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Old 14th April 2007, 09:48 PM   #221
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Hi John,

Look similar ?
http://www.decware.com/newsite/mainmenu.htm
See article dated April 2007.

Cheers ...... Graham.
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Old 14th April 2007, 10:40 PM   #222
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Default Re: Terrific Thread

Quote:
Originally posted by Lynn Olson
In the German forums, they've come up with a method to overlay the standard waterfall plot (CSD) with a +40 dB raised version of the 3rd-harmonic distortion over time. Since the overlaid plots are in color, you can see the decay of the main component vs distortion - something I have never seen anywhere before

Lynn,
I would love a look at that - do you happen to remember which forum that was?

TIA,
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Old 14th April 2007, 10:51 PM   #223
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Graham,

That's OK, I borrowed my idea from his sub-only imperials. Personally I think he's on the wrong track with a resonator, because that's a monopole source for bass, even if he tunes it to sound good, it's still cheating. With a decent xmax coax 10" I'm confident that I can get what I want in an open alignment. That is a compact single point source OB which doesn't need a sub.


Bud,

Do I need to know the problem frequencies or does cone size give me the answers? Am I understanding correctly, that the felt dissipates this stray unwanted energy as heat and/or its absorption is what prevents the ringing?
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Old 14th April 2007, 11:18 PM   #224
SunRa is offline SunRa  Romania
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Thanks for the ilustration Bud. As JohninCR, I am intersted in actualy understanding this kind of treatment. For now I just try to find the "literature" available on net.

JohninCR,

I hope I am not boring with repeating the question , but how were your results with the double waveguide ended up? I am quite intersted in determening the optimal shape for an open baffle.
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Old 14th April 2007, 11:31 PM   #225
BudP is offline BudP  United States
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JohninCR.

The Mamboni process does indeed work by dissipating the energy to the point that it cannot reflect off of the cone terminus. I am sure that the heat production is relatively low and that most of the energy is simply lofted into the pressure wave being created in the adjacent air. Again, keep in mind that both processes work into a third vector. Without that tid bit of infromation you can devise schemes that ought to work, and do, for two vectors. I know, I have the carcasses of a few of those projects in my closet of horrors.

The Mamboni triangles are applied to the "back" of what ever driver and mounting style you are using. In the case of your dipole endeavors this would be the side you cannot see from the listening area.

Because energy transferred to a cone/time extension surface is a two sided pulse of energy, what you do to one side affects the information content and coherence of both sides. Hence the Mamboni process controls the termination of the energy that is traveling on both sides of the diaphragm even though they are offset physically from each other by some portion of their energy pulse train length and are emitting from opposite faces of the diaphragm.

The EnABL process is more a wave trap within the boundary layer of the emitting surface and just uses the conservation of energy in it's original expression, to effect a one way gate at the terminus at BOTH ends of the cone surface, not just the outer rim. The EnABL process has less mass than the Mamboni process and actually will not diminish the energy efficiency of the driver at all. In fact most drivers will work quite a bit more efficiently and this can be a problem in a multi driver system. If you review the CSD sectors displayed on the last three pages of my paper you will see that the tweeter has a net gain in efficiency of as much as 9 dB for selected frequencies.

http://www.positive-feedback.com/Iss...ndingwaves.htm

This is not to say that the Mamboni process is going to drop efficiency some great amount, it will not. What it will not do is correct for the irregularities in boundary layer and it's terminus on the front side of the driver. Neither would the EnABL process, if applied only to the back side.

So I am advocating the use of both and a much lighter EnABL process than would be needed without the Mamaboni triangles on the back. And once you have attempted to treat the back of a cone with the EnABL process you will know why I am advocating the use of both.
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Old 14th April 2007, 11:38 PM   #226
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Quote:
Originally posted by SunRa
Thanks for the ilustration Bud. As JohninCR, I am intersted in actualy understanding this kind of treatment. For now I just try to find the "literature" available on net.

JohninCR,

I hope I am not boring with repeating the question , but how were your results with the double waveguide ended up? I am quite intersted in determening the optimal shape for an open baffle.
SunRa,

Didn't mean to ignore you. There's some stuff on pages 14 & 15 here. I haven't made any changes or tried other drivers in them yet. I still need to resolve diffraction showing up as vibrations in those solid wood roundovers, and start my measuring process.

A concensus regarding optimum baffle shape is what I hope will result from this thread. I'll post some drawings later to get back to that, but Bud's input may lead to much more flexibility regarding baffles, so we can design them soley to address bass making things much much easier.
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Old 14th April 2007, 11:50 PM   #227
BudP is offline BudP  United States
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JohninCR

You do not need to know anything special about the drivers that get treated. Really, most modern drivers are so much better than their counterparts were in the 70's, when I developed this process, that the EnABL blocks are finally just doing what I had originally envisioned as their job, eliminating standing waves.

What testing I have done does not show an alteration in phase Vs frequency nor distortion content, though some of the grass in the THD by order plots, looks a little suspicious. The time to rest, from an impulse is radically shortened and it does appear that an increase in emitted energy is also occurring. So the total energy transform is probably not affected, but the net information that is retained in the original packet structure is more complete, once the energy has been emitted into the air.

The EnABL process will not address systemic resonances, like the characteristic resonance spike of an aluminum tweeter, but it will narrow the effect of the spike in frequencies being corrupted and will shorten the duration of the remaining ringing. It is quite possible that the Mamboni process will help to control these systemic resonances. At least that is what I am going to go looking for shortly.

Bud
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Old 15th April 2007, 12:53 AM   #228
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Default Mo' Links

It's hard to describe the LC-1A driver without pictures - so here they are.

Note the unusual conical deflectors on the cone, never tried on the competing Altec Duplex or Tannoy Dual Concentric. But HF Olson was nobody's fool, and he literally "wrote the book" on acoustics. People who have heard the LC-1A put it in a class of it's own, not surprising considering the very sophisticated design that went into it. This driver is an completely different league than the primitive full-range whizzer cones of the day.

The German poster Baseballbat wrote his post at http://www.diyaudio.com/forums/showt...13#post1181413

This graphic is worthy of close examination - it shows the 3rd-harmonic distortion (in green) of the metal-cone driver persisting long after the main sound has faded away. This is a very significant finding, and is almost certainly why Mamboni and EnABL treatments sound the way they do. I also suspect the HF Olson conical deflectors would deliver similar improvements, since they break up lateral modes while also breaking up the HOM of the short horn formed by the straight-sided cone.

I echo the concern in previous posts about adding mass to very lightweight cones - the EnABL treatment looks like it adds almost nothing, but the added weight of the Mamboni felt strips could add several grams, which is a big deal for an ultra-lightweight Lowther/AER cone. Doubling the mass of a cone results in one-quarter the efficiency, so you can see adding mass is a big deal that can easily lose 1, 2, or 3 dB of efficiency.

Adding mass to the voice-coil is especially troublesome - there isn't much mass difference between a 8 and 16-ohm voice coil, but it can reduce HF extension in a full-range driver from 12 to 9 kHz. So the trick is to combine light weight, strength to resist the huge G forces where the VC-former joins the cone, and control of energy storage and cone-mode resonances.

The reason I mention G forces is that dynamic drivers operate in a constant-acceleration mode - i.e., when response vs frequency is flat, the acceleration vs frequency is constant. So the louder the driver gets, the higher the G forces present in the cone - and the areas with the highest G force are the most prone to cone breakup.
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Old 15th April 2007, 12:59 AM   #229
ScottG is offline ScottG  United States
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..well back in this thread I had difficulty characterizing what I found "wrong" with good horns.

Well, here is a recent description pretty much "nailing" what seems to be wrong - even though it is describing the recording process rather than the horn directivity (..and in fact "enhanced" midbass "dynamics" also comes into "play" here):

http://www.positive-feedback.com/Issue30/tetra_606.htm

" Compressed recordings, no matter how slight the compression ratio, "squeeze" sound and add sonic force and vividness. That process, even with the best compression quality, enhances dynamic impact but creates a somewhat less than truthful sound stage presence. In sum, compression (to an extent sometimes overlooked) replaces the inherent relaxation, temporal pace and sonic ease of sound in its original ambient spaceóreplaces those innately musical properties with heightened, strengthened sonic force. The compressing of sound partially robs it of ambient accuracy if, by that term, you recognize the actual impact of any note or musical phrase upon the ear to be a direct function of the ear's placement in proximity to the physical activity of musical performance. In actual performance space, hearing is dependent upon the acoustic envelope that carries sound and music. This "envelope" is what gets somewhat exaggerated or deformed by compression.

A debate can easily be generated regarding the positive aspects of gentle compression loading on ambient-recorded music. A slight degree of compression can actually have the effect (i. e., create the sonic illusion) of bringing the ear closer to a musical performance. To that end, compression not only enhances the vivacity of listening, but also reinforces the sense of space and air and ambient acoustic detail.

The outcome of that trade off comes to this: during many of the most intense and pleasurable listening moments one is likely to enjoy, the accuracy of "actual musical space" is likely to have been compromised for the sake of sonic impact, reinforced vividness of detail, and the experience of enhanced musical drama."
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Old 15th April 2007, 01:26 AM   #230
Zen Mod is offline Zen Mod  Serbia
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Default Re: Mo' Links

Quote:
Originally posted by Lynn Olson
It's hard to describe the LC-1A driver without pictures - so here they are.

............................

first -thank you to pointing to new (at least for me unknown) Vintage Trader Site ;I have stashed almost everything from his old site in my puter , but since than I just can't find him on the net........
I admit that I liked more old one-with much more text on pages..........

second-I can give you more fresh pictures (of old RCA drivers ) if you give me schmtc of Olson's four 6F6 amp .......

just joking...... I'll shoot as many pictures you wish,if you wish........
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