Dual 505 update
 

On Wed, 11 Mar 2015 19:46:25 GMT, (Don Pearce) wrote:

On Thu, 12 Mar 2015 06:40:05 +1100, Trevor Wilson
wrote:


**Well, it would, wouldn't it? Phase shift and all that.... The human
hearing system is exquisitely sensitive to phase shift.


The human hearing system is essentially totally deaf to phase shift.
I've seen an experiment in which the phase of the harmonics of a
square wave was cyclically shifted. You could see the waveform
changing shape on a scope. Even with the picture in view, it was
impossible to hear any change in the resulting sound.

Deafness to phase shift is the reason why Orban's Optimod system is
able to operate inaudibly.

d

I've managed to recreate something like it. Have a listen, then look
at the waveform on an audio editor. This will show you how human
hearing deals with phase shift.

http://www.soundthoughts.co.uk/listen/phase.mp3

d

Dual 505 update
 

In article , Don Pearce
wrote:
On Thu, 12 Mar 2015 06:40:05 +1100, Trevor Wilson
wrote:


**Well, it would, wouldn't it? Phase shift and all that.... The human
hearing system is exquisitely sensitive to phase shift.


The human hearing system is essentially totally deaf to phase shift.
I've seen an experiment in which the phase of the harmonics of a square
wave was cyclically shifted. You could see the waveform changing shape
on a scope. Even with the picture in view, it was impossible to hear any
change in the resulting sound.

A snag being that nonlinearities, etc, in audio equipment may well be
affected in a way that changes with the relative phases of components in a
signal. So the phase shifts may become audible as a result.


Deafness to phase shift is the reason why Orban's Optimod system is able
to operate inaudibly.

Hmmm. Its a shame that "is able to" may not always translate into "does"
because of the ways it gets used in practice. Problem here is partly down
to stupidity of the operators, partly due to the obsessions with making
things LOUD. The more knobs and sliders there are on the desk to provide
'improvements', the more scope there is for the controller to foul up the
results.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Dual 505 update
 

On Wed, 11 Mar 2015 19:46:25 GMT, (Don Pearce) wrote:

On Thu, 12 Mar 2015 06:40:05 +1100, Trevor Wilson
wrote:


**Well, it would, wouldn't it? Phase shift and all that.... The human
hearing system is exquisitely sensitive to phase shift.


The human hearing system is essentially totally deaf to phase shift.

+1

I've seen an experiment in which the phase of the harmonics of a
square wave was cyclically shifted. You could see the waveform
changing shape on a scope. Even with the picture in view, it was
impossible to hear any change in the resulting sound.

I was going to mention the effects of phase shift on the harmonics of
a 500Hz squarewave played back from analogue magnetic tape where,
despite the oscilloscope display showing it looking nothing like a
square wave, it still sounds just like the original squarewave. Also
the trick, when dubbing copies from a master tape, of playing the
master and slave recorders in reverse to cancel the effect of the
phase shifts, largely restoring the waveshape back to a semblence of
'squareness'.


Deafness to phase shift is the reason why Orban's Optimod system is
able to operate inaudibly.


I guess the phase shift sensitivity reference Trevor is thinking of
is in relation to stereo detection of the direction of sound sources
rather than the percieved quality of the sound by each individual ear.
--
J B Good

Dual 505 update
 

On Wed, 11 Mar 2015 20:42:59 GMT, (Don Pearce) wrote:

On Wed, 11 Mar 2015 19:46:25 GMT, (Don Pearce) wrote:

On Thu, 12 Mar 2015 06:40:05 +1100, Trevor Wilson
wrote:


**Well, it would, wouldn't it? Phase shift and all that.... The human
hearing system is exquisitely sensitive to phase shift.


The human hearing system is essentially totally deaf to phase shift.
I've seen an experiment in which the phase of the harmonics of a
square wave was cyclically shifted. You could see the waveform
changing shape on a scope. Even with the picture in view, it was
impossible to hear any change in the resulting sound.

Deafness to phase shift is the reason why Orban's Optimod system is
able to operate inaudibly.

d

I've managed to recreate something like it. Have a listen, then look
at the waveform on an audio editor. This will show you how human
hearing deals with phase shift.

http://www.soundthoughts.co.uk/listen/phase.mp3


Nice one, Don.

Back in the day, 40 odd years ago, there was no easy way to produce
such test tones other than comparing input and output signals with a
'scope of a three head tape recorder that would let you switch between
source and replay.

Even then, all you could do was switch between two specific
waveshapes with such a set up. Despite having the necessary kit to do
the test, I was happy to take the author's assertion on trust since it
saved me having to haul a 60 or 70 Lb 'scope up and down the basement
stairs to run the test.

Another fact, of some importance to analogue tape, is our relatively
high tolerance to intermodulation distortion. Even the professional
multi-track studio recorders, running at 30 ips could show routine IM
distortion levels as high as 30% on master tapes.

You can see very sound technical reasons for the practice of direct
cut recording of acetate masters for vinyl reordings. These days, use
of digital recording methods in place of the traditional studio master
tape to recreate such direct cut vinyl records offers the benefits of
tape to vinyl transfer but without any of its deficiencies.

Anyone still catering to this specialist demand for direct cut vinyl,
if they've any understanding of the orginal reasons for using such a
difficult method to make such disks, would simply use a digital
intermediate master and save themselves the grief of an actual direct
cut process - the end result will be indistinguishable from a true
direct cut (other than for the tighter control of the variable groove
pitch with level).
--
J B Good

Dual 505 update
 

On Thu, 12 Mar 2015 09:29:59 +0000 (GMT), Jim Lesurf
wrote:

In article , Don Pearce
wrote:
On Thu, 12 Mar 2015 06:40:05 +1100, Trevor Wilson
wrote:


**Well, it would, wouldn't it? Phase shift and all that.... The human
hearing system is exquisitely sensitive to phase shift.


The human hearing system is essentially totally deaf to phase shift.
I've seen an experiment in which the phase of the harmonics of a square
wave was cyclically shifted. You could see the waveform changing shape
on a scope. Even with the picture in view, it was impossible to hear any
change in the resulting sound.

A snag being that nonlinearities, etc, in audio equipment may well be
affected in a way that changes with the relative phases of components in a
signal. So the phase shifts may become audible as a result.


Deafness to phase shift is the reason why Orban's Optimod system is able
to operate inaudibly.

Hmmm. Its a shame that "is able to" may not always translate into "does"
because of the ways it gets used in practice. Problem here is partly down
to stupidity of the operators, partly due to the obsessions with making
things LOUD. The more knobs and sliders there are on the desk to provide
'improvements', the more scope there is for the controller to foul up the
results.

Jim

I agree, non-linearities do render most things moot in hearing. But
listen to my sound at a normal, comfortable level, and it remains
unchanging throughout.

d

Dual 505 update
 

On 11/03/2015 16:42, Johny B Good wrote:



Yes, this all rather begs the question of _just_ how far we should go
in pursuit of 'perfect reproduction' of the original 'sonic
experience'.

Lots of interesting stuff snipped for brevity...

Such a comprehensive and well written set of comments that I have to
acknowledge it although I have only skimmed through it so far. Your
mention of the response to sudden high sound levels and simulation of
same in Wolfenstein 3D reminded me of a similar technique used in modern
'Dance' or 'Clubbing' music. As you probably know, much of it is based
around electronically processed kick drum sounds and the spl in venues
is often colossal. To further enhance perception of this already loud
and pulsing '4/4 to the floor' sound the producers use 'ducking' (also
called 'side chaining') whereby the rest of the music fades rhythmically
in time to the beat. Even played at home at reasonable levels there is a
distinct impression that the kick drum beat is louder than it actually
is in this type of music.

The technique has now become rather a cliche and I've even heard music
in that genre with extreme 'ducking' but without much of a drum beat at
all.

Dual 505 update
 

In article , Sumatriptan
wrote:
To further enhance perception of this already loud and pulsing '4/4 to
the floor' sound the producers use 'ducking' (also called 'side
chaining') whereby the rest of the music fades rhythmically in time to
the beat. Even played at home at reasonable levels there is a distinct
impression that the kick drum beat is louder than it actually is in
this type of music.

Good grief! They've re-invented what EMI used to keep doing with
re-re-releases of 'The Shadows' music during the 1970s onwards where
applying lousy level compressors caused the resulting sound to pump up and
down enough to make you feel sea-sick! Had the result of making people
assume the original was as bad.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Dual 505 update
 

Johny B Good wrote:

I was going to mention the effects of phase shift on the harmonics of
a 500Hz squarewave played back from analogue magnetic tape where,
despite the oscilloscope display showing it looking nothing like a
square wave, it still sounds just like the original squarewave.


** That is not true of the vast majority tape machines which are well capable of reproducing a good square wave at 500Hz.

True of any decent cassette deck or R to R and includes Roland tape echo machines as well.

My standard test for a Roland 201, 303 and 501 models involves recording a 500Hz square wave and I except to see a good looking result on the scope.

Sure you were not thinking of 50Hz?



Also
the trick, when dubbing copies from a master tape, of playing the
master and slave recorders in reverse to cancel the effect of the
phase shifts, largely restoring the waveshape back to a semblence of
'squareness'.

** Very hard tobeiev it worked or was in any way necessary.


I guess the phase shift sensitivity reference Trevor is thinking of
is in relation to stereo detection of the direction of sound sources
rather than the percieved quality of the sound by each individual ear.


** For certain.


.... Phil


--
J B Good

Dual 505 update
 

Johny B Good wrote:




Another fact, of some importance to analogue tape, is our relatively
high tolerance to intermodulation distortion.


** Not one bit true.


Even the professional
multi-track studio recorders, running at 30 ips could show routine IM
distortion levels as high as 30% on master tapes.


** That would be very audible.

Now you are just making stuff up.



..... Phil

Dual 505 update
 

On Thu, 12 Mar 2015 21:24:47 -0700 (PDT), Phil Allison
wrote:

Johny B Good wrote:




Another fact, of some importance to analogue tape, is our relatively
high tolerance to intermodulation distortion.


** Not one bit true.


Even the professional
multi-track studio recorders, running at 30 ips could show routine IM
distortion levels as high as 30% on master tapes.


** That would be very audible.

Now you are just making stuff up.


Not me. I was quoting what I learnt from 'learned' articles from
either "Hi-Fi Magazine" or "Studio Sounds" magazines I _used_ to
subscribe to back in the mid 70s to early 80s.
--
J B Good