Bob, do you mean his paper "SPACIOUSNESS AND LOCALIZATION IN LISTENING ROOMS" ?
It's interesting reading. Seems that Griesinger finds similar things to what I hear. De-correlated bass (reverb, mostly) gives a sense of space and envelopment.
We kind of got off on a sidetrack about whether bass can be located or not. There are better frequency ranges for locating sounds, for sure. But I hear a lack when all the bass is summed mono. It kills a lot of the space.
It's interesting reading. Seems that Griesinger finds similar things to what I hear. De-correlated bass (reverb, mostly) gives a sense of space and envelopment.
We kind of got off on a sidetrack about whether bass can be located or not. There are better frequency ranges for locating sounds, for sure. But I hear a lack when all the bass is summed mono. It kills a lot of the space.
I can't remember which paper. I read most of them. It took a long time to do that. I don't know if "locating the sound" is necessarily the right goal for very low frequencies. Feeling the space, and how it compliments the rest of the range seems more the goal to me.
From about 80HZ to about 800HZ it's pretty well documented that we locate an image primarily by timing comparisons (phase - same thing). and from about 2kHZ - 6kHZ it's all about amplitude comparisons. Above 6kHZ it gets into where the pinea of the ear locates things on the vertical axis. It's been said that the region between 800HZ and 2kHZ has a lot to do with determining if the image is in front or in back of us. I don't know a lot about that. I have a binaural recording that when played through high quality headphones, demonstrated that something definitely makes that difference. I was astounded.
I guess the point I'm trying to make here is that the ear-brain mechanism determines image location in a variety of ways, depending on frequency. At some frequencies the distinction may be contingent on learning, or developing a feel for the immediate environment. Below 80HZ seems to be relatively uncharted territory for image locating, probably due to the way rooms affect that frequency range.
Another issue that's maybe just as important as stereo bass, is acoustically flat bass, at the listeners ear, despite the damage done by the room. For that, I recommend woofer towers with smaller diameter drivers, so the room is illuminated on all three axis. Maybe four 8 inch drivers in each of two towers, that stands maybe 4 feet tall for example. And of coarse active electronic EQ to get it just right down to 30HZ. And a 4 pole cutoff at the top end. If your bass is boomy due to room acoustics, you run the risk of believing that tone controls are a bad thing. (sorry - getting off subject again)
From about 80HZ to about 800HZ it's pretty well documented that we locate an image primarily by timing comparisons (phase - same thing). and from about 2kHZ - 6kHZ it's all about amplitude comparisons. Above 6kHZ it gets into where the pinea of the ear locates things on the vertical axis. It's been said that the region between 800HZ and 2kHZ has a lot to do with determining if the image is in front or in back of us. I don't know a lot about that. I have a binaural recording that when played through high quality headphones, demonstrated that something definitely makes that difference. I was astounded.
I guess the point I'm trying to make here is that the ear-brain mechanism determines image location in a variety of ways, depending on frequency. At some frequencies the distinction may be contingent on learning, or developing a feel for the immediate environment. Below 80HZ seems to be relatively uncharted territory for image locating, probably due to the way rooms affect that frequency range.
Another issue that's maybe just as important as stereo bass, is acoustically flat bass, at the listeners ear, despite the damage done by the room. For that, I recommend woofer towers with smaller diameter drivers, so the room is illuminated on all three axis. Maybe four 8 inch drivers in each of two towers, that stands maybe 4 feet tall for example. And of coarse active electronic EQ to get it just right down to 30HZ. And a 4 pole cutoff at the top end. If your bass is boomy due to room acoustics, you run the risk of believing that tone controls are a bad thing. (sorry - getting off subject again)
the bass is summed to mono and played from a single sub at one location then I would agree. But using multiple subs spaced around the room excites the modes with different phases and decorrelates the bass resulting in a very appealing and natural (as well as acoustically flat if done correctly) LF sound field. In this configuration I do not see how "stereo bass" would change anything. Further decorrelating each source, as I have described here on numerous occasions, has an even better effect making stereo bass totally unnecessary.
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That is my goal, also. The debate about localizing bass is important, tho - because if we simply can't, then all else is moot. Or if all recordings are mixed to mono in the bass, then there is also no point in stereo bass.
I was interested in David Griesinger's experiments (just found them) with changing bass phase. He was working fairly high, into what I would call the midrange, but still worth noting. I decided to try a little experiment here similar to what he was doing. I built a software filter that shifts the left and right bass phase by 45 degrees in opposite directions. You can see what it does below.
Certainly noticeable. It's an odd effect - midrange voices and instruments don't change place in the image, but there is a definite widening to the image. In fact the widening of the lower registers seems to peg the midrange more solidly to the middle.
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I doubt it makes it unnecessary. It may be a pleasant effect, even with mono bass, but is it as desirable as uncorrelated bass that comes from the recording itself? (If the recording has it). In my listening I don't find that it is as satisfying or as real, but maybe some combination of the two could bring benefits.
markus,
I understand exactly how the DBA is claimed to operate.
Part way through the linked thread, I see some extremely impressive results posted as graphs.
Seems to me this approach has some merit, the idea of a planar wavefront and active cancellation on the rear wall. The graphs are outstanding looking.
Still trying to understand the placement requirements on the wall and side wall idea. Seems at the moment that one would need more than 4 or 4+4 drivers on a wall that was much wider than most listening rooms... not sure if that is discussed explicitly or not.
The idea of the sub behind your head, I'm afraid is not for me since it ceases to function as intended once I move my listening position - which I do.
Also the OP in that thread mentions in the first post (in passing) that this method is mostly focused on HT and that audiophile applications might not be quite so good.
Pano, you might want to look at the group delay and phase shift inherent in the woofer ur using, and perhaps it has some sort of effect on the relationships with the higher frequency stuff? Dunno, just thinking. (sort of)
I understand exactly how the DBA is claimed to operate.
Part way through the linked thread, I see some extremely impressive results posted as graphs.
Seems to me this approach has some merit, the idea of a planar wavefront and active cancellation on the rear wall. The graphs are outstanding looking.
Still trying to understand the placement requirements on the wall and side wall idea. Seems at the moment that one would need more than 4 or 4+4 drivers on a wall that was much wider than most listening rooms... not sure if that is discussed explicitly or not.
The idea of the sub behind your head, I'm afraid is not for me since it ceases to function as intended once I move my listening position - which I do.
Also the OP in that thread mentions in the first post (in passing) that this method is mostly focused on HT and that audiophile applications might not be quite so good.
Pano, you might want to look at the group delay and phase shift inherent in the woofer ur using, and perhaps it has some sort of effect on the relationships with the higher frequency stuff? Dunno, just thinking. (sort of)
Another random thought.
It seems to me that the ideal placement for a woofer to appear to be part of a wider array, ie. use the boundary to create a phantom source, would be to put the woofers, or at least the outermost woofers, at the boundary of the back wall and side wall?
(same principle as a line array standing on the floor...)
_-_-bear
It seems to me that the ideal placement for a woofer to appear to be part of a wider array, ie. use the boundary to create a phantom source, would be to put the woofers, or at least the outermost woofers, at the boundary of the back wall and side wall?
(same principle as a line array standing on the floor...)
_-_-bear
Correct! You are talking to someone who can hear the difference in the bass.
People who can't hear it - needn't worry, I suppose. Mono bass is good enough. That would also hold true if the majority of your recordings have summed bass.
This 45 degree (90 total) shift intrigues me. Since the wavelengths are huge compared to the dimensions of the typical listening room (in my case anyway), I don't know if decorrelation would achieve much more than constantly varying bass amplitude at any given location (tremolo?), but a fixed delay or phase shift would effectively move the location of a given woofer relative to the other woofer and any room boundaries. In a room where it's just not practical to put the woofers where they interact best with room acoustics, this method might offer significant improvement in acoustic frequency response where the listener sits anyway.
Side wall? DBA (SBA) needs to have drivers (absorption) at opposite walls. Please see Double Bass Array ? Wikipedia
It's in German but Google Translate should help.
Well, that wasn't the question. The question was if flat and mode-free bass can be done in acoustically small rooms. I've shown 3 different real-world examples.
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Markus, iirc, one of the examples showed 4 speakers on the rear wall and two on each side walls, spaced... as far as I am concerned the absorption on the rear wall is a separate question as to how one launches a planar LF wave to the rear of the room.
the SBA I saw was decidedly non-flat.
The speaker behind the head, becomes non-flat at positions other than very near to the speaker.
The DBA appears to be very appealing, but is likely only useful for mono bass.
_-_-bear
the SBA I saw was decidedly non-flat.
The speaker behind the head, becomes non-flat at positions other than very near to the speaker.
The DBA appears to be very appealing, but is likely only useful for mono bass.
_-_-bear
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it's an interesting effect - on my system anyway.
I tried his Left minus R bass and Right minus L bass approach and it certainly does "something". It sounds more spacious than normal, even with content that is not >100 Hz heavy.
What I did was remove the bass content below 100 Hz from the Left channel that comes from the right, and vice-versa. I.E., decreasing crosstalk under 100Hz. It's subtle on the tracks I tried, but pleasing.
No. Where did you see that?
Yes. But absorption is crucial to such an approach because length modes are driven maximally.
No. Not sure what you've been looking at.
Yes. I sit still while listening or watching a movie. Others might not.
Yes.
Sorry but I still get this error with your "modes" app 1.0.0.8:
Looks like the app is trying to access files that are only available locally to your PC.
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Markus
Thanks for trying. I'm still trying to figure out how to place the DLL's so that the app can find them. The "Publishing Wizard" does not seem to do this correctly.
Anyone out there an expert at Visual Studio and Web publishing? I'd hate for this to not work out as the app is so cool.
Weather here is the worst I have seen in decades. Can't even leave the house.
Thanks for trying. I'm still trying to figure out how to place the DLL's so that the app can find them. The "Publishing Wizard" does not seem to do this correctly.
Anyone out there an expert at Visual Studio and Web publishing? I'd hate for this to not work out as the app is so cool.
Weather here is the worst I have seen in decades. Can't even leave the house.
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