4th wall in my recording room

[Sven85]

Hi Guys,

I got the tip to post my question in this forum and I am happy to find a sub-forum that's called Studio Construction, because it seems the right place for my issue.

I have a basement recording room which is approx. 4,40 (L) x 4,55 (W) x 2,22 (H) with 3 concrete walls and 1 self-built dry construction wall out of pressed wood with fibreglass wool inside, approx. 15 cm thick.

I think the room dimensions of 4,55 x 4,4m are not very ideal in regard of room modes and I'm thinking now to rebuild the self-built wall / to move it.

My main question is now; would there be a difference between only moving the existing dry-construction wood wall or shall I remove it completely and build a new wall out of bricks, Ytong Stones or sand-lime bricks because they would be heavier and maybe better in regard of room modes? Because I'm not sure if my self-built wall works like a real limit for low frequencies or maybe the room is for low frequencies still with the old dimensions like 6 x 4,55 meters?

I have attached a small drawing of the room with my self-built wall (red/yellow).

Thank you for your help and advice!
Sven

[Soundman2020]

Hi Sven. Please read the forum rules for posting (click here). You seem to be missing something!

1 self-built dry construction wall out of pressed wood with fibreglass wool inside, approx. 15 cm thick.

What type of pressed wood did you use there, and how thick is it? There are different types, with different characteristics. For example, OSB, MDF, LDF, etc. Also, did you put panels of that wood on BOTH sides of the frame, or just one side?

approx. 4,40 (L) x 4,55 (W) x 2,22 (H)

Right. Not such a good ratio. The ratio is Room Ratio: 1 : 1.99 : 2.04, which means that the room is almost exactly square, and not only that, the height is almost exactly half of the length and width. Which means that ALL of the axial modes occur together at the same frequencies. In your case, multiples of about 78 Hz. The worst point is going to be between 76 and 79 Hz.... which just happens to be where kick drums typically have a lot of energy. There are also large modal gaps in the low end: there's only one mode between 40 Hz and 76 Hz, another large gap in axials between 79 and 112 Hz, then yet another large gap between 117 and 150. There are a few tangentials and obliques in there, but even those are all bunched up together

If you do an acoustic test of your room, these issues should be very evident. Here's how: How to calibrate and use REW to test and tune your room acoustics

would there be a difference between only moving the existing dry-construction wood wall or shall I remove it completely and build a new wall out of bricks, Ytong Stones or sand-lime bricks because they would be heavier and maybe better in regard of room modes?

Changing the construction materials won't change the modal distribution. It might change the intensities, but not the frequencies. The only way to change the frequencies, is to move the walls, so that the dimensions are different. For example, if you move that dividing wall in by 25cm, making the width 4.15m, then you would solve the problems in the width direction... but not in the length direction. To fix that, yu would need to make the room longer, or make the ceiling higher.

Changing the materials won't fix the modal problems: changing the dimensions will help. And so will acoustic treatment: If you put enough treatment of the correct type in the correct locations in the room, then that would help to get the modes under control.

But first test your room the way it is right now with REW, so you can see what your problems are, then use that to help you decide what to do about it.


- Stuart -

[Sven85]

Hello Stuart,

I have updated my location

EDIT, please note: the pictures below are in the wrong, exact opposite order to my post.

So first of all thank you for your reply, I really appreciate your help.

For a better understanding I have attached some pictures of the building of the wall. It's approx. 9cm thick and covered with press board and filled with fibre glass wool.

So regarding the room measurements:
I have also attached an picture of a room mode calculator in the web of the actual room measurements and also of the planned room measurements. In my case I would change the room from 4,40 x 4,55 to 4,30 x 4,55.

So if you say it doesn't matter so much the material of the wall, I could easily move the wall to other measurements and my room acoustics should be better. I also would place the door in the middle of the moved wall that I can place the other two mega traps/gobos also angled in the corner, that I have all 4 corners filled with them. Then I could place the drum in the middle of the room with it's new measurements 3,30 x 4,55 x 2,22m

Would you recommend this changes or would you do anything other or more?

I also noticed that you said it would be ok to reduce the measurement only of 25 cm. But I would go for more because then I can build my workstation in the room of the other side of the wall, because then I would have enough space for the desk and computer there etc.

And by the way, I don't have a room measurement mic and sound level meter. Anyway do you think it's a good idea to change the wall (to what ever room dimensions) without measuring anything or would you highly recommend buying this stuff and doing this? I'm not sure...

Thanks again for your help and best regards