Hi there!!
I'm Roman. I've been sicked for a long time and still recovering. A beginner to the flute, and having a lower resistance, I'm not satisfied with my overall tone quality when I blow it( especially on middle to high registers). Its thinner than normal, like a whistle, maybe like a piccolo.
Aside from weak resistance, I suspect the lenght, thickness and diameter of my C flute as factors. It has thinner wall and shorter and smaller diameter.
Am I right?? What are your comments? Are there websites that discuss these factors?? thanks to all of you..

maybe because of ur embouchure

Hmm.. I don't think it has much to do with that if you are a beginner.

no, and 2nd hand.

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or slightly used. but the brand is Khonn

I see. Previously I thought diameter of the tube and length contribute to flute's pitch/tone. a longer and wider tube produces a bigger sound but a shorter produces a smaller/thinner,whistle-like/shrill sound. I have no teacher but self studying. Topics on the internet can help me i think.
thanks..