Ethan Winer wrote on Mon, 05 February 2007 17:42 |
But if you sit in the center, your left ear is a few ms closer to the left speaker and vice versa for your right ear and speaker.
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Which helps a lot with the whole stereo hearing thing... directional cues for the signal processor between our ears come from these very small differences in arrival times.
By the way, to revive a bit of the older posts in the thread, one good way to think about large room vs. small room is where the cutoff frequency or Schroeder frequency gets low enough that all bands of interest have a modal density that prevents marked peaks and nulls. Of course there is disagreement about how exactly to calculate the cutoff frequency, and how much modal density is enough, but you can get in the ballpark of the accepted range and call it a day.
As Fran observes, most all rooms that we deal with in recording studios are small rooms, acoustically speaking. As touched on above, the higher the frequency band, the greater the modal density, which is to say that with increasing frequency, the spacing between modal frequencies gets smaller and smaller This has the effect of reducing the obtrusiveness of the peaks and valleys and makes a generally pretty even room response (certainly not ruler flat, but subjectively pretty even from a modal point of view). The larger the room, the lower the frequency where the modal density is great enough to reduce the obtrusive inconsistencies.
Once the cutoff frequency gets down to 20 Hz, you really have no worries about modes lower than that for our purposes. This is a definitely large room by anybody's standard, and is probably a small to moderate-sized auditorium. The determination depends on the RT60, total surface area, desired modal density, and a little bit of math. Depending on the criteria, different acousticians will make the call from small to large in different palces, though nothing below Fran's example of 6000 cu. ft. would ever be called large. In fact, I'd personally probably make the call somewhat larger on purely technical grounds, depending on the conditions present, but I agree that a certain something happens at around 6000 cu. ft. that is good for recording spaces.