|
Dan,
Actually - at the levels we're speaking about - it's a flat room either way.
I don't believe that there is any really significant difference between the goals of today and the goals of yester-year. There have been a lot of different methods over time attempting to achieve what is basically the same thing.
That "thing" is a listening room that doesn't really color the sound coming out of our speakers.
If one can acheive that - then one can accurately mix recordings that will translate well in other environments.
When you speak of truly flat versus 3dB boosts here or there - you are (for all intent and purpose) talking the same thing - FLAT. A 3 dB boost or cut in the ranges we're discussing here is almost the same as no boost or cut at all.
As far as the actual roll-off goes - I tend to lean in the direction of the ITU recommendations, which means that you actually have a fairly narrow band through the mid/high lows to low highs - and then it's a wee bit more travel in the high frequencies - both up and down - and the same in the low frequencies (although down is a wee bit tighter than the highs allow in range.
If you picture how most people set up their stereo systems - you'll see why this makes perfect sense.
In almost every home I have ever been in with decent to excellent quality sound systems - the EQ is set up in what I refer to as the "EQ Smile".
Lows and highs are boosted - and slowly smooth out to a fairly flat middle.
The reasons for this are well known - the human ear does not hear sound in a linear manner - we hear low and high mids much easier than we do at either end of the spectrum.
So in order to listen to anything and enjoy it - we have to boost frequencies we are normally fighting to listen to. "Tuning" a room to give us a slight nudge in that direction can only make sense.
When designing a room - if one can acheive +/- 3 dB that really is quite a feat - and is pretty near darned flat (for all intent and purposes).
If you study the Fletcher/Munson loudness curves you'll find that from 500Hz to 2000Hz - the human ear hears sound pretty darned flat - 10 dB tones sound the same loudness to us across that board.
From 2000 Hz to 6000 Hz, 6dB tones sound like that same 10 dB loudness (The scale there actually floats a bit - with the max variance around 5000 Hz - but I am sure you get the picture) So our hearing is he best in that range.
BUT - by the time you get to 10,000 Hz - it takes 20 dB to sound the same loudness as 10 dB in the mid range.
The low end is even worse...... at 100 Hz - it takes 30 dB to sound as loud as the mid range at 10 Hz..... and by the time you reach 20 Hz - 75 dB to sound the same loudness.......
Those little 3 dB bumps you're talking about are nothing more than a window you can fit within to acheive a flat sound rather than an action taken to enhance the amplitude at those frequencies.
When you examine the scale used for listening rooms designed within the ITU recommendations, you'll find that those numbers are roughly the high end of an allowable variance - perfectly flat as well as a slight frown also fits within the guidelines. All of which is considered acceptable variances for design or final treatment purposes.
I have never encountered a set of recommendations from any source that suggested anything other than a range to fit within it's always +/- , never a tight range at all. I would be happy to examine a source that IS rigid if you have one.
Sincerely,
Rod
|