Nasty bass in monitor room.

[theantony]

I've moved to a new studio, and I'm not happy about the monitor room. There is a not very nice bass hole in the middle of the room where the bottom end gets huge, i prosume its the window to the side. Maybe it's because I am so use to my old mixing room which sounded great and with very little treatment.

I'm thinking maybe I've put to much treatment into my new room, the sound doesn't feel free it feels compressed and I have to work at loud volumes to get anything from the monitors (Adam a77x which aren't pictured there A7). Should I move the desk?

The dimensions are 9ft by 18ft.
Here's a link for pics to a build page on gs.

http://www.gearslutz.com/board/photo-di ... ost8817617

[Soundman2020]

Hi there "theantony", and welcome to the forum!

The room looks great! Nice work. But clearly isn't performing the way you want it. And unfortunately, the basic reason is also clear:

The dimensions are 9ft by 18ft.

There you have it. The length is twice the width, and from the photos I'm guessing that the ceiling height is also pretty close to 9 feet?

Use this calculator, and plug in your those numbers Length 18, width 9, height 9:
http://www.bobgolds.com/Mode/RoomModes.htm

You'll see the issue as soon as you hit "compute". Reds and purples are really bad news, yellows are somewhat bad news, greens are good news.

So what you describe about how you feel in the room, fits that data, to a "T".

The solution is to change one of the dimensions, either partially or fully. There are several options. I'm sure you don't want to change the front of the room much, and the width is already narrow, but it would not bee too painful to reduce the length of the room a bit. For example, even taking just one foot of the length and modifying the cloud to get an effective height of 8 feet, will re-arrange the modal response to a much better position. Still not fantastic, but anything is better than having dimensions that are mathematically related. So modifying the rear wall to bring it a foot, and modifying the cloud, would be the first suggestion.

However, even after that, there will still be issues, so you'll still need additional treatment, or to modify what is there already, to make it better suited to the problems.

I'm thinking maybe I've put to much treatment into my new room,

That room needs about 400 sabins of absorption to meet ITU / EBU specs, but there does not seem to be anywhere near that much. So I don't think the room is over-treated. More likely under-treated, and some of the treatment that is there might not have been done the best way.

There is a not very nice bass hole in the middle of the room where the bottom end gets huge ... the sound doesn't feel free it feels compressed and I have to work at loud volumes to get anything from the monitors

That's what I'd expect from a room with dimensions that are integer multiples of each other. It is not due to the window, but rather to the dimensions.

(Adam a77x which aren't pictured there A7).

Nice! They should work well in that room. But I would set them up better than that. The way you have them right now is probably making things sound worse, not better.

Should I move the desk?

Probably not, but you should move the speakers. There's several ways you can improve on what you have there, and they should noticeably improve the way things sound in the room. But before you do that, I'd really suggest running an proper acoustic analysis on the room, and posting the result here. If you don't have it already, then download REW and run that. It will show exactly what is happening in there, and that will lead to the right solutions. So run REW, post the resulting data file, we can analyze that for you, then suggest what you can do to fix the room.

The good news is that it CAN be fixed! Maybe not 100%, but it should be possible to at least make it usable.


- Stuart -

[theantony]

Thanks for the response. I had no choice with the length. I will make a proper measurement tomorrow to get it more accurate.
When you say reduce the length shall I just move the desk away from the wall. I will say that the back wall has two doors on the corners one to the kitchen another to live room so I can't trap them. I'm guessing I should diffuse the rear wall as well.
I will run a rew test but wondering in mics. I have a load of omni condensers that can set flat can I just use that instead of the suggested behringer. And also with the cloud are you suggesting I lower it? I can put another one over the rest of the room. I would add that it is broadband and not hard backed.

[Soundman2020]

When you say reduce the length shall I just move the desk away from the wall.

That sounds like the best option if there are doors in the rear wall. Moving the desk back a bit will allow you to take off the drywall on the front wall, build a new stud frame a few inches away, then put new drywall on that. It's a shame to have to do that when the room looks so good already, but there really isn't much else you can do when you have a room with directly related dimensions.

I will make a proper measurement tomorrow to get it more accurate.

Excellent! Measure the length, width and height as accurately as you can.

I will say that the back wall has two doors on the corners one to the kitchen another to live room so I can't trap them.

How about posting a photo of that rear wall? There several ways you can bass trap a room...

I'm guessing I should diffuse the rear wall as well.

The room is probably too small for diffusion, or at least too small for typical numeric-sequence based diffusers. But I would use the rear wall for absorption and trapping, as much as possible. Photos of that wall would help to decide what can be done with it.

have a load of omni condensers that can set flat can I just use that instead of the suggested behringer.

That would be fine. Any good omni with flat response down to very low frequencies will be fine. Place it at the mix position, exactly where your head is while you are working. Take three measurements: one with just the left speaker operating, one with just the right, and one with both of them.

And also with the cloud are you suggesting I lower it

I would angle it, and put a hard back on top. Tilt it lower down at the front, over the speakers. Try to get at least a 15° angle, if you can. And also put some 4" OC-703 on top of it, after you put the hard back on.

I would add that it is broadband and not hard backed.

That's fine for normal first reflection point treatment, but in order to break up the modal response, it must have a solid, thick hard back. 3/8" plywood, MDF or OSB would be the way to go, then 4" of 703 on top of that.


- Stuart -

[theantony]

That's great advice.
I'm going to start with backing and angling my cloud, you suggest mdf, or plywood or chipboard. Would add that my bass traps and side baffles aren't hard backed either should I do those as well, I will move my desk out when my a77x go in as there to big to go where it is know. Ill post a pic of the back wall later. You mention speaker positioning, what do you suggest. I will run a rew test and post.

Many thanks.

Antony

[Soundman2020]

Would add that my bass traps and side baffles aren't hard backed either should I do those as well,

No, because that's a different principle that those devices work on. They need to be open backed, since they are against walls already. The cloud is different, because it is hung away from the ceiling. That CAN be left open (no hard back) if all you want is god absorption at the first reflection points, but in your case you need the hard backing because you need to try to break up the modal issues to a certain extent. The hard back will do that, since it is a massive, solid, rigid surface, so low frequency sound waves are forced to go around it (diffraction) rather than through it. And it needs to be angled so that it is presenting some surface area to the front-back direction of the room, which is where your lowest frequency axial mode is, plus it's harmonics. Right now it is only having an effect on modes in the vertical direction, but angling it helps to have some effect on the horizontal modes too.

I will move my desk out when my a77x go in as there to big to go where it is know

Moving the desk alone is not going to accomplish anything: you have to physically move the boundary of the room, by furring out the front wall a few inches. Modes happen between the hard boundary surfaces of the room, regardless of where the desk is. All that you will accomplish by moving the desk is to get your head in a different set of modal problems. The optimum location for your head in that room as it is now, is about 6' 10" from the front wall (about 2.1m). That's the point where the modal activity is least noticeable, theoretically, so position your desk such that your ears are 6' 10" from the front wall. But even there you are still going to have big modal issues, simply due to the dimensions. The only real option is to change the dimensions of the room by moving the front wall.

You mention speaker positioning, what do you suggest.

First, get the speakers off the meter bridge. It looks cool like that, and many studios do it out of ignorance, but in reality it is a really bad idea, acoustically, especially when the room already has big issues. Instead, get your speakers on to stands just behind the desk. The stands must be massive, heavy, and solid: Some people stack up concrete blocks for that, others use hollow metal stands willed with sand. The point is, they must be very heavy, and they must be just the right height so that the acoustic axis of the speaker ends up exactly 1.2m above the floor (47 1/4 inches). Note: This is about the ACOUSTIC AXIS! Not the top or bottom of the speaker, so you first need to know where the acoustic axis of your speaker is, and position the stand so that the axis is 1.2m above the floor.

Next, the speakers should always stand upright, unless they are specifically designed to be used laying down. The A77X IS designed for that, since the tweeter is in the middle, so it can be used laying down, but the A7s that are in the picture at present are not meant for that. So until you get the A77Xs, turn those A7s vertically, the way they should be. Yes, some studios do use speakers laying down, and the Adam manual even shows that as a possibility, but in reality it is a bad idea, since it places the tweeters off-axis with the mid-range drivers, so as you move your head a bit left or right while you work, you are also moving into a different area of the sound field, where the balance between highs and lows changes. Our brains are very sensitive to changes in the horizontal plane, since our ears are on the sides of our heads, but we are NOT so sensitive to changes in the vertical plane, because we don't have ears on our foreheads and chins! Also, we don't move our heads up and down much while we mix, but we do move side to side a lot. So orienting the speaker vertically is the correct way to do it.

So for now, turn your A7s to stand up straight on the stands.

In your room, the speakers should be placed hard up against the front wall, and 2' 7" from the side walls (once again, that 2' 7" refers to the position of the acoustic axis, not the side of the speaker cabinet). Place a 4" panel of OC-703 between each speaker and the wall behind it, to help reduce some of the artifacts. That will place the speakers about 6' 6" from each other, which is fine. Now angle them carefully so they are pointing just past your ears, so that the acoustic axes of those two speakers meet at a point about 10" behind your head.

That's the optimal positioning for your speakers and you, in that room. It should be better than where you are now, but it still won't be good until you change one of the dimensions of the room itself, and install enough treatment.


HOWEVER! I just noticed that over on the Gearslutz thread you say the room is 10' x 21', but here you say it is 9' x 18'. So which is it? There's a very big difference between those two sizes, in terms of acoustics! All of the measurements I gave you above are for the 9 x 18 size. If it is really 10 x 21, then that's a whole different story. So please post the actual true dimensions of the room, not including the treatment: Measured to the actual walls themselves, the hard boundary surfaces of the room. That's what matters, acoustically. And try to measure accurately, to the closest half inch.


- Stuart -

[theantony]

Here's the room dimensions exact. L.w.h, 15.6ft x 8.75 x 7.87.

And here's the back wall.

[theantony]

Great info, I did research my traps a lot and that is why I built them that way but just a thought, as for the cloud it makes sense after your explanation, so ill adapt that ASAP.

The dimensions posted here now are exact, the bob gold link you gave for room dimensions now shows as all green bar a few red, so I guess that's a start.

I agree with the speakers I have stands and will use them I put the a7 like that as to get the tweet align with my ear. I was concerned about having them behind the bridge on the desk because of reflection from the desk etc. I am not as concerned about the look as the sound so whatever works.

As for treating the front wall behind the speakers I have standard 300x300 auralex is that not sufficient or should I go thicker.

[Soundman2020]

Here's the room dimensions exact. L.w.h, 15.6ft x 8.75 x 7.87. ... The dimensions posted here now are exact, the bob gold link you gave for room dimensions now shows as all green bar a few red, so I guess that's a start.

It's a start, but not far enough, I'm afraid. There's a lot more information on Bob's calculator that needs to be considered too, such as these:

- 1.1w / h < l / h < ((4.5w / h) - 4): Fail
- l < 3h & w < 3h: Pass
- no integer multiple within 5%: Fail (ratio3 = ratio1 * 2)

So those dimensions fail two of the three "acid tests" used by the BBC for rejecting rooms as possible studios.

And also this:

Code: Select all

Nearest Known Ratio:
-  "24) A worst case scenario calculated by RPG" 1 : 1.075 : 1.868

Finally, there's the Bonello graph: also not very good.

I was concerned about having them behind the bridge on the desk because of reflection from the desk etc.

Actually, if you work out the angles, in most cases moving the speakers further back (away from the desk, towards the front wall), turns out to improve things: The reflections occur at more shallow angles, lower down, which is good.

As for treating the front wall behind the speakers I have standard 300x300 auralex is that not sufficient or should I go thicker

Both bigger and thicker. That room is way short on absorption, and that area behind the speakers is a good place to put it. I would go floor-to-ceiling with 4" panels of 703.

And here's the back wall.

Definitely not enough there! Use the space in front of that beam above the door, and also below the beam, for bass trapping, in the "superchunk" style, and also replace that tiny panel in the middle of the wall with a very large, thick panel (full panel, floor to ceiling). Find somewhere else to plug in whatever those wires are. Also put absorption panels on the backs of both doors. For the door with glass in it, just do from the bottom of the glass down to the floor.

- Stuart -