Well edge diffraction is in effect a secondary time-delayed radiation source, the interaction of which with the direct radiation from the drive unit causes nulls & peaks. in the overall frequency / amplitude response. Which underlines the point that flush mounting drive units which are designed to be used that way is always a good policy providing you have the tools and ability to do it.
What mechanism are you referring to? Since as noted, I have no wish to waste my time, or yours, in speculating.
Sure. Variations have often been done. I don't know if foam core has been used, but certainly thin wood plys, MDF and materials with higher damping properties have like soft corks, felts & other cloths, suede etc. have all been used. The latter is probably the more useful approach. Foam core will be leaning in the latter direction, which is not necessarily a bad thing providing it's laminated to a suitably solid core.
One sub-variation I recall was a chap who built a set of Lynn Olson's Ariels from BB ply. He didn't have a router to flush-mount the drivers, so he scored through individual layers of ply with a craft-knife, then carefully removed each with a chisel. Obviously more patience and skill with hand tools than I have (granted, that isn't difficult), but it worked fine
Earl Geddes talks about it here: http://www.gedlee.com/Papers/Philosophy.pdf
I thought the problems of early reflections were well known?
I thought the problems of early reflections were well known?
'Page 5' (with all the dark inevitability of Greek Tragedy) is a page of text, which contains six independent paragraphs. Either state specifically what you are referring to, which is not a difficult task, with the conclusions you are drawing from it and the reasons for these, or stop wasting my time. I am not a mind reader, and I refuse point blank to speculate, infer, or assume what you may, or may not be thinking.
I like flush mounting as it really improves aesthetics. In my case it's an existing pair of 6" Karlsons that I modified recently.
I also have considered turning some rings on the lathe similar to those used on the Eliptoflex of Lafayette days of old but have no way of evaluating the result. However I may add overlays.
The paragraphs are related, I don't consider it a difficult task to understand what he is saying. Basically the diffraction is like a very early reflection that is detrimental to imaging. Do you not think this is what's happening when people say reducing diffraction improves imaging?
Matt(?), this image/imaging word appears many times. I guess that it refers to something forming in front of the speakers, probably due to stereophonic recording. I guess that this image need good focusing to be viewed 
The analogy with photography stops here. Slow propagation phenomenon Vs light.
The analogy with photography stops here. Slow propagation phenomenon Vs light.
True, but also the way the information is received and then processed is different, I don't think the analogies work well. Earl's explanation strikes me as a likely one when you consider what people report about the audibility of diffraction.
Perhaps a stereoscope would be a better analogy, how does the brain make sense of that and how easily is the image distorted?
Perhaps a stereoscope would be a better analogy, how does the brain make sense of that and how easily is the image distorted?
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Eek, thank you.
Not what i wanted to hear, lol.
Diffraction in horns, sure.
Surround a dome tweeter in felt (dunlavy), sure, i would not not do it.
Probably want to not frame the box either then like actual fern & roby "raven".
Dang it.
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The sound from two speakers in a room listened to through two ears is going to be subject to multiple reflections and interference, the FR is averaged between the ears and smoothed in the brain. The timing issues are more relevant to the audibility of the edge diffractions involved with surface mounting drivers as opposed to flush mounting.
So Earl speculates in the pdf paragraphs you are very loosely referring to. However, they are also written in highly generalised terms, sans data, in line with the intent, and title of, the document (it being a simplified presentation of his design philosophy), so it is largely a matter of his opinion being presented, rather than fact per se. While he covers the matter in more detail elsewhere, it, and the HOM concept for that matter remain subjects of debate. What I'm finding more puzzling though is that you joined the thread implying flush mounting & diffraction effects do not matter, yet appear to have spent some time since then arguing the opposite. It makes it a little difficult to hold a useful conversation when directly contradictory stances appear to be given (no doubt inadvertently), so perhaps you could clarify what your views are.
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