Originally Posted By: PaulH
I've looked at that weblink of yours but don't understand what I'm seeing?

http://amroc.andymel.eu/?l=530&w=200&h=300&r60=0.6

Bottom line is - this room is being converted into an office - but I will use it for mixing & recording also. So pulling it off has to be because that's where my computer will be. Because I have mixing headphones also I do have the best of both worlds surely?


Paul,

The display that you see, once you type in your dimensions, are the acoustic 'modes' of the room, or in other words, the natural frequencies of the room itself. Another way to think about it is these are the standing waves that will happen in the room, unique to the dimensions of the room.

The issue you will experience is that your listening position is right in the middle of the most narrow dimension and nearly at the center of the longest dimension, where the standing waves will have a 'nodes' or points which will have very weak bass response.

The strength of acoustic cavity modes generally weakens with larger rooms and as the modes go higher in frequency.

To see nodes, look at the wikipedia article on room modes:
https://en.wikipedia.org/wiki/Room_modes

The nodes are those points where the amplitude is near zero - for the axial modes (those that look like the top picture in the article) you have a node. On the graph in the calculator website, the primary axial modes are the 32Hz - which is the primary axial mode from the long dimension (your's won't be this exactly because the high-shelf wall is not the full 530cm to the door. That primary axial mode will be somewhere between 32 Hz and 44 Hz (44 being the result if you consider the shelf not being there) and it will not be as strong. The 57 Hz mode is the floor to ceiling mode, if your ceiling is 300cm from the floor. Your listening height while sitting is probably going to be something like 125 cm or so, correct? Since you're listening height is not right at the middle, you are actually going to hear a bit of boost at 57 Hz or nearby in frequency.

But the modes between 80 and 90 Hz, the fact that there are two strong modes adjacent to each other, the first axial mode (1,0,0) of the 200 cm dimension and the 2nd axial mode (0,2,0) of the long dimension, that's going to really give you grief while monitoring and recording with a mic if you have the mic anywhere in that general vicinity of the room.

Something that you could possibly do with this room is use the 'high shelf' area for a bass trap. Many ways to go about this, but I'm thinking you might have a potential boon with this area. Several things you could try:

1. Hang a heavy curtain across the opening to the shelf area, while at the same time use open-face fiberglass batting (is this mineral-wool in the UK?) lightly stacked in the space. Use the type where the fiberglass fibers are not covered with paper or plastic.

The blanket will function as a sort of barrier that is moveable and the primarily axial modes of the long and floor-to ceiling dimensions will work against this barrier and even the oblique modes in the room will work against that curtain. The mineral wool will act as a general broad band absorber.

2. You can also do a bit more construction effort and make more of a door, hung at an angle and again using the whole space with mineral wool lightly stacked in there and get more absorption of the floor/ceiling and oblique modes. Have a google search look for home constructed bass traps for ideas.

However this is not going to fix the issue that I believe the physics to reveal as your main issue, the primary and secondary axial modes of the 200 cm dimension at 84 and roughly double that, are going to give you grief while monitoring and somewhat while recording if your sources have significant content that low.

To make it work for you, I will again suggest that you are going to have the most success learning to mix using a good set of headphones and reference recordings to compare against using those headphones.

The other issue with such small dimensions is that you will need to acoustically treat the walls that make up the small dimension otherwise comb-filtering will occur in your recordings. At least treat one wall with some acoustic wedge type material designed for acoustic treatment that is 3" deep at least.

http://www.acousticfields.com/comb-filtering-relate-room-acoustics/

Actually, you might want to spend some time on that site above - they have some decent videos that will help explain your challenges.

watch the video on that site called "Your room doesn't care what you want" to start.


-Scott

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