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object based audio and large number of speakers (4 replies)

Rajdeep S
2 months ago
Rajdeep S 2 months ago

can we get wide sweet spot by using more number of speakers in a small room?

Qiang C
2 months ago
Qiang C 2 months ago

false       because  listeners are closer to speakers which reduces the good listening area(sweet spot)   many of the acoustical design principles utilized in large spaces fail to compensate for small room problems

chen qiang

Gerry Lemay
2 months ago
Gerry Lemay 2 months ago
1 like by Rajdeep S

The question is not as simple as you might think; there are two factors at work.  The first factor relates to the definition of the sweet spot or sweet area.  As interpreted by the HAA, this is the listening area in the room where Focus is optimized.  This means that the LCR speakers create a balanced sound field and allow placement of stereo images in the proper position and size (i.e. Focus) in the soundstage.  We traditionally calculate the locations where LCR speaker sound levels are balanced and Focus is perfected as being within a triangular area; the sweet triangle. The concept put forward by Trinnov is that by adding more speakers, the dependence of Focus on stereo imaging is reduced by simply placing more speakers in between the usual pair of imaging speakers.  Theoretically, one can render stereo imaging as unneeded by simply installing enough speakers to allow the creation of an image at any given location by virtue of placing a speaker at that location. 

Imagine the scenario of an infinite number of speakers representing every possible position one would expect to hear a focused image.  Every sonic image would be heard directly from a single speaker or closely placed pair of speakers perfectly localizing the desired image location.  Such a mono source delivered by a single speaker has no defined sweet spot; listeners will hear the image location perfectly from any room location.  Instead of a true stereo image we hear the speaker(s) located where the image should be placed.  The question I believe Trinnov explores is at what quantity of speakers does one achieve this kind of coverage short of infinity.  I'll report back once I better understand this question. 

The other factor I mentioned is actually not about the sweet spot size but rather about speaker localization.  A listener located a short distance from any speaker (8 ft or so) makes it much easier to notice the presence of a speaker.  Even with multiple speakers, the listening area will be limited by the proximity of surround speakers.  In this case, not only would the image of a panning object allow the localization of a nearby speaker but also the bed channel ambient background could also allow speaker localization.  Speaker localization reduces envelopment and the immersive effect.  In HAA we call this the Exit Door Effect.  Ganging all speakers to reproduce bed channel sounds would allow them to play at a lower level, however the object information would still need to be reproduced at the proper level of the individual speaker.

Another issue that needs to be considered is the quality of the processing.  While the accuracy of Dolby's Atmos object placement is not being questioned, many times sounds are recorded in a natural way depicting not only the image location of the sound but also an intricate network of simultaneously recorded instruments and all recorded reflections which help render a better three-dimensional depiction of the sound.  An example might be a string quartet in a small chamber room recorded with only two microphones.  The recorded spatial information is considered best reproduced by the same number speakers as microphones.  I'm a fan of the new Dolby Surround processing changing stereo to 7.1 but I'm curious how such a complex alignment of sounds will be rendered through so many more speakers.  I'm not a doubter but mainly curious.  One of the criticisms of Dolby Atmos versus Aura involves this delicate reproduction of such precisely recorded soundtracks... but then that's for audiophiles and not so much for movies.

Bottom line is that, the assertion that the sweet spot is enlarged with a greater number of speakers is essentially true but dependent on more factors than simply adding a few more speakers.  7.1.4 system does not expose any advantage of this kind over a 7.1 system in a small room.  Maybe 11.1.6?  But probably not.  I am keen to discover just how many speakers are needed to capitalize on this concept and in what size room.  I'll work on this and report back.

 

 

Gerry

Li Zi J
2 months ago
Li Zi J 2 months ago

An expanding range of desserts area can increase the listener appropriately, if the room listener too many, will cause the listener distance is too close to a speaker, thus affecting the listening effect.

Gerry Lemay
2 months ago
Gerry Lemay 2 months ago
1 like by Rajdeep S
Accepted answer

Yes the "desserts" area or sweet area is expanded just as the sweet triangle is expanded by adding the center channel.  There is still a "red" zone near closely placed speakers.

Gerry

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