Any Room Mode Xperts out there

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Matheon

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i'm wondering about a room i have.. its 19' x 14' x 10' i'm not sure if those measurements are exact.. but my question is..

near the bottom wall.. well.. snuggled up right next to the wall... there is a 2' x 2' square supporting pillar. (a pole with gypsum around it covering some wires)

would something like this have a terrible effect on my room modes. i'm not sure how to calculate for this.

anyone advise?
 
would something like this have a terrible effect on my room modes. i'm not sure how to calculate for this.
No. Room modes are resonances caused by fundamental frequencies with wavelengths equal to the 3 dimensions of the room. This is because most rooms have parallel surfaces with the same dimensions. These are low frequency wavelengths, which will simply diffract around this column enclosure :D It may cause odd reflections and diffuse wavelengths which equal its width or smaller somewhat, but I bet NO ONE would hear it. Where is it in relationship to your engineering position? If it DOES produce some odd reflection, you could wrap it with rigid fiberglass(and fabric) and make it disappear :p

BTW, there are MANY MODAL peaks and nulls which contribute to the acoustics of a room. The fundamental resonance between two parallel sufaces such as walls, or floors and ceilings occurs when a wavelength equals the distance betwen these surfaces. A similar resonace occurs at 1/2 and 1/4, 1/3 etc etc wavelength of this frequency which are the modes of that dimension.
fitZ
 
yeah, thanks for the reply.

its nowhere near my engineering position as i'm building a smaller room adjacent for that. just in a live room.. but i'm covering all the bases making sure i can get the best live room possible.. as i get to build it from scratch i may as well do it right :)

i know all the very very basics of room mode mechanics.. i can do the math on a rectangular room.. i wasn't sure whether when adding a column of this sort i needed to calculate modes from the walls of the column to all the walls of the room along with the other walls in the room.. if that makes sense..

like a 22' room with a 2' column in the middle cutting it in half would leave two 10' apart walls.. giving 2 additional axial modes at 56.5, 113 etc... causing spikes in those frequency ranges.

however
i think i get what you're saying.. but let me make sure.. because of the small size of the column. it won't have a noticeable effect on any low frequency waves in the room because due to the size of the waves they'll just wrap around it rather than bounce back and forth on it.. this makes sense.. i don't know the math but it sounds correct to me that a 2' column won't have a huge effect on a 10' wavelength.

sorry to ramble on like this. its just good to hear something positive about this dreaded column in my live room.. my friends are saying "that's gonna completely ruin it" and i've been worried :D

and thanks again
 
. my friends are saying "that's gonna completely ruin it" and i've been worried
Hardly. EVERY object in a room INFLUENCES what a mic or your ears hear. Whether or not you could tell the difference depends on many factors. However, your question was regarding this influence of the column on the "modes", which is low frequency. IF, you had a mic positioned adjacent to the column in such a way as it would pick up short path "comb filter" effects, you might hear it on your monitors, which is the whole point of having a reflection free zone and a TDG(time delay gap) in the control room engineering position, that is LONGER than in the STUDIO. Masking of comb filtering effects by control room early reflections is why most HR enthusiasts can not hear them while monitoring. This is only posible though, when you have a seperate control room with a TDG greater than that of the studio. It is this TDG in the studio that you need to hear in the control room to determine its effect on the recording, good or bad. At least from my understanding.

As to ruining the acoustics in your room, hardly. If anything, it might break up specular reflection off the entire wall, although it would be frequency dependent, and very small if any noticeable diffusion at all. Actually, large geometrical protrudences like this are INTENTIONALLY built in LARGE pro studios to diffuse large wall/ceiling specular reflections, but still, they are only as good as the wavelength/size relationship. Other types of diffuser designs such as QUADRATIC RESIDUE SEQUENCE or prime number devices, function by RANDOM time shift of reflections by using wells of varying depths and widths, which is exactly what the column would do, but at what frequency who knows. A reflection off the column face may introduce a phase shift of some kind at some frequency, but thats diffusion for you.

If anything, you could incorporate this column as a series of wells that just might help LOW FREQUENCY diffusion if the room were large enough and the wall long enough. It would have to be included in the well depth and width calculations though, to maximize the randomness of the diffusion effect. Of course, there is a school of thought that says ....simply using a random pattern of geometrical offsets in depth and width may acheive a diffusion of sorts better than a specular reflection off a long wall. And THEN, there is the school of thought that says FORGET the geometrical device concept.. A good start at diffusion can be had by simply use PATCHWORK pattern of small absorption panels around the room, like a checkerboard. And then there is a school of thought that says a diffuse sound field in SMALL rooms can NOT exist anyway, as RT-60 decay rates of differnt frequency bands vary significantly. Thats why ABSORPTION is your friend in small rooms.

There is lots of information on these subjects here. Much more than a little post by me could give anyway. Hahahahaha!

http://forum.studiotips.com/index.php
Well, hope this helps a bit more. My disclaimer is in full force here though...ie...I'm NO expert. :D
fitZ :)
 
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