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Old 6th July 2008, 02:27 PM   #1021
gedlee is offline gedlee  United States
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Graff

If there is a feature of the Japanese paper that is notable it is that they realized that abrupt changes in wall contours is a big mistake. But they still hadn't figured out how to make the contour that had the smallest changes. Abrupt changes will be very obviuos in the impulse response.

The Ai designs and some of what I have published can have slightly different crossovers as this was constantly evolving over the years.
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Old 6th July 2008, 03:49 PM   #1022
MEH is offline MEH  United States
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Quote:
Originally posted by gedlee


Actually Wright was a trained engineer and architect
Actually, no. The University of Wisconsin had no program in architecture during the brief time that Wright attended, so he studied engineering there, but he came nowhere close to receiving a degree. Wright's training was as an apprentice -- briefly to J.L. Silsbee, later and longer to Louis Sullivan. Sullivan was better educated than Wright, having spent one year at MIT and one year at the École des Beaux-Arts, but Wright's engineering skills were never top-notch, and often inadequate to his design aspirations.

Wright did not invent reinforced concrete, and he was no master of it -- as the millions of dollars of work needed at Fallingwater to compensate for Wright's engineering mistakes (principally inadequate reinforcing steel) attest.

Wright was world famous before he was 45, having completed almost all of the Prairie Houses by then, and having the important Wasmuth Portfolio of his early work published in 1910-1911.
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Old 6th July 2008, 04:43 PM   #1023
graaf is offline graaf  Poland
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Quote:
Originally posted by soongsc

I am wondering what improvement they mean? Most irregular impulse shape would probably be due to the throat and it's matching to the driver as Dr. Geddes has mentioned. Looking at the impulse in his papers and the AI site, these two look a bit different which makes me wonder if the AI site has problems with matching the throat with the driver or not. But it would be interesting to see what the Japanese impulse looks like.
impulse response of GS-1 waveguide taken from original 1984 AES paper was posted above
and considered as "above average" by Dr Geddes

best,
graaf
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Old 6th July 2008, 04:48 PM   #1024
graaf is offline graaf  Poland
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Quote:
Originally posted by gedlee


In general I don't see much advantage to a changing cross-section in the waveguide, certainly not from circular to square. Circular to elliptical I could understand - if done right!!! - but not to square.
what would be the advantage of changing cross-section shape "from circular to elliptical"?
"if done right" of course

BTW - has anybody ever done it right? Are there any commercial designs of such kind?

best regards,
graaf
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Old 6th July 2008, 05:01 PM   #1025
soongsc is offline soongsc  Taiwan
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Quote:
Originally posted by graaf


impulse response of GS-1 waveguide taken from original 1984 AES paper was posted above
and considered as "above average" by Dr Geddes

best,
graaf
If that is not composed from an MLS sequence, then it does seem pretty good. I do wonder what it would look like looking at it on a 5msec scale instead of 20msec though.
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Old 6th July 2008, 05:44 PM   #1026
soongsc is offline soongsc  Taiwan
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Quote:
Originally posted by graaf


what would be the advantage of changing cross-section shape "from circular to elliptical"?
"if done right" of course

BTW - has anybody ever done it right? Are there any commercial designs of such kind?

best regards,
graaf
Some ideas are brewing in my mind.

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Old 6th July 2008, 06:04 PM   #1027
JLH is offline JLH  United States
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Quote:
Originally posted by angeloitacare
hi John

thanks for your answer. The polar response matching of two horns at crossover point might in fact help integration . I've not given importance to the vertical distance between the two horns at my draw, as this was not the focus of the question. There will be the tweeter between them, so there is a little more distance , and i thought to place it on axis, vertically, too. Or do you think, it would be better, to bring the two horns as close together as in your example, and the tweeter on side of them ? When you say 112hz of the 27" horn at half size, you want to say at half space, floor positioning, right ? I am getting 187hz free space, and 160hz half space. This , if the horn loads down to Fc. Have you tried, where the best crossover point would be with a 35" midbass horn , and the size of the OB in combination with it ? Lets say, we use a Fane Studio 8M in a 27" horn, which loads the driver to 160hz. Below it transmits down to ~ 90hz as a direct radiator. What difference would be perceived compared to the same driver, used in a 35" horn, which loads down to 125hz at half space ? would it be only efficiency, or might there be a different tonal behaviour ?

Angelo
Angelo,

Getting the two horns/wave guides to integrate is more important than the tweeter integration in my experience. You still want to time align the tweeter; just try different locations until you find what works the best. Moving a small tweeter around is much easier than building a new stand for a heavy horn or wave guide.

Yes, the 112Hz tractrix is placed in ˝ space and is made to have a mouth size equal to ˝ space, i.e. approximately 27” in diameter. In my simulation I get -6dB at 111Hz in ˝ space. The woofer is the B&C 10MD26.

Click the image to open in full size.

Anytime you change woofers you will get a tonal difference. For example, the B&C 8PE21 and the Fane Studio 8M do NOT sound the same. The Fane is more forward and clearly has more high frequency energy than the B&C. However, the B&C can become the better choice if you have a shorter horn. In a shorter horn, less than 30” deep, the Fane can become tiring and a little bit too much in your face. The Fane 8M has a flux density of 1.7T, and the 8PE21 has 1.25T. It makes sense that they will not sound the same. I’ve found the 10MD26 to be a nice happy medium between the two. I also find that the woofer can make as much a difference as the enclosure/horn it is mounted in. I must also disagree with Earl's comment concerning the woofer not mattering as much.

You should not really consider the direct radiation of a woofer in a horn. You should only focus on the horn loaded portion. Do not become distracted with the notion of direct radiation in a horn. If you are relaying on direct radiation, then you have not designed a proper horn.

Rgs, JLH
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Old 6th July 2008, 06:07 PM   #1028
gedlee is offline gedlee  United States
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Quote:
Originally posted by MEH


Actually, no. The University of Wisconsin had no program in architecture during the brief time that Wright attended, so he studied engineering there, but he came nowhere close to receiving a degree. Wright's training was as an apprentice -- briefly to J.L. Silsbee, later and longer to Louis Sullivan. Sullivan was better educated than Wright, having spent one year at MIT and one year at the École des Beaux-Arts, but Wright's engineering skills were never top-notch, and often inadequate to his design aspirations.

Wright did not invent reinforced concrete, and he was no master of it -- as the millions of dollars of work needed at Fallingwater to compensate for Wright's engineering mistakes (principally inadequate reinforcing steel) attest.

Wright was world famous before he was 45, having completed almost all of the Prairie Houses by then, and having the important Wasmuth Portfolio of his early work published in 1910-1911.

Back in those days it was not uncommon for an engineer to not have completed a degree but still work in the profession.

I think the criticizm of Falling Water is unfounded as reinforced concrete - not widely used at that time even if Wright did not invent it - was not well understood and the need for rust resistant steel was not appreciated. It wasn't really available even if it had been appreciated. Wright used what was available and made the same mistakes that virtually any other engineer would have made. Had Falling Water not been such a remarkable piece of work it would have simply been torn down when it reached the end of its useful life, which was really a long time ago. There are details which I may not know, but from having been at Falling Water several times my recollection was that Wright's design was really up to the best knowledge that they had at the time for doing something which no one else would have ever even attempted for fear of exactly what Wright got - criticism of the fact that it had a finite life span. Most engineers thought that it would collapse in about twenty years. It's lasted almost 100. That, to me, is nothing short of remarkable.

Most of the designs that people think of when they think of Wright were done well after he was 50. I've seen his earlier work and it's, well, not all that impressive. I thought that Spring Green was done when he was well past 50.
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Old 6th July 2008, 06:17 PM   #1029
gedlee is offline gedlee  United States
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Quote:
Originally posted by JLH
I must also disagree with Earl's comment concerning the woofer not mattering as much.

Rgs, JLH
You can of course disagree, but your data is all non-blind circumstantial while mine is under well controlled conditions with multiple blind listeners. Hardly on the same footing. I'm certainly not going to change my opinion based on such data.

But lets be clear that your comparisons are not what I am saying. When we compared the TAD and B&C the two systems were optimized. I didn't just swap components. Of course swaping two drivers with different paramters without optimizing the system is going to sound different. My point is that I can optimize a system around almost any set of drivers and for the most part they will sound virtually identical. They won't be identical, even the B&C and the TAD had a different sound, its just that they were subjectively rated as being about the same. The sound differences were small even though the driver difference were large. The major effect is the system design and the drivers have a relatively minor influence. Certainly far far less that the price difference!!

The fixation on driver details is simply not warranted IMO.
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Old 6th July 2008, 09:54 PM   #1030
MEH is offline MEH  United States
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Quote:
Originally posted by gedlee



Back in those days it was not uncommon for an engineer to not have completed a degree but still work in the profession.

I think the criticizm of Falling Water is unfounded as reinforced concrete - not widely used at that time even if Wright did not invent it - was not well understood and the need for rust resistant steel was not appreciated. It wasn't really available even if it had been appreciated. Wright used what was available and made the same mistakes that virtually any other engineer would have made. Had Falling Water not been such a remarkable piece of work it would have simply been torn down when it reached the end of its useful life, which was really a long time ago. There are details which I may not know, but from having been at Falling Water several times my recollection was that Wright's design was really up to the best knowledge that they had at the time for doing something which no one else would have ever even attempted for fear of exactly what Wright got - criticism of the fact that it had a finite life span. Most engineers thought that it would collapse in about twenty years. It's lasted almost 100. That, to me, is nothing short of remarkable.

Most of the designs that people think of when they think of Wright were done well after he was 50. I've seen his earlier work and it's, well, not all that impressive. I thought that Spring Green was done when he was well past 50.
Yes, a lack of formal education among architects and engineers was not all that uncommon in Wright's youth. That said, there were many better educated building engineers and architects contemporary to Wright. Some of them told Wright during the planning phases of Falling Water that his concrete reinforcement engineering was inadequate and that the cantilevers would sag (they did not say, as Wright claimed they did, that the house would collapse into Bear Run), and they were correct. Wright ignored them and presumed more technical expertise than he actually had in a material that had by that time been in use in building construction for 70 years. He also made the rudimentary error at Falling Water of failing to account for the initial, self-weight deflection of the cantilevers, much less for live loads or for materials deterioration and creep over time. That meant that the cantilevers sagged from the moment the forms and scaffolding were removed. In fact, had the contractors built to Wright's specification and not secretly added additional reinforcement to the building, Falling Water might well have had a very short lifetime. Constructed as it was, it has required a tremendous amount of work to survive intact just past its 70th birthday.

I'm as big a Wright fan as anyone, but if you get away from the cultists (some of whom are tour guides) and their hagiographic texts and do some rigorous study of Wright and his works (and I have literally spent more time formally studying Wright than he spent at the University of Wisconsin), then you will quickly find that Wright was not nearly as great an engineer as he and his followers claimed. Daring and innovative, but often not very technically successful.

Your favorite buildings may be from Wright's last phase, but I can assure you that your opinion is not universal. Many consider his Prairie Houses to be his best work (owing, in no small part, to the exquisite drawings done by Marion Mahony Griffin for the Wasmuth edition that made Wright's fame in Europe), and that many of his later buildings (many Usonian houses in particular) are uninspiring, cookie-cutter efforts churned out by his staff without a lot of influence from the Master. Many consider the middle phase of his career, when he was in his 50s and building textile block houses in California and the Imperial Hotel in Tokyo, to be a curious exploration of what turned out to be largely a dead-end, both technically and aesthetically. By his late 50s and early 60s, Wright was mostly a has-been in the world of architecture, and he was in little demand during the Depression. Given those depths, the last 25 years of his career are a remarkable return to glory and acclaim that he hadn't seen since his early 40s.

Now as for Wright's buildings near Spring Green, they span almost the entirety of his career, from the Romeo and Juliet windmill in 1896 when he was not yet 30, to the Hillside Home school of 1902, to Taliesin (first built in 1911, rebuilt twice after major fires in 1914 and 1925, and in near continuous building and rebuilding throughout Wright's time in residence), to the Midway Barns and the Drafting Studio addition to the Hillside Home school building after the founding of the Taliesin Fellowship in 1932. Because they comprise the only site that Wright was actively involved with throughout his career, the buildings around Taliesin afford a unique opportunity to study the evolution of Wright's aesthetic and design sensibility -- as I did during my time in architecture school.
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