I was browsing through my June edition of the Evaluation Engineering magazine (I get it free at work) when I stumbled on an article about Sound Quality Measurement. The article displayed this chart and talked about how our ear sensitivity isn't flat and is dependent on both volume and frequency. The way to interpret this chart is basically a 100 Hz signal will need to be played at 65 db in order for it to sound as loud as a 5 kHz signal that is being played at 50 db. But as you increase the volume the perceived loudness flatens out across the lower frequencies and our hearing becomes more sensitive. But even at movie reference levels the mid to high frequencies seem as much as 10-20 db louder than the low end. So while our speakers may measure a perfectly flat response using instrumentation, our ears don't hear a flat response. Then when listening to music, which we typically do at much lower levels (because it's hard to carry on a conversation with loud music), our hearing sensitivity drops drastically for the lower frequencies. Am I misunderstanding this? Shouldn't speakers be designed with this in mind? It seems we should really want the speaker response curves to match those found in the chart above and not be flat.