New controlroom design!

Hi Folks! I'm moving my studio and have found a new location. The room I'm planning to use as my new controlroom is almost quadratic, 5000mm wide and 4965mm deep. The ceiling height is 2760mm. I's located in an old wooden building (1880). I'm planning to build angled side walls and ceiling in front end (see drawing) and would think that that would make the room 'not quadratic' in an acoustic perspective. My question is if this dimensions is going to be an issue? Best, Jamzone

Just to get you started on the road less traveled: Help adapting a Wes Lachot control room design

Your ratio is very, very close to square: I haven't plugged in your numbers to the mode calculator, but my guess is that you'll have a bunch of modes in very close proximity: Not good. And as far as I know adding insulation does not change that. From what I recall reading, you always take your measurements from the hard surfaces of your walls / ceiling / floor, not from the surface of the insulation that covers them. If you build that angled front wall, then you'd have your speakers firing across the shorter dimension of the room, but what is recommended here is to have them firing down the longer dimension. If that were my room, I think I'd sacrifice a bit of space to get a better ratio, by building an inner-leaf wall on the left hand side of the room (covering up those windows). That would also make the room more symmetric, and allow space in the left rear corner for the bass traps. - Stuart -

That's correct! But as you see, I've planned to build splayed walls (marked plasterboard) in the room. Would'nt that affect dimensions? Will also treat rear wall in some way. Go to have windows... Otherwise no music's being made!! :mrgreen: Best, Jamzone

The link was not an end but a beginning. You have much travel in front of you to get to your desired destination. Room ratios, symmetry<<<<< balance, all kinds of things go into this control room area. All I can do is point you to a start, it is you who must make the first step. You still have a square room and it, acoustically speaking, is unacceptable :) Were it acceptable, there would be no want for rectangles.

I've planned to build splayed walls (marked plasterboard) in the room. Would'nt that affect dimensions?

Not really, if I understand your plans correctly. You have splayed walls labeled as "plasterboard", but you also have the entire front end of the room (between the splayed walls) labeled as "cloth" over "insulation". So the acoustic length of your room is measured to the wall behind that "cloth" and "insulation". All that the splayed plasterboard will do is to create reflective surfaces that affect higher frequencies, and act as panel resonators that affect lower frequencies, but it will not change the dimensions of your room: the sound will just pass around the plasterboard, through the cloth and insulation. In fact, you are probably creating some kind of strange tuned cavities behind that plasterboard: I have no idea what effect that might have, acoustically, but my guess is that it won't be helpful. However, since the cloth and insulation is basically transparent to low frequency sound (which is where the problems are) the acoustic dimension of your room is still the same: the end wall, on the other side of the insulation. In effect, all that you have there with the plasterboard splayed "walls", is a couple of angled gobos. They don't change the dimensions of the room, because sound can get past them and around them, especially low frequency sound (long wavelengths). Unless you build that entire front wall as a single solid unit, using a coupe of layers of plasterboard, and sealed airtight, then it will not affect your room dimensions.

Go to have windows... Otherwise no music's being made!!

OK, but you are sacrificing acoustic quality for aesthetics. Personally, I wouldn't do that, but hey, it's your room! However, it does mean that you will have no space to install your bass traps exactly where you need them. I guess you could install bass trapping below and above the window, and up to the edge of the frame, but you are wasting a lot of good bass-trap space, and you'll have to do the same on the other side of the room, in the area marked "tiled stove", to keep the room symmetrical. Symmetry is VERY important. By the way, what is that "tiled stove"? - Stuart -

Please explain. I've planned to use double 13mm plasterboard on those. It's not square anymore, right?? The front to back/side to side in a small portion is the same dimensions but would'nt it be better to treat this areas then?? Do one always have to start with a 'golden ratio' and screw it up later?? Best, Jamzone

Soundman2020 wrote:

I've planned to build splayed walls (marked plasterboard) in the room. Would'nt that affect dimensions?

Not really, if I understand your plans correctly. You have splayed walls labeled as "plasterboard", but you also have the entire front end of the room (between the splayed walls) labeled as "cloth" over "insulation". So the acoustic length of your room is measured to the wall behind that "cloth" and "insulation". All that the splayed plasterboard will do is to create reflective surfaces that affect higher frequencies, and act as panel resonators that affect lower frequencies, but it will not change the dimensions of your room: the sound will just pass around the plasterboard, through the cloth and insulation. In fact, you are probably creating some kind of strange tuned cavities behind that plasterboard: I have no idea what effect that might have, acoustically, but my guess is that it won't be helpful. However, since the cloth and insulation is basically transparent to low frequency sound (which is where the problems are) the acoustic dimension of your room is still the same: the end wall, on the other side of the insulation. In effect, all that you have there with the plasterboard splayed "walls", is a couple of angled gobos. They don't change the dimensions of the room, because sound can get past them and around them, especially low frequency sound (long wavelengths). Unless you build that entire front wall as a single solid unit, using a coupe of layers of plasterboard, and sealed airtight, then it will not affect your room dimensions.

Go to have windows... Otherwise no music's being made!!

OK, but you are sacrificing acoustic quality for aesthetics. Personally, I wouldn't do that, but hey, it's your room! However, it does mean that you will have no space to install your bass traps exactly where you need them. I guess you could install bass trapping below and above the window, and up to the edge of the frame, but you are wasting a lot of good bass-trap space, and you'll have to do the same on the other side of the room, in the area marked "tiled stove", to keep the room symmetrical. Symmetry is VERY important. By the way, what is that "tiled stove"? - Stuart -

'Tiled stove' is like the main heating source in old buildings. It's the center of the building made of, well, tile! Not to be moved!! As a composer I could just as well sell all my gear and sit around until all my royaltie money run out if I did'nt get any inspiration from my workplace. Would'nt have chosen that building in the first place. Hate basement studios. Best, Jamzone

Soundman2020 wrote:

However, since the cloth and insulation is basically transparent to low frequency sound (which is where the problems are) the acoustic dimension of your room is still the same: the end wall, on the other side of the insulation. - Stuart -

Ok. That's 300mm (12inches) of insulation on the front wall. Is that transparant to low frequencies?? In that case I'm lost... And the hangers in the corners and behind the 'hard wall' would do something, right?? What I could do to improve ratio is to build an extra leaf on the right side?? Have also thought about using the ceiling as a bass trap... Is symmetri that important behind you if you achieve RFZ?? Best, Jamzone

Allright, a new one... Really rough!! Windows there... Best, Jamzone

Ok. That's 300mm (12inches) of insulation on the front wall. Is that transparant to low frequencies??

Yep. Theoretically, it is transparent to all frequencies with a wavelength longer than 1.2 m (four times the dimension of the insulation), which means all frequencies lower than 285 Hz. In other words, it is transparent to the entire low end of the spectrum. Sorry, but the numbers don't lie.

And the hangers in the corners and behind the 'hard wall' would do something, right??

Well, they will absorb bass, yes, but they won't stop bass. This is not very intuitive, but there are two totally different concepts here: Isolation and acoustic treatment. They are not the same. In fact, they are roughly opposite! "Isolation" means blocking sound, preventing it from going through your wall to the other side. "Treatment" means controlling sound inside your room, to stop it bouncing around (reflection, reverberation, resonance), or to control how it bounces. Absorption is very good at stopping sound form bouncing around (good for stopping reflections, reducing reverb, etc.), but very bad at stopping sound from going through the wall. Sheetrock (drywall, plasterboard) is very good at stopping sound from going through, nut very bad at stopping it from bouncing around. So materials that are good at blocking sound, are bad at treating it, and materials that are good at treating it, are bad at stopping it. You have to separate the two concepts in your mind: Isolation is one thing, treatment is another. They are not really related. Absorption stops reflections well, but does not block sound well, especially low frequencies. Low frequencies just pass right through absorptive materials. Mass blocks sound well, but does not stop reflections. In fact, it CREATES reflections. Massive, solid walls block sound, and also reflect sound. That's where your room ends, as far as low frequency sound is concerned: the surfaces of your walls mark the acoustic "boundaries" of your room. The wall surfaces are the dimension, and that does not change by putting "absorption" in front of them.

Have also thought about using the ceiling as a bass trap...

That's good! That will help a lot. But the room corners are the best place for trapping, since you get 12db boost in trapping for free, due to having two surfaces meeting in the corner! That's 6dB more than from your ceiling. I'll take every dB of trapping I can get, especially when if it comes for "free"!

Is symmetri that important behind you if you achieve RFZ??

Yep. The sound will still bounce off the surfaces behind you, and get back to your ears. If your room is not symmetrical behind you, then your ears will hear different reflections things at different times. RFZ only refers to early reflections off your side walls and ceiling. Unless you have a totally dead anechoic chamber behind you, then you will get reflections coming back at you from the walls, floor, ceiling and other objects back there, and they will confuse your imaging if they don't come back symmetrically. You should try to make your room as symmetrical as you possibly can, according to the experts. - Stuart -

Then all insulation based bass-traps can go down the drain... Check new idea!! :D Best, Jamzone

Then all insulation based bass-traps can go down the drain...

Huh? How did you arrive at that conclusion? That makes no sense. That's not what I said at all! You didn't understand what I was saying. I think you need to re-read it and try to understand it. I think you are still confused about the difference between isolation and absorption. Insulation-based bass traps work very well. But they do not work by blocking sound. They do not prevent it from passing through. That is not the purpose of a bass trap anyway. This type of bass trap works by absorbing sound, not by isolating sound. You need to understand the difference between "isolation" and "absorption". They are not the same. Mass isolates, insulation does not. Insulation absorbs, mass does not. Insulation (rockwool, fibreglass, etc.) does not isolate: it absorbs. Mass (sheetrock, concrete, brick, etc.) does not absorb: it isolates. You could say that mass deals with the pressure component of sound, absorption deals with the velocity component. Two totally different concepts. They are exact opposites. Bass traps that use absorption are very effective, but they do not block sound, they do not stop it from passing through. If you could put your ear inside a bass trap, you would still hear sound in there. Absorbing sound inside a room is NOT the same as preventing it from getting out of the room. - Stuart -

I was being ironic... I want to keep a window and get a good sound in the room. So I have to make an additional leaf somewhere... And keep one window. Any ideas folks?? Best, Jamzone

Build the speaker walls so that the equivalent depth makes the width 4.5 m. These walls must be dense, reflect the low frequencies. Double 15 mm gyproc or equivalent would be good. Leave a 20 cm gap at the top and 30 cm gap at the bottom. With the seating position 38% back this also gives you enough space to make side walls if splayed reflective. Make these side walls slat absorber/diffusers. Use a 10,15 5, order with 20% width gap adjacent to each. Fill the space behind the walls (the green area) with light insulation (32 kg/m^3 or less). Make the ceiling absorptive with 20 cm thick absorption if possible in the front portion. The attached images are dimensioned per what you have said. After doing the above report back and we will address flutter echo if present. Good luck! Andre

Super thanks, Avare!! Look's like a good solution. Some thoughts; 'Build the speaker walls so that the equivalent depth makes the width 4.5 m.' I assume It's included in the drawing? You mean the splayed walls make the width 4.5m? I'm not going to soffit mount... Just wondering if that's what you ment with the white rectangel? What depth of the slats did you have in mind?? Made some 60 cm slats for my old CR (sayers design). Maybe they could be used i some way?? (60*240) Thanks! //Jamzone

Another thing, if you have existing finished walls inside this square room do you plan to remove that? You have been here for a few years according to your signup date so you are aware of putting a three leaf in and what to expect from it if you do?

I know. Can't do anything with the existing construction... It's 'K-märkt', meaning protected as a building of significant cultural value! 8) //Jamzone

your last post to me is getting into details that you did not give or were not obvious from your post. Yes, the 4.5 m equivalent is designed into the speaker wall in the dimensions I gave. A room, its acoustic treatment and speakers are a system. What I showed for the slat side walls is as part of your entire room system, taking into account all the restrictions you have described. If you are building slat absorbers on an ad hoc basis, there is no value to systems design, as I did. Andre

Thanks again! Some more specific drawings;

AVare wrote:

your last post to me is getting into details that you did not give or were not obvious from your post. Yes, the 4.5 m equivalent is designed into the speaker wall in the dimensions I gave. A room, its acoustic treatment and speakers are a system. What I showed for the slat side walls is as part of your entire room system, taking into account all the restrictions you have described. If you are building slat absorbers on an ad hoc basis, there is no value to systems design, as I did. Andre

Hey Andre! Still haven't got the depth spec's of the described slat you recommended!! Best, Jamzone

Jamzone wrote:

Still haven't got the depth spec's of the described slat you recommended!!

We are missing something in communication. I think all the depth dimensions are in the second image I attached to first post. Which dimensions are missing or not clear? Andre

Allright... No separate cavity for slats? Think I got it... At what frequencies would the slats be effective according to your calculations? And the gaps in top and bottom would make the whole construction act like a big helmholtz resonator... Really low though! Maybe low enough to make it a 'no issue'... Sorry to ask, but how would the construction of the slats look like? Just cloth on the inside and insulation all the way back?? Best, Jamzone

Good. we are making progress!

Jamzone wrote:

No separate cavity for slats?

Correct.

Think I got it... At what frequencies would the slats be effective according to your calculations? And the gaps in top and bottom would make the whole construction act like a big helmholtz resonator... Really low though! Maybe low enough to make it a 'no issue'...

Your room has the problem of almost identical length and width AND little opportunity for absorption in the rear corners due to the window and wood stove. The large monitor baffles are necessary to change the width to be sufficiently different from the length, so large bass traps are not viable option below the monitors. Although they appear like Helmoltz resonators, the effective neck effect does not start till the % open area is less than around 15%. In this case the open area of the slats 20%. The effect is one of a low pass filter on the absorbers. High frequencies are reflected and diffused at the edges of the slats. With the sizes of the slats specified, the reflection will start as low as ~2 kHz with the 150 mm slats. the slat sizes are varied because each slat will have effective diffusion for about an octave. The slats are too shallow to provide any neck effect, as written in the paragraph above, The large openings at the top and bottom of the slats AND monitor wall provide for low end absorption.

how would the construction of the slats look like? Just cloth on the inside and insulation all the way back??

Exactly. Have a look at the slat absorber in Blue Bear as one example. An advantage in your room is that you have enough space that the Initial reflections from the side walls are delayed so much that you do not need to have absorption on the first reflection points with the geometry of the design. Keep the questions coming. The more you know, the better your room will be! Andre

Great, we're on the same page then... Just throwing in a question here, How difficult would it be to soffit-mount my 8050's in that wall?? Would gain some space... And what about adding insulation on the front wall (in the case not soffit mounted) to prevent reflection from wall?? One could get some weird comb-filtering issues otherwise... If you could post the Sketchup file I could show you what I mean. Best, Jamzone