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Old 24th April 2007, 01:14 AM   #471
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Default Re: Re: Re: Re: Simple might be best

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Originally posted by ThomasW
That's just the prototype and no it's not MDF. It's multiple layers of 1/4" 'hardboard' laminated together with epoxy.
Homemade plywood of a sort... The PEARL PR2 is made from a similar "ply" he uses 7 thinner layers. Not sure what glue he uses but it was carefully selected... then put in a multi-ton press.

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Old 24th April 2007, 01:40 AM   #472
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Default well...

berm I think that you are looking at a differnt mode of operation and with the high mass of your structure (diaphragm) you will have a bigger and more complicated job of fudging it all into polite operation. I am afraid you are on your own there. People have done this to varying degrees over the years. one of our early prototypes used a head phone VC and motor driving an 8.5 x 11 inch piece of 1/8 inch glass plate. Not very loud but boy did piano sound real and that was about it with no midbass or lower.
You might try a bass version of a Lineaum driver where you build in intentional loss into the diaphragms. Woth a try.
Lynn I think that it ends up somewhere in the middle. Bud has been discussing surface energy and I think that is where the thin foil comes into paly for the most part. Unless you have real balanced constrained layers (prestressed even better) a thin foil layer is not going to add much if any stiffness to the base substraite material (cone), if anything given the foil and the adhesive used you probably pick up some extra mass and some damping of upper modes of the cone.
I suspect that you are on track with thinking that the faster material (harder) lets the surface energy launch additional useful sound but that as a composite you get a little effect of the harder on the softer(in this particular example). With out laser measurement it would be a Dog's breakfast to really figure out properly but you can sound such stuff out by ear. I think tha you (and Bud) re right there is the acoustical wave to deal then there is the surface energy to deal with as well. Wish I could offer more information /answers but that is as much as I know. Regards Moray James.
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Old 24th April 2007, 02:06 AM   #473
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Default Surface Propagation

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Originally posted by moray james

Lynn, I think that it ends up somewhere in the middle. Bud has been discussing surface energy and I think that is where the thin foil comes into paly for the most part. Unless you have real balanced constrained layers (prestressed even better) a thin foil layer is not going to add much if any stiffness to the base substraite material (cone), if anything given the foil and the adhesive used you probably pick up some extra mass and some damping of upper modes of the cone.

I suspect that you are on track with thinking that the faster material (harder) lets the surface energy launch additional useful sound but that as a composite you get a little effect of the harder on the softer(in this particular example). Without laser measurement it would be a Dog's breakfast to really figure out properly but you can sound such stuff out by ear. I think tha you (and Bud) re right there is the acoustical wave to deal then there is the surface energy to deal with as well. Wish I could offer more information /answers but that is as much as I know. Regards Moray James.
Well, I was thinking of an inverse to the Mamboni mod where you add triangular-shaped strips of metal foil to a paper cone. Similarly, the EnABL treatment could be applied as simply as a stencil, or the lift-off lettering used for front panels.

I've also wondered for many years how an amorphous metal like gold foil would behave, as opposed to metals with crystalline structure. All of these things must surely affect wave propagation through the cone.

I've kind of gone past rescuing those coaxes - every blessed one of them has the worst freq resp curves imaginable. That indicates geometrical problems, like severe standing waves in the cone attachment/VC former area, or something ugly like a dustcap that has one or more cavity resonances.

Fancy cone treatments can clean up the cone and greatly reduce energy storage, but I don't see them correcting gross abnormalities like bad dustcaps or design errors in the cone attachment/VC former area. You put a perfect driver in a tin can, it's still gonna sound like a tin can.

I certainly sympathize with the horrendous difficulties that confronted your design team. Optimizing rigidity (low IM distortion) while keeping desirable energy-dissipation characteristics (rapid decay and freedom from resonance) seems to have eluded driver designers for many decades.

The current crop of audiophile drivers actually seems to be going backwards in this area, despite the availability of greatly superior measurement tools. That's why I'm looking at archaic materials like hemp and HF Olson's work - I suspect a great deal of "company proprietary" information has simply been lost over the last several decades, due to corporate infighting, good engineers leaving and taking their intellectual property with them, and VC losing interest in alternative technologies. It would be tragic if all the hard work your development team put in simply disappeared in a flurry of hand-written notes.

I briefly worked for NASA in the summers of 1969 and 1970, and was horrified a few years when I found out the Saturn V technology no longer exists - the USA would have to start from scratch if we wanted to return to the Moon. It's an unsettling thought that aerospace technology has actually regressed - quite a bit - over the last 35 years.

The SR-71: scrapped, all tooling destroyed (by order of Nixon)

The Boeing 2707 Mach 3 Trans-Pacific SST: scrapped by Congress

The Space Transportation System with a continuously occupied moonbase, nuclear-engined (NERVA) long-distance interplanetary transports, and a Mars Mission by 1990: scrapped, leaving only a crippled Space Shuttle with degraded performance specs

Jet transportation: airspeeds are slower than they were in 1970 (to save fuel), passengers must use a hub-and-spoke system instead of direct city-to-city flights (to maximize economy for the airlines), and levels of service that combine Greyhound-bus-terminal crowding, filth and dirt with Federal prison treatment at every airport.

No wonder the elites avoid all this unpleasantness and are driven in their limos directly to their corporate jets, where the pilot of the plane meets them, hangs up their coats, and serves them a pleasant refreshment from the bar before taking off - in planes that fly higher and faster, and go directly where they want to go.
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Old 24th April 2007, 02:52 AM   #474
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Lynn,

Thanks, that was depressing. It's definitely time for a technological leap forward in terms of energy. I'm an optimist, so I don't think we have to wait long at all.
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Old 24th April 2007, 02:55 AM   #475
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Default you might consider...

cryo treating your foil as this has the affect of reducing material surface tension so that oought to speed the foil up. Gold leaf sound like an experiment to check, you can cryo that as well. If you want I would be happy to cryo treat your foil materials for you if there is no local treater willing to do so for free, just PM me for my address and send it over (I am in Calgary so it won't take long back and forth in the mail).
Thought I would mention that Tannoy do sell (at much reduced cost a lot of drivers through thier pro and or install branch. They have a new 4 inch true dual concentric that can be had in an inwall frame for about $150.00 each. This is the same driver that they use in the miny westminster design which sell for about $2K to the audio market. I have listened to these and they are very good and can play loud around 103 db continous and peaks around 113 db (single units). They could make a cool scaled down version of your OB design and in a medium to smallish room be most of what people are looking for. Not to mention that the project cost would be reasonable. Tannoy have 6.5 inch DC and 8" DC drivers available as well. You are right in that you can not make that silk purse from the pigs ear so the Tannoy ought to get you as close as you can get with this technology for a reasonable prive. Close enugh to decide if custom drivers are worth investing in.
I think that the foil idea (wedges) could be combined with the felt wedge idea. Sounds like the impact of the felt wedge treatment goes beyound what anyone could expect from a damping (mass) point of view. Would be reasonable to think that the increase of air load due to the fiber tangle impacts the impedance match of the cone/felt combination to the surrounding air. Might the Olson multi cone design have a similar impact? Not only in respect to increasing the cone surface area but also in terms of complex air load on the driver? I wonder if (don't laugh now) if a speaker might benefit from tha addition of a brush cut wig? If you placed a wig like web with hair like fibers on a cone which started short at the VC and grew longer toward the outer edge of the cone the surface energy would get progressively distributed up off of the cone surface? This would kind of tie into your idea of the mesh termination. Hair fiber direction and length would be easy to control. Might also explain why ZZ Top sound so good. This idea combines to some degree both the enable idea along with the felt
This reminds me I have some raw factory piezo cones made by motorola (felted paper) about 1.75" total dia. including a small flange. These are the cones used in piezo drivers. If you are interested in experimenting with some of these on a fullrange driver cone I would be happy to send you some. Let me know. You might be able to reproduce similar results to that Olson did. Combinning Bud's enable techniques to these cone might also produce results. Stands to reason that nobody will allow you to play with thier Olson designed RCA's so this might be the closest that you are going to get for free (almost) you still need to provide a raw driver set to play with. Best regards Moray James.
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Old 24th April 2007, 04:01 AM   #476
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Having worked as a lowly GS-4 Graphics Aide for NASA HQ in the glory years gave me a ringside seat in what should have been the technology of the Seventies, Eighties, and Nineties. Surprisingly, I had no security classification, and signed no non-disclosure agreements, yet I was making 8 x 10 Vu-Graphs for presentations for Von Braun and top management, and was the one that tape-recorded the meetings for later transcription. As a result, I saw, and heard, all of the plans that NASA had for the years 1970 through 2000.

The Space Shuttle we have now is a militarized travesty of the original. The original was to have used JT-79 engines modified to run on liquid hydrogen, giving it the ability to fly back and land on any airport in the world, under controlled powered flight. The first-stage launcher was designed to have a fly-back capability as well, and looked like a really big delta-winged rocket.

Since the Space Shuttle is basically a glorified low-altitude truck, without the ability to attain high-altitude synchronous orbit, a complementary system called the Space Tug was intended for visits to synchronous and above. A version of the Space Tug was optimized for visits to the moon and back, supplying the moonbase from Low Earth Orbit.

The Apollo missions were designed to continue indefinitely, building up a moonbase of discarded LEM parts (the middle habitation module), and planned to be continuously occupied from 1975 onward. Experience gained at the moonbase was to be applied to the long-duration Mars mission, planned for the mid-Nineties (that was the "conservative" schedule - the "aggressive" schedule had them landing in 1983).

We got none of that. Instead, we got Vietnam, a succession of resource wars that continue to this day, and what appears to be class war (marketed to the public as globalism). The USA had a choice between the future of Kubrick's 2001 (which was quite accurate at the time) and an empire, and chose empire.

All of this is to underscore the point that the future doesn't always bring advancements - or if it does, it may happen somewhere else, not the center of an empire. We have the Internet (free pR0n!) and almost-free electronics from China, but many other technologies have stagnated or gone backward. Real per-capita incomes have stayed the same since the 1970's, while prices for housing and automobiles have gone up in real dollars. Kind of a mixed bag - some wins, some loses. The Internet does let us get together and create new communities, hooray for that!

Returning to audio, I need to re-read HF Olson's books again, and look for those revealing little asides that point to areas of further research that were never undertaken. The whole experience of digging up Western Electric's Harmonic Balancer was a shock - here's a circuit that is as important as negative feedback, by the people that invented negative feedback, that was lost to all of the literature after the Thirties. Gone. Forgotten. Invented by the most advanced electronics lab in the world, and still forgotten by the time of the Williamson in 1948.

So there's a lot of stuff to dig up, and why I most sincerely hope the work of BudP, Mamboni, and Moray is developed further, or at the absolute minimum, is widely published. Audio is filled with brilliant work that is forgotten for reasons that have nothing to do with technical merit.

It does make you think how much was lost when religious fanatics burned the Library of Alexandria, which contained all the knowledge of the classical world. What we have now are only scraps and scattered fragments, badly copied by a handful of medieval monks. We know they had batteries - what did they use them for? We know they had mechanical clocks - what else did they have? The emotional and spiritual center of classical Greek civilization were the Mysteries of Eleuisis - and we know almost nothing of a religious ceremony that was in use for a thousand years.
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Old 24th April 2007, 04:46 AM   #477
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Quote:
Originally posted by Lynn Olson
We got none of that. Instead, we got Vietnam, a succession of resource wars that continue to this day,
Hey, maybe things will turn around. Just read in yesterday's paper that the cost of the US embassy under construction in Bagdad has been trimmed from 1billion to 600million.

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Old 24th April 2007, 04:49 AM   #478
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Quote:
Originally posted by Sheldon


Hey, maybe things will turn around. Just read in yesterday's paper that the cost of the US embassy under construction in Bagdad has been trimmed from 1billion to 600million.

Sheldon
W00T!!! Great news! There's light at the end of the tunnel! Can I have my flying car now? With the MR FUSION power unit?
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Old 24th April 2007, 06:52 AM   #479
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Default Lynn would you mind?

scooting me a PM I have a question for you. Thanks Moray James.
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Old 24th April 2007, 08:09 AM   #480
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Huh. The admin has disabled private messaging, so why don't you visit Nutshell Hi-Fi and scroll down past the News section. You'll see the contact information there. Look forward to the message!
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