I totally agree that more than 1 but probably not more than 4 subwoofers are an noticable advantage in a room for below 100Hz or infrasound Frequencies.
What i am wondering/thinking of is really if our hearing do not use the clues of the overtones or distorsion overtones from subwoofer elements to fool us in to beliving we can hear direction of really low frequency sounds. I have only had the trouser flapping experience once my self and I do not think I could have defined from which direction the first "flap" where comming, had it not been a around 110dB disco sound level in the room where I stood in the doorway. Or can we really feel the "Punch" in our chest or in the back? > very briefly, I think decorrelated Lfgives better 'spaciousness', and highly > correlated Lf (as obtained by feeding 'W' to subs) causes the opposite - that > lack of externalisation or 'in the head' feeling Dr Peter Lennox How much decorelation is needed, do unsymmetrical placement of the subs produce that? How much actual subfrequency decorrelation can you really get when decoding a FOA b-format signal? I am following a swedish forum www.faktiskt.se where we "Hifi nerds" are discussing and experimenting with http://www.linkwitzlab.com/thor-intro.htm deployed in large scale, the largest installations I have read about are with 8 to 16 Subwoofers on the front speaker wall. Also other solutions are discussed. For example this forum thread http://translate.google.com/translate?js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&sl=sv&tl=en&u=http%3A%2F%2Fwww.faktiskt.se%2Fmodules.php%3Fname%3DForums%26file%3Dviewtopic%26t%3D36564%26list%3Dfull where we are discussing the reproduction of the frequency range 5 to 80Hz with low distorsion and a price performance aspect. I notice google translate gives up a bit in to the thread, so may better to read page by page. I am a bit more modes and I am thinking of building 4 of these http://www.faktiskt.se/modules.php?name=Forums&file=viewtopic&t=36647&list=full and thrusting the room gain to extend the -3 dB point in room to around 20Hz. Bo-Erik -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Eric Benjamin Sent: den 4 maj 2011 19:18 To: Surround Sound discussion group Subject: Re: [Sursound] Minim AD7 for sale - Speaker configs. > from psychoacoustics we cannot really hear directions of sound below > 80 Hz I know that it is frequently written, but it's not true. Of the two localization mechanisms active at low frequencies, Interaural Time Differences (ITDs) are the ones that give useable localization cues in free space. The time difference depends only on the direction of the source and not on the frequency. Unofrtunately there is very little information in the psychoacoustical literature about low-frequency localization. They consider 250 Hz to be 'low' and 100 Hz to be very low. Maybe some day I'll do some research on that... It is true that the threshold of hearing rises substantially at low frequencies, and for that reason localization acuity decreases. Here's what I think really happens. For low frequency sounds reproduced in ordinary rooms, the first arrival at the listener's two ears naturally has ITDs that correspond to the direction of the source. After a short period of time, reinforcement of the sound by reflections from the room boundaries changes the phase of the sounds at the ears. This can be more easily seen by considering the modal structure of the room at low frequencies. The room has relatively few modes and the sound wave quickly becomes constrained to travel in the modes. Because of the relative energy of the transverse, oblique, and tangential modes, the sound effectively "comes from" the direction of the mode, not of the source. In practice, large ITDs AND ILDs are seen at the listener's ears. As a result, the percept will probably be that the sound is coming from a direction other than its actual source. This is what I actually hear when using low frequency test signals in real rooms. But there's more going on that that. Almost always, the low-frequency sound has actually a fairly broadband spectrum. With that sort of signal the auditory system clearly evaluates several cues as to the source direction and gives a best estimate of the actual direction of the source. There are good reasons to use several subwoofers in a multichannel reproduction system. At least the following two papers support that idea. [1] Subkey, A., Cabrera, D., Ferguson, S.; "Localization and Image Size Effects for Low Frequency Sound", AES preprint 6325 (2005 May) [2] Martens, W., "The impact of decorrelated low-frequency reproduction on auditory spatial imagery: are two subwoofers better than one?" presented at the AES16th International Conference, Rovaniemi, Finland, (1999 April) Having said that, I only have one (large!) subwoofer in my multichannel listening room. But the reason for it has more to do with $$$ than my believing that one is enough. Eric _______________________________________________ Sursound mailing list [email protected] https://mail.music.vt.edu/mailman/listinfo/sursound
