Well controlled directivity will give large sweet spot where image shifts are very small. As far as room goes, theoretically the more accurate results are obtained when there is minimum room interaction, meaning an anechoic room would reveal the most accurate performance. However, when considering the size of the bass, and it's response, it makes sense to utilize room modes in a appropriate region to help enhance the perception of bass by extending it's duration.
Yeah but listening to music (or even sitting) in an anechoic chamber is really unpleasant. So much for theory. 🙂
Yes, this is a significant point, because it shows that taking the idea of "excluding the room" to an extreme only leads to a bad situation. In an anechoic chamber directivity and power response - all the things that we talk about here - are completely irrelavent and only the response on the listening axis matters. Basically all speakers become the same when listening in an anechoic chamber. But only those who have actually done this know that this IS NOT the answer. The sound is not at all appealing. As the room becomes more reflective, the polar response becomes more important, but also the sound becomes more pleasant. I do not see how one can argue that this "tendacy" towards narrow CD being the best solution in a "lively" room is not obvious.
Hence we have - dead room, all speakers sound the same -> bad - no spaciousness at all, a very flat non-realistic sound. While in a live room there is a strong preference for narrow CD speakers, which sound good - good imaging from a controlled direct field and good spaciousness from the room and the controlled power response of the speakers. Unfortunately, the wide non-CD speakers still sound bad - poor imaging because of early reflections, coloration from same, and coloration from a non-flat reverbeant field.
There simply is almost universal agreement among those people who have studied this problem on these points. Why there is such uncertainty here at DIY is beyond me.
Just moving speakers from an ordinary room too a mixing room makes a significant difference. I think that we are just not used to such anechoic envronment. My farther seldom uses a hearing aid because he thinks it's too noisy. One he had his hearing aid on while it was raining hard outside, and he asked "what't all that noise about?"
When I was working in the then largest anechoic chamber, the Guardian of The Room used to pipe in good music through his hifi intercom. Bland and disembodied but voices were very intelligible. Funny, the anechoic chamber had a quite noticeable "sound" of its own not to mention certain scary features like no floor.
Although nearly everybody recognizes that different speakers suit different rooms (and that seems to be what Earl posted above), I have yet to hear how the directivity parameter points to what kind of room or not. Or more germane, what should I (and people like me) do to their rooms to get the same result?
Nice of people to write long posts about why people on this thread are too busy to provide a simple straight comment.
Although nearly everybody recognizes that different speakers suit different rooms (and that seems to be what Earl posted above), I have yet to hear how the directivity parameter points to what kind of room or not. Or more germane, what should I (and people like me) do to their rooms to get the same result?
Nice of people to write long posts about why people on this thread are too busy to provide a simple straight comment.
could this be linked to the "live occasion" listening experience, with the expected reflections of the "big room" which are not captured in proportion to the direct signal sent to the recording?
Could that be telling us that our ears cannot be fooled by the added ambience that tells us it was a church hall, or a toilet, or outdoors, or a night club and recognises real reflections as realistic but recorded reflections lack some ingredient that ours ears miss and want?
I can't suggest it's an ideal listening environment, but the environment allows more things that you normally don't hear to be heard. More power is necessary to drive the speakers to the same listening levels as in an average home envoronment.
Read Earl's paper and do what it says. Briefly, you want a live room and speakers with the type of pattern he describes.
Ben, at some point you need to help yourself. For example, you might ask yourself this question: "Am I more interested in finding clever excuses to reject and dismiss knowledge, or am I more interested in acquiring it?"
If you will only accept knowledge when it is served on the kind of tray you like, then you will have to find it on your own. If you have a perceptive and unprejudiced mind, then the serving tray will not matter.
And sometimes, the people who have the most knowledge about a topic are the people whose area of professional expertise happens to be that exact topic.
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I agree that Earl's approach appears to be the most reasonable but we're seriously lacking knowledge to be sure. Furthermore there are uncertainties when using his approach in different rooms. The sound field of narrow directivity speakers is highly directive and the reflection pattern changes significantly with room shape and furniture. What is the reflection pattern we are looking for? What are the thresholds for single detrimental reflections? What does the indirect sound field have to look like in order to avoid coloration? Does the room acoustics of the mixing/mastering studio have a significant impact on coloration?
Our hearing is quite accute as to the angle from which a sound arrives. In a recording, we can add the "timing" of the rooms reflections, but with two channels we cannot reproduce the correct angle - thay (the recording reflections) all come from the same angle. The room then adds its own set of reflections, usually earlier and hence more noticable - hence the local room will dominate the situation and only a large amount of recording reverb will override this. But then that large reverberation is still not correct as to angle, etc. and in the end it just doesn't work.
Marcus - I know what you are saying - that there are still a lot of holes, but its not like we don;t know anything. To your questions
1) The reflection pattern should be such that there is as large a gap from the direct sound to the first reflections as possible. It can never be too large (in a small room), but it can certainly be too small.
2) Blauert lists some good information about thresholds of individual reflections (but you know that of course). Having read all that I am not sure how important it is in the final analysis.
3) to the extect the indirect field is important it is obvious that matching the indirect field to the direct field would not be colored, but how close this match needs to be is unclear.
4) I would describe the "mix" as having a dominate effect on the perceived sound and its hard to believe that the mixing room does not enter into this aspect.
is that you confirming our ears compute both timing of reflections and the apparent approach angle of those reflections and calculates whether we hear "real ambience" or recorded ambience.
Evolution is clever. All this to tell us some some predator is approaching from the near left and I better get ready to run! Well I'm not staying to fight, I left my spear at home again (memory problem!).
Floyd Toole's book fills in a lot of gaps, and the data presented supports Earl's approach (though not explicitly).
We want the reflections to be spectrally close to the first-arrival sound regardless of what the pattern is. One reason is, our perception of loudness is partially based on how long a sound lasts. So if some energy is audible for a longer time because there is more of it in the reverberant field (due to lumpy off-axis response), that colors the perceived tonal balance.
There is another mechanism at work here, and this is something I learned from Toole: The ear is very good at separating out the sound of the source from the room acoustics (the exact reasons for this ability are not yet known). As an example, you do not even notice how much a person's speaking voice changes from one room in your house to another, and that is because your ear is able to focus on the source. With reproduced music, it can sometimes take a minute or two to become accustomed to the acoustics of a new room, but after that the ear is once again quite accute in perceiving sound source issues, which means they are not masked by the room. According to Toole, in this context a critical characteristic of the sound source is the spectral balance of the reflections, especially the early ones. If anything, this psychoacoustic phenomenon calls for getting the speaker right to begin with rather than relying on room treatment to fix things.
Some of this is covered in Toole's book; briefly, what Earl is doing is consistent with the data Toole presents and analyzes. I think they disagree on how long the gap should be before the onset of reflections, and my own informal experiments support Earl's recommendation to delay the onset of early reflections as much as is practical.
Duke
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This from the one who is so insistent on the need to have system response with CSDs that show the most rapid and smoothest decay possible? Room modes that extend the decay time is a good thing you say? You want certain regions to be accentuated with longer decay?
Dave
I agree....Once I built my HT room with 2" OC703 on first reflection points and 4" OC703 behind the main speakers everything sounded so much better.
Its not anechoic but its far better then any untreated room.
Do you have any data that supports this claim? I know the literature and I know where those guidelines historically come from but I also know that there are no studies that conclusively tell us if and how early time gap (or arrival time gap or whatever you'd prefer to name it) is an important parameter in sound reproduction. Studies suggest that level, angle, spectrum is more or equally important.
All those studies are tremendously important but nevertheless most tests were carried out in anechoic spaces with single reflections or headphones were used. Mostly special test signals were used instead of music. There are virtually no studies of multichannel reproduction in acoustically small places with "normal" recordings. Naqvi tried to generate useful data but somehow never finished his work - see
AES E-Library: Active Listening room simulator: Part 1
AES E-Library: The Active Listening Room Simulator: Part 2
AES E-Library: The Active Listening Room: Part 3, A Subjective Analysis
Not necessarily. If the mixing engineer EQs signals in a way so the timbre sounds correct in his room (direct sound plus reflections), there's no guarantee that the same recording sounds correct in the listener's room because the ratio of direct sound to reflections and the reflections themselves most likely differ.
Correct.
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Spatial hearing is to some extend a learning process, so the answer is yes.
If we could finally show what cues are relevant to make a virtual space sound real then anechoic spaces that provide those cues would probably be the most straight forward approach in optimal sound reproduction.
P.S. No Earl, I'm not saying that this is a practical approach.