Room modes

[Kaj]

Hi! I have two questions about room modes. I plan to build a studio from
scratch, and I´ve been reading a lot of good facts, but there are a
deviation or I might just not get it right. I read (understood) that it is the outer room that normaly is giving the boundry of the room mode.
As for a typical CR 6,73 X 4,95 X 3 metres (Source from BBC RD 1993/8), is this the inner room ratios or the outer room?

Second question; Is there any benefit to make the outer room similar to the inner room regard to a polygon shape as the most finnish product of the inner room drawings are designed to.

I´ve been thinking to build outer room in moulded concrete or blocks or Ytong (light weight thick kind´a concrete blocks), I will try to get the accoustic properties of Ytong, it has a good K value and the producer claim it to be good at reduce noise transmission.

Thanks in advance for any help and/or guidiance to learn more.

[AVare]

Not a straight, but honest answer. Use the walls that reflect more at the frequencies being analyzed.

No acousitc need to follow the same layout for the outer walls.

Andre

[lovecow]

Kaj,

As for a typical CR 6,73 X 4,95 X 3 metres (Source from BBC RD 1993/8), is this the inner room ratios or the outer room?

Are you talking "inner" and "outer" in terms of, respectively, "treatment" and "isolation shell"? If so, then the BBC dimensions would be the outer.

If you are talking about simply "room within a room," then the BBC dimensions would be the inner.

If you can be more specific about your construction, things might get clearer.

Second question; Is there any benefit to make the outer room similar to the inner room regard to a polygon shape as the most finnish product of the inner room drawings are designed to.

I´ve been thinking to build outer room in moulded concrete or blocks or Ytong (light weight thick kind´a concrete blocks), I will try to get the accoustic properties of Ytong, it has a good K value and the producer claim it to be good at reduce noise transmission.

And the inner room? If it is similar, then the shape will depend only on the amount of isolation you need. (This would be "room within a room" mentioned above.) If it is not similar ("treatment room" inside "isolation shell"), then the shape could affect the room acoustics as well. It will then depend on how much damping (absorption) you have between you and the outer shell.

Best regards,

Jeff D. Szymanski
Chief Acoustical Engineer
Auralex Acoustics, Inc.

[Kaj]

Thanks, Andre and Jeff, sorry for not letting my mind condens as clear wordings.
The issue are that I wonder if a inner room (a room inside the room) ref BBC, and Jeff you gave me the answer thanks for clear answer.
I asked because I read that LF are reflecting and make a standing wave when it meet a dence wall if walls are paralel, this might be an misunderstanding. In that case but this is what this forum are designed to help us "non pros" with, so please continue to put me back on track.
I will start to draw my initial embryo plan of a studio within some days, just unsure of what program to use. Powerpoint seem to be a no no area, please advice what program to use.

Thanks Kaj

[lovecow]

Kaj,

No worries. Some thoughts:

• With "room within a room" construction, you are going to have, for all intents and purposes, a rigid inner room. This (inner room) will be the room with the dimensions you'd like to use from the BBC.

• Non-parallel walls is something to consider carefully. John here can help you with that if you need it. The key thing is to get them parallel enough to minimize mid and high frequency problems. Low frequencies won't really care how non-parallel the walls are. Modes will still exist. That's why getting your thoughts up here would help others, particularly John, with any angles you are considering.

• I am afraid I have nothing to suggest for your room design program. If you'd like to play with a pretty good acoustical prediction program that also can be used as a pretty neat room designer, check out CARA: www.cara.de or www.rhintek.com in the US. (I use AutoCAD, but I doubt you're going to want to fork over several thousand $$ for something you'll use once. ) Perhaps others have thoughts???

Best regards,

Jeff D. Szymanski
Chief Acoustical Engineer
Auralex Acoustics, Inc.

[knightfly]

Most of our members, including John, use Smartdraw - you can get a free trial version (good for 30 days, I think) for free - after that, I think it's about $60 USD - here's their site info -

http://www.smartdraw.com/

For a lot of the simpler drawings I do, I just use the Paint program that comes with windows - if you're on a mac, sorry. I use CAD for more complex drawings, then convert to PDF to maintain some resolution... Steve

[Kaj]

Here are the draft of my CR to be. Dimensions of CR 6,73 X 4,95 X 3 metres. I have on my mind to have bass traps in all four corners and slat resonators from the front, on walls and ceiling to just behind listing positon. (have an idea to vary the frequency absorption with low mid at front and upwards and than downwards att mix position. Behind mix pos. diffussion, not sure of what type I will go for here, but think I will use a more HF absorbtion and Mid diffusion. Back with a Membrane absorber and a Screen of light fabrics ( might be strips or prtially screened, to ballance the HF.
The floor coated with carpet, maybe cork, hard wood under mixing console and chair. Front side of mixing pulpet coated with rockwool 30 mm and covered with fabrics, this will be attached to detachable doors for access of electronic gear.
Any obvious overlook by me regard layout or acoustic treatment ? I appreciate any advice.

[giles117]

Sounds decent. are your monitors ina 45 degree angle there????

I prefer 30 degrees, but everyone likes something different and according to research there is no Major notable difference.

There is a thread on it around here

2nd had trouble keeping up with you, but carpet the rear of your room with hardwood/laminate flooring in the front. If that is what you said, kudos.

Just my 2 pennies

[Kaj]

Thanks Bryan, Yeah! you got me right, but I might just ensure I am clear in exact where the hard wood (reflective surface on the floor goes) it is the circle under the chair by the mixing place in the plan, rest of the floor with carpet, not too soft, thinking about the coco matts? dont know if you call it the same over there. The 45 deg, are more a result of the bass trap. I could split the angles more and get 30 deg, I have no preferred solution.

Thanks.

[giles117]

Should be larger than that.

I'd take it from the front wall to the middle of the room