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Bass can be directional and here's how. When a planer wave below the rooms Schroeder frequency is generated it starts at one end of the room and propagates down the length of the room until it reaches the rear wall, it is either reflected back towards the front wall or it can be canceled out or absorbed. The initial planer wavefront is directional the subsequent multiple reflections that may occur in the room can obscure the directionality of the bass. See CABS discussion here. http://www.audiocircle.com/index.php?topic=106838.0Your ability to detect the direction of bass frequencies may be very poor however. If you had a single sub-woofer with a 24dB/oct crossover and you set it for 40Hz and then played back a continuous 32Hz tone you probably couldn't tell where in the room the sound was originating from. If you use a SWARM setup consisting of multiple sub-woofers spaced around your listening room it is unlikely that the bass will be directional because no coherent planer wave has been produced by the subs. The SWARM is more akin to dropping multiple rocks in the water at the edge of a square pond, the pattern of ripples produced will be incoherent and chaotic with no large waves anywhere.Scotty
What you are describing is correct - but that doesn't make it directional. At the same time it's going down the length to come off the rear wall, it's also hitting the floor, side walls, and wrapping around the cabinets to hit the wall behind the speaker. If bass were directional as you describe only, then a dipole would not have a figure 8 pattern as it could not cancel on the sides.Bryan
But omni means firing in all direction from source which would be the sub, but depending on the cut off frequecy, and if is high enough, a wide front baffle could intefer the results. This goes to show that the subwoofer ( the box and the woofer) is not a source because it could intefer. What if we take the room out of the equation? Then there will be no refletion.
Frequecies that low are very hard to localize. But at 80, is a different matter. The question is, is bass still consider omnidirctional or non directional for the proper wording?
I personally dont agree with either, but most people, even lots of designer says that frequencies belwo 80 hz are hard to localize so they are omnidirectional.
Ricardo,You are either misunderstanding/conflating what is said, or "they" saying it are confused. An enclosed piston source/cone (like a woofer in a box) radiates essentially hemispherically and when the wavelengths radiated are large relative to the baffle or enclosure, these waves simply wrap around, creating essentially omni-directional radiation. "Sub" frequencies wavelengths of say 100hz-20hz, will vary from around 11 to 56 feet, i.e much larger than the piston/enclosure. If a closed sub was lifted up in the air outside, say 20' and the dustcap was made the center point, then a mic at any point around say, a 2m sphere, would measure near exact same frequency response. It radiates omni-directionally at "sub" frequencies. This is a completely separate issue from localization.The reason why it is said to be difficult <80hz, is because we use a "difference" signal (intensity and time) between our L and R ears to detect direction of a source. Because wavelengths have become so large <80hz, the "difference" between a signal coming from say the left of you, is relatively (very) small compared to the length of the wave itself, so there is no (or minimal) difference component to detect.Now a tweeter, especially one mounted on the top of an enclosure ala B&W, is also radiating essentially "omni-directionally" at the lower end of its range (say 3k), but it would be quite easy to localize, as those wavelengths (around 4") are relatively small compared to the distance between your ears (and the "shading" provided by your head).cheers,AJ
Just put on any philharmonic symphony orchestra recording where you know where the double basses, tympani, kettle drums, contrabassoon, pipe organ, and you will be able to define said instruments within the soundstage, either live or when using stereo subs.Psychoacoustic's are how we hear and represent things. While low bass is a form of energy unto itself, it is directional with relation to a proper soundstage. Call it a form of trump loy.Jim
