Or perhaps three 60° waveguides horizontally arrayed. The user could attenuate the ceiling vs wall reflection ratio
Bill, if I may ask, did you notice an improvement of intelligibility of phantom voices?
I do use ambient channels from the back in my room, after first absorbing early reflection energy (*). While that ambient channel placement didn't allow me to run it up at higher frequencies, as that made me notice the back channels as a separate entity, it did improve the intelligibility of the phantom center...
I started with only delayed and band passed L-R and R-L signals, but that made the phantom center stand out by sounding much dryer. After mixing back in a bit of center in these ambient channels things improved tonally. It isn't obvious at all that there is (separate) sound coming from the back, it does change the perception of the sound coming from the front, giving it more space around the separate entities within a song.
I've always wanted to add ambient channels from the front too. The ambient back channels I use are running up to 3.5 KHz, while the phantom part that's mixed in is running up till about 7 KHz. Adding a gentle reverb algorithm to these channels further helped me get even more pleasing results.
Basically trying to further decorrelate the ambience from the mains. Even if the true SPL level is down quite a bit compared to the direct sound, it still has quite an influence on perceived tonality from the front mains.
An ITD gap sure helps to keep the good imaging qualities, the stage perception changes with each song that's being played. Before I absorbed the early refections I would get similar wide staging on all songs, now it changes along with the song's own material.
(*) even the back wall behind the listener did count as an early reflection, so that wall has a damping panel too, not enough space in my room to try diffusing behind me. The ambient channels are delayed within DSP and aimed to the sides. I did try aiming them at the ceiling long ago, but with my hard ceiling surface that didn't work out.
I do use ambient channels from the back in my room, after first absorbing early reflection energy (*). While that ambient channel placement didn't allow me to run it up at higher frequencies, as that made me notice the back channels as a separate entity, it did improve the intelligibility of the phantom center...
I started with only delayed and band passed L-R and R-L signals, but that made the phantom center stand out by sounding much dryer. After mixing back in a bit of center in these ambient channels things improved tonally. It isn't obvious at all that there is (separate) sound coming from the back, it does change the perception of the sound coming from the front, giving it more space around the separate entities within a song.
I've always wanted to add ambient channels from the front too. The ambient back channels I use are running up to 3.5 KHz, while the phantom part that's mixed in is running up till about 7 KHz. Adding a gentle reverb algorithm to these channels further helped me get even more pleasing results.
Basically trying to further decorrelate the ambience from the mains. Even if the true SPL level is down quite a bit compared to the direct sound, it still has quite an influence on perceived tonality from the front mains.
An ITD gap sure helps to keep the good imaging qualities, the stage perception changes with each song that's being played. Before I absorbed the early refections I would get similar wide staging on all songs, now it changes along with the song's own material.
(*) even the back wall behind the listener did count as an early reflection, so that wall has a damping panel too, not enough space in my room to try diffusing behind me. The ambient channels are delayed within DSP and aimed to the sides. I did try aiming them at the ceiling long ago, but with my hard ceiling surface that didn't work out.
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What I find interesting from an auditory perception viewpoint is that these late reflections do not just expand the soundstage, make the room & speakers less obvious but that they make the bass more defined, sounds deeper and smoother & instruments easier to differentiate in recordings.
It is clear to me that reflections play a significant role in perceptions in ways that I'm not sure has been studied in auditory perception research but I may be wrong?
I can understand reflections being used by auditory processing to evaluate the position of a sound within the soundfield but how does that enhance the bass perception - is it that the higher harmonics of bass notes become a larger factor in its definition?
It is clear to me that reflections play a significant role in perceptions in ways that I'm not sure has been studied in auditory perception research but I may be wrong?
I can understand reflections being used by auditory processing to evaluate the position of a sound within the soundfield but how does that enhance the bass perception - is it that the higher harmonics of bass notes become a larger factor in its definition?
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Yea, thanks, I've read Griesingers papers before & his LOC concept of envelopment & intelligibility - AFAIR, his studies in large concert halls were that the energy of the reflections need to be below a certain power level ratio to the power of the main signal for perceptual envelopment.
But I'm trying to understand this at a deeper, more fundamental level which exposes or highlights auditory processing principles - maybe LOC is a principle of auditory processing but maybe its just a rule that follows a more fundamental principle which explains it?
Can't say I noticed that, but the intelligibility from the waveguides was already about as good as I know of (synergy horns seem to excel at that). I don't think the ambience drivers reduced intelligibility, though. They did help separate the different sound sources/instruments/voices in the program, (somehow), maybe a byproduct of the room in general sounding bigger.
That's one of the most unexpected results. The ambience drivers I run have no output even near bass frequencies but still that happens.
I find early reflections quite appealing, in my listening setup i have a large table in front of me, my work area, with computers, tools, papers, books, parts, it is a bit messy. Quite diffusive to sound i think. When a lean forward i got a very airy and crisp sound from the reflections from the table, when i lean back the sound becomes more dark and damped. Some records sounds better with those added early reflections, but others, with complex music it just sounds messy.
It might be that i have a room with acoustics that is slightly unbalanced, when needed to add certained freqs to the playback it should be a sign of some fault
It might be that i have a room with acoustics that is slightly unbalanced, when needed to add certained freqs to the playback it should be a sign of some fault
This may help give an intuitive grasp of David Griesinger premise and its application moving out of the concert hall into the home listening room :
Loudspeaker and listener positions for optimal low-frequency spatial reproduction in listening rooms. Author: David Griesinger
Spatial perception of reverberation
Before discussing how room modes allow us to hear spatial properties in a recording, it is well to briefly discuss how spatial properties of a hall are perceived at low frequencies. This subject is extensively discussed in reference [1] and [2], and will be summarized here.
When we are in a large reverberant space such as a concert hall, low frequency sounds – particularly moderately impulsive sounds such as a plucked string bass – are both easily localized, and seem to have a life of their own. When the bass is plucked, a direct sound wave is created that travels to the listener. The direction of the sound is determined from the arrival time difference between our two ears. There is plenty of time for this direction identification to occur, as usually the reverberant energy from the note arrives 50 to 100ms later. However, when the reverberation arrives, it arrives from all different directions, and at a complex variety of time delays. The perceived direction of the sound becomes chaotic. The sound seems to swirl around the head.
The sound is perceived as external, but coming from all around the listener. Aesthetically the hall is providing a living property to the rather dry sound of a pizzicato cello or bass. The effect is highly involving. Instead of perceiving the music as static and in front of the listener, only the attack of the note is in front. The body of the note seems to be all around the listener, drawing him or her into the performance. In short – the sound is beautiful.
Reproduced sound in a small room lacks this living quality. Often low frequencies are not perceived as external, but inside the head. This is because the low frequencies lack any pressure gradient; the interaural time delay is zero, and remains zero when the head is rotated. Not knowing how to localize these sounds, we perceive them as internal.
Reproduced music with this property is so common we have come to accept it as inevitable, perhaps even desirable. But it is far from real, and it is not involving.
The question is: can we reproduce the experience of external, living bass in a small room?
To do so, we must somehow cause the apparent direction of the reverberation to fluctuate chaotically around the listener, and to make the rate of change of direction mimic the reverberation in the original concert hall. We can if we are careful. The trick does not work in all rooms. But in many common room and loudspeaker arrangements the effect is easily heard.
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Thanks Kazap
It was good listening to Griesinger again. I see he now follows Bregman's Auditory scene Analysis (ASA) concepts of perceptual foreground/background streaming & auditory objects.
But neither his presentation nor what you quoted from his paper(I presume) explain why a LCS perceptually enhances the bass when there is no output at LF frequencies - Griesinger explains a lot about envelopment when those LF frequencies arrive as decorrelated late reflections so it does give very strong hints but doesn't quite nail it.
It was good listening to Griesinger again. I see he now follows Bregman's Auditory scene Analysis (ASA) concepts of perceptual foreground/background streaming & auditory objects.
But neither his presentation nor what you quoted from his paper(I presume) explain why a LCS perceptually enhances the bass when there is no output at LF frequencies - Griesinger explains a lot about envelopment when those LF frequencies arrive as decorrelated late reflections so it does give very strong hints but doesn't quite nail it.
no, with pillows on table reflection points and leaning forward the sound is damped and identical to when i lean backwards.
my setup is similar to a studio control room, where i have my table is instead for a large mixing console, i wonder how they control reflexions from the console?
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