I think your problem may be a result of the room itself, so the Z2 is kicking into Turbo mode to try to cool the machine. Our basement is in the high 60's to low 70's and I don't notice mine kicking on higher speeks. Heat alwasy rises, so the upstairs of a home usually is hotter than lower levels.

I don't think the higher fan speed is hurting anything, it is probably just annoying to you when your watching a movie.

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