feline1 wrote:Pianoteq seems to have a maximum sample rate of 48k.
I did ask before if there were plans to increase it to 96k -
I expect real pianos also make acoustic energy in that extra octave of harmonics between 20kHz and 40kHz,
and I continue to wonder if the pianoteq model would sound any different if it took this into account
There are 2 issues here. (1) would PTQ sound better if its sample rate was 96 kHz? (2) do frequencies emitted by instruments above 20kHz need to be reproduced?
(1) The answer depends on the frequency limit set when the PTQ piano sound is compiled. As this is internal to the software implementation of the synthesis, it can be made to simulate a perfect theoretical "brick-wall" anti-aliasing filter (in fact that would be the simplest filter to implement!). So, as long as this frequency limit is below 0.5 x sampling rate, there cannot be any sonic improvements from adopting a higher rate.
This is quite different from recording and digitising piano sounds, where the the microphone used may have a small but significant frequency output above 20KHz - and the downstream recording equipment is designed to accommodate this - so that the data stream output from the D/A converter contains frequencies which potentially could alias back into the audible range at low level and be perceived as a more or less subtle distortion.
(2) This has been an issue that has been around in acoustics and audio for decades. It has generally been assumed that since the human ear cannot hear sine waves above (nominally) 20kHz, that it is not necessary to reproduce them. I have seen some research from the 1990's done with gamelan music and using equipment that could reproduce 50-60kHz, which indicated that the presence/absence of these frequencies is detectable. But because a difference can observed, does it mean that it is important to reproduce sound to 60KHz? I am not convinced (and not just because I cannot hear 10kHz any more )
There is a simple example of an observable difference, that does not seem to have a large bearing on reproduced music - the absolute acoustic phase of a sound wave. Consider the recording of a kick drum: the mic is placed on the audience side of the drum. The initial sound that arrives at the mic is a compression wave . That means that in a domestic living room, etc the initial sound should be delivered by the speakers as a compression and not a rarefaction, i.e. the drive unit diaphragms to move outwards. In practice, many people can hear a difference - you can try it easily by simply reversing the loudspeaker + and - leads. (To my ears the difference is quite gross). But it is not evident from "blind" listening which is the correct sound. And it is of course impossible to know when listening to recorded music which is the intended sound. The recording chain may contain equipment which reverses the phase 180 degrees - indeed, most recording consoles have a button expressly for that purpose.
Gilles wrote:I get 256 samples (24 bits) giving 5.3 ms latency at 48KHz which, to me, is instantaneous.
Latencies mentioned on sound driver control panels often do not include additional latencies due to internal data buffers. The only way of determining the real latency is with "round trip" methods. I think it is due to the fact that real latencies are not known, that the empirical rule of thumb has evolved to set latency in the driver as low as possible, but not so low that causes audible glitches or breakups.
I think a reasonable latency to aim for in the equipment is 3 ms. This number was discovered by accident long before computers. In the early days of sound reproduction, cinema speakers used multi-way horns. At first, these horns were aligned with their mouths in the same plane. All seemed well - until the film showed an actor tap-dancing (Mr Bojangles?). Then the sound had clear and distinct echoes. This was due to the path difference between the different drive units. When the horns were moved so that the difference between the horn throats was less than about 1 metre, the echoes disappeared.
It's easy to appreciate that a drummer playing an electronic kit may be disconcerted by an acoustic latency, especially if the speakers are more than about 2m from him. But pianists invariable face a latency in the hammer action of a real piano that is an order of magnitude greater than this 3 ms psychoacoustic limit.