John Sayers' Recording Studio Design Forum Archive

Hello folks !
My name is Jimmy, and i'm in the process of buying an apartment near Paris, France. One room of that apartment is going to be my home-studio / geek-room, and i would like some advice on adequately using that space for rock music writing, recording (mostly guitar/bass) and mixing.

The thing is, that apartment is a duplex, and the room in question is on 4th (last) floor of the building. At 17.5 m² it's meant as a large bedroom, and has almost no shared wall with other flats (roof above, outside-facing walls on three sides, rest of the same apartment below). As i will not be making a lot of noise, i do not plan to improve isolation, just some acoustic treatment.

The room :
It is almost a rectangle, with a small cupboard-like space making it into a l. The main space is 5.20m long x 3.15m wide x 2.41m high, with the "cupboard" being 1.31m long x 0.9m deep (same height). Please see the map: It narrowly escapes having the length equal to twice the height. There is a large set of windows on one side, including two glass doors to a balcony. All external walls are made of structural concrete 23cm thick, 7 cm insulation (probably polystyrene) and drywall (surely 11mm thick). The ceiling is made of drywall and 20cm fibreglass insulation, the attic space above is unused. The floor is a concrete slab covered with (laminate) wood. The building dates from the 1990's, with rather good construction standards.

The set-up:
I have a pair of Genelec 8030A monitors, and the main question is where to put them ... Right now i have a corner desk, and the monitors are set up quite high (above computer screen), but i plan to buy/build a more suitable desk after moving into that apartment.
My thoughts so far : using the room lengthwise is probably roomier, e.g. to put a sofa at the back, and some space to rock around in the middle. But then the windows on one side is not too good for symmetry, and the "cupboard" too. I've done a quick ray-tracing simulation in that orientation, with listening position at 38% of the length, and about a meter between monitors and walls. Using the room in the other direction would mean having the window either right behind the monitor, or as a reflective back wall.
I will probably use the cupboard space for a small electronic workshop area. Or maybe as a real cupboard closed by doors or curtain, and have that workshop desk under the window.

The sound:
As i said, i will not make a lot of noise: i'm no drummer, and play the electric guitar and bass at very reasonable level. I may record a singer from time to time. For mixing i also use a conservative level, calibration at 0dBFS = 83dBC but average level way below that. The surroundings are pretty quiet, that was a major criterion in choosing that apartment.
I have not done any acoustic measurement for the moment, as i'm not yet the owner of that place. Just a quick hand-clapping test in the empty room revealed no nasty ringing. I may arrange something with the estate agent, to spend some time there with a speaker, a mic and a REW-equipped laptop ...
Here are some room modes simulations results (of the main rectangle): http://amroc.andymel.eu/?l=520&w=315&h=241&r60=0.6
There are some grouped resonance frequencies around 95-98Hz, 108-113Hz, 130-134Hz, and 163-166Hz. Above and below, the modes seem quite evenly distributed.

The plan:
Of course, a fair amount of bass-trapping would be required. Unfortunately, installing superchunks will be difficult, because radiators are in two corners, the door in the third one, and the "cupboard" space in the fourth. I could make triangular panels in top corners (above radiators and door), and maybe hangers at the top of the cupboard space.
I also plan for some absorption panels at first reflection points, including the ceiling and the windows. Those could benefit from heavy curtains as well.
I don't know if diffusion would be of any use, for example in the back wall if the room is used lengthwise. I've heard that it needs quite a lot of space to be useful.
I don't have a definite budget yet (heck, let's see what's left after buying that flat), but i'm willing to build DIY panels, and i'm not in a hurry. Let's say 500 to 1000€ as a first approximation.

The questions:
- Where should i put my desk and monitors for the best sound ?
- How much bass trapping is required in that room, and where is the best place to put it ?
- How much mid/high absorption is required, and where is the best place to put it ?
- Any other treatment idea ?

Thank you for reading this long post !

Hi,
I've finally found the opportunity to take some acoustic measurements in that room ! I'm still not the owner yet, but i will be next thursday and move there a week after.

I took REW measurements in three different positions, two of them using the room lengthwise.
I've used a Superlux ECM999 measurement microphone, and a Genelec 8030A monitor, both on mic stands. The room is empty, with all reflexive surfaces (wood floor, painted drywall or concrete walls & ceiling, big windows) so waterfalls and RT60 will not look good. That's a baseline, i'll take further measurements with furniture in a couple of weeks.

The .mdat file is available here.

The question i'm trying to answer now is where my desk should go, in order to put it in the proper place right away. It's a corner desk, but i'll be using without corner until i find (or build) a better-suited one. It puts the speakers quite high, but i can angle them adequately.
I guess i can eliminate one option right away : having the speakers fire towards the windows (positions E and F) creates a huge peak at 65Hz and a big dip at 108Hz. I suppose that those would be very hard to attenuate. At least symmetry is good ...

Symmetry is indeed the problem with the other two options, with that recessed area in the corner, and windows on the other side.
Positions A & B bring the listening position to the desirable 38% of the length, with quite a lot of lost space behind the desk. Then right speaker in position A is 1m from both the front and right wall, that's probably not good. Indeed, the bass response seems very uneven.

Putting the desk closer to the front wall would be the most practical, but again the bass response is all over the place and not symmetrical at all. The speaker in position D is right in the middle between the right wall and the back of the "cupboard", again that should not be good.

My plan so far is to set the room as in position C & D unless someone has a better idea, and take new measurements with furniture in, including a sofa opposite the desk that should help damp the reverb a bit. Then find out what kind of treatment is needed ...
I'm looking at things like that (mostly because i like the color) :
http://www.thomann.de/fr/eq_acoustics_p ... s_blue.htm
http://www.thomann.de/fr/eq_acoustics_s ... l_blue.htm
http://www.thomann.de/fr/eq_acoustics_c ... s_blue.htm
but i'll definitely also look at making DIY panels and bass traps. I don't know if some kind of diffusion panel would make sense or not in that room. If so, this design seems interesting :
https://www.gearslutz.com/board/6062490-post360.html

Any suggestions of best placement, and amount of treatment needed ? Thanks !

There is a large set of windows on one side, including two glass doors to a balcony.

that's going to be problematic! You will likely have to build treatment on stands, or that hangs from the ceiling, up against the glass, in some places.

external walls are made of structural concrete 23cm thick, 7 cm insulation (probably polystyrene) and drywall (surely 11mm thick).

... which creates a panel resonator tuned to somewhere between and 77 Hz. ...

I have a pair of Genelec 8030A monitors, and the main question is where to put them ...

There's only one feasible location for a good setup in that room: the monitors need to tight up against the wall on the right side of your diagrams, label "3.15m".

They need to be 88cm from the side walls (meaning they will be 139cm apart). That refers to the location of the acoustic axis of your speakers, not the sides of the cabinet. Genelec has a document on their website that shows the location of the acoustic axis for all of their speakers.

That is the only usable position in the room.

Yes, that speaker position might conflict with the way the main door opens into the room: If so, hire a carpenter to flip the sense of that door, so it opens the other way, where it will not cause a problem-. Simple.

is where my desk should go, in order to put it in the proper place right away. It's a corner desk,

:aah: Umm... No. Just NO! Forget that. Bad, bad, bad idea. And the speakers should never, ever, NEVER be on the desk. Never! Put them on stands behind the desk, up against the front wall. The stands must be massive (very, very heavy!) and of the correct height. "correct height" means that the acoustic axis of the speaker will be 1.2m above the floor, or maybe a little higher (not more than 1.3m for those speakers in that room)

Just get a simple flat desk that is just big enough to hold your console and/or DAW.

To position your desk: Set up your chair so that your head is 190cm from the front wall, and centered side to side. Sit on that chair, and move the desk until it is in a comfortable position for you to operate your gear.

Now set up a mic stand vertically so that the tip is 40cm behind your head, on the room center-line. Angle the speakers until they are both aiming at that point. Now move the speakers slightly away from the front wall, leaving a slight gap of about 10cm between the rear edge of the speaker and the wall, so you can put absorption panels in there. The speakers will touch the absorption panel. Adjust the angles of the speakers again, so they are both aiming at the top of the mic stand.

That is roughly the correct setup for that room. After you have the basic treatment in place, try moving yoru head back and forth to see if there is a better spot close by, and try moving the speakers a few cm left and right (while keeping symmetry!), re-aiming the angles each time, to see if there is a better spot. But the optimum position will be very close to that.

It puts the speakers quite high, but i can angle them adequately.

No you can't! Speakers cannot be much above your ear height, which is 120cm above the floor, and the speakers can never be angled down. Of you put the speakers up high, angled down, then you will get reflections off the desk, comb filtering, phasing, and other nasty artifacts.

Symmetry is indeed the problem with the other two options, with that recessed area in the corner, and windows on the other side.

Yes it is: that0s why you cannot orient the room to face that way. This is not an option.

I'm looking at things like that (mostly because i like the color) :

Color doesn't affect acoustics! First find treatment that does what you need in your room, by looking at the technical specifications, then look at the aesthetics...

don't know if some kind of diffusion panel would make sense or not in that room. If so, this design seems interesting :

I started reading that, but got as far as this comment: "there's no scientific approach behind this design": That's where I stopped and closed the page. Forget that. Only use treatment that behaves in a predictable manner, and whose specifications match what you need to do in your room.

Any suggestions of best placement, and amount of treatment needed ? Thanks !

You will need about 350 to 400 sabins of absorption to get that room under control. That will have to have to be chosen to hit the specific problems in your room (correct coefficients of each panel) and located at the correct positions.

- Stuart -

Thank you for your quick and very complete answer ! It helps me a lot !

Soundman2020 wrote:There's only one feasible location for a good setup in that room: the monitors need to tight up against the wall on the right side of your diagrams, label "3.15m". They need to be 88cm from the side walls (meaning they will be 139cm apart). [...] That is the only usable position in the room.

That's exactly the kind of advice i was hoping for, thanks a lot ! That's not quite the way i intended it, but as there's no alternative then the choice is simple. I'll devise the rest of the room setup from that.

The triangle formed by speakers and listening position is not equilateral, would that not be a problem ? Less so than bad modal resonance i suppose.

Soundman2020 wrote: :aah: Umm... No. Just NO! Forget that. Bad, bad, bad idea. And the speakers should never, ever, NEVER be on the desk. Never!

Yes, i agree. That's what i have right now, but the plan is to change it and have heavy stands (maybe built with bricks) and a simpler desk.

Soundman2020 wrote:Speakers cannot be much above your ear height, which is 120cm above the floor

I was concerned that 120cm height is exactly in the middle between floor and ceiling. Setting my chair a bit lower (it's OK i'm not a tall guy) gets my ears slightly away from that point. Once i get rid of the corner desk i'll set the speakers acoustic center at the same height.

Soundman2020 wrote:

There is a large set of windows on one side, including two glass doors to a balcony.

that's going to be problematic! You will likely have to build treatment on stands, or that hangs from the ceiling, up against the glass, in some places.

I was thinking of rigid-backed panels covering part of the windows, at specific reflexion points. I'll do some raytracing and use the "mirror technique". There is a little space between window frames to devise some support hardware.
Heavy curtains would probably not absorb enough sound, and letting some light in would be nice.

Soundman2020 wrote:

external walls are made of structural concrete 23cm thick, 7cm insulation (probably polystyrene) and drywall (surely 11mm thick).

... which creates a panel resonator tuned to somewhere between and 77 Hz. ...

Oooh, i did not think about that. I thought drywall was considered rigid enough to be a room boundary.

Soundman2020 wrote: Color doesn't affect acoustics! First find treatment that does what you need in your room, by looking at the technical specifications, then look at the aesthetics...

My point is, i know i'll need at least bass-trapping in all five top tri-corners, maybe in vertical edges as well (above radiators) and absorption at first reflexion points. But how much treatment is "350 to 400 sabins of absorption" ? (btw, if i understand correctly there are metric sabins and imperial sabins ?) It's difficult to find comprehensive specifications on acoustic panel manufacturer websites.

After the move i'll take new measurements in the position you recommend, and see which frequencies need attention first.

The triangle formed by speakers and listening position is not equilateral, would that not be a problem ?

Not a problem. What is important is that the distance from the left speaker to your left ear is the same as the distance form the right speaker to your right ear. That does not need to be the same as the distance between the speakers.

the "standard" triangle that you see in so many books,and all over the internet, is misleading, and even I'd go
so far as to say that it is plain wrong. The reason is simple: that would be fine if your ears are in your eyeballs! Since you want the speakers aimed at your EARS not your EYES, the apex of the triangle cannot be in the middle of your head! It has to be behind your head.

In fact, for a wide soundstage, it turns out that the speakers need to be aimed at bit outside of your ears, so you don't lose the stereo image as you move your head left to right while seated at the mix position.

The actual angle of the speakers isn't that important: 30° would be ideal, but in reality anyplace between about 25° and 40° will work. You could even go up to 45°, but that tends to stretch the soundstage a bit too much.

Less so than bad modal resonance i suppose.

the plan is to change it and have heavy stands (maybe built with bricks)

Excellent! That would work fine.

I was concerned that 120cm height is exactly in the middle between floor and ceiling.

Not if you hang a hard-backed, angled cloud over the desk... Which you will need anyway...

Also, this isn't mas big a deal as you'd think: Since you have to be on the center-line of the room to get symmetry, stereo image, soundstage, etc., that means your ears are automatically the same distance form the left and right walls... But it's unavoidable, and necessary. so you are always on the mid point for one axis: being there for two is not such a huge deal. Being there for all three is bad! But as long as your modal response is under control, things are acceptable.

Oooh, i did not think about that. I thought drywall was considered rigid enough to be a room boundary.

Yep! Provided that you have enough mass on it, and a deep enough air gap, with sufficient suitable insulation. But a single sheet of 11mm drywall isn't very massive, a 7cm air gap isn't deep at all, and polystyrene insulation has no acoustic uses at all!

The original post should have said "somewhere between 55 Hz and 77 Hz.", but somehow the "55" got lost... Sorry about that!

But how much treatment is "350 to 400 sabins of absorption" ?

That's the same as 350 to 400 square feet of open window. So just cut ten holes in your walls and the ceiling, each measuring about 6 feet by six feet...

One sabin is one square foot of perfect absorber. There is no such thing, of course, and you don't need it the same for all frequencies anyway, so you choose different absorbers for different purposes to keep it all smooth and balanced, such that the decay times are roughly the same for each frequency band (1/3 octave).

if i understand correctly there are metric sabins and imperial sabins ?

Right! Sorry, I should have mentioned that I was talking imperial there. Imperial sabin is one square foot of perfect absorber, metric sabin is one square meter of perfect absorber.

But there's no such thing as a "perfect absorber" anyway... (maybe a black hole?)

- Stuart -

Thanks again, i'm learning a lot !

Soundman2020 wrote:The actual angle of the speakers isn't that important: 30° would be ideal, but in reality anyplace between about 25° and 40° will work.

Soundman2020 wrote:Not if you hang a hard-backed, angled cloud over the desk... Which you will need anyway...

Oh, yeah, i should have thought of that too.

Soundman2020 wrote:But a single sheet of 11mm drywall isn't very massive, a 7cm air gap isn't deep at all, and polystyrene insulation has no acoustic uses at all!

I had these figures from the "energy diagnostic form" which is now mandatory in France when selling a flat or a house. Maybe the insulation is fiberglass, i'll know for sure when i'll drill holes in the walls ... Anyway i suppose that drywall is fixed with some kind of studs (wood or metal), and that there is no air gap, the insulation layer would take all the space.

So, if the walls do act as panel resonators, would it be bad, or would it be like a free bass-trap ?

(maybe a black hole?)

If possible, i'd like to avoid having such a thing in my new home ... that really sucks.
(at least, two of those colliding make the same kind of chirping sound as a REW measurement !)