This phase thing

Dedicated to those large boxes at one end of the room
User avatar
Nick
Site Admin
Posts: 15706
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#1 This phase thing

Post by Nick »

In a attempt to show the difference that phase can have, I have created two WAV files, both made up by adding up the first 10 harmonics of a 440Hz note, The harmonics are at these levels (0, -10, -12, -20, -18, -28, -24, -14, -32, -40). The levels were found from a FFT of a violin. I created two wav files. The first have all the harmonics in phase

http://www.lurcher.org/nick/HARM1.WAV

the second has each harmonics offset by 5 degrees, so second harmonic 5 deg, third 10 deg, fourth 15 and so on, thats in this file

http://www.lurcher.org/nick/HARM2.WAV

To make it easier to hear the difference, I have created another file where the two waves alternate every second

http://www.lurcher.org/nick/ALT.WAV
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
User avatar
Dr Bunsen Honeydew
Old Hand
Posts: 1358
Joined: Mon Sep 21, 2009 10:50 am
Location: Muppet Labs

#2 Re: This phase thing

Post by Dr Bunsen Honeydew »

Sorry basic misunderstanding this has nothing to do with tones, you will hear no difference IMO. It is when the infinite multitude of combined tones i.e. music are happening at the same time. The communication between them is lost because they are out of time with each other, even in a minutest sense it is audible, we are very sensitive. I can hear when a guitar string is a minute degree out of tune, that is why *most* of us hear this. Perhaps that is the answer the people who can't hear it or buy LS3/5As are tone / pitch deaf, and that constitutes the problem I am talking about, think about it. This is a meaningless exercise.

FFS listen to music.
Last edited by Dr Bunsen Honeydew on Fri Apr 07, 2017 8:04 pm, edited 1 time in total.
Cressy Snr
Amstrad Tower of Power
Posts: 10552
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

#3 Re: This phase thing

Post by Cressy Snr »

Interesting that Nick.
I heard no difference when comparing the two long tones, but there was a definite wah wah effect at the instant that each tone switched to the next, and back on the one second of each sequence.
I think this will be significant on music, where fast transients are happening. This could, I reckon, be easily extrapolated to the smearing of leading edges of notes and all manner of other fast transient ills that can creep into the time aspect of the presentation of speakers.

Just my gut feeling of course, but.....lose this time coherence by messing up the phase and you have basically buggered up the timbre, texture and everything else that enables the suspension of disbelief so that you can be there at the virtual performance.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
User avatar
Scottmoose
Needs to get out more
Posts: 1802
Joined: Sat Sep 08, 2007 11:03 am
Contact:

#4 Re: This phase thing

Post by Scottmoose »

To a point, probably true. You take two otherwise identical speakers sharing basically the same overall response & general characteristics, but one has better phase-tracking than the other: many subjective listening tests indicate you'll get a level of coherence from the latter the former can't manage. Not necessarily night and day, but it's there. Unfortunately there are too many variables involved to just snap your fingers & say 'it's that'; although given the number of different circumstances & the generally similar results, there's reasonable support.
'"That'll do," comes the cry of the perfectionist down the ages.' (James May The Reassembler)
Website www.wodendesign.com
Community sites www.frugal-horn.com & www.frugal-phile.com
User avatar
IslandPink
Amstrad Tower of Power
Posts: 10041
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#5 Re: This phase thing

Post by IslandPink »

Need to get those onto a disc so I can hear them on the main system. Thanks Nick !
"Once you find out ... the Circumstances ; then you can go out"
User avatar
IslandPink
Amstrad Tower of Power
Posts: 10041
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#6 Re: This phase thing

Post by IslandPink »

Actually I didn't - that's quite audible on the computer speakers, on the alternating one . Very interesting ! - Especially because those phase shifts are pretty small - less than you'd get on most crossovers.
"Once you find out ... the Circumstances ; then you can go out"
User avatar
Dr Bunsen Honeydew
Old Hand
Posts: 1358
Joined: Mon Sep 21, 2009 10:50 am
Location: Muppet Labs

#7 Re: This phase thing

Post by Dr Bunsen Honeydew »

Perhaps I have become a Luddite in my old age. I am beginning to see the point, please carry it on as I sold my gear capable of looking at this years ago.
User avatar
Dave the bass
Amstrad Tower of Power
Posts: 12273
Joined: Tue May 22, 2007 4:36 pm
Location: NW Kent, Darn Sarf innit.

#8 Re: This phase thing

Post by Dave the bass »

In isolation I can't hear any difference between HARM 1 or HARM 2, but, every other 'step' on the ALT example sounds as though its modulated on a ripple or something to me.

Any chance of a longer section of each sample in 'ALT' mode? I wondered if it was the rapid switching creating that effect maybe?
"The fat bourgeois and his doppelganger"
User avatar
Nick
Site Admin
Posts: 15706
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#9 Re: This phase thing

Post by Nick »

This is 3 seconds of each wave, but with the last 10th sec silent to try and provide a smother transition.

http://www.lurcher.org/nick/ALT30.WAV

Source code:

Code: Select all

#include <stdio.h>
#include <math.h>

double harm[ 10 ] = { 60, 50, 44, 50, 42, 48, 36, 46, 28, 20 };
double phase[ 10 ] = { 0.0, 5.0, 10.0, 15.0, 20.0, 25.0, 30.0, 35.0, 40.0, 45.0 };
double fund = 440;
int rate = 44100;

main()
{
    int i, j, k;
    double step;
    double val;
    double mx;
    short data[ rate * 30 ];

    /*
     * move to be relative to fundimental
     */

    for ( i = 1; i < 10; i ++ ) {
        harm[ i ] = harm[ i ] - harm[ 0 ];
    }
    harm[ 0 ] = 1.0;

    /*
     * convert from dB to relaitive levels
     */

    for ( i = 1; i < 10; i ++ ) {
        harm[ i ] = pow( 10.0, harm[ i ] / 20.0 );
    }

    mx = 0.0;

    for ( i = 0; i < 10; i ++ ) {
        phase[ i ] = phase[ i ] / ( 2 * M_PI );
    }

    mx = 3.0;

    step = ( fund * 2.0 * M_PI ) / rate;

    for ( k = 0; k < 10; k ++ ) {
        for ( i = 0; i < rate * 3; i ++ ) {
            val = 0.0;
            for ( j = 0; j < 10; j ++ ) {
                if (( k % 2 ) == 0 ) {
                    val += harm[ j ] * sin((( step * i * ( j + 1 ))));
                }
                else {
                    val += harm[ j ] * sin((( step * i * ( j + 1 )) + phase[ j ] ));
                }
            }
            val /= mx;

            if ( i > rate * 2.9 ) {
                data[ i + k * rate * 3 ] = 0;
            }
            else {
                data[ i + k * rate * 3 ] = (int)(val * 0x7FFF);
            }
        }
    }

    write_wav( "ALT30.WAV", rate * 30, data, rate );
}
http://www.lurcher.org/nick/harm.c
http://www.lurcher.org/nick/make_wav.c
http://www.lurcher.org/nick/make_wav.h
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
User avatar
Dave the bass
Amstrad Tower of Power
Posts: 12273
Joined: Tue May 22, 2007 4:36 pm
Location: NW Kent, Darn Sarf innit.

#10 Re: This phase thing

Post by Dave the bass »

Thanks Nick.

Nope, I dont hear a difference anymore.
"The fat bourgeois and his doppelganger"
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#11 Re: This phase thing

Post by pre65 »

I tried listening with headphones on my laptop and I could not tell the difference either.

My 66 year old ears are supposedly "good for my age".
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
User avatar
Dr Bunsen Honeydew
Old Hand
Posts: 1358
Joined: Mon Sep 21, 2009 10:50 am
Location: Muppet Labs

#12 Re: This phase thing

Post by Dr Bunsen Honeydew »

Back being a Luddite - what DO YOU expect this to show us. Now you have made it disconnected tones I don't see how it can show anything as there is no transition. Still confused as to the point, when you can hear it so clearly with music.

Take my simple cheap Chinese drivers. Build one with 1st order and one with 2nd order and I will build one doped, mounted on simple ply baffle to make it cheap - bake them off WITH MUSIC.

We establish baffle size. As I say I will build the doped one we need one or two volunteers to build the crossovered ones.
User avatar
Scottmoose
Needs to get out more
Posts: 1802
Joined: Sat Sep 08, 2007 11:03 am
Contact:

#13 Re: This phase thing

Post by Scottmoose »

Very useful. :)

But this takes us to the question of the speaker's overall phase tracking, and the phase rotation brought by the filter. It's possible to have a speaker that has excellent overall phase tracking, but a high[er] amount of phase rotation in its transition band, in the same way that it's possible to have a speaker that has equally excellent overall phase tracking, but a low[er] amount of phase rotation in its transition band. Which is more audible? Leaving all other factors aside (improbable) that's going to depend on the width of the transition band (crossover order) and the XO frequency itself. In theory lower order electrical and acoustical slopes, with less phase rotation, should sound better, providing none of the other factors come into play. Since they almost always do, we're back to playing the game of trade-offs. :cry:
'"That'll do," comes the cry of the perfectionist down the ages.' (James May The Reassembler)
Website www.wodendesign.com
Community sites www.frugal-horn.com & www.frugal-phile.com
User avatar
Dr Bunsen Honeydew
Old Hand
Posts: 1358
Joined: Mon Sep 21, 2009 10:50 am
Location: Muppet Labs

#14 Re: This phase thing

Post by Dr Bunsen Honeydew »

More bullshit, what has this got to do with music and ears.
User avatar
Scottmoose
Needs to get out more
Posts: 1802
Joined: Sat Sep 08, 2007 11:03 am
Contact:

#15 Re: This phase thing

Post by Scottmoose »

More ad hominem I see Richard. :roll:

Short answer? A lot. Recorded music in these circumstances is the signal sent from the amplifier to the speaker. Ergo how the speaker behaves is intimately relevant to that music. Are you seriously saying it isn't? Don't be so silly. You know, if you'd bothered to read the post and think about what was there before posting abusive comments, you might have noticed that what I wrote [while noting significant caveats] actually supports some of your own beliefs.
Last edited by Scottmoose on Sat Apr 08, 2017 3:14 pm, edited 2 times in total.
'"That'll do," comes the cry of the perfectionist down the ages.' (James May The Reassembler)
Website www.wodendesign.com
Community sites www.frugal-horn.com & www.frugal-phile.com
Post Reply