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General Asylum General audio topics that don't fit into specific categories. |
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General Asylum General audio topics that don't fit into specific categories. |
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In Reply to: The Folly of Chasing Nostalgia and the Reality of the Room posted by Mister Pig on December 28, 2024 at 09:25:03:
Hi
A frustrating and confusing area is how loudspeakers interact with a room. In an area where big money is involved AND the rooms are larger to huge, the room is even more of a factor in the sound quality and ability to understand words. Frustrating because there are at least two different things involved that effect your perception.
IF you want to hear what the loudspeakers do, set them up outside, away from walls etc and then you hear what they do. In a room, you hear both the speakers and their radiation pattern. Outside, you primarily hear the sound from the driver that traveled to your ears. You do not hear the sound you would hear if you moved over a foot or two.
You also hear there is less low end than indoors and usually the phantom image between the two speakers is much stronger. There are a number of loudspeaker things that enter here.
But when these same speakers are indoors they have more bass and less stereo image than outside.
They have more bass because acoustically the room is huge at 20KHz (a wavelength is about 5/8 inch) and tiny at the low end and the wavelength is 1000 times larger at 20Hz) The room absorbs sound but since it is much smaller the lower you go, the absorption decreases and containment increases. A great deal of work has been done on what is the ideal response curve at the listening position.
The object in stereo is to reproduce a signal faithfully enough so that your brain interprets this is a sound coming from a different place in front of you. It is hard to capture and hard to reproduce convincingly (where your not aware of loudspeakers as the source)
The loudspeaker can radiate additional information so that it is easy to locate the speaker's distance with your eyes closed and this is not a good thing so far as the phantom image as the sources locations are not part of the recorded image and harm the illusion..
Speakers usually radiate energy to the sides and when this energy reflects off the walls and arrives at the listener, this late image interferes with the original direct and harms the phantom image. This is why moving speakers away from the side walls normally provides a stronger image.
Dipole radiators produce a figure 8 radiation pattern and so they radiate much less energy sideways and off the side walls and so can have a larger "near field" where the direct sound is stronger than the reflected sound.
Directivity is related to the acoustic size of the source and most loudspeakers are not large enough to have much directivity until the hf area. The race to make "sugar cube" speakers has moved the market away from the larger systems that can produce directivity in the home.
Horns offer a way to have significant directiivty down into the mid or lower frequencies.
A thumb rule is a horn controls the pattern angle down to a frequency where F = 10^6 /angle/ mouth dimension inches. In commercial sound the room is so much larger and so room issues that Horns are very common some like we make are large full range horns.
Tom
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Follow Ups
- RE: The Folly of Chasing Nostalgia and the Reality of the Room - tomservo 06:45:59 12/30/24 (0)
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