When I was a kid, like most kids in most places, the amount of money available to me even after I got my first after-school job (at $1.10 an hour) was far less than sufficient to feed my "needs". Oh, it wasn't that I went without food, shelter, clothing, the latest rock 'n roll record (Sh'Boom, or Little Darlin' perhaps, or something by The Platters), a bicycle (I had a "hotsy-totsy" Raleigh Clubman [Woo-Woo!] ), or even the two custard-filled chocolate doughnuts I bought at the German bakery every day, on my way to work. Instead, unlike most kids, who lusted after baseball cards; comic books (Recently and outrageously raised in price from a dime to 25 cents); clandestine copies of Playboy magazine; or some other, more ordinary, kid-obsession; the only thing that could satisfy the monkey who had been on my back since I was twelve years old was Hi-Fi gear.
I had been introduced to high-fidelity sound at that early age when a friend of my father bought a "hi-fi set" from a local dealer and invited us my father and me along to help him make his decision. Because that was 1954, the "set" he bought was mono (Stereo records didn't come along until 1957); because our friend was quite well-off and had chosen a good dealer to buy from, it included a Bozak B-310 speaker (Only one remember that in those days, everything was mono); because the Bozak was, even back then, able to do real 24Hz bass (nearly a full octave below most of even its better competition); because one of the pieces of music we heard featured George Wright playing "the mighty Wurlitzer pipe organ", and because I had never before heard any real bass at all, let alone the deep bass I heard then, it got me I swallowed it hook, line, and sinker, and I still haven't recovered, even now.
From that point on, I lusted after a hi-fi set of my own and started earning as much and saving as much as I could to make that glorious dream a reality. There were certain problems, of course: Just the Bozak speaker was around a thousand dollars and I was, after all, just twelve years old, with, at least initially, no money at all other than what I could cadge from my parents or gather (at 2 cents each) by finding and returning soda pop bottles (yes, bottles, NOT cans) or (for just a dollar or so, each) mowing lawns.
Obviously, I couldn't buy the speaker I wanted, or the amplifier, or any of the other components of my "dream" system, but there was something I could do: I (and all of my young Hi-Fi Crazy friends) could and did collect "product literature".
All of the hi-fi equipment manufacturers of that day (and many, even now) published "spec sheets" describing their products, telling of their wonders and glories, and providing detailed specifications of all of what were seen to be their significant performance criteria. Among the numbers published were "frequency response" (usually stated within plus or minus 3 dB) and distortion (usually stated in two ways, as "Total Harmonic Distortion" ["THD"] and "Intermodulation Distortion" ["IM"]). Also stated, for electronics and tape recorders, was "Signal to Noise Ratio" ("S/N"), which told of how much internal hum or noise (not counting record "clicks" or "pops") could be expected to be generated (added to the music) by the tested device as compared to the music signal it was playing or recording. For turntables, which have no effective frequency response range, figures were shown for speed accuracy, "wow", "flutter", and "rumble". And for speakers, "sensitivity" was published, to tell how loud they would be if heard with a one Watt input signal and with the listener (actually a calibrated test microphone) exactly one meter away.
Those were perfect for a penurious kid: Spec sheets were free (available from any local hi-fi dealer for the product of interest or, if there was no dealer nearby, by writing to the manufacturer); they allowed me and my friends to become "experts" in all the very latest hi-fi products, even though we'd never actually heard most of them and none of us actually owned at least initially -- anything more than a DIY home-diddled, "hot rod" record player; and it permitted us, after wed confirmed our expert status by memorizing every piece of literature or spec sheet that we could get ahold of, to spend endless hours talking about, even if not listening to, the best the industry had to offer.
That was great fun, and it wasn't until years later, when most of us had a regular source of income (read that as a part-time after-school and/or weekends job) and could actually afford to BUY stuff (even if, in many cases, we had to buy it used) that we started to discover the real truth: We had always thought that sonic perfection was possible, and that all it required was a system with absolutely "flat" (+/- 0dB) frequency response from 20Hz 20,000 Hz and with vanishingly low distortion all through "the signal path", from the music source to the speaker(s).
Floyd E. Toole, Ph.D., the famous speaker designer and Vice President Acoustical Engineering for Harman International Industries, Inc., apparently still believes it, but now, and even starting many years ago, most of us have come to disagree. First, except for digital recording and playback, a relatively recent development that does claim (near) absolutely flat frequency response (and that many people still find sonically unsatisfying) there's never been a system that could meet that standard. Speakers are still typically rated (if frequency response specs are provided at all) at from whatever frequency to whatever other frequency, plus or minus three dB. What we Hi-Fi Crazy kids-and-now-Hi-Fi Crazy adults have come to learn is that "plus or minus three dB" can either mean "no variation from flat of greater than 3 DB at any point in the frequency range" or "as much as 6dB variation from 'flat' at one or more points within the frequency range, with all such variations either above or below the 'flat' line, but not both".
It's all how you state it; and when you consider that a variation of just 3dB means "Twice as loud" or "half as loud" at the stated frequency, and that 6dB is twice that much, again, it becomes apparent why speakers claiming the same range of frequencies (20 to 20k, for example) with the same degree of variance from flat (+/- 3dB), can sound wildly different! Then, when you add-in the fact that, even in the "glory" days of "Mid-Fi", when solid-state Japanese electronics were routinely claiming total distortion figures in the range of 0.000001% (one ten thousandth of one percent), people still found them to be "awful-sounding", the picture becomes complete and, at least we who believe ourselves to be the (self-designated) cognoscenti finally came to understand that, while spec sheets are certainly fun to look at and even to collect, for real world product evaluation, they're useful only for "ruling-in" products for purchase consideration, but not for ruling them out.
For making a final selection, the only thing that really matters is not the specifications, but your own ears, preferably listening to recordings you're familiar with, in if you can arrange it an in-home audition, with the product to be evaluated playing through your own system, in your own listening room. Then you can really do a good job of it and, when you're finished, go back to whichever setup sounded best, put on your favorite recording, lean back, close your eyes, and...
Enjoy the music!