Amplitude, Frequency and Phase

[mansr]

To get near 100% destructive interference, you'd need to have the speakers at exactly the same distance from the listener, and the room + placement of the speakers would have to be designed to give (near) perfect symmetry of all reflections. Assuming that one of the speakers have the signal shifted 180 degrees. And then you'd only get a single "dead" spot at a strict listening position.

That's what I'd imagine. I could be wrong though. Acoustics are still a bit of a mystery to me.

With two speakers playing a tone, one can easily observe cancellation at various points in the room. The location of those points and the strength of the cancellation depend on the frequency of the tone, the phase difference between the speakers, and reflections from walls. It's a very simple experiment that everybody should do as a child. If playing a more complex signal containing multiple frequency components, the cancellation points will be different for each. In an anechoic room with one speaker playing the inverse of the other, any point equidistant from both speakers will have (nearly) full cancellation. In a normal room, the amount of reflections mean the cancellation will never be particularly strong, and that's generally a good thing.

 

[tomtoo]

Not quite.
Two identical frequencies don't need to have the same identical phase, the phase difference can span the full circle, the important thing is that this difference is constant over time, a stable fixed value. This is phase lock. The frequencies add as constant vectors (including adding up to zero).
Different frequencies means a constantly varying phase difference and vice versa.
When amplitudes have the same order of magnitude and the phase rotation is slow which means frequencies are almost equal then we have beating.
Finally, when the frequencies are farther apart (phase difference rotates like wild) the whole thing disintegrates into two independant frequencies.

Yes thats absolutly right and it shows why a Piano player and a Guitar player would not be recorded "in phase" at a microphone. Maybe for a tiny short time. And that only if we forget any room reflections. In realty you not even have a phase lock. Couse the two instruments will never be exactly on the same frequency. And they will not be on the same distance to the mic, couse it would be hard for the guitar player . So they will also not be on a phase lock. And that means they will be out of phase. And thats my realistic opinion of the situation. Out of Phase. Mybe a good song titel?

 

[AudioStudies]

Couse the two instruments will never be exactly on the same frequency.

Do you mean because of the overtones? The fundamental frequency would be the same, I think, if they are playing the same note.

 

[mansr]

Do you mean because of the overtones? The fundamental frequency would be the same, I think, if they are playing the same note.

There's always some inaccuracy in the tuning.

 

[AudioStudies]

Can anyone here either confirm or deny a rumor I heard a while back? I was told that in Mozart's time the piano keys played a half-step different than modern pianos, and because of that -- one of the Pioneer turntables was designed with pitch control, to enable hearing the music played a half-step off.

 

[tomtoo]

Do you mean because of the overtones? The fundamental frequency would be the same, I think, if they are playing the same note.

In theory. But they will always differ a littel. Like i told. If you talk about phase on a oszilloskope with two perfect stabel sine oszilators it's very different to two instruments recordet in a room. In reality the two instrument will not have exactly the same frequence, the will not start at exactly a phase null and they will not be constantly at the same distance to the mic. And thats without thinking about reflections of the room. So it's easy to say they will be out of phase.

 

[mansr]

Can anyone here either confirm or deny a rumor I heard a while back? I was told that in Mozart's time the piano keys played a half-step different than modern pianos, and because of that -- one of the Pioneer turntables was designed with pitch control, to enable hearing the music played a half-step off.

Several different tuning standards have been used over the years, some lower and some higher than the currently most common A440. See https://en.wikipedia.org/wiki/Concert_pitch for a brief rundown. I have no idea about the turntable.

 

[AudioStudies]

spectral centroid

I looked it up. Thanks for the insight.

It is calculated as the weighted mean of the frequencies present in the signal, determined using a Fourier transform, with their magnitudes as the weights:[2]

where x(n) represents the weighted frequency value, or magnitude, of bin number n, and f(n) represents the center frequency of that bin.

 

[dfuller]

I was told that in Mozart's time the piano keys played a half-step different than modern pianos

That's actually true - pitch has inflated over time. Current standard is calibrated to A4=440Hz, but in Mozart's time it was all over the place (there was no standard "A4=___hz") and probably was lower - but could've been higher, too. Beethoven had a tuning fork that was tuned to A4=455Hz.

 

[AudioStudies]

Can anyone comment regarding which manufacturer of digital pianos comes closest to the real thing? What is the best digital piano in the world, and how close does it come to real? Where do digital pianos fall short with respect to some of the topics we have been discussing = fundamental frequencies, overtones, etc.

 

[tomtoo]

Can anyone comment regarding which manufacturer of digital pianos comes closest to the real thing? What is the best digital piano in the world, and how close does it come to real? Where do digital pianos fall short with respect to some of the topics we have been discussing = fundamental frequencies, overtones, etc.

Now you are in the realm of musicians. And thats mostly subjective. I enjoy the sound of yamaha e pianos. They are imo on the bright side, what i enjoy. But thats realy complicated, you could als enjoy the sound of a multisampeled bosendorfer or a old bar piano. Whats the real thing?

 

[AudioStudies]

Beethoven had a tuning fork that was tuned to A4=455Hz.

Did he roll over?

 

[AudioStudies]

Whats the real thing?

You giving me help is the real thing, and I am grateful. Yeah, good point, even the best acoustic pianos in the world differ, so what is the real thing? Years ago, they claimed it was Coca Cola. I didn't stick with the keyboards for long enough, regrettably. But I did own a mid-level Roland a few years ago and it was pretty darn good emulating piano sounds. Sucked when trying to replicate the organ though. I hope all is well across the pond.

 

[dfuller]

Can anyone comment regarding which manufacturer of digital pianos comes closest to the real thing? What is the best digital piano in the world, and how close does it come to real? Where do digital pianos fall short with respect to some of the topics we have been discussing = fundamental frequencies, overtones, etc.

The best ones aren't artificially generated - they're sample libraries of real recorded pianos! Most are Kontakt sample libraries from the likes of 8Dio and similar.

 

[AudioStudies]

The best ones aren't artificially generated - they're sample libraries of real recorded pianos! Most are Kontakt sample libraries from the likes of 8Dio and similar.

Fascinating !!

 

[AudioStudies]

Dont get me wrong but you mix so much thinks up its hard to get even a point what you like to know?

I hope it became more clear as the posts progressed. I will try to avoid what my father used to call Ross Perot Syndrome = opening mouth before engaging brain . . .

 

[tomtoo]

I hope it became more clear as the posts progressed. I will try to avoid what my father used to call Ross Perot Syndrome = opening mouth before engaging brain . . .

Yep i realy know this problem. And this is a place of music and science. And both is beatyfull. And we all suffer a little from this syndrom. So all is cool.

 

[tomtoo]

You giving me help is the real thing, and I am grateful. Yeah, good point, even the best acoustic pianos in the world differ, so what is the real thing? Years ago, they claimed it was Coca Cola. I didn't stick with the keyboards for long enough, regrettably. But I did own a mid-level Roland a few years ago and it was pretty darn good emulating piano sounds. Sucked when trying to replicate the organ though. I hope all is well across the pond.

Seperate it. Seperate the way a meal is cooked. Than the way it's transported to you. And the way you eat it.
Cooking is making musik. The transport is the medium and your hifi system. The way you eat it, is what you enjoy.

 

[AudioStudies]

old bar piano

Perhaps the old bar piano is analogous to tube amps and a state of the art acoustic piano is analogous to a fully-calibrated high end Dolby Atmos system.

 

[tomtoo]

Perhaps the old bar piano is analogous to tube amps and a state of the art acoustic piano is analogous to a fully-calibrated high end Dolby Atmos system.

Ah cool same moment, just read the last post from me. Than you see that it's different. As long as you make music there is no good or bad it's all a mater of taste.

When it comes to the transport there is good and bad. Usually you like the meal like it was cooked.

But if you enjoy some tabasco on it? Why not?