Frankww,
Then are we just at the mercy of the room modes and that is all there is to it? Diffusion is not going to do anything for the buildup of those pressure waves just bounce them over a wider area, so what is wrong with some specific absorption in a room? In a small room it would seem even more acute than in a large room with a higher loss factor and greater distances from all radiation sources. With a normal 2x4 stud wall and drywall construction again is that really a high loss membrane at the sound levels we can produce in a small room?
Then are we just at the mercy of the room modes and that is all there is to it? Diffusion is not going to do anything for the buildup of those pressure waves just bounce them over a wider area, so what is wrong with some specific absorption in a room? In a small room it would seem even more acute than in a large room with a higher loss factor and greater distances from all radiation sources. With a normal 2x4 stud wall and drywall construction again is that really a high loss membrane at the sound levels we can produce in a small room?
Just working with unrelated pure tones I don't think would indicate anything either way. My experience, and probably also of Pano, indicates to me that the brain wants to understand the acoustic meaning of what it hears, and if the "message" is that of say a very large acoustic, reflections with significant delays, that is the "picture" the brain sees. However, harmonically unrelated sound with no echoes that match, correspond to the acoustic "size" of the main sounds will stand out as being different, very distinct, will attract your attention.
A real life example is say a musical work being performed in a large church, and a kid sitting in front of you starts rubbing his shoes annoyingly on the floor. Your brain will "fly" to the source of that irritating element, your brain will localise that aspect in spite of the volume, and reverberations of the main sound.
Frank
Makes me wonder what they hell they're smoking - and can I get some?
That is not all you ever said, but so what? You say "dominate source" or that <700Hz doesn't matter. Just how dominate? If we can localize a source below 700Hz, even far below, how can that not be important? Sure, if the source contains a lot of energy >700Hz, that might be what we mostly pick up on, but that about sources that do not? Do they not exist? Are they not important?
That may be, but how do you have music and speech with no content below 700Hz? Just how do you test this? I'll have to read it over again.
In my tests I tried to locate a tone that was panned back and forth between two speakers. I found pure tones very difficult to locate, no matter the frequency. When I used broadband noise or noise that was sharply filtered, it became easy. Below a certain filtered frequency - near 80Hz (IIRC) I couldn't follow the shifting sound any more.
I'd be happy to try the tests again with different speakers, for example Meyer Sound, and in a bigger space or perhaps outdoors. I don't doubt that midrange signals will be easier to locate than low frequency tones, but my experience has been that low tones are not all that difficult to locate.
Just to add to my previous post, if the reflections of the distortions in the listening room are significant then the brain will be in conflict: it's trying to decipher the recorded acoustic signature as well as the reflections of that, AND on top of that the reflections of the distortion. This is more than the brain can make sense of, and it gives up ...
Frank
There is also a subtlety to the >700 Hz claim. Does it also mean that reflections from < 700 Hz are not detrimental to localization?
A key aspect of reflections that is often misunderstood: is it correct to assume that a reflection of a 500 Hz wave is heard as 500 Hz? Not likely. Here's a post by speaker dave that speaks about it:
http://www.diyaudio.com/forums/mult...-covers-common-discussions-2.html#post2759273
He says, "We talk about reflections as if they are heard in issolation and have a particular frequency spectrum that is important. The reality is they combine in a particular way with the direct response based on their delay (and perceived based on direction and the ears inherent time windowing). So a flat spectrum reflection will combine with the direct sound for a very comb filtered response. The major deviation is around the first or second comb filter nulls. I have listening simulations and there are always major pitch effect determined by the particular delay. Flat plus flat does not equal flat.
At higher frequencies the comb filtering is dense, within a critical bandwidth, and the reflections add brightness."
Given all these points, how can we disregard reflections of (or directivity for) sounds < 700 Hz?
A key aspect of reflections that is often misunderstood: is it correct to assume that a reflection of a 500 Hz wave is heard as 500 Hz? Not likely. Here's a post by speaker dave that speaks about it:
http://www.diyaudio.com/forums/mult...-covers-common-discussions-2.html#post2759273
He says, "We talk about reflections as if they are heard in issolation and have a particular frequency spectrum that is important. The reality is they combine in a particular way with the direct response based on their delay (and perceived based on direction and the ears inherent time windowing). So a flat spectrum reflection will combine with the direct sound for a very comb filtered response. The major deviation is around the first or second comb filter nulls. I have listening simulations and there are always major pitch effect determined by the particular delay. Flat plus flat does not equal flat.
At higher frequencies the comb filtering is dense, within a critical bandwidth, and the reflections add brightness."
Given all these points, how can we disregard reflections of (or directivity for) sounds < 700 Hz?
+1Makes me wonder what they hell they're smoking - and can I get some?
. . .
In my tests I tried to locate a tone that was panned back and forth between two speakers. I found pure tones very difficult to locate, no matter the frequency. When I used broadband noise or noise that was sharply filtered, it became easy. Below a certain filtered frequency - near 80Hz (IIRC) I couldn't follow the shifting sound any more.
A simple test that anyone can do with even the most rudimentary DAW feeding their speakers . . . split a mono signal (anything will do, even Mozart) at 700 Hz., put the "above" in either (stereo) channel and pan the "below" back and forth, left and right.
Tell us whether you hear any difference.
Tell us whether you hear any difference.
Makes me wonder what they hell they're smoking - and can I get some?
I always wonder about this expression, why would you want to smoke something that makes you incorrect
doesnt sound like a very euphoric/sublime experience 
Certainly if there are instruments that cover both sides of that range, you will hear constant shifting of image.
I would expect reflection to increase indirect sound path plus diffusion plus absorption to work best.
It's the speed of the build up of correlated HF reflections to a steady state which is too loud: they behave like noise. Subjectively, they mask the direct sound from the speakers including the recorded spaciousness cues. But too much absorption kills the modes necessary for reflection giving spaciousness and comfort. (Been there, got the T shirt - it doesn't take a lot of absorption. I also have a small back room full of books and music in there sounds really awful).
(LF can maybe sorted with multi subs and EQ since the problem with them is a scarcity of modes)
So, what's wrong with absorption on the wall behind and (maybe) beside the speakers, using directional speakers to avoid too early reflections, keeping the rest of the room live, using some diffusion in the live portion to give more decorrelated reflections. AND (gasp!) using delayed and rolled off helper surrounds to make the room subjectively larger? My thinking with this latter is that done right it ought to make the D/R ratio better, subjectively.
(LF can maybe sorted with multi subs and EQ since the problem with them is a scarcity of modes)
So, what's wrong with absorption on the wall behind and (maybe) beside the speakers, using directional speakers to avoid too early reflections, keeping the rest of the room live, using some diffusion in the live portion to give more decorrelated reflections. AND (gasp!) using delayed and rolled off helper surrounds to make the room subjectively larger? My thinking with this latter is that done right it ought to make the D/R ratio better, subjectively.
No, you've said that <700Hz is unimportant. That's something entirely different.
I agree that >700Hz is dominant but this is not the same as saying <700Hz is unimportant. You might have never heard it because of the amount of LF dampening in your room. But most people listen in rooms that don't have good LF dampening. So you're talking about a special case that might not be very relevant to most of us.
well, this is what 4 limp mass corner traps do:
http://imageshack.us/photo/my-images/221/timlimpmass.jpg/
An externally hosted image should be here but it was not working when we last tested it.
not too shabby hey?
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well, maybe it is a very good and convenient number when you build speakers.
just a compromise, maybe?
lolo, can't read the labels. Got a description/pictures of those absorbers?
Edit: Found the thread - http://www.gearslutz.com/board/8062579-post57.html
Edit: Found the thread - http://www.gearslutz.com/board/8062579-post57.html
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are we talking transients?
two examples. listen to Mahler's n.1 opening with Paul Magi. What the conductor achieved is a window in a trully new mental space. Can you localize the sounds?
next. 2L "Divertimenti", track 2. Can you now localize precisely every instrument despite the reverb?
Markus, here is the link for these traps:
http://www.gearslutz.com/board/bass...etc/743040-tims-limp-mass-bass-absorbers.html
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