In all honesty, the room itself is going to be used for mixing 90% of the time anyway,
Then it would probably be a good idea to set it up for mixing! Maybe have some reflective panels that can be opened, slid, or rotated in front of the absorption, if you need longer decay times for music, but they would normally be in the "absorption" position.
Ill be using my synths and stuff without need of using mics. Most micing ill be doing is my wife for her classical/music theater stuff and some voice over narration/audiobooks she wants to do.
It is quite feasible to track vocals in a control room environment. Vocals and some instruments usually sound very good when recorded in the control room, with typical control room decay times.
But, wouldn't replacing the diffusers with the panels make the room over-treated?
Not necessarily. I would ask the guys at GIK what there estimate is for the decay times in the room, at the mix position, with that treatment. The ceiling in a control room usually needs a lot of treatment, and most of that is usually bass trapping, or at least some form of absorption, to reduce flutter echo and control modes in the vertical direction.
Have you checked your room ratio and other information in detail? Use one of these Room Ratio calculators for that:
http://www.bobgolds.com/Mode/RoomModes.htm
http://amroc.andymel.eu/
Both of those are very good, and will help you to decide how best to build your room. They give you tons of information that is really useful, especially the Bob Golds one: it calculates how much absorption you would need to make that room meet the specs for a critical listening room of that size.
It's a long room, a little over 15ft long,
Excellent! Although "long" is relative... Acoustically, it's not that long. The wavelength of a 20 Hz tone (the lowest that human can hear), is about 56 feet, so that wavelength would not even fit into your room: thus, you have no room modes at such low frequencies. Going up the scale a bit, a 6-string bass can get down to about 33 Hz, so the wavelength there is about 34 feet: still doesn't fit. Going higher still, a kick drum fundamental is often around 80 Hz, where the wavelength is about 14 feet, so you that would be the longest wave that would actually "fit" into your room. So "long" is relative....
But longer is better! In general, you want a long room, such that the diffuse field is delayed as long as possible. I did mention that 20ms is the SHORTEST gap that is useful: 30 ms is better. This is sometimes called the "Haas time" and refers to a psycho-acoustic effect known as the "precedence effect" or the "Haas effect", named after the scientist who discovered and explained it. It's rather complex, and is related to the way our ears and brains work to perceive sound, but basically if a sound and a reflection of that same sound arrive within the "Haas time" (ie, less than about 20ms), then your ear and brain cannot differentiate between the direct sound and the reflection: they are too close in time for you to perceive them as two separate sounds. Instead, your ear and brain try to interpret that as though it were a spatial reference clue: your brain ends up thinking that the sound came from a different direction from where it actually came, and that the frequency response was actually different from what it really was. It's not a bad effect, if you are just listening to music for pleasure, because it adds to the "spaciousness" or "airiness" of the music: the music seems to "surround" you more, and can be quite pleasant. Which is why concert halls tend to emphasize such "early reflections" for the audience, as it makes the music sound better, more enveloping, warmer, mellower nicer. But that's no good for a control room! In a control room, you do NOT want the music to sound "better" or "wider" or "more surrounding"! Not at all. You want it to sound exactly like it really is, nothing added, nothing removed. You want to hear ONLY the direct sound from the speakers as you sit and mix. You do not want the room to change that in any way: You want to hear the truth, with no "coloration". Therefore, you do NOT want to have any reflections at all arriving at your ears inside the Haas time, because your brain misinterprets them, fooling you into hearing things that are not really there. So you'd think that it would be better to have no reflections at all, ever! Just let the sound go past, and never come back.... Well, that doesn't sound good either. A totally dead room like that, which just "sucks up" all the sound is not so pleasant. There are such rooms, and they are called "anechoic chambers", because they kill all sounds, all echos, all reflections: nothing comes back from the walls, floor, and ceiling. Very silent. Very dead. And very unpleasant to work in for long. It just does not sound natural: Your brain WANTS some acoustic clues about the size of the room, in order to correctly interpret what it is hearing. Therefore, the current best control room designs do return that diffuse field after about 20ms, or maybe 30 ms, or maybe even 50 ms in a large room, and that gives your brain all the clues it needs to figure out the room that it is in, and correctly interpret the acoustic "signature". As long as the "gap" is at least 20ms long, and up to about 50ms, your brain is happy: the room sounds natural, neutral, open, neither too dead nor too live, and you get to hear only the pure, clean, unmodified sound exactly as it came out the speakers, not colored in any way by the room, or by these subtle psych-acoustic effects.
So, to summarize: the direct sounds comes out your speakers, hits your ears, then carries on past you, where it eventually hits the rear wall, rear side walls, rear ceiling, and is reflected back to your ears. So for every sound that comes out the speaker, you hear the direct sound, then silence, then the reflected field coming back from the rear wall. That "silence" is sometimes called the "initial time delay gap" or ITDG, and the sound that follows it 20ms later, is often referred to as "terminating" the ITDG: it ends the silence. Of course, the "silence" is not really silent at all, since other sounds that left the speaker earlier are already getting back to your ears, but your ears and brain are really smart, and can figure it all out... as long as there's a 20ms gap for EACH sound.
Now, you might think that you could just put a big piece of wood across the back of the entire room, 10 feet behind your head, and you'd have a wonderful "termination" to the ITDG. You would, but it would be way too strong! It would be overpowering: the reflection would be nearly as strong as the direct sound, and it would be "specular", coming back at you from a very specific direction... and that would once again mess up your ability to perceive the real sound from the speakers. Those powerful reflections arriving after 20 ms would tend to mask similar direct sounds just arriving at your ears from the speakers, once again messing with your perception.
So, the sound field that comes back at you from behind 20ms (or more) after the direct sound, also has to be at least 20 dB lower than than the direct sound, and it has to be diffuse, not specular. In most control rooms, that is achieved with a combination of acoustically absorptive surfaces (to reduce the level by 20 dB), acoustically reflective surfaces (to send a little bit of the sound directly back, but not much) and acoustically diffusive surfaces, to break up the sound into a diffuse field.
So, the basic goal is that there is an ITDG of 20ms or more, then you get the diffuse sound coming back, 20 dB lower in level, then the diffuse field dies away slowly, until you can't hear it any more after the full decay time for the room. So if the decay time for your room was 250 ms, then you would hear: DIRECT SOUND! [silent itdg 20ms] .... TERMINATIOnnnnnnnnn..and..difusse---field---d.ec..ay....ing------slo--w----ly---for--230ms----more----.....
Now, if your room is bigger, then the ITDG can be longer: 30ms is good too! And you can also have a slightly lower level, such as maybe 25 dB down, especially if he room is large, ... as long as you still have an overall decay time that isn't too short for the size of the room.
The problem comes for small rooms, where there just isn't enough space to the rear wall to have a 20ms ITDG... Small rooms are a problem. You have to get very creative to deal with that, and get good results.
So, anyway: your room, at 15 feet long, is a decent size. Your head will be about one-third of that distance away from the front wall (about 5 feet), and therefore there will be about 10 feet between your head and the rear wall, which is fine for the 20ms ITDG.
so no matter how I treat the portion behind me I'm going to have a long delay as sound returns to me since it's going to be at least a distance of 10ft.
And that's a GOOD thing! Longer is better. Provided that it doesn't get VERY long.... 15 feet is about the minimum length to be able to get this effect easily. Longer would be better, but 15 feet is OK.
The only way to fix that (I'm assuming) would be to reposition my mixing desk and then that would effectively mean I had no space to track.
There's a theoretical ideal position for your head in the room, that supposedly minimizes modal issues: it places your head at spot where the modal issues are least intense. That spot is 38% of the room length. However! That's just the THEORETICAL "best" point: in reality, many engineers prefer a spot a little closer to the front wall, at maybe 35-30% of room length. So that's where your head will be, and your desk will be set up in front of that spot, at a comfortable location where you can reach everything easily.
There's a lot of "rules of thumb" for setting up a room, but it helps to understand WHY those rules are there.
But of course, rules can be broken too!
It is possible to set up a room that defies some of the rules, and still get success. Studio designers often have to do that, for various reasons. But for first-time studio builders, it's better to follow those "rules", or at least use them as guidelines, to set up the layout correctly.
- Stuart -
