yes, You're right, moreover a typical audiophile room is likely to have a higher average absorption coefficient which moves the critical distance even farther from the speakers
I quoted their calculation here because it is done explicitly for an omni so it applies specifically to Oliver's omni speakers: Demokrit or Demokrit-T
I believe it dominates in some aspects, in others it doesn't
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Wierd. All of my tests on high directivity tweeters have lead to failure in terms of imaging. The tweeters become perceivable as sound sources, and symptoms of the interaural cross talk become unbearable too.
Ok, good to know.
because I find a requirement for a reflection to be 10 dB louder than the direct sound for an "image shift" to be experienced quite surprising, and that with speech!
I have found that level difference of about just above 5 dB at 5 ms is enough for the perception to ignore the direct sound and make the first reflection as the direction of the image. It appears that the functioning of my single speaker stereo SSS somehow relies on this phenomena.
- Elias
That's about the value I found too but only for percussive high frequency sounds.
yeah
anyway it looks that an early reflection must be really strong to cause any image shift - relative level around -4<0 dB for a delay of below around 8 ms and all later reflections are unable to cause any shifts unless they are stronger than the direct sound, according to Meyer and Shodderyeah, and this phenomenon is perfectly consistent with results of those studies to which Toole refers
yeah
Yes the reflection must be stronger than direct sound, BUT still the level difference is not too big. This means it can be utilised as a benefit by a clever design.
It will surely increase the credibility of my SSS speaker then
Toole is next to God, right ? - Elias
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Propably for the same reason I found the psychoacoustic filter in my SSS speaker is mandatory. It cuts treble from the forward sound and boosts the treble for side sounds. Without the filter the speaker is more easily perceived as a sound source. With the filter there is no such problem.
It appears that adequate difference of forward and side sounds is just above about 5 dB, which is very doable by simple passive filter.
I believe you did not try this type of a filter in your stereo sphere (TM) ?
- Elias
Wow, fast moving thread...
There are omnis that are rather big like German Physiks. I am not convinced that they provide the full omni experience without other side effects.
Just compared to wavelength.
There are omnis that are rather big like German Physiks. I am not convinced that they provide the full omni experience without other side effects.
Dave said it before I could reply, the reverberant field will be stronger but not perceptually. This can't be true.
Not exactly sure what you mean but the direct sound diminishes anyway. Flatter though than 6db per double distance like shown in Toole's.
In my room an setup, 1.8m is the max. listening distance with Demokrit. And based on several estimations, the critical distance for an omni is indeed below 1 m in my room. So the example you posted is not unrealistic at all and shows exactly the point that I was mentioning about distance.
This is basically the whole idea of the precedence effect (or law of the first wave front). The direct sound dominates localization (even when reflections are stronger than the direct sound). In virtually every situation the reverberant field is stronger than the direct sound (except when you're in a very dead room or at < 1 m from the source), yet it is easy to identify the source while we usually do not notice reverberation very much.
This can change if we hear recorded reverberation being reproduced over loudspeakers. It is more difficult to "de-reverberate" the recorded sound when reproduced than in the live setting, which makes the recording sound like it has way too much reverberation. Speech intelligibility can sometimes be drastically reduced compared to the live situation.
I think the cause of this is that if the FR is split in 2 (directional highs and omni lowes) it is perceived that the high frequency image is closer and therefore dominate. So you have high FR seemingly closer and low FR further away.
Not very good for image perception?
Also, in-room power response is uneven.
It's ok to use horns for the high FR response outside, because there are no reflections.
Yeah, thanks for calling the name of the baby. I was just so baffled by this that I was questioning the context. Such a book can't be that wrong. However, Dave has added a wrinkle to it and slighlty pushed it into another light.
The original says:
"Therefore the quality of the reverberant field is an important aspect of the performance of any system which produces..."
That is true if you look at the eveness of RT60 for example. It is an aspect.
Dave said:
"Whats really wrong with this quote is that they state that the reverberent field is stronger (likely true) and that it therefore dominates perception (not true!)."
Unless I am missing something we have to be careful with conclusions.
I cannot speak for Elias but this is one of things that bothers me. The tweeters draw way to much attention and the phantom image suffers while the bass is often way beyond two times the critical distance and simply underperforms therefore.
And the uneven power response that kind of unmasks tweeters.
I have to modestly say that im not as knowledgable as most in this debate. If i understand correctly, then i would liken it to playing electric guitar wearing headphones. Then i would add a small pinch of reverb, just enough so that it isnt 'anechoic' in the headphones. Then remove the headphones and play through the speaker instead. The sound doesnt sound the same. Id find i would have to increase the reverb level, in order to perceive the amp reverb, through the rooms' character. I generally enjoy a 180 degree pattern, or smaller. In my room at least i found narrow vertical dispersion to be a huge improvement.
From 2pi home page quoted earlier:
Just to point out that this concept of critical distance and the perception further away is a symptom of loudspeakers which are not functioning in full harmony with the listening room. I think omnis belong to this handicapped category as well, since they suffer from distance problems.
To give an opposite example, and to propose a cure to limited listening area, I direct you to single speaker stereo loudspeaker SSS. Interesting is that it has a 'critical distance' but it is a minimum distance. Everywhere beyond that distance in the room the sound field is very good.
- Elias
Just to point out that this concept of critical distance and the perception further away is a symptom of loudspeakers which are not functioning in full harmony with the listening room. I think omnis belong to this handicapped category as well, since they suffer from distance problems.
To give an opposite example, and to propose a cure to limited listening area, I direct you to single speaker stereo loudspeaker SSS. Interesting is that it has a 'critical distance' but it is a minimum distance. Everywhere beyond that distance in the room the sound field is very good.
- Elias
The problem is solely the unability of stereo to form stable phantoms at treble frequencies.
Easiest way to confirm this is to do stereophonic panning tests with high passed signals. Better yet only play your tweeters alone.
- Elias
Then you have not touched the gold mine yet
Are your horn experiments documented somewhere ?
Don't know what your problem here is. I can hear panned HF noise just fine.
Interesting observation I made just today: I can hear the difference between correlated and inverted (one channel) HF pink noise (HP 48dB 4kHz) with speakers whereas I can't hear it with headphones.
Here're the test signals I've used:
https://dl.dropbox.com/u/21936387/Pink-Noise_stereo_correlated_HP48dB4kHz.wav
https://dl.dropbox.com/u/21936387/Pink-Noise_stereo_inverted_HP48dB4kHz.wav
Then you have not touched the gold mine yet
Are your horn experiments documented somewhere ?
Yes, here
Getting some polars tomorrow.
Well, I don't think that's the sole inability. I think what I said above has some merit.
HRTF are a subject for another thread.
I'm just staying in context of this thread.
But, I whole heartedly agree with you. I don't even listen to stereo anymore.
You know I contributed significantly on the "try ambiophonics" thread.
And I did build the "event horizon"
Precedence effect. There are numerous problems in current psychoacoustic studies and their applicability in living room environment as is the title of this thread. Almost all of the perception studies with numerical data employ only one single reflection in addition of direct sound. This is not the case in a small room. What the precedence effect does not tell you is what happends when there are multiple of reflections in a short time window. That is the small room case. I could even go to great lengths and declare the applicability of precedence effect in small room is questionable at best.
For a mind teaser, take a look at the attached wavelet plot from a small room. There is a direct sound from a single loudspeaker at 0 ms, and first strong reflection comes at 5 ms and after that comes multitude of reflections. According to precedence effect we would expect the perceived direction to be at the location of the speaker. But, that is not the perception. In this case there is no perceived direction at all, the sound is coming from somewhere at frontal hemisphere, the location cannot be expressed more accurately than that. The precedence effect according to puplished literature does not explain this.
It is such easy to trick your hearing against common beliefs. The surprise is great when you first read something from a book, and then conduct your own experiments to find out your perception does not match the written word.
Who are we to believe then ?
An externally hosted image should be here but it was not working when we last tested it.
- Elias
I don't even listen to stereo anymore.
I know the feeling
I propably should stop writing at this thread and go back to my own thread lolOne should also be alert of the moderators, they can always come out from the bushes and split a thread, just like that !
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