Accurate & Uncolored
This leads me to consider the concept of making a system “flat” versus equalizing to a target curve.
Think about it—do you want a console that alters the frequency and phase response on every channel in some arbitrary fashion? Of course not.
You might want to alter a given channel yourself with respect to EQ, dynamics, timing, effects, but how far would you get if there was a hidden deviation from a relatively flat, even response in the signal path that could not be removed? You’d spend all of your time working around such an obstacle, instead of optimizing the musicality and intelligibility of the performers.
The same is true with loudspeakers. Whatever goes in is what should come out. No more, no less. You can apply “house” curves if you like, but the basic foundation of the system should be a response that’s as flat as you can reasonably make it, in the time allowed.
It’s simple to exaggerate bass or high frequencies (or both) for hip-hop, dance, metal (or whatever) music in order to overwhelm the listeners. But it’s quite a different story to deploy such exaggerations (and I’m not saying there’s anything wrong with them) to a system that is accurate and uncolored.
When a reasonably even response has been achieved as the starting point, then the process of “tuning to taste by ear” becomes quicker, simpler, and far more effective. Instead of a mountain of bass, you’ll have definition. The tonality of the kick drum won’t be buried in the bass guitar, and vice versa.
Some practitioners look at Fletcher-Munson curves and come to the conclusion that a good sound system should have a different response at different sound pressure levels, but that would be mistaking the intent of these admirable researchers. What Fletcher and Munson did do was to identify that human hearing exhibits varying sensitivities, at varying frequencies, as the overall SPL is increased or decreased.
This is not the same as saying that a sound system should change its response characteristics as the operating level is altered. Quite to the contrary, it should normally remain equalized exactly the same way, regardless of operating level.
Staying Faithful
Of course, there are exceptions. If the system is at low level, such as background music in a noisy environment, then some degree of exaggeration of the LF and HF will give it more presence. But if it’s a performance system, intended to command the attention of the audience, then it should be provide as even and flat of a response as possible.
This might seem confusing because many sound systems become brittle, strident, and outright distorted as they’re driven hard, and especially as they approach their maximum power capability.
This justifiably causes a consciousness operator to want to reduce the HF content to help save everyone’s ears—not the least his or her own. But it has nothing to do with Fletcher-Munson curves.
Distortion is far more damaging to human hearing than clean, accurate sound presented at an identical SPL. This is because of the exaggerated harmonic content that takes place when LF, MF, and HF drivers enter into their “breakup mode,” which means they no longer are faithfully reproducing the input signal but are adding harmonics of their own that are not present in the program source.
It also applies to amplifiers that are driven into clipping, as well as preamps, microphones, and just about anything else in the signal chain. In a word, it doesn’t sound good when distortion occurs.
Unfortunately, some practitioners push a given system into severe distortion because it’s what they believe represents a fat, rich sound. Fat it may be, but bearing any resemblance to music, it is not.
