Massive clean up of this thread. Many posts have been moved here:http://www.diyaudio.com/forums/everything-else/173283-cmp-framing-what-you-mean.html
Keep this thread on the topic "Zero Difraction Loudspeaker." Threadjacking will not be tolerated.
DT, yes, i will build a wide dispersion speaker. ZDL does not mean that there is no difraction but that difracted sound does not create destructive interference if posible. The OX tweeter will get more directional in the upper frequency range and i think this is a good thing. I do not build an Omni because i think too much indirect sound can make the sound foggy. A ZDL has better image focus i think. Distortion in the crossover was discussed here too. We did discuss if phase distortion is audible and when how much. I reported about my experience with the Essex system.
Hello,
My comments were meant to be positive and focus on the ZDL. I am hanging to hear your impression of how your sub and mid integrate in the wide field.
Currently I am switching my listening between a pair of OB’s and a pair of Behringer near fields with wave-guides, looking for the place between the two.
DT
All just for fun!
My comments were meant to be positive and focus on the ZDL. I am hanging to hear your impression of how your sub and mid integrate in the wide field.
Currently I am switching my listening between a pair of OB’s and a pair of Behringer near fields with wave-guides, looking for the place between the two.
DT
All just for fun!
Isn't the problem that its destructive at some points in space and constructive at others. This means that only if the diffraction is mimimized can we minimize its effects. We can't arrainge to have it only constructive or only destructive.
On the psychoacoustic evidence that nulls are less invasive than peaks, I'd argue its constructive interference in the short delay listening window that we want to minimize. However I think Joachim categorized them all as "destructive" from a qualitative, not waveform addition, perspective.
I think sitting in the nearfield ( closer than 2m ) in front of a ZDL the timegap until disturbing interference comes can be made big enough. Certainly a speaker made like that ( the Stoll speakers ) sounds very much to my liking. In the farfield i prefer waveguides or line sources. I general, the closer we sit to the speakers the more dispersion we can afford i think. That was the discussion about DI ( directivity index ) also held on this thread.
Yes, constructive interference is a phenomenon too. I just posted that picture because Michael said that "destructive interference" has a well defined meaning. In posting that picture i wanted an answer if we can agree on what happens in this picture or if "destructive interference" is something else.
Everybody would be happy to only have "destructive interference to silence" as your picture shows. But as Earl already said - destructive makes only sense as a qualitative term (meaning something negative). You can't have destructive without constructive, if you apply it to SPL levels IMHO.
Hello ,
The room is the room, there will be reflections from the floor, ceiling and walls. The type of speaker will not stop the reflections. In terms of the speakers disappearing in the space the latency between the direcly radiated and reflected sound has more importance than the fact that there is reflected sound. Speaker generated noises are a dead giveaway in terms of the ear-brain being aware of the physical address of the speaker.
Speaker generated noises, sounds made by the operating speaker that are not musical and do not sound like the program ruin, for me, the illusion of being there or it being real. A couple of examples; velocity noise caused by air moving through a port and air moving around sharp edges. Turbulence causes noise. I cannot think of any inference that is positive.
Any other distracting speaker caused noises we can possibly control or eliminate in the design of the ZDL?
DT
All just for fun!
The room is the room, there will be reflections from the floor, ceiling and walls. The type of speaker will not stop the reflections. In terms of the speakers disappearing in the space the latency between the direcly radiated and reflected sound has more importance than the fact that there is reflected sound. Speaker generated noises are a dead giveaway in terms of the ear-brain being aware of the physical address of the speaker.
Speaker generated noises, sounds made by the operating speaker that are not musical and do not sound like the program ruin, for me, the illusion of being there or it being real. A couple of examples; velocity noise caused by air moving through a port and air moving around sharp edges. Turbulence causes noise. I cannot think of any inference that is positive.
Any other distracting speaker caused noises we can possibly control or eliminate in the design of the ZDL?
DT
All just for fun!
The diffraction issues are actually very complex, and so are just the driver diaphragm vibrations. I would not know how to put it in words. I tried to do it then read it and could not understand it myself.
Hi Earl,
We debated this early in the thread, before it went off the rails.
There I formulated two simple Axioms that state:
In order to maintain the same direct sound to reflected sound ratio a speakers DI must increase with increasing listening distance.
In order to maintain a correct tonal balance for a number of listening positions ("sweet spot") we need to decrease DI with falling listening distance.
I have "known" this for many decades, ever since I learned about acoustics, but I have never seen it stated directly and clearly.
What this suggests clearly is that for near-field listening (which is what Joachim intends his ZDL for) a wide dispersion is a necessity and we hence must take care to control diffraction effects carefully.
If we were working on a speaker intended for long listening distances we would have to apply a much more controlled directivity and issues related diffraction would be much less.
The axioms formulated above certainly explain why there is so much difference in approaching the issues of directivity and diffraction control and they underscore that there is no single Answer that is "right" and can be applied dogmatically everywhere.
Ciao T
We debated this early in the thread, before it went off the rails.
There I formulated two simple Axioms that state:
In order to maintain the same direct sound to reflected sound ratio a speakers DI must increase with increasing listening distance.
In order to maintain a correct tonal balance for a number of listening positions ("sweet spot") we need to decrease DI with falling listening distance.
I have "known" this for many decades, ever since I learned about acoustics, but I have never seen it stated directly and clearly.
What this suggests clearly is that for near-field listening (which is what Joachim intends his ZDL for) a wide dispersion is a necessity and we hence must take care to control diffraction effects carefully.
If we were working on a speaker intended for long listening distances we would have to apply a much more controlled directivity and issues related diffraction would be much less.
The axioms formulated above certainly explain why there is so much difference in approaching the issues of directivity and diffraction control and they underscore that there is no single Answer that is "right" and can be applied dogmatically everywhere.
Ciao T
Joachim,
Yes, I know Martina. I'm not sure about that problem.
Personally I do not like the AMT's I have heard. They audibly compress and they always have this honk, unless you use super steep filters. Metal ribbons may have suprasonic resonances, just like metal (or other hard) domes, some people react negative to these.
However with decent ribbon it should be possible to push these resonances far above what we hear.
Ciao T
Yes, I know Martina. I'm not sure about that problem.
Personally I do not like the AMT's I have heard. They audibly compress and they always have this honk, unless you use super steep filters. Metal ribbons may have suprasonic resonances, just like metal (or other hard) domes, some people react negative to these.
However with decent ribbon it should be possible to push these resonances far above what we hear.
Ciao T
Those axioms imply that you think of a fixed direct/indirect ratio as a value in itself. Why not let the listener decide, what ratio is best for him? Simply by moving his chair to and fro.
Do you have any idea, how to construct a loudspeaker which maintains the same ratio regardless of listening distance?
It also implies that room behaviour is a constant. It's not. Far from it.
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Yes, direct sound, power response as it relates to the direct radiation and polar response, room absorption, listening distance all relate to the ratio of direct/reflected sound at the listener's ears. Please carry that over the "flat is not correct for stereo thread". 🙂
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