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Room Acoustics

----  Theory  ----  The best rooms  ----  The listening room  ----  Whatever happened  ----

 

The best rooms ...

The best rooms ...

The best rooms are at least 15 feet wide, 20 feet long and have a ceiling height of 8 feet or more. This allows the two loudspeakers of a stereo system to be placed symmetrically and with their tweeters at least 3 feet from side and rear walls. With the loudspeaker tweeters 8 feet apart the sweet spot is located on the room symmetry line and at 8 feet from left and right loudspeakers. This leaves more than 9 feet behind the listeners for the sound to travel before it is reflected back. It is very important for balanced phantom image creation that the immediate vicinity around the two loudspeakers is symmetrical. 

Rooms can, of course, be much larger than 15 x 20 x 8 feet and with the loudspeakers much further than 3 feet from the walls, but the optimum listening distance for phantom imaging remains equal to the loudspeaker left-right separation or up to 1.5 times that value. 

Room construction can vary widely, which tends to affect low frequency reproduction and sound transmission to and from the neighbors. You take what you get and try to correct one or two frequencies if necessary. But, if the room is pleasing to live in, to have a conversation or to relax, is neither a dungeon nor a stuffed pillow, then it is also suited for accurate sound playback. The room should be furnished, have irregular hard surfaces, books and shelves for sound diffusion, rugs, pillows and soft surfaces for sound absorption at higher frequencies. Just keep it lively. The best loudspeakers will make you forget the room, if the room talks back from all directions in the same familiar voice.

Actually, the loudspeaker is the problem

The room is usually considered to be the problem when a loudspeaker does not sound right. Actually, the loudspeaker is the problem, because it illuminates the room unevenly with sound at different frequencies. The room merely talks back and the listener's brain cannot withdraw attention from it. Room correction will make the loudspeaker sound different but it cannot fix its off-axis frequency response, which is heard via the room. 

Below you will find a lot of theory that you can safely ignore, because your room is most likely not one of those ideal cases that can be described mathematically. No one can tell you the right room proportions, though many have and are trying. Listening rooms in the home are much more difficult to understand and describe than concert halls, because their acoustic size varies from being small compared to a 56 foot wavelength at 20 Hz, to being very large at 10 kHz with 1.3 inch wavelength. Concert halls are acoustically large even at the lowest frequencies and thus easier to analyze and they have been studied extensively. Even so, concert hall design is still a blend of art and science. For your listening/living room design and layout follow the simple guidelines above and forget what you read about 1/3rd rules, costly room treatment products, magic wood blocks, etc. and use appropriate loudspeakers.

Accurate Stereo performance tests                                                                  SL - October 2009    

 

My observations and promise:

It is possible to reproduce a stereo recording in an ordinary living room such that listeners have the illusion that the two loudspeakers have disappeared. When they close their eyes, they can easily imagine to be present at the recording space, as they listen to the phantom audio scene in front of them. 

The vast majority of loudspeakers that have been sold - the typical box speakers - can only produce this effect to a limited degree because of a fundamental limitation: they radiate sound into the room with different intensity at different frequencies and angles, though they measure flat on axis. Consequently the many reflections from room surfaces are sonically colored in a way that is characteristic for box loudspeakers. We always recognize the sound as coming from a box rather than being live. It is the generic loudspeaker sound.

It has been a fascinating journey for me
to come to this understanding

Loudspeakers with frequency independent, constant directionality such as omni, dipole or cardioid loudspeakers, cause reflections in a room that are essentially delayed replicas of the direct sound and which are therefore less colored. Your ear/brain perceptual apparatus does not get confused by sound replicas. Instead it compares them to the familiar acoustic behavior of your room and readily blankets the redundant information and thereby the room. This automatic brain response is related to the Precedence Effect in psychoacoustics and is essential for creating the illusion of "being there" by withdrawing attention from the living room acoustics.

It has been a fascinating journey for me to come to this understanding. Early on, electrostatic panel loudspeakers had intrigued me, because they seemed to do something fundamentally right when properly set up, and this despite their obvious limitations. I can see in hindsight that a few loudspeaker designers had pointed to the benefits of omni-directional loudspeakers. The ORION+ has demonstrated to me what more is possible in 2-channel sound reproduction, provided that the recording contains natural spatial cues and is not merely an artificial sound mix. 

Accurate sound reproduction is in reach for you too. Surprise yourself with the believability of the illusion when two loudspeakers properly stimulate your room, ear and brain. You find yourself lost in music and space.

Hearing, Loudspeakers and Rooms       Accurate Stereo                  Siegfried Linkwitz, August 2009

 

 
What you hear is not the air pressure variation in itself 
but what has drawn your attention
in the two streams of superimposed air pressure variations at your eardrums

An acoustic event has dimensions of Time, Tone, Loudness and Space
Have they been recorded and rendered sensibly?

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Last revised: 06/28/2014   -  1999-2014 LINKWITZ LAB, All Rights Reserved