On 26/04/2013 00:28, Sampo Syreeni wrote:
On 2013-04-25, Fons Adriaensen wrote:
For first order the 'extrapolation' works well up to a distance of
around 1/4 to 1/3 of a wavelength.
So, in English, what your subwoofer plays back is usually cut off at 80
or 120Hz. There the wavelength would be a bit over 4 metres to under 3.
The ideal reconstruction area would be 1/4 of that, so a circle 3/4 to 1
metre in radius. Good enough for a living room sofa, definitely not good
enough for a gallery or an open party.
At middle C, 440Hz, you're downto under 20 centimetres.
Ah, now found the source of the "pitch" thread. I have just wasted some
time trying to find the original "Pitch" topic! Yes, middle C is not
440. A "just" Middle C (perfect major 6th down from standard A440) is
264Hz (~= 130cm), and will otherwise vary according to temperament, and
beyond that the whim of players. Still far too many scientists want it
to be, or believe it to be, exactly 256Hz for no better reason than
having a sentimental devotion to powers of 2. There are school textbooks
in print today which assert this frequency.
A wavelength of 20cm is approx 1720Hz, so a flat "top A".
Richard Dobson
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