Beyond the Ariel

Big snowstorm here in Colorado, the first of the year. 1 foot of snow drifting against the back fence, and another foot due by the morning. Stayed indoors today and plan to do the same tomorrow. By Saturday, it should be cleared out enough for the Halloween trick-or-treaters to get around, although it will be around freezing in the evening.

Interesting discussion, folks - don't mind me, I'm just looking out the window at all the snowflakes drifting out of the night sky. The pix was taken a couple of years ago, but it looked pretty similar today.
 

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The I-25 corridor running up and down the Front Range pretty much got dumped on at once. Really wet stuff at first, big fat snowflakes that turned to slush when they hit the ground. But they kept on coming, the temperatures dropped, and we had a steady 20 mph wind out of the North. Sometimes a whiteout condition - I didn't envy the few drivers when this happened - but fortunately most schools and many businesses are closed, so traffic (as seen on Channel 7 News) looked light.

As temps dropped, snowflakes got smaller and more wind-blown, and kept on coming steadily out of the North. I'm looking out my window now (which faces East), and I see pools of light from the streetlamps with snow drifting sideways through the cone of yellow-orange light. The sky is a pearly dark color, that smooth featureless sky of a snowstorm at night. Beautiful in an eerie way, but I'm very glad I'm warm and cosy inside and the electric power in Northern Colorado is reliable.

Colorado is a beautiful place, but it can also kill you - anyone outside tonight better be well-protected wearing boots with a good grip. A snowstorm with near-whiteout conditions and a steady 20 mph wind out of Canada is nothing to fool with, as Karna and I found out a few years ago when we were surprised by a sudden change in weather when we were in Boulder. A 15-mile drive back home sounds easy enough when the weather is bright and clear, but it's another thing altogether in the dark with snow coming directly at the windshield and no sign of the road except for marker poles every 50 feet or so.
 
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Stay tuned with Channel 7 News, which is what Karna and I were watching today. I don't envy the commuters, although the main roads (as usual) are clear. It's the residential areas that don't get plowed as often. It looks like schools across the Front Range cities will be closed tomorrow as well. Traffic at the airport is reduced although flights are still coming and going on a regular basis.

This isn't as bad as the 7 successive snowstorms a couple of years ago (when I had my accident) that pretty much shut down things all across the state, with people sleeping at the airport for days at a time and thousands of cattle starving on the plains. The old-timers (anyone that's been here more than a few years) said you had go back 15 years to get a succession of blizzards that matched that one. You can bet I'm careful after that experience - I wear only hard-core outdoor clothing when I have to go outside in snowy weather. If I had been wearing good boots that day the accident probably would have resulted in nothing worse than skinned knees and elbows. No more snow-shoveling either - next year we bought a Honda snow-thrower to keep the driveway and sidewalks clear, instead of doing it the hard way with a snow-shovel.

The forecast is for this thing to clear out by tomorrow evening, and clear, cold, and sunny over the weekend. It's so dry here that the sun alone melts a lot of snow - it sublimates directly into the air without turning into slush, as it would back East. It'll be clear and cold, and you see the weird sight of 3 feet of snow piled in windblown drifts on the Northern side of buildings while it is bone-dry and clear everywhere else.

The coldest weather is usually very dry - the time when it dropped to -15F the snow was only a light dusting on the ground, and the stars were razor-sharp at night. Cold like that feels unusual - oddly enough not as bone-chilling as New York City with that terrible icy wind off the Atlantic, but more something that gradually crept up on you, as parts of your face went numb. If you breathed too deep, you'd feel it - the cold would burn your lungs and you'd cough.
 
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Since you asked, this is what it looks like outside my window right now - adjusted in Photoshop to match the subjective impression. What you can't quite see are the snowflakes flying through the cones of light cast by the streetlamps.

What's interesting about this picture is that the mast for the powerlines, along with the distant hillside, can't be seen at all visually, but the camera saw it just fine. On the other hand, the camera doesn't quite capture the smooth tonality of the sky, and it took a lot of Photoshop twiddling to get the color even halfway right. It does convey the impression of a dark, cold night, and that's what it looks like outside the window right now.
 

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Was a really nice trip to the second order gradient design - but seems I'd rather stay with dipoles through the modal region for now. Thanks all for clarification !

Already did that here.

From what you outlined in your page about modes excitation with regard to dipole orientation - would you think there might be some significant benefits if dipole woofers are orientated such that they are not in parallel with walls to not "exclude" any perpendicular room modes ?

In other words - for normal (rectangular) rooms would you suggest to ensure a certain amount of elevation and azimuth to get all sorts of room modes excited "equally" by a dipole ??


Lynn - love the mood in you pix.

Michael
 
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Another good day to stay home. Not much fun at the airport or the Interstate highways going north and east.

Fortunately, the snowfall tailed off by mid-day, and it was just cold with a bright pearly-white overcast. On Friday the clouds should part and the sparkly Colorado winter sun return, helping to melt the snow. Karna and I will be out and about again, wearing our heavy-duty boots and jackets.
 
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Blue skies smilin' at me
Nothin' but blue skies do I see
Bluebirds singin' a song
Nothin' but bluebirds all day long

Never saw the sun shinin' so bright
Never saw things goin' so right
Noticing the days hurrying by
When you're in love, my how they fly

Blue days, all of them gone
Nothin' but blue skies from now on
(Blue skies smilin' at me
Nothin' but blue skies do I see)

Never saw the sun shinin' so bright
Never saw things goin' so right
Noticing the days hurrying by
When you're in love, my how they fly

Blue days, all of them gone
Nothin' but blue skies from now on
Nothin' but blue skies from now on
 

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And a beautiful sunset too ...

As you can probably tell, I'm happy to have a sunny day after the drama of the snowstorm. After 30 years in the gloomy winters of the Pacific Northwest (similar to the weather in Northern Europe), I'm surprised how fast I got used to the 330 days of brilliant, high-altitude sun we get in Colorado. Even a few days without and Karna and I start to feel sort of mopey and down, then cheery again when it comes out. Silly enough, but the mood swings are real. Now I know why Northwesterners are always sitting in their coffeeshops all winter long.

I was wondering if it would be possible to scale up Michael's two-dimensional JMMLC horn for a vertically stacked pair of 12" drivers. The OmniTop 12 uses a 4" wide by 9" high throat aperture for each 12" driver, along with a pair of expanded-foam half-discs that fill in the parts of the cone that are not in this aperture.
 

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To sum up, the OT12 is a rear-vented horn with a throat approximately 8.5~9" high (the top and bottom are circles that follow the outline of the cone) and 4" wide. The mouth is 15" high by 22" wide, and the horn portion is about 10" deep. If I'm reading the tea leaves correctly, it is a short conical horn that covers the range from about 200 to 1600 Hz, and uses the broad peak of the Helmholtz resonator of the rear chamber to fill in the range from 100 to 200 Hz.

The Altec A-series, the eXemplar, and the Blue Thunder appear to work in the same way. The big trick with this sort of design appears to be synchronizing the rolloff of the horn with the Q and magnitude of the Helmholtz resonance of the rear chamber, otherwise the response will be quite lumpy, or have a large shelf between the two operating regions.

There's nothing sacred about the OT12, the Altec A-series, or any of the modern audiophile versions. All of them are efficient, but only a few have flat response - and there is the further issue of confirming that the response at one meter is actually the same at 2~4 meters (thanks to changes in directivity).

A scaled-up version of Michael's 2-dimensional horn wouldn't be all that different than the OT12, which has most of the horn expansion in the horizontal plane. The OT12 is a simple, straight conical, while Michael's has the distinctive JMMLC contour. Choose a high enough T ratio, and the JMMLC starts to have the slow rolloff characteristic of a conical, with presumably less diffraction at the mouth, thanks to the inherent round-over.
 
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And a beautiful sunset too ...

As you can probably tell, I'm happy to have a sunny day after the drama of the snowstorm. After 30 years in the gloomy winters of the Pacific Northwest (similar to the weather in Northern Europe), I'm surprised how fast I got used to the 330 days of brilliant, high-altitude sun we get in Colorado. Even a few days without and Karna and I start to feel sort of mopey and down, then cheery again when it comes out. Silly enough, but the mood swings are real. Now I know why Northwesterners are always sitting in their coffeeshops all winter long.

I grew up in Pierce County Washington. I left at 18 and moved to SoCal for 5 years. I now live in the NYC area. I don't love the weather here in NYC, but my job is here. I can truly say I don't miss the PNW at all. My family still lives there and I still visit but I don't ever want to move back there for the reasons you stated above. The weather really got to me, even as a child.
 
beautiful pictures, Lynn, thanks.
As to living in the PNW (Pacific Northwest), it is said of the westcoast marine climate "if you don't like the weather, walk a mile". I live in Victoria which has 24" of rain a year, 1/4 that of Vancouver BC, and even areas 5 miles away as the seagull flies.
With the moist air, the slightest topographical disturbance causes precipitation and much of the area is as you describe. Even Captain Vancouver, who spent about 4 years mapping the area from San Francisco to the panhandle of Alaska, took his ships and 100 men down to Hawaii every winter around 1791-95. He spent the winters mapping some of the Hawaiian Islands.
The amazing exploits of Captain George Vancouver
 
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