Hi there "mbira", and welcome back!
I'm using Adam monitors for nearfield monitoring
![Thumb :thu:](./images/smilies/thumb.gif)
Good choice! But which model? They make a whole range of speakers, from tiny to huge, with very different characteristics...
I may be adding a small sub to the setup once the room acoustics are sorted and if I still need it
If you are going to add a sub, then you should do that now, before planning the treatment, since the go hand in hand. There's no point in adding bass trapping designed for a spectrum that goes down to 25 Hz if your speaker system cannot produce 25 Hz! And vice-versa: There's no point in having a sub that produces 25 Hz loud and clear in a room that isn't designed to handle it.
When I design a studio, the very first starting point is the speakers. I design the room around the speakers, since that's the only way that makes sense.
So FIRST decide on what speakers you will be using, THEN design the treatment based on that.
My control room is 19' x 19' with 10' ceilings.
![ahh! :ahh:](./images/smilies/ahh.gif)
Opps! It's square! That's a big problem. All of the modal issues related to the width direction will line up perfectly with those related to the length direction, and will be 6 dB more intense that if the room were based on a good ratio.
The office actually has 14' ceilings
Then the dimensions of your room are not 19 x 19 x 10: they are 19 x 19 x 14. The dimensions are to the hard, solid, massive boundary surfaces that delimit the actual room itself, not any soft, flimsy surfaces that happen to hang around inside it. When you do your room ratio calculations, make sure you use the actual size of your room, which is 19' x 19' by 14'. Those are the dimensions that define the modal response of your room. Acoustic tiles are pretty much transparent to low frequencies.
I need to keep the desk where it is.
The you are starting out with a handicap! You should ask yourself this basic question: "Do I want this room to be the best it can, acoustically? Or do I want it to look the way I like it, and screw the acoustics!". Sorry to be so blunt, but that's about the way it works out. If you start with pre-conceived limitations on where things can go in the room, then you are also placing limitations on how good the acoustics can be. If you truly do want this to be an optimal mixing room, then the old architectural adage should take first place: "Form follow function". So you have to first decide if the function of the room is a mixing room with good acoustics that also has some other stuff in it which won't affect its primary purpose? Or is it a general purpose room with poor acoustics that also has a couple of speakers and a DAW in it, that won't affect the primary purpose of being a general junk room?
The white desk is where I do DIY audio electronics stuff so that can move, but it will be somewhere in the room.
No problem. It can go where it will do the least damage to room acoustics. Which will be in the rear half of the room (further back than your head).
My goal: Basically, I'm just trying to get the best sounding room for me to be mixing in without getting too much adverse influence from the room.
Great! Then you already answered the above question! It's a mixing room, first and foremost. So it's time to let go of any limitations you wanted to place on the room, that would prevent you achieving that. Get used to the idea that things might end up in different locations in the room...
Should I consider the 4' dropped ceiling to already be a substantial bass trap?
It isn't right now, but it could be if you wanted it to be.
I can potentially bass trap three corners but not the place where the door is. Should I not do that third corner and only do two?
In a small room like this, the answer is simple: More is better! You can never have too much bass trapping in a small room. And if you are only considering four corners, then you are forgetting about a full two thirds of the possible corners. rectangular rooms have 12 corners, not 4.... Think about it.
Here's a link to a room that I designed a few years back, and recently re-tuned when the owner upgraded his speakers:
http://www.johnlsayers.com/phpBB2/viewt ... =2&t=20471
There are multiple bass traps in there, including several feet above the ceiling, above the soffits, behind the cloud, in the rear corners, in the top corners, on the back wall, inside the soffits, under the raised sofa platform, and in a few other places too. Even the cloud functions as a bass trap in there. (But there still isn't quite enough...
![Smile :)](./images/smilies/icon_smile.gif)
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So yes, put in as much bass trapping as you can, and make it BIG. The ones you show in your diagram at present are not doing anything useful at all.
However, there's a secondary principle here that also must be taken into account: symmetry. The front section of the room must be perfectly symmetrical, or you won't have an accurate stereo image and sound stage. The rear of the room (behind your head and up to the back wall) isn't so important, but the front is critical. So you'll probably need to rotate your room orientation 90° to the right, or 180°, such that the door is no longer in the front of the room. That will enable you to have symmetrical treatment in the front.
Thanks for any thoughts!
Well, first of all we need to get your room geometry set up optimally. Right now, you show your speakers set up away from the front wall, but the room probably isn't big enough for you to be able to do that properly. It's borderline actually. You didn't mention which speakers you have (model), but assuming that they put out a reasonable amount of energy at 35 Hz, they would need to be about 10 feet away from the front wall to ensure that the first SBIR dip is below that. In your room, that's out of the question, obviously. If your speakers only go down to 45 Hz, then you could get away with six foot spacing to the front wall, which is possible but not recommendable. Even if you wanted to use a sub and crossed over at the typical 80 Hz point, you'd still need to have them at least 4 feet from the front wall. That is much more do-able in your room, but there's a better way.
For small rooms where the speakers cannot be far enough away from the front wall, the best option is to put them right up against the front wall, which pushes the first SBIR dip way up into the low end of the mid range, where it can easily be dealt with using treatment on the front wall.
OK, I should backpedal a little here, and say that the absolute best location for speakers is NOT in the room at all, but rather flush mounted in front-wall "soffits". That takes front wall SBIR off the table completely, as well as eliminating edge diffraction, power imbalance, comb filtering, and a bunch of other problems, in addition to all of the benefits that it provides, such as low-end extension, smoother. tighter bass, better loading, etc. So that would be the best possible situation, if you wanted to go that way. In your case, that would also be very beneficial for the modal response of the room, since it would modify the dimensions enough to shift the modal response: the room would no longer be square.
But assuming you don't want to build soffits, then second best is to have your speakers tight up against the front wall.
"tight up against", except for a 4" gap. You need that 4" gap to install the 4" acoustic panel that will deal with the SBIR.
So, to get your geometry correct: Move your speakers up to be 4" away from the front wall, and 65" away from the side walls (implying that they will then be 98" apart). Put them on very heavy, massive, rigid stands, such that they are 47 1/4" above the floor. Careful! Those last three measurements refer to the acoustic axis of the speaker, not the surfaces of the cabinet. So the acoustic axis of the speaker will be 47 1/4" above the floor, and 65" from the side wall, while the rear corner of the cabinet will be 4" from the front wall (almost touching the front face of the acoustical panel). Depending on your speakers and desk, you could actually put the speakers a little higher, up to around 49", but not more than that.
Now for the mix position: in that room, your head will need to be 84" from the front wall. Actually, that's where your
ears need to be, so set up your chair such that your ears are 84" from the front wall when you are seated in the typical posture you use while mixing. Now set up a vertical pole (eg, mic stand) directly behind your head, still on the room center-line, and 102" from the front wall (in other words, about 18" behind your head). Carefully rotate the speakers on top of their stands so they are both aimed directly at that pole. I use a laser pointer for that, tape to the top of the speaker cabinet, directly above the acoustic center, and running perpendicular to the front baffle.
That will get you the correct acoustic geometry for your room. Theoretically correct, of course: you might still be able to find a slightly better location using REW, starting from that position.
With all of that in place, you can add your bass traps in the corners: I would do superchunks in that room, at least 36" along the sides, and floor to ceiling. I would put hangers in the 4' gap above the drop ceiling, and in fact I'd pull out that drop ceiling completely, replacing it with fabric, and hang a cloud over the mix position. Hard-backed, and angled.
I would then cover the entire rear wall with at least 6" of porous absorption, with a good diffuser in front of it (your room is big enough to use diffusion). Maybe a simple Schroeder diffuser, tuned with the low cut off at around 1 kHz, or a bit lower, or perhaps a Skyline (QRD is preferable to PRD),or even better, a multi-level fractal diffuser, since you do have the space to do that well. You might even consider doing hangers across the rear wall, with a fractal diffuser in front. You can spare the space.
You would also need 4" porous absorption on your first reflection points.
Once all of that is in place, test the room with REW to see what else needs doing, then design additional treatment as needed to deal with it. I'd guess that you would need a couple more panels on the rear side walls, and maybe one or two other things, but even with just the basic treatment in there, you'd have a reasonably good acoustic environment.
Depending on how big it is, the "white desk" might be able to fit up against the front wall, between the speakers, or if not then it would have to go either on the rear wall to the side of the couch, or on one of the side walls, right next to the superchunk.
- Stuart -