Posted by Chaba (A) on January 04, 2009 at 14:13:32

Hi,

I need your help in the following:

I have a dedicated listening-room for my stereo system. Unfortunately I have a square room (16.4x16,31x10.5 feet), with little treatments like some absorbers on the side walls at the first reflection points. My main problem is the bass and I must also isolate the room more effectively from the two conjunction rooms of the house. The listening room has brick walls, the two outer walls are around 1.25 feet thick and the two inner walls are around 0.4, one window, two doors.
My plan is to change dimension of the room first and later treat the room with acoustical panels traps etc. I may also quit one of the doors.
I found this web page for room modes calculator:
http://www.bobgolds.com/Mode/RoomModes.htm
It suggests that by changing the room dimension to 15.98x14.96x9.94, I can get a better room.
I'll try to keep the room as large as possible.
I thought to apply gypsum boards and mineral wool to get the desired dimension.
I would put the gypsum boards along the side walls, the ceiling and the front wall.

Could you please comment if the new dimensions and the gypsum boards are proper to get a better bass response?
How critical is the 2500 sq. feet volume as a minimum (I red it at realtraps.com) ?
Shall I treat the rear wall too?

Any comment or suggestion is welcomed, thanks!

Csaba

• http://www.bobgolds.com/Mode/RoomModes.htm   (Open in New Window)

• RE: Squarish room - Ethan Winer 11:35:17 01/05/09 (1)
  In Reply to: RE: Squarish room posted by Chaba on January 04, 2009 at 14:13:32

  > It suggests that by changing the room dimension to 15.98x14.96x9.94, I can get a better room. <
  
  I wouldn't bother. Having a room be larger often trumps having a "better" ratio.
  
  And Yes, the rear wall is important to treat, especially if it's not very far behind you. Of course, you'll benefit from corner bass traps too.
  
  --Ethan
  
  

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  • RE: Squarish room - Chaba 14:28:32 01/05/09 (0)
    In Reply to: RE: Squarish room posted by Ethan Winer on January 05, 2009 at 11:35:17

    Thanks Eathen,
    If I got your point right, my listening room can work with its current dimensions if I use proper room acoustic treatments. So there is no sense to spend extra money on changing the room dimensions I would be better off to fine tune the room after furnishing it. In my case where would you put the speakers? Along one of the thick walls or rather in front of one of the thinner ones? The thick walls are pendendicular to each other (the thinner ones too)so room symmetry cannot be assured.
    If I wish to place bookshelves in the room, where should I put them? Along the rear walls behind the listening postion or along the side walls?
    
    
    Csaba
    
    
    

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• RE: Squarish room - KlausR. 02:34:51 01/05/09 (3)
  In Reply to: RE: Squarish room posted by Chaba on January 04, 2009 at 14:13:32

  From listening experiments it appears that square rooms are not necessarily worse than rectangular rooms, only different:
  
  Fazenda et al., “Perception of modal distribution metrics in critical listening spaces - Dependence on room aspect ratios”, J. of Audio Eng. Soc. 2005, p.1128
  
  All formulas for room mode frequencies and "optimum room dimension ratios" are based on the assumption that the room is 1. empty (no furniture) and has 2. perfectly reflecting walls with no openings. The measured mode frequencies can be considerably different from the frequencies as calculated by the formulas. The formulas for "optimum dimension ratios" have one basic flaw: in order to experience the benefit of such ratios one must excite and perceive all of the modes simultaneously. The only way to do that is to place loudspeakers and listener in corners:
  
  Toole (2006), “Loudspeakers and rooms for sound reproduction – a scientific review”, J. of the Audio Engineering Society, p.451
  
  You seem to have enough ceiling height so what I would suggest is to use an acoustic ceiling. Our living/listening room has a ceiling made of stretched synthetic fabric with 66 inch air space above and it works extremely well:
  
  
  
  
  As for room volume, the larger the room, the smaller the frequency region where room modes are potentially disturbing.
  
  As for treating the rear wall, from scientific research it appears that reflections from front and rear walls are less preferred than reflections from the side walls so treating these walls may have some benefit in some circumstances.
  
  
  Klaus
  
  

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  • RE: Squarish room - Chaba 14:04:29 01/05/09 (2)
    In Reply to: RE: Squarish room posted by KlausR. on January 05, 2009 at 02:34:51

    Thanks Klaus,
    66 inch air space above the ceiling! Surely doesn't apply to my case, but of course I got your point. I thought squarish shape is one of the major enemies of listening rooms. It is good to hear that it is not the case therefore it is not obligatory for me to make the room smaller just to get better room ratios.
    However if I have to use gypsum boards with studs and fiber wool for isolation porposes at least on one wall does it mean I have to cover the opposite wall as well? Should I place the speakers in front of the gypsum board walls or against them? Or one can tell on situ only?
    
    Csaba
    
    

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    • RE: Squarish room - KlausR. 23:43:32 01/06/09 (0)
      In Reply to: RE: Squarish room posted by Chaba on January 05, 2009 at 14:04:29

      The more air space above the fabric the better the absorption in the lower registers. With that much air space our ceiling is at about 8.2 ft, which is standard for Europe.
      
      Room dimension ratios work well on paper but reality is different. Like so often in audio you cannot rely on a theoretical approach, you must listen.
      
      As for one gypsum board: a slight left-right acoustical asymmetry is good because it decreases the interaural cross-correlation which improves spatial impression. If that board is on front or rear wall, I would not bother covering the opposite wall.
      
      Speakers against the wall have the effect of increasing bass output. Unless you have speakers designed for that particular position or speakers which allow for adjustment, a position against the wall may result in bass overload. I think that in situ listening is the only way to know whether you like it or not.
      
      Klaus
      
      

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    • RE: Squarish room - Ethan Winer 09:20:37 01/06/09 (0)
      In Reply to: RE: Squarish room posted by Chaba on January 05, 2009 at 14:04:29

      In a square room the orientation doesn't matter so much. So I'd set up whichever way keeps windows etc away from the reflection points.
      
      --Ethan
      
      

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