Just that the term diffraction horn doesn't sound quite as sexy does it? It is exactly what this device is, just in axi-symmetric guise as opposed to that what pro-manufacturers might provide.
They will surely gloat about power response, but I doubt whether they would want someone run a cepstral over their impulses, especially near axis.
They will surely gloat about power response, but I doubt whether they would want someone run a cepstral over their impulses, especially near axis.
"First off, the "home depot" foam insulation cans are generally closed-cell foam to provide ... well, insulation (i.e. prevent the movement of air). I'm not sure they'd work so well as a transmissive phase plug."
If you're referring to what I did, I had no intention of using that as the HOM absorber, it was to slice up into patterns for cutting 30 ppi foam.
"Second, you'll need a urethane compatible mold release. there are several spray-on products available from anywhere that sells molding products. not expensive."
Thanks for the tip, I'll check at TAP Plastics
If you're referring to what I did, I had no intention of using that as the HOM absorber, it was to slice up into patterns for cutting 30 ppi foam.
"Second, you'll need a urethane compatible mold release. there are several spray-on products available from anywhere that sells molding products. not expensive."
Thanks for the tip, I'll check at TAP Plastics
Sitting at the beech in Phuket at the moment, hoping no Sunami's happen by.
A lot of good questions.
I should say that one of the more interesting observations in these posts was that for waveguide > 45 degrees there can only be a single reflection. This is obviously quite true. In my work, the mathematics seems to nearly collapse (fails to converge in math jargon) when the waveguides exceed 90 degree coverage, which is why I have only ever published data below this limit. Also for this reason, I would not consider a "lens" that is > 90 degree coverage to be a "waveguide" in my definition of the term. These shallow lenses are not really waveguides to me. To me these devices have a comparitively small effect and do not truly achieve the narrow CD coverage that I am after. Hence I haven't done much with them and can't really comment on them.
The foam in layers may work, but I worry about the interface between the layers. I would certainly NOT glue this. The effect of these layers vibrating, etc. concerns me which is why I use a block. I cut it with a hot wire. I would not be too concerned with fit, and yes I do use a simple cone. Perhaps an accurate fit right at the throat would work better, its just hat this would be darn near impossible to cut into a block.
The actual manner in which a wave reflects/diffracts off of a slope is in fact almost impossible to imagine from just thinking about it. Thats why it was so significant to have a theory which could tell me exactly how this does happen. BUT, this theory can only be applied in a very few number of contours. So when someone asks how will "such-and-such" act, its only a guess, and likely not a very good one at that. In my experience small deviations from the ideal/optimum cause large deviations in the results. So it doesn't take much of a change for an intuitive guess as to the results to be way off.
This is exactly the reason that I stick so close to the ideal rather than deviate from it by even a small amount. In doing so it is done at ones own risk.
I started making waveguides because I found that they were getting a bad name from people trying to make them. They weren't working very good. but when I looked into this, I found that no one was really sticky precisely to what I said. They were making "small" changes and expecting small deviations. This was not what they found. When I then built some to my precise formula they worked marvelously. I have never deviated from this formula since.
A lot of good questions.
I should say that one of the more interesting observations in these posts was that for waveguide > 45 degrees there can only be a single reflection. This is obviously quite true. In my work, the mathematics seems to nearly collapse (fails to converge in math jargon) when the waveguides exceed 90 degree coverage, which is why I have only ever published data below this limit. Also for this reason, I would not consider a "lens" that is > 90 degree coverage to be a "waveguide" in my definition of the term. These shallow lenses are not really waveguides to me. To me these devices have a comparitively small effect and do not truly achieve the narrow CD coverage that I am after. Hence I haven't done much with them and can't really comment on them.
The foam in layers may work, but I worry about the interface between the layers. I would certainly NOT glue this. The effect of these layers vibrating, etc. concerns me which is why I use a block. I cut it with a hot wire. I would not be too concerned with fit, and yes I do use a simple cone. Perhaps an accurate fit right at the throat would work better, its just hat this would be darn near impossible to cut into a block.
The actual manner in which a wave reflects/diffracts off of a slope is in fact almost impossible to imagine from just thinking about it. Thats why it was so significant to have a theory which could tell me exactly how this does happen. BUT, this theory can only be applied in a very few number of contours. So when someone asks how will "such-and-such" act, its only a guess, and likely not a very good one at that. In my experience small deviations from the ideal/optimum cause large deviations in the results. So it doesn't take much of a change for an intuitive guess as to the results to be way off.
This is exactly the reason that I stick so close to the ideal rather than deviate from it by even a small amount. In doing so it is done at ones own risk.
I started making waveguides because I found that they were getting a bad name from people trying to make them. They weren't working very good. but when I looked into this, I found that no one was really sticky precisely to what I said. They were making "small" changes and expecting small deviations. This was not what they found. When I then built some to my precise formula they worked marvelously. I have never deviated from this formula since.
Roy Lewis said:
Some of the people on this thread will probably remember years ago when Dr Geddes would get flamed into oblivion nearly every time he posted. In my opinion, the unusually civil reception he's getting these days is due to the fact that companies like Seas JBL and Mission are coming around, and using waveguides. In other words, I think the market's acceptance of waveguides has cut down on the flaming due to a new respect for the theories.
Maybe JBL will license the acoustic lever next
As for the Seas design, the response looks good. One thing that concerns me is that the improvements are relegated to a frequency spectrum that is not very audible. In other words, the GRAPHS look good, but the audibility of the improvement would be FAR less noticeable than an improvement to the directivity around 1khz or 2khz.
In addition to the ears insensitivity to high frequencies, I believe Dr Geddes once posted that ultra-high frequencies are also more susceptible to absorbtion and reflection due to their shorter wavelength.
ScottG said:
Nice!
..and of course after a bit of sun there is soi bangla.
I'm not familiar with that soi, but I can guess - This is Thailand!!! I'm back in BKK now, but I went to Phuket with my family and there are just some places that one should not go with an 8 year old boy. Took him to Patpong and had to block his view about every other step.
Ed LaFontaine said:
If you are talking about waveguides, I would suggest my book. The chapter on waveguides has material that is not in print anywhere else. It also has the answers to many of the questions about "permissible contours" and it lists all of the contours for which there are solutions and a minimum of diffraction. Maybe I'll post that chapter as a pdf when I get back to the states (not till Sept.)
Patrick Bateman said:
Some of the people on this thread will probably remember years ago when Dr Geddes would get flamed into oblivion nearly every time he posted. In my opinion, the unusually civil reception he's getting these days is due to the fact that companies like Seas JBL and Mission are coming around, and using waveguides. In other words, I think the market's acceptance of waveguides has cut down on the flaming due to a new respect for the theories.
Maybe JBL will license the acoustic lever next
I had concluded this same thing. Clearly my ideas contradict a lot of "gospel" and it was evident that many people felt the need to protect their turf. The attacks were way too personal and irrational to have been anything but a knee-jerk reaction to a fear that ones "faith" is under attack.
gedlee said:
amen to that (..kids grow up to fast as it is these days).
bangla road off of patong beach is basically phuket's version of patpong (..though I hear patong beach itself now has so many "freelancers" it might as well be bangla road).
(I'm actually considering moving there for a bit
, though not to appease any appetite 
but rather for the timezone, sand&saltwater, and fairly low living costs.)
(I'm actually considering moving there for a bit
I may end up moving here, its a dream place. As one young guy I met said to me "Life is TOO GOOD here!" I only wish that I knew about it when I was a bit younger - and SINGLE!! (Not that that makes all that much difference.)
gedlee said:
Be careful though.. you may run into some cultural hurdles in the long-run, (and possibly because of it), it might not be the best place to raise a child.
While this account (link) is oriented for a very different purpose, and it is biased on the negative side of things - it does provide at least one person's long-term viewpoint with cultural differences:
http://www.stickmanbangkok.com/Reader/reader1803.htm
I think its an interesting read - and in some respects (sadly) parallels more than a few current trends in the US (..popular music being one of them).
Well. Neither are most large cities in the US for that matter! There are areas to avoid, that's all, but they're very small. It just so happens that every tourist is immediately channeled to places where no one else actually goes on a daily basis. I am going to Phuket next month for a family vacation, and if you don't go to the actually very few notorious spots, the other 98% of that place are sleepy countryside with quite a few areas that look more like a tropical Thousand Oaks, CA, and the land prices too.
But you're right, at first the cultural differences make for very easy misunderstandings. Especially, the softspoken and gentle reactions of people can easily be misunderstood as agreement. Basically the average Westerner at first just can't tell when he has just seriously offended someone, with consequences to come (sometimes much) later. And, there is no free lunch in Asia either. A price will still have to paid, just (sometimes much) later.
With that in mind and knowing people living in Phuket, I think it really is great for living, and I think for kids too. I'd be much more worried about possibly entering byzantine legal business arrangements and the like, this can really bite, and while you may leave anytime when you stop liking the way of life, your money may not be so lucky.
MBK said:
Actually I was thinking more along the lines of formative education with respect to social habits (i.e. not formal education per se, but rather social interaction and learned peer behavior in a school environment). It is of course a concern in any school, be it public or private in any country. Its also counterbalanced by parenting, but its likely that at least some behavioral aspects (good and bad) will be en-grained in a child from social interaction in a school.
Now the US is kind'a funky in this regard with respect to schools in varying states. I believe that Earl hales from a central state - with that in mind, you can actually get a good, (assuming you have the ability and have chosen to live in a good school district), public education. The "formal" aspect of it might not be as good as a private school (particularly in comparison to some of the better northeast coast private schools) - but social interaction can be pretty good. In reference to the author's concerns in the link - something like "intellectualism" isn't usually "dampened" (unless you fall into a minor "click" that supports this), nor is overachieving "rationalizing" fostered - at all. Again though, this is only in reference to the author's concerns - which might very well be misleading (..don't know). Additionally, there could well be exceptional advantages to raising a child in Thailand. In this respect then my caution was just that, only a caution and something that might bear consideration.
Anyway.. completely off-topic.. and hopefully back to our "regularly scheduled program".
ScottG said:
Too long to read completely, but here is my overview opinion.
The (apparently young) writer is discovering the difficulty in relationships and the specifics of the asian mentality.
I have been married to a Chinese woman for nearly 13 years, while not Thai, the similarities far out weigh the differences. I have also been married to a "white" woman before. Both have their problems just as all relationships have their problems.
Thais are also, in general, a fairly ignorant group, as Asians are in general. Education here is for the few not the masses. Most problems that I have seen come from ignorance and not from maliciuos intent. The woman are, in general, far less eduacted and therefor ignorant. Even if they are educated they don't get the "street wise" education (from TV mostly) that westerners get. I think that the honesty issue stems more from ignorance that intent. Woman here are still 2nd class and they act that way. Until Asian changes this sexism the situation won't change. My wife won't live in Asia because of sexism - she's been spoiled by the US.
I'm not a youngster who is still trying to sort out life and relationships - they are not that big a mystery to me anymore. You can't make a relationship into what you want it to be, it is what it is - accept it or not.
My Chinese wife never admits she is wrong and never appolgizes for anything, but she tries to do the right thing. My American wife appologized all the time, but was deliberately deceatful and dishonest.
You have to play the hand that you are dealt.
ScottG said:
I wouldn't send my kids to a public school (fortunately I can afford not to). They just aren't up to the private schools because of things like "no child left behind" etc. that prevent the public schools from being top notch. Public schools target the lowest achiever - there is no accomodation to excell.