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Old 4th July 2009, 12:42 AM   #5901
datesx is offline datesx  Hungary
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Default Altec horns -- the Woodstock Bins

I hope you will enjoy it: excerpt from Wikipedia:

Sound for the concert was engineered by Bill Hanley, whose innovations in the sound industry have earned him the prestigious Parnelli Award. "It worked very well," he says of the event. "I built special speaker columns on the hills and had 16 loudspeaker arrays in a square platform going up to the hill on 70-foot [21 meter] towers. We set it up for 150,000 to 200,000 people. Of course, 500,000 showed up." ALTEC designed 4 – 15 marine ply cabinets that weighed in at half a ton a piece, stood 6 feet (1.8 m) straight up, almost 4 feet (1.2 m) deep, and 3 feet (0.91 m) wide. Each of these woofers carried four 15-inch (380 mm) JBL LANSING D140 loudspeakers. The tweeters consisted of 4x2-Cell & 2x10-Cell Altec Horns. Behind the stage were three transformers providing 2,000 amperes of current to power the amplification setup. For many years this system was collectively referred to as the Woodstock Bins.

http://en.wikipedia.org/wiki/Woodstock_Festival
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Old 4th July 2009, 01:37 AM   #5902
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I was there, about 2/3 way to the rear of the audience. The sound was the best I had heard to that time (for a reinforcement system) and remains a benchmark for me. I remember the sound of the echo of a trumpet fanfare at the start of the Janis Joplin set returning from distant hills. The whole thing sounded to me like a decent home system (for the time) at ideal living room levels.
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Old 4th July 2009, 02:44 AM   #5903
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Hi Guys

Catapult has found the patent application, with that number, I found a more detailed drawing here.
The drivers I have been using on our horns is made just like this one (this is probably a drawing of it). I’ve been using them in our multiway horn products for nearly 7 years now and they are still my favorite hf driver.
Fb, I am not sure of the angle but this appears to be a construction drawing so you could get pretty close by scaling it and printing on paper

http://www.google.com/patents?id=Zi4...bstract&zoom=4


Also here referred to in prior art, fwiw, I would bet the device being patented here would be horrible in a conical horn as it would appear to result in a converging wave front like many ring of slots phase plugs do.

http://www.google.com/patents?id=uUc...bstract&zoom=4

Lynn, I have a soft spot in my heart for Altec, piles of theater gear were what they used for concerts in the old days at the Aragon. I felt sad when they started to slip.
True sonic I wasn’t as familiar with but they made nice drives what I could see (and my one example).
Want to see what modern production methods can do relative to the old days?
The link was huge to so do a “Google image” search for “turbosound dendritic horn”
I have not heard one but you can clearly see the method they used to resolve the problem of creating the right wave front shape over a large area
While a competitor of ours at work, I have to say it is a clever idea and execution.

Soongsc; I wasn’t so much concerned with who made it but what size it was and what the geometry immediately surrounding the radiator was. To me, a narrow notch like that over a wide angle says you have a reflected or time delayed signal look for something which could cause a reflection, around 1 / 4 wavelength at 16KHz.
What is the diameter?

Best,
Tom Danley
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Old 4th July 2009, 03:03 AM   #5904
Pano is offline Pano  United States
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Dendratic
Click the image to open in full size. Click the image to open in full size.

This is just the throat of the waveguide, right?
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Old 4th July 2009, 05:37 AM   #5905
soongsc is offline soongsc  Taiwan
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Quote:
Originally posted by Tom Danley
...
Soongsc; I wasn’t so much concerned with who made it but what size it was and what the geometry immediately surrounding the radiator was. To me, a narrow notch like that over a wide angle says you have a reflected or time delayed signal look for something which could cause a reflection, around 1 / 4 wavelength at 16KHz.
What is the diameter?

Best,
Tom Danley
Thanks Tom,

If we look at the response of the raw driver, the notch is already there. This is actually caused by diffraction due to transition from concave to a different surface shape. So we really want a good transformation from the diaphragm to the expansion part of the waveguide without assuming a specific mathematical wave front shape. The elliptical waveguide used an OS shape calculated from the spreadsheet posted in the Geddes thread. If you look through my later waveguides, the notch is shifted up and reduced significantly. It is interesting to see that this notch does not show up in BEM sims which leads me to beleive it would be very difficult to get a simulation or math model to be able to predict that with good accuracy. The driver which is used is a 1 inch driver. I thought it would have been obvious in the latest BEM profile I posted.
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Old 4th July 2009, 10:00 AM   #5906
mige0 is offline mige0  Austria
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Quote:
Originally posted by panomaniac
Dendratic
Click the image to open in full size. Click the image to open in full size.

This is just the throat of the waveguide, right?

Thanks - thats kind of what I would like to know more about.

Just that - for my app - it dosn't make any sense to severly delay the middle parts of the wave front as seen in the pix.

The multicell pix seen must be intended for driver stacking IMO, where a plane to plane transition of the wave front is somehow beneficial - or the driver used forces a very strange wave front that has to be corrected for - nothing that applies in my case.

The question is :
are there adverse "boundary flow" effects that translate into a sonic pattern - I mean, we immediately have plenty of surface the waves have to travel along when going the multicell route?



Michael
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Old 4th July 2009, 10:17 AM   #5907
mige0 is offline mige0  Austria
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Quote:
Originally posted by soongsc

Thanks Tom,

If we look at the response of the raw driver, the notch is already there. This is actually caused by diffraction due to transition from concave to a different surface shape.

Don't think so.
The notch (from a plain driver) is due to the interference form rays of different time of flight - originating from different points of the diaphragm. You could check if you vary mic distance - this should vary notch centre frequency then.

You *can* enforce that notch pattern by the "right" (or should we say the wrong?) reflections from a horn contour - also - like playing over several boundaries in billiard - from the mouth reflections bouncing back from the horn contour and re-radiating through the mouth again.

Thus I see simus of the wave front propagation and the sound field *inside* the horn to be so beneficial, even so they are – in case of CARA – severely limited in "scientific" accuracy.

On the other hand all the calculations form Webster over HOM and BEM are severely limited too

Meaning - at the time being - we need a patchwork of equations and simus to cover "all" effects of interest.

Michael


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Old 4th July 2009, 11:58 AM   #5908
soongsc is offline soongsc  Taiwan
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Quote:
Originally posted by mige0



Don't think so.
The notch (from a plain driver) is due to the interference form rays of different time of flight - originating from different points of the diaphragm. You could check if you vary mic distance - this should vary notch centre frequency then.

You *can* enforce that notch pattern by the "right" (or should we say the wrong?) reflections from a horn contour - also - like playing over several boundaries in billiard - from the mouth reflections bouncing back from the horn contour and re-radiating through the mouth again.

Thus I see simus of the wave front propagation and the sound field *inside* the horn to be so beneficial, even so they are ?in case of CARA ? severely limited in "scientific" accuracy.

On the other hand all the calculations form Webster over HOM and BEM are severely limited too

Meaning - at the time being - we need a patchwork of equations and simus to cover "all" effects of interest.

Michael


Well, if we consider path distance of every point on the diaphragm, then the notch would not exist. Due to averaging. At this point, only a second ring source would result in this kind of pattern, which is the diffracrion wave.
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Old 4th July 2009, 01:41 PM   #5909
mige0 is offline mige0  Austria
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Quote:
Originally posted by soongsc

Well, if we consider path distance of every point on the diaphragm, then the notch would not exist. Due to averaging. At this point, only a second ring source would result in this kind of pattern, which is the diffracrion wave.

Depends on how close you look at "diffraction > reflection > delay > interference"

Click the image to open in full size.

clearly diffraction "as a ring source" happens even from a membrane *without any suspension or borders* at the sides - simply by the fact that the plane wave front "has room to its sides" where it *must* bend into due to the law of balancing pressure.

This "bending to the sides" of the wave front actually is diffraction and "kicks back" too (point source behaviour - in this case not of a "second source" but integral part of the "original sorce")

All the rest simply is "delay and interference"

Michael
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Old 4th July 2009, 02:45 PM   #5910
soongsc is offline soongsc  Taiwan
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I think you are talking about a dipole or bipole configuration. I am not.
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