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
School of Technology, Faculty of Arts, Design and Technology University of Derby, UK e: [email protected] t: 01332 593155 ________________________________________ From: [email protected] [[email protected]] On Behalf Of Eric Benjamin [[email protected]] Sent: 04 May 2011 18:18 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 ----- Original Message ---- From: Bo-Erik Sandholm <[email protected]> To: Surround Sound discussion group <[email protected]> Sent: Wed, May 4, 2011 4:41:02 AM Subject: Re: [Sursound] Minim AD7 for sale - Speaker configs. Yes, I have a few woofers available BUT according to what I understand from psychoacoustics we cannot really hear directions of sound below 80 Hz, as the ear/brain is changing method of decoding soundwaves between 80 to 100 Hz? So do I really need more than a pair driven in mono (or 4) to even out the excitation of the room modes? If I where to add a low frequency decoder how should I do that? Is it not so that the speaker feed to all of the 10 speakers are in phase for frequencies lower than Some "undefined" frequency? That is using Ambdec? Should I have a highpass filter before or after the decoder for the 10 "small" speakers, if I add a low frequency feed, either mono or decoded? Bo-Erik -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Peter Lennox Sent: den 4 maj 2011 11:32 To: Surround Sound discussion group Subject: Re: [Sursound] Minim AD7 for sale - Speaker configs. Quick suggestion: - as you're having to use more than 8 channels anyway, you're likely to be using a 16 channel card; thus, you would have some channels left to decode (horizontal only) to 3 or 4 subs Dr Peter Lennox School of Technology University of Derby, UK tel: 01332 593155 e: [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Bo-Erik Sandholm Sent: 04 May 2011 08:09 To: Surround Sound discussion group Subject: Re: [Sursound] Minim AD7 for sale - Speaker configs. I still want to suggest a setup that I will soon have in operation, I have written about it before. It uses 10 channels, it is a hexagon in the horizontal plane with a speakers at front back. The Z is handled by for speakers, placed where the 4 hexagon side speakers will end up if the Hexagon is rotated 90 degrees around a axis through the front and back hexagon speakers. Fons A has created a ambdec for me of this setup. I have the possibility to have all speakers except the 2 floor speakers permanently mounted due to my room geometry. I have the 2 floor speakers mounted on a long wooden plank letting me getting them in place quickly. I have been rethinking my amplifier setup and will now use 3 modules of 4 channel sure swiched amps instead of 2 Home theater amplifiers. The shure amp modules (4 x 100W) cost 98USD including a switched power supply, an will give 30 watts per 8 ohm speakers, I will only be using 2 power supplies so the total material cost is at the moment 3 x 44 US + 2 x 48 USD, that is less than 240 USD. http://www.parts-express.com/pe/showdetl.cfm?Partnumber=320-302 I will be using second hand Kef KHT-2005.2 "Eggs" as speakers. It is a bit of a "bother" that 10 instead of 8 channels are used, when it comes to the sound card setups... Regards Bo-Erik -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Aaron Heller Sent: den 3 maj 2011 20:04 To: Surround Sound discussion group Subject: Re: [Sursound] Minim AD7 for sale On Tue, May 3, 2011 at 10:14 AM, Fons Adriaensen <[email protected]> wrote: > On Tue, May 03, 2011 at 07:15:29PM +0530, umashankar mantravadi wrote: >> >> in fact angelo recommended that i arrange the eight speakers as two >> crossed squares. two speakers in front and back, and four speakers >> mid bottom left and right and mid top left and right, the only >> problem is i do not see a readymade decoder > > A variation on this is an horizontal rectangle, 1 unit wide and 1.73 > deep, and a vertical rectangle in the YZ plane 1 unit high and 1.73 wide. > Or the same rotated 90 degrees. Looking from above you see an hexagon. > > This somewhat improves the rE for horizontal directions (not much), at > the expense of all others. Anything outside the +/- 30 degrees > elevation region will become very fuzzy. I had one of these set up at home for a couple of days and found it better than a horizontal hexagon. The impression of height is a welcome addition to the sense of envelopment. I had a fader set up in Bidule so you could change the Z gain to compare horizontal-only with periphonic. The entire listening panel (my son and I) preferred having the height info, but the rest of the family didn't appreciate having a couple of ladders in the living room. I also tried it with the vertical rectangle in the XZ plane. That works too. Contact me off list if you want the Ambdec config files I used. Aaron Heller <[email protected]> Menlo Park, CA US _______________________________________________ Sursound mailing list [email protected] https://mail.music.vt.edu/mailman/listinfo/sursound _______________________________________________ Sursound mailing list [email protected] https://mail.music.vt.edu/mailman/listinfo/sursound _____________________________________________________________________ The University of Derby has a published policy regarding email and reserves the right to monitor email traffic. If you believe this email was sent to you in error, please notify the sender and delete this email. Please direct any concerns to [email protected]. The policy is available here: http://www.derby.ac.uk/LIS/Email-Policy _______________________________________________ Sursound mailing list [email protected] https://mail.music.vt.edu/mailman/listinfo/sursound _______________________________________________ Sursound mailing list [email protected] https://mail.music.vt.edu/mailman/listinfo/sursound _______________________________________________ Sursound mailing list [email protected] https://mail.music.vt.edu/mailman/listinfo/sursound _____________________________________________________________________ The University of Derby has a published policy regarding email and reserves the right to monitor email traffic. If you believe this email was sent to you in error, please notify the sender and delete this email. Please direct any concerns to [email protected]. 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