Magicos are chesty

The problem is that polypropylene is non-fibrous and tends to store rather than dissipate acoustic energy so it vibrates characteristically - not a good material either for a speaker cone

Wrong. It and paper are the best materials for a speaker cone. Go listen to the Stirling Broadcast LS3/6 and then claim plastic is a poor driver material. They can likely embarrass whatever speakers you're listening with.

Audiophiles and Men like chesty speakers and ladies . Its the American way !

@helomech

I love the sound of polypropylene cones. My first higher end speaker was Energy Pro 22 with a poly mid-woofer woven onto a rubber surround.

That said, my experience is that polypropylene cones almost always sound more rolled off in the 1 to 3 KHz range and more lively around 200 to 300 Hz (a more “chesty” sound). This gives them a “warm” characteristic versus pulp/paper which has a more lively sound. Both can sound good.

In the case of Magico, from internal pictures it seems they use a large internal washbasin size plastic cabinet around the midrange. Ostensibly to limit the backwave from the woofer influencing the mid range. I suspect this plastic tub could add a warm chesty coloration - vinyl shower or vinyl bath tub will give vocals that kind coloration should you be inclined to sing in the bathroom.

I love the sound of polypropylene cones. My first higher end speaker was Energy Pro 22 with a poly mid-woofer woven onto a rubber surround.

That said, my experience is that polypropylene cones almost always sound more rolled off in the 1 to 3 KHz range and more lively around 200 to 300 Hz (a more “chesty” sound). This gives them a “warm” characteristic versus pulp/paper which has a more lively sound. Both can sound good.

In the case of Magico, from internal pictures it seems they use a large internal washbasin size plastic cabinet around the midrange. Ostensibly to limit the backwave from the woofer influencing the mid range. I suspect this plastic tub could add a warm chesty coloration - vinyl shower or vinyl bath tub will give vocals that kind coloration should you be inclined to sing in the bathroom.

I have to disagree. "Chesty" vocals  usually result from the speaker cabinet. Doubtful that a plastic basket could produce this trait in any audible way. If your blanket claim was valid, Harbeths would be chesty, but I've yet to hear one that sounds that way.

Another explanation for the Magico's character is that possibly, the chestiness is actually part of the recording and the Magicos damp it less than other speakers. Magicos tend to produce exemplary measurements with extremely low distortion, so what's the more likely scenario, that they have ill-behaved drivers, or that other drivers overdamp that character? IME, many artists sound a lot more "chesty" in live performances than they do in playback of their studio recordings. This isn't a defense of Magico, as I personally don't care much for their type of sound.

Having sold, installed and set up dozens of Magico Speakers, from the A3 to the Q7. We have to disagree. When time is spent to get the correct setup distance from the back wall, from the side walls, the separation between the speakers as well as the amount of toe-in Magico is not a "chesty" speaker. This is not just our opinion, our room measurements do not indicate an emphasis on the frequency range that your referencing. 
Properly placed and optimized you will get incredible results. Anything less, look at the room and the setup.