I forgot to add that this was VPI's reason for the aluminum over the acrylic of the standard Scout from a review.
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Weisfeld's rationale: "You can machine aluminum much better (+/- .001" in a 29" circumference), it can be damped easily, it is heavy (good), it is temperature and humidity stable, and it adds a sense of life that the acrylic doesn't have without the artificial brightness that acrylic can sometimes bring to the sound."
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http://www.vpiindustries.com/reviews/Classic%20-%20vpi_classic_reprint.pdf
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Weisfeld's rationale: "You can machine aluminum much better (+/- .001" in a 29" circumference), it can be damped easily, it is heavy (good), it is temperature and humidity stable, and it adds a sense of life that the acrylic doesn't have without the artificial brightness that acrylic can sometimes bring to the sound."
____________________________________________________________
http://www.vpiindustries.com/reviews/Classic%20-%20vpi_classic_reprint.pdf