are even worse, and not worth anything at all? Didn't think so. Do me a favor, Phil, co-post your articles to net.flame. This is net.audio, I'm trying to be polite, and I'm trying to keep my sheer annoyance down to a loud scream. If you post an article to net.flame <where it belongs> I'll reply in the tone that I feel is really appropriate. (If I have time and energy, I sometimes wonder if it all matters in net.audio.) ENOUGH! ====================== Everything you know is wrong! Distortion is Fidelity Weakness is Strength Assertion is Truth rabbit!jj <welcome to 1984, Phil>
rentsch@unc.UUCP (Tim Rentsch) (01/14/84)
Just to relate a story: Some years ago people were thinking about deciding on a standard for FM broadcasts (in terms of frequency response). Most people (engineering and technical types) wanted to follow the AM standard, i.e., limit to 5 KHz. Some people at Bell Labs did some experimentation and came out with the "radical" limit of 8 KHz (beyond which no difference could be heard). Well, the radical fringe had its say, and as you all know FM standardized on limiting to 15 KHz. Nowadays, we know that 20 KHz is right. (Or do we?) "From transducer to transducer, sound reproduction that's better than ears." This is the goal. When it is achieved, identical will mean identical -- to all people, in all circumstances.
rmd@hpcnoa.UUCP (01/19/84)
#R:drufl:-77300:hpcnoa:30200015:000:579 hpcnoa!rmd Jan 14 16:03:00 1984 CD players certainly sound more alike than any other class of audio playback equipment. (i.e. turntables and cassette decks) I personally think that it is stretching things to say that CD players sound significantly different from each other. However, there are some things like frequency response which are slightly different and I could believe that these differences could be audible if you spend enough time looking for them. Let me ask a similar question: why does 'high end' analog equipment sound different? It can't all be right. Rick Dow hpfcla!rmd
gwes@inmet.UUCP (01/20/84)
#R:drufl:-77300:inmet:2600029:000:1716 inmet!gwes Jan 16 14:00:00 1984 Re: distortion perceptions, time delays, and reviews 1) Up to 3% (or so) of CORRELATED 2nd harmonic distortion is often not perceived. It is often first noticed as "warmth" in the sound. HIGHER ORDER or UNCORRELATED distortions (time domain) are much more easily perceived, at the low levels of .05% or below. In general, the higher order distortions are much more unpleasant in smaller quantities. 2) The one area of time domain measurements I have done indicates extreme sensitivity to time delays for ambience and placement information. Movements of speaker elements of approximately 1 inch (= 80 microseconds) can be distinguished by comparisons. Proper time correlation is recognized as an "open window" effect, with instrument placement becoming definite. Time delays in filters seem to generate the same type of effects. I have not been able to run controlled experiments to properly examine this, however, the psychoacoustics folks often use Bessel filters for their experiments because of the uniform delay characteristics. They don't (often) care so much about the amplitude ripple. 3) If you really want to get useful information from the advertising noise in Audio, etc., read the reviews carefully. Absence of praise and exact wording is very important. The classic example is the review that praises the beautiful styling of the unit, and leaves performance to last. The reviewer is probably obligated to praise SOMETHING. If he doesn't like the sound, you will notice qualifiers or lack of definition in the review. The graphs and tables DO give you the objective data. Read them. The subjective data can be obtained by subtracting the hype offset. Geoff Steckel (harpo!inmet!gwes)
pmr@drufl.UUCP (01/20/84)
Rick Dow's comments are well taken. Why do high-end components all sound different? Could be a couple of things but I'm not picking on anything in particular: 1. The quality of capacitors used in the signal and feedback paths. Low ESR caps "leak" less and pass a more accurate and correspondingly less distorted version of the original signal. Low end components use budget capacitors that have significantly higher ESR. 2. Quality of circuit design. Low-end components are concerned about things like parts count and individual component prices to make a product sellable in a highly competitive market. Once you decide that price is no object, you can design more sophisticated and correspondingly more sonically accurate circuits, but the number of people who are able to afford this equipment is very limited. 3. Attention to detail. Although it may be hotly debated as to whether design considerations of wide bandwidth and well-regulated power supplies is in fact audible, most high-end stuff will use these considerations in their designs. Things like board layout, positions of input and output stages with respect to the rear panel jacks, and regulators for each gain stage are commonly incorporated in the high end. Low end stuff may not have a regulator even on the front-end circuitry. How does this translate into sonic reproduction? Very well in most cases of high-end gear. But not all high-end equipment sounds good. There seems to be an art involved as well as a science. After all, Fourier never claimed that his mathematical models in any way depicted reality. They were just that, models -- nothing more, nothing less -- but still good approximations. I just don't know why high-end sounds better but I can point to some circuit differences between low and high end that must be at least part of the reason. Yours for higher fidelity, Phil Rastocny AT&T-ISL ..!drufl!pmr