max@eros.uucp (Max Hauser) (10/04/87)
In article <899@uhccux.UUCP> cm450s02@uhccux.UUCP (jeff t. segawa) writes: > Bill Blue: I couldn't agree more with this business about tecnical > specifications and subjective sound quality. I bought my first > stereo based on those distortion specs. ... > ... Maybe the source of a lot of these > "looks good on paper, sounds awful" sort of problems have a lot to > do with the WAY these measurements are taken. For example... > [typical flaky-turntable example] ... Naturally, the spec > sheet told me that the turntable had nearly perfect speed accuracy, > and it did, so long as I played 1Khz test tones. No kidding. Manufacturers who want your money will actually measure specs that are easy, and don't tell you the whole story. Welcome to the real world. It's worse, by the way, in industrial technology, where you don't usually even have your ears to fall back on. That is why I assume that any well-trained engineer knows all about specsmanship (indeed, the clever people who documented that turntable certainly knew about it!). When I was a graduate student at MIT, I took an "advanced circuit-hacking" course from an experienced engineer who understood things like this. One of our first assignments was to take a commercial analog IC (the Intersil 8038 voltage-controlled oscillator), go into the lab, and as he put it verbally, "find five lies in the spec sheet." What I object to in postings like the foregoing is the suggestion -- and I hope it's only in my imagination -- that because a few simple specs per se, the kind usually published by manufacturers, fail to accurately describe an audio component, then ALL specs are useless and we must throw our hands up in the air, abandon specifications entirely, use our ears exclusively, eschew electricity, eat only beets, what have you. Of COURSE little numbers like distortion won't tell you how the component sounds. That manufacturers can oversimplify and lie, and that some engineers (just like physicians) are not familiar with this particular problem, does not mean those specs are useless as a tool, properly applied; or that you could not make further measurements that more completely characterize the component. I think that Jeff also alluded to this in his posting. What we REALLY need, of course, is consumers who are informed-and-critical rather than astonished-and-cynical. Such consumers would know about specsmanship and about the limits of simplistic manufacturers' numbers, with their tacit dependence on assumed linearity, test conditions, and so forth. Then people would not be so shocked at the revelation that it is actually complicated to accurately specify the performance of a sophisticated audio component, and that a few simplistic curves don't tell the whole story indeed. With such enlightened consumers, not only would it be unnecessary for the superstitious to throw out the technical baby with the specsmanship bath (if you will), but also, manufacturers would not get away with the shit they now do because more people would call them on it. I promise you that given any audio component, I can produce nice- looking, and even sexily-named, performance curves that will not reveal the full sound or the weaknesses of the component. By the way, if you need to remove epoxy from a "proprietary" potted module inside of an audio product, as Dick Pierce mentioned, use Dynasolve (tm) 160. It's much cleaner and gentler to the circuitry than "chiseling." I have a whole file of schematics that I got that way in 1971-72. Max Hauser / max@eros.berkeley.edu / ...{!decvax}!ucbvax!eros!max
cm450s02@uhccux.UUCP (jeff t. segawa) (10/05/87)
Max Hauser; You are right, I didn't mean to imply that specs should be thrown away entirely, rather, that they shouldn't be the sole basis on deciding which component to buy. I'd no more buy a new amplifier just on the basis of how it looks on paper any more than I'd buy a sports car just because it had an engine that could produce 300 HP @ 7000RPM. These numbers at least give an idea of what we're dealing with, but it's no substitute for a test drive (listening test). What is needed are specs that have more relevance to real life. I want to see a spec that will tell me if Amp A can drive a speaker (especially a highly capacitive/low impedance load) without blawing itself up every time I power it up, for example. I've seen too many amps (particularly Robertson 4010's) blown up this way. By the way, what is Dynasolve, and how do I get small batches of it? I'm curious to see what's inside those old Mark Levinson and Audio Research modules.