[Bill Noble[_2_]]

"Eeyore" wrote in message
...
Bill Noble wrote:

if you are sampling a sine wave (or square wave) at a single frequency,
so
long as your sample rate is 2X or greater than the fundamental, you will
not
get ALIASING of the fundamental. This says nothing about distortion of
phase or waveform. If phase information is important, a significantly
higher
sampling rate is needed - 10X is much more typical. A control system for
a
large airplane, for example, had a roll off at 4 Hz - we found it
necessary
to sample the input data at 60 hz to prevent phase induced instability.
That's 15X the maximum passband frequency.

I see no reason why this kind of effect does not apply at audio
frequencies
as well.

Because the ear is insensitive to phase info at the relevant frequencies.

Graham


not clear what "relevant" means in this context, but I have run tests
(decades ago), to duplicate what was widely documented, as follows:

pair of headphones, single white noise source - add phase shifting network
to one side only - white noise is indistinguishable via spectrum analyzer
before/after (or left/right). Put on headphones. hear a tone equal to the
pass band of the phase shifting network.

as I recall, I did this in the 1Khz range, but I honestly don't remember.
My point here is that there is significant relative phase detection
capability in the pair of human ears that not commonly understood.

My duplication of these experiments strongly suggests that your statement
about insensitive to phase is incorrect.

[Harry Lavo]

On Nov 25, 11:02*am, "Bill Noble" wrote:
"Eeyore" wrote in message

...





Bill Noble wrote:

if you are sampling a sine wave (or square wave) at a single frequency,
so
long as your sample rate is 2X or greater than the fundamental, you will
not
get ALIASING of the fundamental. *This says nothing about distortion of
phase or waveform. If phase information is important, a significantly
higher
sampling rate is needed - 10X is much more typical. *A control system for
a
large airplane, for example, had a roll off at 4 Hz - we found it
necessary
to sample the input data at 60 hz to prevent phase induced instability.
That's 15X the maximum passband frequency.

I see no reason why this kind of effect does not apply at audio
frequencies
as well.

Because the ear is insensitive to phase info at the relevant frequencies.

Graham

not clear what "relevant" means in this context, but I have run tests
(decades ago), to duplicate what was widely documented, as follows:

pair of headphones, single white noise source - add phase shifting network
to one side only - white noise is indistinguishable via spectrum analyzer
before/after (or left/right). *Put on *headphones. *hear a tone equal to the
pass band of the phase shifting network.

as I recall, I did this in the 1Khz range, but I honestly don't remember.
My point here is that there is significant relative phase detection
capability in the pair of human ears that not commonly understood.

My duplication of these experiments strongly suggests that your statement
about insensitive to phase is incorrect.- Hide quoted text -

- Show quoted text -

I've always found it difficult to accept this notion, based on several
observations as an audiophile for 50 years. Mind you, these are
"speculations" but I would love to see somebody set out to verify
them:

1) Extreme frequency responses. I've always felt that amps with
wideband response at the low end sound more powerful and have better
defined bass than their rolled-off counterparts (i'm talking below
20hz here). And likewise, I've always found amps with wideband high
end to sound more realistic on triangles, cymbal after-ringing, etc.
Conventional theory says one just doesn't hear these things. I've
seemed to, although I will grant you it could just be a placebo
effect.

2) "Rounded" tube sound. Converse to the above, I find virtually all
tube amps have a "rounded" sound that flat 20hz-20khz response doesn't
get at. I suspect tha the more rolled nature (with subsequent phase
shift) of the high and low ends of tube amps has something to do with
why we perceive this. I know of at least two solid state amps that
specifically also roll off about the same as a tube amp, which tend to
share a bit of this characteristic.

3) "It's next door, and it's real" presence. A favorite test of mine
when considering a new component in my system, and I have used it to
build that system. With a really good sound source, acoustically
played and recoreded and "three dimensional" in-room, walk out of the
room....despite frequency response no longer being much of a
factor...some components convey a "they are in the other room"
feeling, and with some the sound just sounds artificial. Of course,
this is through phase-coherent, time-aligned speakers (earlyier
maggies, and then and now full-range Thielfs). Components that fail
this test don't make it into my system.

************************************************** ********

I'd be interested if anybody else experienced any of this, and if so,
tied it to phase-coherence.

[Arny Krueger]

"Bill Noble" wrote in message

"Eeyore" wrote
in message ...
Bill Noble wrote:

if you are sampling a sine wave (or square wave) at a
single frequency, so
long as your sample rate is 2X or greater than the
fundamental, you will not
get ALIASING of the fundamental. This says nothing
about distortion of phase or waveform. If phase
information is important, a significantly higher
sampling rate is needed - 10X is much more typical. A
control system for a
large airplane, for example, had a roll off at 4 Hz -
we found it necessary
to sample the input data at 60 hz to prevent phase
induced instability. That's 15X the maximum passband
frequency.

I see no reason why this kind of effect does not apply
at audio frequencies
as well.

Because the ear is insensitive to phase info at the
relevant frequencies.

not clear what "relevant" means in this context, but I
have run tests (decades ago), to duplicate what was
widely documented, as follows:

pair of headphones, single white noise source - add phase
shifting network to one side only - white noise is
indistinguishable via spectrum analyzer before/after (or
left/right). Put on headphones. hear a tone equal to
the pass band of the phase shifting network.

as I recall, I did this in the 1Khz range, but I honestly
don't remember. My point here is that there is
significant relative phase detection capability in the
pair of human ears that not commonly understood.

My duplication of these experiments strongly suggests
that your statement about insensitive to phase is
incorrect.

Your statement seems to be confusing relative phase with absolute phase.

The ear is very sensitive to phase differences between two sources that are
heard at the same time. For openers, there is a frequency response change
due to cancellation in the air and at the ear. One source becomes the
reference and we are far more sensitive to phase differences in the other
channel because our ear has a reference, and the difference is relative to
the reference.

However, when we speak of the ear being insensitive to phase, we're talking
about phase changes that affect both sources or channels identically.

For example, the low pass filters in a CD player would affect both channels
identically. There is no reference that is separate, so you are expecting
the ear to hear an absolute difference.

[Eeyore]

Bill Noble wrote:

"Eeyore" wrote
Bill Noble wrote:


I see no reason why this kind of effect does not apply at audio
frequencies as well.

Because the ear is insensitive to phase info at the relevant frequencies.

not clear what "relevant" means in this context,

The ones claiming to be 'undersampled'.


but I have run tests (decades ago), to duplicate what was widely documented,
as follows:

pair of headphones, single white noise source - add phase shifting network
to one side only - white noise is indistinguishable via spectrum analyzer
before/after (or left/right). Put on headphones. hear a tone equal to the
pass band of the phase shifting network.

as I recall, I did this in the 1Khz range, but I honestly don't remember.
My point here is that there is significant relative phase detection
capability in the pair of human ears that not commonly understood.

At 1 kHz I can certainly believe that. At 15 or 20 kHz (if you hear that high
still) ? How a bout checking that.


My duplication of these experiments strongly suggests that your statement
about insensitive to phase is incorrect.

I didn't say the ear was totally insensitive to phase. That would be absurd. You
misread or misunderstood my statement.

Graham

[Sonnova]

On Tue, 25 Nov 2008 21:24:19 -0800, Harry Lavo wrote
(in article ):

On Nov 25, 11:02*am, "Bill Noble" wrote:
"Eeyore" wrote in message

...





Bill Noble wrote:

if you are sampling a sine wave (or square wave) at a single frequency,
so
long as your sample rate is 2X or greater than the fundamental, you will
not
get ALIASING of the fundamental. *This says nothing about distortion of
phase or waveform. If phase information is important, a significantly
higher
sampling rate is needed - 10X is much more typical. *A control system for
a
large airplane, for example, had a roll off at 4 Hz - we found it
necessary
to sample the input data at 60 hz to prevent phase induced instability.
That's 15X the maximum passband frequency.

I see no reason why this kind of effect does not apply at audio
frequencies
as well.

Because the ear is insensitive to phase info at the relevant frequencies.

Graham

not clear what "relevant" means in this context, but I have run tests
(decades ago), to duplicate what was widely documented, as follows:

pair of headphones, single white noise source - add phase shifting network
to one side only - white noise is indistinguishable via spectrum analyzer
before/after (or left/right). *Put on *headphones. *hear a tone equal to the
pass band of the phase shifting network.

as I recall, I did this in the 1Khz range, but I honestly don't remember.
My point here is that there is significant relative phase detection
capability in the pair of human ears that not commonly understood.

My duplication of these experiments strongly suggests that your statement
about insensitive to phase is incorrect.- Hide quoted text -

- Show quoted text -

I've always found it difficult to accept this notion, based on several
observations as an audiophile for 50 years. Mind you, these are
"speculations" but I would love to see somebody set out to verify
them:

1) Extreme frequency responses. I've always felt that amps with
wideband response at the low end sound more powerful and have better
defined bass than their rolled-off counterparts (i'm talking below
20hz here). And likewise, I've always found amps with wideband high
end to sound more realistic on triangles, cymbal after-ringing, etc.
Conventional theory says one just doesn't hear these things. I've
seemed to, although I will grant you it could just be a placebo
effect.

2) "Rounded" tube sound. Converse to the above, I find virtually all
tube amps have a "rounded" sound that flat 20hz-20khz response doesn't
get at. I suspect tha the more rolled nature (with subsequent phase
shift) of the high and low ends of tube amps has something to do with
why we perceive this. I know of at least two solid state amps that
specifically also roll off about the same as a tube amp, which tend to
share a bit of this characteristic.

Square wave tests of modern class AB tube amplifiers show a certain amount of
roll-off at low frequencies (expected due to the output transformer), but
usually show nice sharp corners indicating extended high-frequency response
to at least 100KHz.

3) "It's next door, and it's real" presence. A favorite test of mine
when considering a new component in my system, and I have used it to
build that system. With a really good sound source, acoustically
played and recoreded and "three dimensional" in-room, walk out of the
room....despite frequency response no longer being much of a
factor...some components convey a "they are in the other room"
feeling, and with some the sound just sounds artificial. Of course,
this is through phase-coherent, time-aligned speakers (earlyier
maggies, and then and now full-range Thielfs). Components that fail
this test don't make it into my system.

Well, there is a palpability about live music that no reproduced music can
match except in the grossest way. There are times when a very good stereo
system MIGHT fool a passerby for a few seconds on some instruments, but in
order to do that at all, the recording must be very close-up, and the
ensemble must be very small or a solo instrument. Orchestras, big bands, etc,
never will fool anyone, and neither will brass. There is something about the
sound of live brass that simply cannot be reproduced by any audio system that
I have ever heard. For one thing, speakers don't seem to be able to move as
much air in the required frequency band for reproduced trumpets or trombones
to have the necessary bite that says "this is real".

I recall once walking down the street in an area of San Francisco famous for
its night clubs (out Geary street) and passing a nondescript little joint
that had its front door propped open. As I passed the door, I was hit with
the sound of some jazz playing inside. I knew instantly (even though I
couldn't see inside) that the music coming through that doorway was LIVE,
unamplified music. I didn't need to be told, didn't need a double-blind test.
My ears told me all I needed to know. I went in and spent one of the most
pleasant evenings imaginable listening to a really good quintet play in that
tiny bar. Real music will pull you in, Hi-Fi can't do that.

************************************************** ********

I'd be interested if anybody else experienced any of this, and if so,
tied it to phase-coherence.

My Martin Logans are phase coherent above 400 Hz, anyway and I have owned
MG-II A, Tympani III, and MG-3B Maggies, all of which were phase coherent.
While all of these speakers did some things extremely well, I never noticed
that the phase coherence added anything to the palpability of the
performance.

[Arny Krueger]

"Sonnova" wrote in message


My Martin Logans are phase coherent above 400 Hz, anyway
and I have owned MG-II A, Tympani III, and MG-3B Maggies,
all of which were phase coherent. While all of these
speakers did some things extremely well, I never noticed
that the phase coherence added anything to the
palpability of the performance.

There are many reasons for that, but probably the most important reason is
that the phase coherent acoustic waves coming out of a speaker are quickly
turned to mush by just about any real world listening room.

IME the best way to portray a maximally-coherent sonic image in a typical
listening room involves the use of loudspeakers with carefully-controlled
directivity. This automatically precludes the use of dipolar planar
speakers, although in some ways they are better than classic cone/dome
audiophile speakers.

If you want directivity control over the widest possible frequency range for
a reasonable cost, the speaker system will be composed of a large direct
radiator and what well-informed people call "waveguide speakers", but the
general public calls "horns".

One of my friends is a world-renowned expert in acoustics and loudspeaker
design, who has many leading-edge papers to his credit, and has consulted on
the design of a wide range of reproducers for a number of well-known
manufacturers. He also owns a large stable of relevant patents that he has
licensed to various manufactures. Here is his own personal line of
consumer-oriented products:

http://www.gedlee.com/Summa.htm

I don't use speakers that much for serious listening, so I will probably
never again make a large investment in speakers for my home. However, were I
to do so, my next speakers would no doubt have controlled directivity.

Waveguide or horn speakers have risen in favor among audiophiles, and also
fallen out of favor. In the 1950s and 1960s, many high end speakers
including those by Klipsch, JBL, EV, and Altec included waveguides. They
often had obvious and characteristic audible flaws.

The technology of acoustical waveguides made many significant technical
advances during the 1980s and 1990s. Their use remains the rule for high
quality sound reinforcement, so there is plenty ready money for research and
development related to their design and use. The obvious characteristic
audible flaws have been fully addressed for several decades.

Since I am obliged to make cost-effective choices, I would probably pick my
next speakers from the better commercial products designed for high quality
sound reinforcement.

I am currently experimenting with replacing the suffet-mounted Boston
Acoustics CR-9 speakers in my living room with EV ZX-1s. The sonics of the
ZX-1s (as equalized) vastly surpass the CR-9s (as equalized) in *all* ways.
The comparison is probably a little unfair due to the age of the CR-9s.
OTOH, the price comparison is not extreme.

The basic technology of the CR-9s, which are composed of an approximate 7
inch woofer and a small dome tweeter is representative of most modern
residential loudspeakers in the same price class. The ZX-1s use an 8 inch
woofer and a waveguide/driver assembly. Their strong advantage in clarity is
due to the fact that they have controlled directivity.

I've also auditioned ZX-5s in my living room and they are of course suburb
if properly equalized. My long-term choice would probably be ZX-4s as the
extreme dynamic range capabilities of the ZX-5s would go unused in almost
any residential listening situation. The controlled directivity down to even
lower frequencies than the ZX-1 has proven to be a significant sonic
advantage.