"Noah Katz seems to be reluctant to accept the argument that was made along the lines that I stated."
True; I'm an engineer, not a physicist/mathematician, and I'm unable to accept that there can be modes w/o boundaries.
Even in the case where there are walls at infinity, isn't the amplitude of all of the modes zero because of dimunition w/distance?
True; I'm an engineer, not a physicist/mathematician, and I'm unable to accept that there can be modes w/o boundaries.
Even in the case where there are walls at infinity, isn't the amplitude of all of the modes zero because of dimunition w/distance?
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Joined 2003
Ya got me thinking...it's really an interesting solution 
My only reservation is "wasting" almost half the horsepower. What do you think about a passive solution on the back wall? Membrane absorber, etc. I could vent the entire floor / back wall intersection, maybe even the ceiling / back wall as well, but don't know how well it would work.
My only reservation is "wasting" almost half the horsepower. What do you think about a passive solution on the back wall? Membrane absorber, etc. I could vent the entire floor / back wall intersection, maybe even the ceiling / back wall as well, but don't know how well it would work.
noah katz said:
Once again - you have to look at the limiting case NOT the end case. What happens as the room gets larger and larger? This same trend MUST continue since the physics doesn't just abruptly change at some point and all of a sudden the modes "go away".
The modes get denser and denser and denser until at an infinite volume they form a continuum. Just like in optics.
"Once again - you have to look at the limiting case NOT the end case. What happens as the room gets larger and larger? This same trend MUST continue since the physics doesn't just abruptly change at some point and all of a sudden the modes "go away"."
Maybe this is just over my head, but it seems to me that walls moving to infinity and no walls are distinct cases, and that the mathematical solution to the latter not is being inappropriately applied to the former.
Maybe this is just over my head, but it seems to me that walls moving to infinity and no walls are distinct cases, and that the mathematical solution to the latter not is being inappropriately applied to the former.
Paul W said:Ya got me thinking...it's really an interesting solution
My only reservation is "wasting" almost half the horsepower. What do you think about a passive solution on the back wall? Membrane absorber, etc. I could vent the entire floor / back wall intersection, maybe even the ceiling / back wall as well, but don't know how well it would work.
Yeah, if you could build a rear absorber that would handle down to the first longitudinal mode, that might be the best of all worlds. Absorb the modes but allow the room to pressurize below there. Building an absorber like that might be tough though. Buying more drivers might be cheaper and use less volume out of your room.
Hello Earl,
You mentioned earlier in this thread that among of the challenges we face in trying to get good sound in a small room is miminizing detrimental early reflections (before 10 milliseconds) while preserving beneficial late-arriving reflections (after 10-15 milliseconds). I am under the impression that it would be nice to have more late-arriving reverberant energy than what we typically get in most home listening rooms, assuming there wasn't an accompanying penalty in additional early reflections.
Coming from a dipole speaker background, wherein we try to position our dipoles a good six feet or so in front of the wall (which gives the reflected backwave a good 10 milliseconds or more time delay), I see a possible window of opportunity. And so I jumped out of it.
I will be displaying a pair of controlled-pattern offset bipolar speakers at the Rocky Mountain Audio Fest this coming weekend. They will have the same 90-degree pattern waveguide and TAD woofer as the Jazz Modules, but will have a second waveguide and woofer on the rear of the enclosure. The rear-firing array will be offset about a foot lower than their front-firing counterparts. This is to stagger as much as is practical the location of my low frequency sources with respect to room boundaries and the listening position.
The enclosure is considerably wider than it is deep, to minimize the on-axis wrap-around dip that occurs in the lower midrange when the path length from the rear-facing woofer to the listener is one-half wavelength farther than from the front-facing woofer to the listener. I think this dip largely disappears in the power response.
The net effect is a higher ratio of late-arriving reverberant energy to direct energy, and with proper positioning I don't think there are any additional detrimental early reflections. Whether this is worth the additional cost is probably debatable.
One rainy day just for kicks you might try a bipolar array with your ESP speakers. I don't think it would be worthwhile for discos, nor for small rooms where proper placement isn't possible, but I think it has merit under the right conditions.
What are your thoughts?
Duke
You mentioned earlier in this thread that among of the challenges we face in trying to get good sound in a small room is miminizing detrimental early reflections (before 10 milliseconds) while preserving beneficial late-arriving reflections (after 10-15 milliseconds). I am under the impression that it would be nice to have more late-arriving reverberant energy than what we typically get in most home listening rooms, assuming there wasn't an accompanying penalty in additional early reflections.
Coming from a dipole speaker background, wherein we try to position our dipoles a good six feet or so in front of the wall (which gives the reflected backwave a good 10 milliseconds or more time delay), I see a possible window of opportunity. And so I jumped out of it.
I will be displaying a pair of controlled-pattern offset bipolar speakers at the Rocky Mountain Audio Fest this coming weekend. They will have the same 90-degree pattern waveguide and TAD woofer as the Jazz Modules, but will have a second waveguide and woofer on the rear of the enclosure. The rear-firing array will be offset about a foot lower than their front-firing counterparts. This is to stagger as much as is practical the location of my low frequency sources with respect to room boundaries and the listening position.
The enclosure is considerably wider than it is deep, to minimize the on-axis wrap-around dip that occurs in the lower midrange when the path length from the rear-facing woofer to the listener is one-half wavelength farther than from the front-facing woofer to the listener. I think this dip largely disappears in the power response.
The net effect is a higher ratio of late-arriving reverberant energy to direct energy, and with proper positioning I don't think there are any additional detrimental early reflections. Whether this is worth the additional cost is probably debatable.
One rainy day just for kicks you might try a bipolar array with your ESP speakers. I don't think it would be worthwhile for discos, nor for small rooms where proper placement isn't possible, but I think it has merit under the right conditions.
What are your thoughts?
Duke
Duke
The problem with these posts is that they need to be kept short - so they are often over simplified. That may be the case here.
There is some evidence to suggest that reverberant energy to be perceived as spatiousness needs to come from the sides and the rear. We do not seem to perceive energy from the front as reverberation as readily as we do that from the rear and the sides. In architectural acoustics it is well know that the reverberant energy should be dominately lateral. Hence I am not sure that your proposal is as "sound" as you might hope.
This is precisely why I believe in a very narrow direct field slightly toed in. Bbecause in this configuration virtually all of the reverberant energy will be from behind, especially if the back of the room is lively - as all of my designs are.
Also, it appears that your proposal would require a room to be at least 18 feet in depth - 6 from speaker to front wall, 6 from speaker to listener and 6 behind the listener - and these are minimums I would think. Given that most rooms tend towards square, this is a fairly big room.
The problem with these posts is that they need to be kept short - so they are often over simplified. That may be the case here.
There is some evidence to suggest that reverberant energy to be perceived as spatiousness needs to come from the sides and the rear. We do not seem to perceive energy from the front as reverberation as readily as we do that from the rear and the sides. In architectural acoustics it is well know that the reverberant energy should be dominately lateral. Hence I am not sure that your proposal is as "sound" as you might hope.
This is precisely why I believe in a very narrow direct field slightly toed in. Bbecause in this configuration virtually all of the reverberant energy will be from behind, especially if the back of the room is lively - as all of my designs are.
Also, it appears that your proposal would require a room to be at least 18 feet in depth - 6 from speaker to front wall, 6 from speaker to listener and 6 behind the listener - and these are minimums I would think. Given that most rooms tend towards square, this is a fairly big room.
Thanks for commenting on my bipolar idea.
While it's true that the initial arrival of the rear-firing array's energy is from the front, I would think that after that it would mix in with the rest of the reverberant energy in a more clearly beneficial way, improving the relative balance regardless of what the room's acoustics are (preferably reverberant and fairly diffuse). And I recommend they be set up like you showed me on the Summas - toed in enough to avoid that early same-side-wall reflection.
Remember the Cheetahs? Given the wizzer-coned fullrange driver, they probably should have sounded a lot worse than they did. The only excuse I can think of for them not seriously sucking is that they must have been doing something right, and my guess is it had to do with putting more energy into the reverberant field.
In a side-by-side comparison, in my opinion the new bipoles sound better than my equivalent monopoles. Non-controlled data point of one. Okay make that two - Lori agrees.
On the other thread you mentioned your success rate in selling to prosound customers. Sounds like there's no comparison. Congratulations! It's great to hear that your work is not just admired from afar, but paid for and admired from up close.
Duke
While it's true that the initial arrival of the rear-firing array's energy is from the front, I would think that after that it would mix in with the rest of the reverberant energy in a more clearly beneficial way, improving the relative balance regardless of what the room's acoustics are (preferably reverberant and fairly diffuse). And I recommend they be set up like you showed me on the Summas - toed in enough to avoid that early same-side-wall reflection.
Remember the Cheetahs? Given the wizzer-coned fullrange driver, they probably should have sounded a lot worse than they did. The only excuse I can think of for them not seriously sucking is that they must have been doing something right, and my guess is it had to do with putting more energy into the reverberant field.
In a side-by-side comparison, in my opinion the new bipoles sound better than my equivalent monopoles. Non-controlled data point of one. Okay make that two - Lori agrees.
On the other thread you mentioned your success rate in selling to prosound customers. Sounds like there's no comparison. Congratulations! It's great to hear that your work is not just admired from afar, but paid for and admired from up close.
Duke
As far as I can tell, in this thread one issue has not been discussed yet in detail: a stereo image that makes sense.
To explain: my issue with ordinary stereo is, that it only works in a fairly narrow position. Here, it sometimes works exceedingly well. Completely off axis, no imaging, but that's ok as long as the power response is smooth. My speakers for instance do both very well.
But it's near the "sweet spot" that 2-chennel stereo becomes illogical. Any center image by moving away from the phantom image and more to the side, wanders _with_ the mover. Say when moving to the right the phantom center also moves to the right. In nature, of course, by moving to the right of a source displayed in front, the aural position now moves more to the left.
I'd like to know whether there is a good solution to this issue. Various exotic approaches have been mentioned but not really discussed. Multi channel, in my limited experience, exacerbates the problem by making image shifts een more illogical and image position-dependent. A L+R (mono) mixed center might help, at the cost of a third full range box, hardly a cost and space effective solution. Or maybe a L+R center fullrange, with tiny and far apart HF sources mixed L-R and R-L, respectively, just for ambience?
Again what I am asking is not whether good spacious sound with good imaging can be achieved, it can. And no question that perfect imaging can not be achieved at any arbitrary position in the room. But I would like, at the very least, a solution where off center listening does not lead to illogical phantom images.
To explain: my issue with ordinary stereo is, that it only works in a fairly narrow position. Here, it sometimes works exceedingly well. Completely off axis, no imaging, but that's ok as long as the power response is smooth. My speakers for instance do both very well.
But it's near the "sweet spot" that 2-chennel stereo becomes illogical. Any center image by moving away from the phantom image and more to the side, wanders _with_ the mover. Say when moving to the right the phantom center also moves to the right. In nature, of course, by moving to the right of a source displayed in front, the aural position now moves more to the left.
I'd like to know whether there is a good solution to this issue. Various exotic approaches have been mentioned but not really discussed. Multi channel, in my limited experience, exacerbates the problem by making image shifts een more illogical and image position-dependent. A L+R (mono) mixed center might help, at the cost of a third full range box, hardly a cost and space effective solution. Or maybe a L+R center fullrange, with tiny and far apart HF sources mixed L-R and R-L, respectively, just for ambience?
Again what I am asking is not whether good spacious sound with good imaging can be achieved, it can. And no question that perfect imaging can not be achieved at any arbitrary position in the room. But I would like, at the very least, a solution where off center listening does not lead to illogical phantom images.
MBK said:
You need to read my work and hear my speakers because there is no "sweet spot". There is a solution, it works well, and its readily available, especially to you.
Albeit, I would like to say that a center channel does improve things, but its a marginal improvement, not a massive one.
Hi Earl,
true, I haven't heard your speakers - yet - in their recommended configuration. Also while I've been through a fair share of your work I sure haven't read all of it.
The Summa white paper while it was posted on your site gave me the clearest idea of your concept (toe-in with directional speakers to hit the opposing side wall first, rather than the adjacent side wall, and generate mostly lateral reverb with a sufficiently long time delay even in a small room - that's what I understood).
So far so good. I tried the toe-in with my own open baffles (with conventional, non waveguided tweeter as main limitation, and fairly directional bass and mid as main plus). It does produce a much more position-forgiving image and more general reverb. Yet I can't quite see how the problem of increasing SPL from one side when moving closer to it, and the resulting intuitively "wrong" loudness-generated image cues, are being solved. When moving closer to one side, the nearer side side becomes louder, the image moves towards that side, and from a certain point on collapses towards the nearest speaker.
Then again my speakers are not directional enough in the mid treble so I can't fully test the concept with my materials at hand.
true, I haven't heard your speakers - yet - in their recommended configuration. Also while I've been through a fair share of your work I sure haven't read all of it.
The Summa white paper while it was posted on your site gave me the clearest idea of your concept (toe-in with directional speakers to hit the opposing side wall first, rather than the adjacent side wall, and generate mostly lateral reverb with a sufficiently long time delay even in a small room - that's what I understood).
So far so good. I tried the toe-in with my own open baffles (with conventional, non waveguided tweeter as main limitation, and fairly directional bass and mid as main plus). It does produce a much more position-forgiving image and more general reverb. Yet I can't quite see how the problem of increasing SPL from one side when moving closer to it, and the resulting intuitively "wrong" loudness-generated image cues, are being solved. When moving closer to one side, the nearer side side becomes louder, the image moves towards that side, and from a certain point on collapses towards the nearest speaker.
Then again my speakers are not directional enough in the mid treble so I can't fully test the concept with my materials at hand.
I was a dealer for the Summas, so spent a fair amount of time with them. I also owned speakers with other formats, including 8" fullrange wizzer-cone drivers. And my speakers are similiar to the Summas in configuration, only on a smaller scale.
In my experience the strong toe-in defiintely works best with the 90 degree pattern waveguide speakers. It didn't really work with any of the others I tried.
Even with a 90 degree waveguide speaker, there will still be distances & angles from which the off-centerline listener has the image pulled to one side somewhat. For my listening style, it is still a worthwhile improvement. When using this setup at audio shows I've had many listeners content to remain in an off-centerline seat even when the coveted "sweet spot" centerline seat became available. In most cases there is still something of a central image even when listeners are seated directly in front of one of the speakers, provided they aren't too far back or too close.
Duke
In my experience the strong toe-in defiintely works best with the 90 degree pattern waveguide speakers. It didn't really work with any of the others I tried.
Even with a 90 degree waveguide speaker, there will still be distances & angles from which the off-centerline listener has the image pulled to one side somewhat. For my listening style, it is still a worthwhile improvement. When using this setup at audio shows I've had many listeners content to remain in an off-centerline seat even when the coveted "sweet spot" centerline seat became available. In most cases there is still something of a central image even when listeners are seated directly in front of one of the speakers, provided they aren't too far back or too close.
Duke
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