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Looking for insights into Magico's amazing off-axis measurements

mwmkravchenko

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I have not read every reply.

But I have designed drivers for quite a few years. And to fill in the holes described there are a few fairly simple things that could be done on the cone shape, surround shape that could really mitigate those problems. Also as pointed out a ring radiator has problems all to it's own. Changing to a dome tweeter will create different problems as it solves some of them. There has never been a free lunch in any decision related to audio.
 

mwmkravchenko

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Excellent detective work! I hadn't noticed that. I think a deep notch in the woofer's response at 2 kHz, as with my speculative notch filter placement, would have precluded the possibility of a suckout like that. Thanks!



I think you're right! Here are some statements about Magico's midrange cone. From John Atkinson's write-up of the M2:

"The cones of the M2's 6" midrange driver and 7" woofers use multiple layers of woven carbon-fiber, incorporating graphene, a form of carbon in which the atoms are assembled in a sheet just a few atoms thick that is said to be 100 times stronger than steel. The resulting cone is both light and stiff, pushing breakup modes well above each unit's operating passband."

And from Magico's M2 page:

"The newly designed Magico six-inch midrange and seven-inch bass driver cones found in the M2 are both manufactured using Multi-Wall carbon XG Nanographene and an ultra-stiff proprietary new carbon weave which is 20% lighter and 300% stiffer than previous cone material we used in Magico loudspeaker offerings."

So these statements are emphasizing STIFFNESS, with John Atkinson stating that the breakup modes are "well above each unit's passband". However they don't actually use the word "pistonic".

It LOOKS to me like in this new generation of midrange cones "the thickness/mass of the diaphragm is nonuniform", EXACTLY as you said. From Atkinson's write-up of the S5:

"It's desirable that a speaker cone be of varying thickness: thickest at the center and the boundary with the voice-coil former, thinnest at the junction with the surround. However, Magico used to use a sandwich core of constant thickness, because the foam material would fracture if the thickness varied. For their new generation of midrange units they developed a process in which the foam is carefully injected between the front and back carbon-fiber, to permit the overall thickness to vary in the desired manner."

And finally, from Magico's "Drivers" technology page:

"The result is a cone that displays bending strength, self-damping and attenuation of ringing that are all an order of magnitude or more higher than that of conventionally manufactured cones."

In my opinion the word "bending" implies "non-pistonic" behavior, which I would have called "breakup". And in my opinion "self-damping" and "attenuation of ringing" imply WELL CONTROLLED breakup.

[I found this online definition of "cone breakup": "At low frequencies a cone moves as a whole. This is the 'pistonic' area of operation. At higher frequencies the cone starts to flex, leading to resonances. This is what is referred to as 'breakup'."]

So maybe this is what's going on: The new cone goes into extremely well-behaved breakup and flexes just the right amount to significantly widen the radiation pattern up into the crossover region, with any "nasty" breakup peaks being well above the driver's passband. And the marketing department chose to emphasize the strength and stiffness of the cone because admitting to "cone breakup" within the driver's passband would hurt sales.

And IF this is what's going on, then in my opinion the marketing department's selective wording IN NO WAY DIMINISHES the amazing accomplishment of Magico's engineering department.

I have ZERO affiliation with Magico... but mucho admiration for their engineering department.


Two cents.

Magico buys drivers from Accuton and Morel. And they have used these cones to better effect lately. All composites like these have ringing and resonances that effect the response. Hopefully out of the desired passband. But they are always there. Even as low as 20db down when the driver is playing loud and proud so are the non-linear behaviors of the driver. There are masking effects, but as the frequency band of interest gets to the area from about 800 hertz to 4khz even non-linearities that are supposedly buried can be audible. You only hear these effects when they are gone. And when you have heard sound reproduction without them you immediately pickup on there existence.
 

Alexanderc

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Maybe so, but on the M2 we have data out to 45 degrees. I don't recall seeing such smooth off-axis behavior out to 45 degrees from a 6" woofer and non-waveguided 1" tweeter combination. It's arguably even better than the 45-degree curve of the Revel Salon 2, which uses a SMALLER diameter midrange (4") and a waveguided tweeter:

View attachment 92674
This paradigm is in the ballpark of the M2 to 45 degrees FWIW
https://www.stereophile.com/content/paradigm-prestige-95f-loudspeaker-measurements
I’m not trying to undersell the Magico speakers. They appear to measure well. If I had the money I would consider them (but I don’t, and never will) :)
 

Juhazi

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I believe that the curved baffle of M's plays a role on smooth off-axis too.

Xo is elliptic acoustically, net result of cone diameter, cone profile, baffle size and profile, impedance peak etc. - careful, skillful and rational R&D!
 

mwmkravchenko

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I believe that the curved baffle of M's plays a role on smooth off-axis too.

Xo is elliptic acoustically, net result of cone diameter, cone profile, baffle size and profile, impedance peak etc. - careful, skillful and rational R&D!

To a more limited degree than with what they have changed on the drivers diaphragms.

A dome tweeter radiates much differently than a ring radiator.

And the changes in the woofer cone is the greatest contributor to the response being cleaned up. You can't filter out a poor basic response. Filters and traps are only useful to limited degree.

You can do quick 1/2, 1/2, and full wavelength calculations from the the inside of the surround and the edges of the baffle. They will give you rather good clues as to where or even if the baffle is contributing to any diffraction effects that may colour the sound. Sufficient attention to those details has been paid on this design and it is showing very well.
 
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