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Old 24th March 2008, 12:32 AM   #101
maxro is offline maxro  Canada
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Quote:
Originally posted by soongsc

I would love to visualize wave propogation in this format.

You can here.
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Old 24th March 2008, 12:56 AM   #102
soongsc is offline soongsc  Taiwan
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Quote:
Originally posted by maxro



You can here.
Thanks, but I was thinking of creating specific memberane shapes as sources.

The measurement method presented in the link to the pdf file John K provided is very interesting.
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Old 24th March 2008, 01:08 AM   #103
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Quote:
Originally posted by maxro



You can here.


Maxro,

Those figures are are not simulations. There are presentations of experimentally measure sound fields with the data obtained using laser techniques.
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Old 24th March 2008, 01:13 AM   #104
Carlp is offline Carlp  United States
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ScottG,


Quote:
Though not loudspeaker related, thought you might like this:

http://www.gizmag.com/bumpy-whale-f...odynamics/9020/
Very cool, particularly since I used to do humpback whale research in Alaska in a former life. Now, to me the real implication of this link is that a simple observation from nature has perhaps generated a paradigm shift leading away from the currently accepted theories. I'm not saying anything like that is at play with EnABL, but it can't hurt to be open to all possibilities.

Carl
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Old 24th March 2008, 03:47 AM   #105
ScottG is offline ScottG  United States
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Quote:
Originally posted by Carlp
ScottG,




Very cool, particularly since I used to do humpback whale research in Alaska in a former life. Now, to me the real implication of this link is that a simple observation from nature has perhaps generated a paradigm shift leading away from the currently accepted theories. I'm not saying anything like that is at play with EnABL, but it can't hurt to be open to all possibilities.

Carl
It is cool.

Of course prop blades for wind generators would be a HUGE market.. As well as passenger and transport aircraft (and maybe its time for a "U3"), BUT I personally think that this coupled with the massive strides in solar power have the potential for essentially a very cheap upper atmosphere satellite network. (..i.e. a "network" of high altitude solar powered UAV's.) Thats IF the technology pans out.

As for Enable..

Functionally I don't "see" it doing much. Not the basic design, but rather the execution. IMO the pattern would need to be embedded into the diaphragm itself rather than simply residing on the surface or being a part of some lightweight surface layer. It just doesn't seem to be effecting enough mass in its current config. - UNLESS its used on a *very* low mass diaphragm that isn't particularly rigid. Given the right circumstances in a commercial design that has it embedded into the driver - then you might have something (..i.e. something that would actually attenuate the transmission to the surround and reduce the "rebound" from the surround back into the diaphragm).
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Old 24th March 2008, 04:09 AM   #106
maxro is offline maxro  Canada
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Quote:
Originally posted by soongsc

Thanks, but I was thinking of creating specific memberane shapes as sources.

The measurement method presented in the link to the pdf file John K provided is very interesting.
Sorry, I guess I misunderstand what you mean Soongsc. I posted the link to the ripple tank applet, because with it, you can create wave simulations that look just like those pictured. Suspiciously, right down to the colour scheme.


Quote:
Originally posted by john k...

Those figures are are not simulations. There are presentations of experimentally measure sound fields with the data obtained using laser techniques.
Well, I gathered that they were just a mock-up illustrating the difference between point and planar sources.
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Old 24th March 2008, 05:15 AM   #107
BudP is offline BudP  United States
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ScottG

Quote:
Functionally I don't "see" it doing much.
I don't think you will see it doing anything. From the rest of your statement it "sounds" like you are about ready to try EnABL out on a driver. Low mass, high mass, stiff, limp, doesn't much matter. Bring an off axis picture to the other EnABL site and I will provide you with pattern placement details.

Quote:
It just doesn't seem to be effecting enough mass in its current config.
Couldn't agree more. This very disconnect appears to be the heart of the "mystery" that surrounds this simple set of patterns.

Bud
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Old 24th March 2008, 06:40 AM   #108
ScottG is offline ScottG  United States
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Quote:
Originally posted by BudP
ScottG

I don't think you will see it doing anything.

Bud
It wasn't a literal statement..

However, while even under most testing you may not actually see much effect either - thats perhaps the point (..and NOT as you have represented).

Rather,

NOT that it doesn't show much effect (or is an extremely limited one), but rather that if utilized in a slightly different fashion it *may* well show a substantial effect.

With regard to my non-literal previous statement..

The one area I *can* "see" it effecting is with regard to surface reflections and upper freq. tonal behavior for a given driver. (..and of course effecting the higher freq. behavior does to some degree effect the *perception* of lower freq. behavior.)

The thing is though, the boundry layer itself may in many applications be contributing more, (perhaps much more), to this than the Enable pattern - and *that* is something most DIY'ers are unlikely to fully assess (regardless of any measured changes or not).

Perhaps limiting its current use even more is that this upper freq. tonal coloration can usually be avoided with a decently designed/implemented low-pass crossover (..and of course the exception would be tweeters).

Still, there are those that use full-range drivers (and often operated full-range). Additionally there are also those that will (for their own reasons), use drivers up "higher" then they ideally should (and/or with a lower order low-pass than is advisable for a particular design).

Still, it *is* speculation on my part - but I think not unreasonable speculation.
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Old 24th March 2008, 07:14 AM   #109
BudP is offline BudP  United States
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ScottG,

And some very good speculations at that.

I think it might be very informative for you to obtain, if you don't already have some, a pair of inexpensive two or three way speaker systems. Since I treated my first ever full range driver just a year or so ago, my previous work has been with multiway systems.

I have some 30 plus years of experience with multi way speaker systems. Some were pretty decent attempts at utilizing drivers within their "piston pass band" and many others were pathetic attempts to do so. For the systems that were serious attempts to use drivers correctly and also utilize their crossovers to mate those drivers correctly, the effects of EnABL were limited to those described earlier, in the original thread here.

http://www.diyaudio.com/forums/showt...01#post1457401

These effects are easily audible from about 200 Hz on up. They are noticeable in lower frequencies as a lack of "noise" in the portrayal of things like Bass Violas, the bottom keys in a piano, the pressure from a sousaphone, the ripples of force from a bass drum.

My personal systems have always been multiway, with all drivers and baffles patterned. Alex from Oz has worked out an interesting adaptation for baffles and bass reflex ports. I do not use single port bass reflex for low frequency propagation, so I have no experience with what he has discovered.

If you are going to speculate and perhaps experiment with embedded patterns, I think you should acquaint yourself with what the current state of this art provides. Certainly a couple of people have gone forward with experiments, Soongsc and Alex, and discovered results that have advanced beyond my applications. I applaud these endeavors and help where I can.

Bud
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Old 24th March 2008, 09:18 AM   #110
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Yesterday John provided this link;-

http://www.acoust.rise.waseda.ac.jp/...-2005march.pdf

Figures 4, 5 and 6 show how CT averaging develops a steady state wave image.

This is fair enough because it was the intention for that project, but is it not the case that we can hear some of the lower level figure 4 abberations as they arise in real time, but which were averaged out ?

Also is it not likely that such reproduction abberations are likely to be greater at moments of drive change and especially with complex waveforms, such that any EnABL investigation needs to record changes in response to live signals.
Should this be the case, and in view of the fact that changes are likely to be greatest below one tenth of average level, if such examinations are completed digitally on live waveforms ( as opposed to already subtracted analogue waveforms ) then the bit/frequency resolution necessary prior to subtraction would need to be far in excess of that necessary for mere listening alone ?

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