small room treatment questions

[geo63]

Hi everybody!
This is my first post and this is also my first attempt at doing some acoustic treatment.
I have been reading this forum for a while now and I really think it is a great source of information!
I am planning to treat a bedroom in my house (3.67meters long * 2.99 meters wide*2.47 meters high) in order to do some mixing at home.
The room is in a quiet part of the house, where I do not disturb anyone (tested and approved!) and there is no neighborhood around, so it is not soundproof at all, and does not need to be.
I know the room is small, so I do not expect it to be perfect, but I still would like it to be decent.

Here is what the room looks like :

bureau vue du dessus.jpg

bureau vue de face.jpg

front wall.jpg

rear wall.jpg

As you can see the window is not centered, and the door is in a corner.

I didn't manage to upload my mdat rew file to show you my empty room measurements, so here is some REW screenshots of the empty room :

rt60 empty room.jpg

spectogram empty room.jpg

spl empty room.jpg

waterfall low end empty room.jpg

waterfall mid+high empty room.jpg

I'm planning to work on the rear wall of the room first.
I want to take advantage of the rear space next to the door, which is 60cm deep to do some bass trapping.
So I thought it would be a good idea to build some hangers in this space as a broadband bass trap.
I would also like to build a superchunk style bass trap in the space above the door.
Here is what it would look like :

hangers+door superchunk.jpg

The hangers would be made of 10mm "isorel mou", the french equivalent of homosote (slightly denser than homosote but in the same ballpark), and 45mm glasswool with a density of 12kg/m3 and an air flow resistivity of 4kPa.s/m². There would be 5 hangers of 75cm deep by 240cm high, 1 hanger of 68 cm deep, 1 hanger of 46cm deep and 1 hanger of 37cm deep. The walls around the hangers would also be covered by 45mm of the same glasswool.
The superchunk would be made of glasswool with a density of 12kg/m3 and an air flow resistivity of 4kPa.s/m².

My questions are :
Should I start treating this room with the rear wall?
Does this design make sense?
I know that the orientation of the hangers is meant to change in the middle of the width of the room, but the door won't allow me to do so. Do you think it would still be effective like that?
Is there some more effective way to treat this space?
Do you think this specific glasswool is a good choice for both the hangers and the superchunk?
Should I cover the superchunk above the door with a thin plastic film to avoid killing the high-end frequencies from the start or should I wait to do some measurements and adjust from there?

Thanks in advance, regards from France,
Geoffroy

[Soundman2020]

Hi Geoffroy, and Welcome to the forum!

I am planning to treat a bedroom in my house (3.67meters long * 2.99 meters wide*2.47 meters high) in order to do some mixing at home.

That's a small room, but usable. It won't be fantastic as a mixing room, because of the size, but it can still be reasonably good.

As you can see the window is not centered, and the door is in a corner.

The off-center window is not really a problem, and the location of the door is unfortunate, you you do still have space for bass trapping.

I didn't manage to upload my mdat rew file to show you my empty room measurements, so here is some REW screenshots of the empty room :

Upload it to a file-sharing service such as DropBox, and post the link here. Then we can download it to analyze it. The scale you chose for your graphs doesn't reveal all of the the information we need to see.

However, it DOES show that the room has modal issues, very long decay times, and several other issues.

I'm planning to work on the rear wall of the room first.
I want to take advantage of the rear space next to the door, which is 60cm deep to do some bass trapping.
So I thought it would be a good idea to build some hangers in this space as a broadband bass trap.

Good plan! Just don't angle the hangers so steeply: try an angle of around 30° - 40°.

with a density of 12kg/m3 and an air flow resistivity of 4kPa.s/m².

That should be OK.

Should I start treating this room with the rear wall?

Does this design make sense?

I know that the orientation of the hangers is meant to change in the middle of the width of the room, but the door won't allow me to do so. Do you think it would still be effective like that?

That's fine. It will work.

Do you think this specific glasswool is a good choice for both the hangers and the superchunk?

I did check it quickly with an acosutic calculator, and it is OK. It should give you decent absorption down to low frequencies.

Should I cover the superchunk above the door with a thin plastic film to avoid killing the high-end frequencies from the start or should I wait to do some measurements and adjust from there?

I always recommend doing once step at a time, and leaving options open. I'd suggest leaving off the plastic at this early stage. Only add it later if it is really needed, and is the best solution.

- Stuart -

[DanDan]

I recommend that you consider simple light cheap fibre in a frame for the whole back wall.
Take a look at boggy's build photos on FaceBook or Instagram. for framing inspiration. https://www.instagram.com/bogic.petrovic/?hl=en
Also there is a nice looking deep BW treatment with vertical laths at https://www.irishacoustics.com
I wouldn't worry about containing fibres in a wall treatment, but I would add polyester batting or double fabric on the overhead cloud.

DD

[geo63]

Hi Stuart!
Thanks a lot for your answer, it is going to help a lot, I read so much great stuff from you, I really appreciate it!

Here is a link to download my REW empty room measurements :

https://www.dropbox.com/s/d247mz2qe9sg6 ... .mdat?dl=0

Here is also a new screenshot of the hangers with an angle of 40° :

hangers v2.jpg

In this version, there are 8 hangers of 60cm and 1 hanger of 52cm. The spaces between each hangers are 4cm.

I will update this post with some pictures and REW measurements as soon as I build it.

Thanks again.

Geoffroy

[geo63]

Hi Dan!

Thanks a lot for your input.
This are great links, very inspiring indeed!

[nona5000]

Howdy Dan!

You rock for your info.

This are extraordinary connections, extremely motivating without a doubt!

[geo63]

Hi everybody!
I build the hangers and the superchunk above the door.
Unfortunately I had a problem with the hangers. Everything was ok when I put the bare boards of "isorel mou" in place to see if they fit, but as soon as I added the glasswool, I noticed that it was a lot thicker than the 45mm it was supposed to be. The result is that the hangers are all touching each others, they are not pushing against each other but still, they are touching, as you can see in the pictures below :

bare hangers.jpg

hangers.jpg

door superchunk.jpg

Here are the REW measurements, first with hangers only, then with the superchunk and the hangers :

https://www.dropbox.com/s/zvsu6hmorfr1v ... .mdat?dl=0

https://www.dropbox.com/s/odlli997148lg ... .mdat?dl=0

My questions are :
Considering my REW measurements, do you feel the hangers and the superchunk work as they should? I see a good improvement on the graphs, but I am a beginner at this so I don't really know what to expect at this stage.
Should I try to cut the glasswool of the hangers to keep a space between the hangers (not sure I can do this in a clean way), or should I let it as it is?
Thank you.

Geoffroy

[Soundman2020]

Well that cleaned up the low end rather nicely! If anyone is in doubt about hangers being effective, here's clear evidence that yes, they are.

Take a look:


FREQUENCY RESPONSE (low end: 15 Hz to 500 Hz). Green curve is "Before" (empty room), red curve is "after" (with hangers and superchunks)):

GEO63--REW--FR--15-500--1..24--before-after-hangers.png

WATERFALL PLOT (low end: 15 Hz to 500 Hz). Green is "Before" (empty room), red is "after" (with hangers and superchunks)):

GEO63--REW--WF--15-500--before-after-hangers.png

SPECTROGRAMS: Two graphs, first one is "before", second one is "after":

GEO63--REW--SP--15-500--baseline.png

GEO63--REW--SP--15-500--hangers.png

And finally, more spectrograms, but this time full spectrum, from 15 Hz to 22kHz:

BEFORE:

GEO63--REW--SP--15-20k--baseline.png

AFTER:

GEO63--REW--SP--15-20k--hangers.png

I think that's pretty conclusive. The hangers are doing fine, and so is the superchunk. Good effect on the axial modes. (and of course, on the rest of the spectrum too).


Regarding your question, you could try taking out one of the the hangers and spacing the rest a little further apart, but I'm not sure it is worth it. They seem to be doing just fine the way they are. If you really wanted to do that, it would be great so we can get to see some real-world data about hangers touching or not touching, and how much change you get from taking out 11% of your hangers. But that's a lot of work just to satisfy our curiosity....

- Stuart -

[geo63]

Hi Stuart!
Thanks a lot for your answer.
I am in fact curious too and I would like to learn as much as possible in the process of treating my room. So I will take out one hanger and space the others so they won’t touch each others, as soon as I will have the time to do so. I will then post the results here.

Geoffroy

[jgoldkamp]

Hi, What program did you use to draw your studio with?

[Soundman2020]

Hi, What program did you use to draw your studio with?

Looks like SketchUp to me...

- Stuart -

[geo63]

Hi!
I have been really busy lately so I stopped working on the room, fortunately I can resume now.
Finally, I won't modify the back wall hangers as I said I would, because they work fine as is, and I would like to go forward now.
Next, I thought I would treat the ceiling, by fully filling it with 20cm of glasswool with a density of 17kg/m3 and an air flow resistivity of 7kPa.s/m².
I also plan to make some measurements after to see if I am not deadening the room too much, in which case I would consider installing some strips of plastic film.

My questions are :
-Am I right to consider focusing on the ceiling at this stage?
-Does this kind of treatment (glasswool type and depth) would be efficient in my case?

Thank you!
Geoffroy

[DanDan]

Impressive decay reductions at 50 and 90 Hz by the hangers only. I am glad to see this, as I have recently seen a massive disappointment where a guy treated his Front Wall with shallow 'standers' recommended by JB.
Clouds are very welcome. I recently prescribed a 'cinema' type suspended ceiling of absorbent only tiles, back by nearly two feet of light cheap fibre.
People often use thin clouds to treat 'first reflections'. What about the vertical modes? In a typical domestic room we sit at half height, disastrous.
So go for as much cloud as possible. If you are concerned about being too dead, add lots of laths.Go for a hard angled cloud, or a mixture.
DD

[geo63]

Thank you for your advices Dan!