Choosing between two rooms for acoustic

Hello everybody! I'm new here and I'm very pleased to find so much interesting things about acoustic there! I spent a lot of time in reading the forum and lots of websites about acoustics. I have now a little idea of what I need to do so as to avoid most of the acoustic problems in the room, as far as possible for a small room. I just expect to have a better acoustic so as to able to make correct mixes. So, I will try to be as concise and as precise as possible for the explanations: I’m living in the family house and I’m using my bedroom as a home studio for many years now. Before showing the rooms’ layouts, I have to precise many points: -I would like to build all myself (no commercial acoustic equipments because it is too expensive) -I have a small budget from 200 to 300 Euros ($250 to $375) -I use to listen to the music and to mix around 60dB to 90dB max. -There is no real problem of neighbors (they are my brothers and they are usually away) -I use 2 pairs of monitors: one pair of Tannoy Reveal passive monitor and one pair of Event TR8 active monitors. - I can't drill any holes in the wall, can't add a door or anything ! I just will be allowed to make some little holes on the ceiling for ceiling bass trap eventually. All the absorber will be mobile. If I forgot any important points to know for you to reply, don’t hesitate to tell me Below are presented 2 different rooms : my current bedroom and another one which would be better IMO for acoustic because of the symmetry of the walls and its shape. In any case both have inconvenient and I need your expert advice for choosing between both! As you'll see the pictures are made with "paint" and not with sketchup... I tried this sketechup software... and after trying drawing one room it made me mad !! I'm sorry but I really can't stand this software, I prefer to use solidworks but I don't have it anymore on my pc ! thanks for your comprehension and sorry for the awful colors .. :lol: The scale is respected on all view, as the thickness of the walls and the room behind walls. If nothing is specified, it means that this is outside. The ceiling is a floating cieiling. Now, let’s have a look to the rooms: • Here is an old picture to show you the disposition of the monitors and the different racks I have (but there are lots of new stuff since the picture had been taken 4 years ago :D ) : • Here is the room as I believe it would give the best acoustic results : the height of the room is 2.5 meters ! The main problem of this room is the hollow low frequencies, which seems normal for a small room. There is also another problem of strong flutter echo, even with all the furniture, bed, desk, etc, in the room. There is no good position possible so as to have walls’ symmetry around speakers. Finally, at the mix position, one side is a small wall, other side is a window, which would not be the best for side reflections (maybe an heavy curtain on the window could damp the excessive reflexions?) • Here is the second room (we will call it room 2). This layout represent how it could be organized for good acoustic : the height of the room is 2.5 meters ! Here is a little picture of the unfinished drawing of the room with "unloved" sketchup lol : The advantage of this room is to have walls’ symmetry around speakers. But as you can see there are the same problem than in the first room : the rooms’ rear is not symmetric because of the little hall and the cupboard, and at mix position one side is a wall and the other is a window too! The main question for the moment is: which room between room 1 and room 2 should I choose? I hope to have explained the problem as clearly as possible :) Thanks a lot for your advice :D

The second. Might wanna loose the "curtain" and replace it for a heavy door. That'll not only isolate better, it'll also keep your room more symmetrical.

Hi Ro ! thanks for your reply ! yes, I thought to make a kind of mobile wall, with a heavy wood plate, but I wondered if it would act as a wall, or if it would act as a kind of Helmholtz absorber. I forgot to tell something very important in my first post : I can't make holes or anything on the wall, I can make small holes on the ceiling if I want, but that's all. So, I will not be allowed to add a door ! :( So, now let's have a look for the second room. I'll post something soon :)

In that case a door on wheel might work :) And no, it's not gonna act as a helm.res. unless you drill holes or whatever and have a cavity in the door. Make it fitt tightly to preserve as much isolation as possible.

Okay ! I feared that it act such an absorber :) Now that I know what room to choose, I have questions about monitors placement : because of the small spaces between the desk, the bass traps and the wall, does it matter if the monitors are very close to the bass trap in the corners ? I thought to build bass trap with 100mm insulation and 100mm air gap between insulation and wall. If the monitors are placed at 50mm from the bass trap, will it make reflections problems in low frequencies ? thanks

Don't worry about putting it "too close" to the woolpanels. Your room is tiny, and you need the space. You'll ALWAYS have low frq reflections. Might wanna consider a full corner absorber, there's another nickname for that. Just check out this forum ;)

Yes I checked about superchunk and different kind of bass trap in corner. I also wondered to mount the monitors in soffit, but I don't know for the moment. This solution would help to save space, but it is something heavier and more expensive to build than just to put the monitors on support.

I'm just wondering why you have your broadband absorbers on the side walls (in room 2) angled towards the speakers, instead of away from them. Is that an error, or is there a good reason to do it that way?

Hi Soundman2020 ! Yes sorry it is an error. This is the reason why I'm here on this forum, because I don't know a lots about acoustic, so, thank you for focusing on that kind of error ! In any case all the bass trap and other panels will be mobile because I can't fix it directly to the wall, I'm not allowed to make holes in the walls, so it will be possible to move them as wanted. About the space problem around monitor, I was wondering : why not building a kind of corner bass trap with a hole for placing the monitors inside ? it would be such a kind of soffit but without the bezel , just insulation all around the speaker. What do you think about that ? About the mix position : one side is a wall and the other side is the window. I fear it will makes side reflection problem.. what do you think about that ? thanks for the advice :)

Phazinhead wrote:

About the mix position : one side is a wall and the other side is the window. I fear it will makes side reflection problem.. what do you think about that ?

Put 2 of your panels on stands, so that you can move them to the exact first-reflection point as needed. Both sides will need an absorber to create your Reflection-Free Zone. Also, put an absorber on the ceiling first-reflection point. See this article for more info.

Thank you Jwl ! yes maybe mobile panels with one insulation panel in a wood frame on stands, it was the former solution I thought about for all the panel in the room !! I'm stupid to haven't thought about this solution again :lol: 1) after reading more on realtraps.com : is it better to have medium size bass trap on walls with many small traps at 45° between walls and ceiling, or to have only big wall bass trap going from the floor to the ceiling ? 2) About the ceiling panel,: 2 panels of 60cm*135cm on top of the desk (mixing area) would be sufficient ? thanks!

Phazinhead wrote:

1) after reading more on realtraps.com : is it better to have medium size bass trap on walls with many small traps at 45° between walls and ceiling, or to have only big wall bass trap going from the floor to the ceiling ?

Generally speaking, bass trapping using broadband absorbers is as much about coverage area as it is about individual trap performance. If you have a given material, I'd spread it out in as many corners of the room as possible, making sure each trap is 4" (100mm) thick or more. I think you'd get better results by using 1 - 2'x4' panel in each corner than by putting all of your traps in one or two corners.

Phazinhead wrote:

2) About the ceiling panel,: 2 panels of 60cm*135cm on top of the desk (mixing area) would be sufficient ?

You want to make sure the first-reflection points, both on the side walls and the ceiling, are covered with absorption. These panels don't have to be as thick (50mm will do).

Generally speaking, bass trapping using broadband absorbers is as much about coverage area as it is about individual trap performance. If you have a given material, I'd spread it out in as many corners of the room as possible, making sure each trap is 4" (100mm) thick or more. I think you'd get better results by using 1 - 2'x4' panel in each corner than by putting all of your traps in one or two corners.

okay, but the only thickness I've found in a shop close to my house is the equivalent of 703 fiberglass panel (50kg/m3) of 75mm of thickness. I planned to make bass trap with those panel and to let a space of 100 to 150 mm between the fiberglass panel and the wall, so as to have as much absorption as possible. I planned also to put corner bass trap in 4 corners made by the walls, but if I understand right what you say, should I also put them in the corner made by the walls and the ceiling ?

You want to make sure the first-reflection points, both on the side walls and the ceiling, are covered with absorption. These panels don't have to be as thick (50mm will do).

that should be okay so with 75mm.

Hi everybody ! After reading this : http://forum.studiotips.com/viewtopic.php?f=8&t=536 I thought to make different type of bass trap based on what I've seen there. Because of my limited budget I'll not build superchunk bas trap because it is to much fiberglass consumming, and the corner shape is complicated to build, so I'll make rectangular panel placed at 45° in each corner. So, if I understood right what is explained in the link above, a good way to have good bass absorbtion is to use 2 panels of insulations together. Could you tell me which one of the panels presented below in the drawings would give the best absorbtion, placed at 45° in each corner ? here is a first design, very simple, using only 2 insulation panels, placed in a wood frame and fabric all around. This drawing represents a cut view of bass trap viewed on top.

here a second design, that uses the principle of the membrane, made with a carpet attached to the top of the wood frame, so that to let it to vibrate freely, such as presented on Sound On Sound there :

then, a third design with wood slat on the front so as to work as a broadband absorber such as described here : http://www.johnlsayers.com/HR/index1.htm

Lots of doors to choice from, quizmaster. hmm, I'll take door nr 6. I think. Hope I made the right choice. The cloth can go straight on to the wool (unlike membranes), the "carpet" membrane... who gave you *that* idea? loose it. Leaving an airspace behind the wool is a good option. take door nr. 8 ;)

Why don't you check them stickies in this forum, there's great examples of DIY absorbing panels

Lots of doors to choice from, quizmaster. hmm, I'll take door nr 6. I think. Hope I made the right choice.

door ? ... its not doors, just the corner bass trap, but I explained before that they will be placed at 45° in corners, because triangular bass trap need too much insulation and moreover, the study of different type of corner bass trap show that double panel bass trap are as efficient as full corner bass trap (superchunk). I thought to make a mix between the different existing techniques for bass traping, using simple insulation panel, insulation panel with a hard front panel (resonator), or insulation with a flexible membrane. My problem was to determine which of the different solutions would work at best as a corner bass trap, such as the ones you can see in the first drawing of the room at the begening of the topic.

The cloth can go straight on to the wool (unlike membranes)

okay ! the "carpet" membrane... who gave you *that* idea? loose it.

the idea comes from the British Sound on Sound magazine.

Leaving an airspace behind the wool is a good option. :)

Is it better to have the bass trap wood frame joining with the wall, so as to make a kind of "closed" box ? in other words, to have no space between the panel edges and the wall A last question. Which one is the best solution : - have long bass trap going from the floor to the ceiling on walls + panels under ceiling - have medium size bass trap at the middle of walls and small bass trap at 45° between wall and ceiling ? such as here : http://www.runet.edu/~shelm/acoustics/bass-traps.html thanks for the advice :D

Phazinhead wrote:

Lots of doors to choice from, quizmaster. hmm, I'll take door nr 6. I think. Hope I made the right choice.

door ? ... its not doors

It was a joke, my kinda humor :)

okay ! the "carpet" membrane... who gave you *that* idea? loose it.

the idea comes from the British Sound on Sound magazine.

You sure? I've got a subscription on SOS and can't always agree on their methods. There's much more good advise on this board (unless it's mine :P)

Is it better to have the bass trap wood frame joining with the wall, so as to make a kind of "closed" box ? in other words, to have no space between the panel edges and the wall

Not if it's not a membrane/panel trap.

A last question. Which one is the best solution : 1 - have long bass trap going from the floor to the ceiling on walls + panels under ceiling 2 - have medium size bass trap at the middle of walls and small bass trap at 45° between wall and ceiling ? such as here : http://www.runet.edu/~shelm/acoustics/bass-traps.html

Bass traps need volume, so bigger is better. The corners are best to place them since bass will get "stucked" there. Doesn't matter WHICH corner. Wall/ceiling will probably take less precious space. But then again, most corners aren't usable anyway so stuff'm with wool as much as you can. That's why full volume traps (aka suppachunk) work so excellent. As per Ethan (yes, I'm a fan :) ), "you can't have enough basstrapps".

Bass traps need volume, so bigger is better. The corners are best to place them since bass will get "stucked" there. Doesn't matter WHICH corner. Wall/ceiling will probably take less precious space. But then again, most corners aren't usable anyway so stuff'm with wool as much as you can. That's why full volume traps (aka suppachunk) work so excellent.

When you say it doesen't matter which corner, you mean it is the same effect if bass traps are placed in the 4 corners wall/ wall, or the corners wall/ ceiling, or wall/floor ? .. I'm not shure to have understood. Another question about corner bass trap : if the bass trap doesn't have a plywood face, how much does it lower its absorbtion? My problem is that the monitors will be very very close to those corner bass trap and I want to lower as much as possible any reflexions from hard surface... so I wondered if corner bass trap such as the number 1 or 2 would not be the best solution...

Another question about corner bass trap : if the bass trap doesn't have a plywood face, how much does it lower its absorbtion?

Why would you want to have a plywood face on a bass trap? Wouldn't that make it into a panel resonator, instead of a bass trap?

Phazinhead wrote:

When you say it doesen't matter which corner, you mean it is the same effect if bass traps are placed in the 4 corners wall/ wall, or the corners wall/ ceiling, or wall/floor ? .. I'm not shure to have understood.

Theoratically, yes it's all the same. Sound is 3D so it isn't picky on which corner it will be present. Every corner matters. So if you're low on floorspace, those ceiling/wall corners are prolly your number one to use. It's better to stuff ALL corners as much as possible.

Another question about corner bass trap : if the bass trap doesn't have a plywood face, how much does it lower its absorbtion?

We're talking different kind of 'traps' here. There's (pure) absorbers (no front, just wool) and resonators (as soundman replied). The wood, in front of and not touching the wool, acts as the resonator in question. In that case, yes, you need a closed trap. I'd suggest to check Ethan's site(s) for such devices. As I said earlier, deeper trap (read: more wool volume) means more low absorption. A panel resonator will reflect much more mid/high back in the room. They do, however, work great as low frq absorber without having to use lots of wool. But its another type of trap which is mostly used on walls, not corners (but it's not impossible to place'm in corners ofcourse). Get to know the differences.

My problem is that the monitors will be very very close to those corner bass trap and I want to lower as much as possible any reflexions from hard surface... so I wondered if corner bass trap such as the number 1 or 2 would not be the best solution...

I'd go with supperchunks anyway.... it's not THAT money consuming. Check out http://www.realtraps.com/, it's crammed with good info on acoustics!

I agree with Ro: I'd go for #6. Or maybe #4 without the carpet. I'm not sure what the carpet in #3 and #4 is for: It doesn't seem like it would have much effect to me (unless it was really, really, really thick, maybe? But in that case a third panel of 703 would be better and cheaper, I reckon). A question for Ro: In this case, if he were to take #4, dump the carpet at the back, and hang a couple of layers of MLV in the middle gap (between the two panels of 703), would that have any useful effect? Or would it just waste money? I seem to recall seeing something similar somewhere (not here!), arguing that the MLV would add more damping, but I can't find the link any more.

mmmm .. yes you're right, I make a confusion between both :lol: In fact I'm talking about that, the first schematic, "corner absorber" : http://www.johnlsayers.com/HR/index1.htm In fact, because of many technical constraint, I would prefer to use flat panels in the corner, based on the principle showed on the link above. If you don't see how I want to achieve it, look at this :