After doing some more reading on CR design I found that a decent Control Room should have a min of 200sq/ft. Is that correct?
Well, yes, that's correct. ... Sort of. Yes, the best specs for "critical listening rooms" do specify 200 ft2 as the "minimum", but that does not mean that if you only have 199 ft2 it will be terrible! Nor if you have 190... or 180... or 170... It's a matter of "optimal" and "slightly less than optimal" and "a little worse". A smaller room can still be pretty good... PROVIDED THAT it is designed carefully and treated accordingly. I can design you a 200 ft2 room that sounds terrible, and I can design you a 160 ft2 room that sounds pretty darn good. John has built rooms inside shipping containers! It just gets harder and harder to do as the room gets smaller.
Yes, bigger is better, for sure, and yes, above 200 ft2 is best (actually, the number is 215.3, because it is specified as 20 square meters....), but your room won't automatically fail if it is smaller.
so I've adjusted my plan and as mentioned in my last few posts eliminated the vocal booth and stretched out the CR an extra 16". It's now approx. 123" W x 226" L x 12' H(at the peek of the roof).
That's a good size for a room, but did you check the "room ratio" to make sure it is acceptable? Use one of these Room Ratio calculators to figure out the best dimensions for your room:
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 to help figure out the best dimensions.
Warning! You do NOT need to go crazy here, adjusting dimensions to get a "perfect" ratio! There is no such thing. As long as your ratio is not close to one of the "bad" ones, and is reasonably close to one of the good ones, then that's fine. It is more important to have as much volume as possible in the room, than it is to hit the "best" ratio.
Doing so gives me a bit smaller Live Room 18.8' W x 12.8' x 12' (at the peek of the roof).
Do be aware that the air volume of the LR should be somewhat larger than the air volume of the CR, if possible. One way of looking at it (not strictly accurate, but it helps to get a mental picture), is that you need to hear the "reverb tails" of the LR when you listen on the speakers in the CR. Reverb tails are the lingering remnants of the sound dying away slowly after the cause has stopped: it's the sound of the room itself, to a certain extent, or the sound of how the music reacts with that room, after the music stops. It's the "life" and "character" of the room, what makes it "sound great" for a musician. But it is low level, and dies away at a rate that is proportional to the room volume. Smaller rooms have faster decay. So here's the thing: the decay in your CR will be "neutral": just right for the room itself. You will tune it that way, because control rooms MUST be neutral: They must not add to nor subtract from the natural direct sound. So if it turns out that the reverb tails in your LR are about the same length as the natural decay time of the CR, you won't hear the reverb tails! When you listen on your control room speakers, you'll hear the natural decay of the CONTROL ROOM, since it will be louder than the reverb tails from the LR in your recording. The tails in the LR need to be substantially longer than the decay time of the CR, so that you can hear those reverb tails in the CR, after the natural decay has already gone by... and you are left hearing the sound of the LR. If your rooms are about the same size, then you'll be challenged to hear what the music really sounds like in the LR, as you listen in the CR.... but the guy listening to your mixes on ear buds, where there is no room at all and zero decay time, will hear everything! Including stuff that you never heard in your mixes...
So the ideal is to have the LR larger than the CR, and if you can't do that, then make the LR slightly more "live" (longer tails) and the CR slightly more dead (shorter decay time), by using the correct treatment in both rooms.
1) After stretching out my current CR design I still only have approx. 192 sq/ft. Is this still manageable for a decent CR? or should I try to stretch even more?
That's fine! As I mentioned above, 200 ft2 is not a sharp cut-off point: it's just a rough marker that shows where performance starts to tail off for smaller rooms. Think of it sort of like the "roll off" in bass response for a good speaker: The speaker spec might say that it goes down to 35 Hz, but that doesn't mean that it produces no sound at all at 34 Hz! It just means that at 34 Hz, the sound is a tiny fraction less than it should be, optimally. And at 33 Hz, it's a little less optimal. Even at 30 Hz, and 25 Hz, the speaker is still putting out some sound. The 35 Hz spec just shows the point where things START deteriorating: It's not a sharp line. Ditto for the 200 ft2 "spec": it's just a rough point where things start rolling off.
2) Is having a smaller Live Room a bad thing or still manageable?
See above: As long as it as larger VOLUME of air than the CR, that's fine. And you can also adjust the treatment of both rooms a little, pushing the LR a bit more to the liver / longer tails side, and damping the CR a little more than it should be.
In some design concepts for control rooms, there's the concept of the ITDG, or Initial Time Delay Gap. That's the small period of time between the instant where your ears hear the direct sound from the speaker, and then hear the first "echo" of that direct sound, that has bounced off some wall somewhere, and come back to your ears. The specs for control rooms often say that the first "reflected" sound should not arrive until at least 20ms after the direct sound, and that when it DOES arrive at your ears, it should be diffuse (not specular), and during that time, the intensity should be at least 20 dB lower than that direct sound. That "20 ms window" is the ITDG. After than time has passed, some specs call for the level to increase again, above -20 dB, then die away slowly. So if you look at a graph showing how the room responds to an "impulse" (a sudden very loud, very short sound, such as a balloon popping), you'll see a tall spike as you hear the direct sound of the pop itself, then nothing for 20ms (or at least, nothing louder than -20db), then you'll start to see the level rise again as the diffuse sound of the balloon pop that has bounced around the room and been absorber and diffused, starts to get back to your ears, at maybe -15 dB or so, but then it dies away slowly for a few hundred milliseconds, until it is completely gone. That "space" where you hear "nothing" after the initial direct sound, is the ITDG: The Initial Time Delay Gap between the direct sound hitting your ears, and the reverberant field hitting your ears.
So, the ITDG has to be long enough to allow you to hear the sound of the LIVE ROOM reverberant field, which hopefully does not have an ITDG, or has a short ITDG, or one that does not go below -20 dB. As long as you have that condition, then you will be able to hear the "sound" of the live room when you listen on the CR speakers. But if your CR has an ITDG that is too short, or too loud (above -20dB), or if the level rises up too high again after the ITDG, then you won't hear those small hints from the LR room sound, in the CR. In that case, it is better to not have a rise above -20 dB after the ITDG: just keep the level low, say -30 dB for the ITDG, don't allow it to rise again above that, then the decay can start after that, at a lower level. That's what I do for small control rooms and small live rooms. It's not easy to get it right, but it does give you a better shot at hearing the subtle delicacies of the LR reverb tail, in the CR.
OK, so some people think this is splitting hairs, since LR tails are low level and subtle in any case, so there's no point in caring about them much. They don't think that "tails" are important at all. Maybe if you only ever plan to record shrieking grunge rock, or mind-mashing heavy metal genres, that scream through the entire song at 120 dB without it ever being possible to have the slightest hint of a reverb tail, then that's OK. But if you plan to record music that has a bit of feeling to it, with subtleties, nuance, ambiance, then this is very important. (And if you only ever plan to record screeching, howling, wailing, bellowing heavy metal, then why bother with a studio at all?? You could record that in a subway station, and not even notice the trains roaring past . . .
).
I can try and stretch the CR a bit more to get me up to 200sq/ft + but I just want to make sure that won't effect the LR in a bad way.
Not necessary. At 190 ft2, you are within the ball park for having a decent control room. Yes, bigger would theoretically allow slightly better, but the difference is not huge, and 190 is still good.
How would I be able to calculate/evaluate modes with a room with slopped ceilings.
Simple answer: you can't! Room mode calculators only work for perfectly rectangular rooms. More complete answer: You can still use the calculators to get a good idea of how the room will behave, as long as the angle is not too great, and as long as you understand what you are looking at.
For example, if it is JUST the ceiling that is off, and your walls are still parallel and perpendicular, then the predictions for axial modes in the length and width directions will still be perfectly correct, and so will the predictions for tangential modes that only involve the four walls. But axial mode predictions related to the ceiling will NOT be correct, and neither will predictions for tangential modes that involve the ceiling, or any oblique modes. However, if only part of the ceiling is sloped (eg, the front half rises, but the rear half is flat), then the predictions will still be valid for the part of the room where the ceiling is not sloped. And it the angle of slope is not huge, then the predictions will not be far off, and you can still use them, as long as you realize that they won't be entirely accurate.
The big issue happens when you have a room that has more than six sides, or when the splay angles on the walls and ceiling are large. The more complex the room is, and the further it is from being a pure rectangle, the less accurate the prediction will be.
Having said all that, you do NOT need to go crazy trying to find the perfect ratio for your room! There is no such thing anyway, and it doesn't really matter all that much, as long as you stay away from the bad ratios. So for example, if you have to reduce the length of your room by 6" to get a good ratio, then don't do it! It's better to have that extra six inches to increase the room volume. The only time I'd do that is if the room was a perfect cube, and the only way I could fix it was by reducing the length or width a bit. And even then, if it was a very small room, I would be very hesitant to take off those 6". For a large room, it would not be a problem to lose 6"... but then again, for a large room there would be no need to lose 6" anyway, since large rooms already have better acoustics than small rooms!
- Stuart -
floor? Anything else I can add that can help a little.