An ideal experiment would have just one variable if the underlying question can be answered that way. Sometimes it can't be, though; for example, given a near-coincident stereo pair of directional microphones, what are the trade-offs concerning the angle between their main axes vs. the distance between the microphones? There's no way to research that with only a single experimental variable.
Microphone comparisons appear to have just one controlling variable--the microphone. But whenever people listen to the recordings from a microphone comparison and choose their favorite one, several hidden variables come into play. I really urge people to think this through.
Thought experiment #1 (although I'd bet that things like this have happened more than once): Say that someone makes a very dull-sounding microphone, with frequency response that rolls off above 2 kHz, and the manufacturer wants to post a comparison recording that makes their microphone sound better than a famous microphone costing 20 times more. Can they do it? You bet; all they have to do is record (say) a guitar amp with its treble control turned all the way up--a sound so piercing that you couldn't stand it if you were in the same room. The better microphone would sound unbearably harsh, while the dull microphone would produce the better-sounding recording, hands down.
Should you buy a pair of those dull microphones, then? It might be worthwhile if they're not too expensive; they can handle a particular type of horrible situation that you might find yourself in some day. But you'd be fooling yourself badly if you thought that the test showed them to be good-sounding microphones in general.
Thought experiment #2: You have several pairs of good microphones, each with distinctly different characteristics, and you want to make a set of parallel recordings that sound as good as possible. Miraculously you are granted time and freedom to experiment and find ideal positions for each pair of microphones. You listen to each pair's signals and adjust each setup until it sounds best to you. Surely all those mikes wouldn't end up in the same place!
But in comparison tests, the microphones are placed as close to each other as possible. I'm not arguing with that; there are very important reasons for doing things that way. But logically, if all the mikes are in one place, and one pair is in the ideal position for its characteristics, all the other microphones can't be in the ideal positions for their characteristics. For all anybody knows, some other pair of your mikes would have gotten much better-sounding results than the "winner" did, if the miking position had been optimized for that pair of microphones. But it wasn't. So the microphones that could have produced the best-sounding recording will fail to do so, and will be judged among the losers, while the second- or third- or ninth-best microphones become the "winners."
Unless you think it through, you could easily believe that your ears are telling you something more meaningful than it actually is. At best, any recording can only give you an idea of the sound you might obtain from a similar sound source, in a similar acoustical situation, given similar mike placement. But you learn just as much from any other recording where you know which microphones were used. And it's really not all that much, frankly. I've heard different people get very different-sounding recordings using identical equipment--to a degree that I would never have expected until I heard it with my own ears. (You tend to remember it when you ask someone to fill in for you, you lend them your microphones, and they come back with a better recording than you ever made with those same microphones.)
As a result of using the one shared setup position, microphone comparisons can give listeners an idea of certain objective characteristics: which microphone has more top or bottom end, which microphone picks up more or less room sound--that kind of thing. And if you know one of the mikes in a comparison very well, you can use that knowledge to characterize the other mikes in relation to it a little more precisely--but again, only in terms of objective qualities such as frequency response or the pickup of room sound. Note that these are all things that you could learn from a spec sheet, if all manufacturers produced them the same way. -- If you're making the comparisons yourself, you can also compare microphone sensitivities whereas usually, those are balanced out, more or less, as part of the comparison.
And of course if you ever want to check whether something's wrong with a microphone, you can compare it to another one of the same model and avoid tedious measurements in many cases. But I would never use my subjective preference in a microphone comparison as a way to decide which microphones to buy or use, and I don't think I've ever known another professional recording engineer who does so, either. The process is way too fallacy-prone. It's like the old Will Rogers saying, "It isn't what we don't know that gives us trouble, it's what we know that ain't so."
--best regards
Topic: Mic comps question (Read 2635 times)