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Old 6th April 2007, 12:48 AM   #91
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Originally posted by Zen Mod
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Are those Olson's RCAs?

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Old 6th April 2007, 12:50 AM   #92
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Originally posted by Zen Mod
but- you're right for P10.........even if I hate him.........because of his shelves...
Come visit... i'll load you down... most of the alnoco has gone to new homes thou (except for the 100+ singles)

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Old 6th April 2007, 01:10 AM   #93
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Quote:
Originally posted by Lynn Olson
The original experience of crawling up a frozen driveway with a leg broken in several places (both tibia and fibula were broken, and the tibia was in several pieces) recalibrated my experience of pain permanently.
Unfortunately, or fortunately, my body blocked most of the pain with shock (or whatever it is that the body does). I can remember getting up off the road and wonderring why only one of my arms would come up to my helmet. By the time my teeth started to grind (my body's way of telling me that I was feeling pain, I assume) I was already in the ambulance and on NO.

But, let's stop torturing ourselves and the others reading this thread.

Dave, interesting idea of yours (or is it already in practice), which reminds me a bit of Linkwitz' Orion in execution, but in a "it's taken steroids" fashion. Are those the FE12x's in the top?
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Old 6th April 2007, 01:45 AM   #94
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Quote:
Originally posted by Cloth Ears
Dave, interesting idea of yours (or is it already in practice), which reminds me a bit of Linkwitz' Orion in execution, but in a "it's taken steroids" fashion. Are those the FE12x's in the top?
It could be... that drawing was actually done for the Lyeco LY401F, and the previous incarnation, an FE108eS + AC ribbon (which i have). For that matter scottmoose won the Lyeco contest and the 401 is headed here 1st.

I have at least a dozen of the vintage Foster 12" woofers (was worth buying the boxes just to sell the tweeters) and they turn out to have T/S right in the sweet spot for the ripoles.

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Old 6th April 2007, 05:40 AM   #95
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Quote:
Originally posted by Scottmoose
You're tuning toward dipoles I find fascinating: quick anecdote, which you might find of interest. I was recently at a local audio meet (including a couple of Ariel owners BTW) where an interesting variation on the dipole was lurking. Powered by vintage 300a drivers from a rather special SET amp, they sang.

Nothing fancy at all. Cheap Eminence Beta 15 bass driver mounted fairly close to the floor, XO to a Fostex FE167E at ~180Hz. Series XO, utilising the natural roll-off of the drivers. The baffle is relatively narrow, roughly 16in, triangular side-pieces forming a semi U frame, roughly 12in deep at the bass, tapering to nothing at the top. Sonics were downright staggering. For the megre price, I've heard little that gets close. Easy 40Hz, seemless transition. I went hunting for the XO, and I flat couldn't find it. Design was by JamesD, who frequents the World Designs forum
Got a link? I searched a bit on the WD forum and couldn't seem to find the specifics on the xover.

Will watch this thread with interest. I have 8 Beta 15's NIB and have been trying various ideas for the >150Hz of so region as thought exercises only atm. The Hemp 15 coaxes or the TT12 and a suitable HF driver seem like good possiblilities.

I don't visit much any more, but thanks Lynn as your Amity article was what inspired me to move back into DIY. I've now built several versions, as well as Ariels and my business partner has the drivers for a pair now and is itching to start the build.

Best of luck with the leg Lynn. Your story of your trip up the drive brought back memories of a drive I had to make with 4 fractured vertebrae. 21 years later with full mobility, it brings a smile and a cringe at the same time.
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Old 6th April 2007, 06:03 AM   #96
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Good to see you Brett.

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Old 6th April 2007, 06:40 AM   #97
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Default Problems with Arrays

Quote:
Originally posted by Floric
Hi Lynn,

Several posts ago you wrote, that a linar array would lead to problems because of the timing - the sonics from the outermost sources of the array reach the ear of the listener later. You proposed a geometry that is tilt towards the listener to avoid this effect.

I Think that you are not right. The effect of a line array is that every driver gets focused in the horizontal plane with the help of the other ones because delays of a half wavelength get canceled (though I have been studying physics for some years, I am not able to explain it a better way with some words - if you want a better eplanation read "QED" from Richard P. Feynman or send me a pm). When you are listening to a line array, you are listening to the speaker that is at the hight of your ears. The problem of a linearray is, that this effect is dependent of the frequency. As a consequence you get this "comb filtering" effect. In normal listening environments this effect is smeared by the room with the consequence of an inaccurancy in the time domain. But you will never hear the sound of the outermost speaker with a delay.

Best regards and best wishes

Floric
I look at it a little differently. Let's assume an array of 2" Jordans - the classic array that converts an ultra-low efficiency driver (82 dB/metre if I recall right) into something a lot more reasonable - with, say, 8 or 12 drivers.

These drivers, due to their small size, are pretty close to hemispherical radiators up to about 10 kHz or so. Now imagine feeding the entire array with a narrow pulse. With one driver, you'll get a very clean return at the 2-meter microphone position, limited only by the energy storage of the driver itself (I am assuming a perfect enclosure here with no diffraction or internal energy storage).

But - with 8 or 12 drivers in a vertical array, the arrival times at the microphone must be non-coincident due to different time-of-flight for each impulse. And this is exactly what you measure with large vertical arrays, whether composed of discrete dynamic drivers or large electrostatic or magnetic-planar panels. This happens with theoretically perfect drivers of zero size - the time dispersion (time smearing) with real-world drivers is worse, since the off-axis HF rolloff of the topmost and bottom-most drivers results in the acoustic centers moving backwards in space, which worsens the time dispersion for the most severely off-axis drivers.

(Anything that rolls off the HF response of the driver, whether electrical, mechanical, or dispersion limiting, always results in the center of radiation moving backward in space. This is why woofers have acoustical centers that are farther back than you might expect, thanks to the crossover lowpass filtering and the natural rolloff of the woofer.)

The greatest number of drivers that will give a synchronous arrival time (on a flat panel) is no more than two. Any more than that, you get non-synchronous arrival times, comb filtering in the frequency domain, and multiple lobes in the vertical polar pattern. In reality, all three domains are simply reflections of what is happening in the time domain (the real world).

The same thing appears in antenna theory - the most directional antennas have the narrowest frequency response, the worst pulse response, and the greatest number of sidelobes. Same for microphones, too - shotgun or parabolic microphones are a long way from hifi devices, and only really useful for surveillance, birdwatching, or newsgathering.

The simplest example of a vertical array, the MTM, are tricky to design thanks to very complicated vertical polar patterns in the crossover region. I found that out the hard way with the Ariel, where the measurements did not coincide with subjective impressions of frequency response. As it was, I compromised about halfway between direct-arrival response and total room response (energy into a sphere).

Which brings me to the other issue with vertical arrays - the power does not drop off according to the square law, thanks to the very narrow vertical dispersion. This means the acoustical joining to a radiator with spherical dispersion, such as a subwoofer or supertweeter, requires a listening-distance compensation. A system that is equalized flat at 2 meters will have excess HF energy at 4 meters, since the SPL for the array falls off less quickly with distance than the spherical radiator.

The same thing happens with horns joined to direct-radiator bass sections. The bass unit is omnidirectional, but the HF horn dispersion is typically 90 degrees or less. This means a system compensated for 2 meters will have too much HF energy at 4 meters, since the horn, like the vertical array, is not dropping off with distance as fast as the omnidirectional radiator.

I think you can see where this line of argument is going - one advantage of a coax dipole is a polar pattern that is fairly constant with frequency, thus minimizing the requirement for listening-distance compensation. The de facto polar pattern is about 120 to 90 degrees over most of the frequency range, and with reasonable care in design, free of the narrow vertical sidelobes of vertical arrays, MTM's, or conventional horns.
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Old 6th April 2007, 07:18 AM   #98
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Quote:
Originally posted by planet10


Are those Olson's RCAs?

dave

ya nutz!!!?

mine,not Olson's!!

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Old 6th April 2007, 07:24 AM   #99
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Default Re: Problems with Arrays

From Paul Taylor "The Line-Source Loudspeaker and its Applications" 1961
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Old 6th April 2007, 07:25 AM   #100
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Quote:
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mine,not Olson's!!
If RCAs, Olson designed them...

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