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Old September 19th 03, 08:59 PM
WBRW
 
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Default AM audio quality: analog vs. digital

After universal complaints about horrendously poor audio quality,
iBiquity has revamped their IBOC digital AM system by switching to the
"HDC" codec -- a slightly warmed-over version of AAC Plus, as used by
Digital Radio Mondial (DRM).

iBiquity claims a large improvement in quality -- but can IBOC, now
with HDC, even match up to the quality that analog AM Stereo has
offered for decades? Listen, compare, and judge for yourself:

http://www.geocities.com/kevtronics


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Old September 21st 03, 01:47 AM
Sven Franklyn Weil
 
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Default

In article , WBRW wrote:
After universal complaints about horrendously poor audio quality,
iBiquity has revamped their IBOC digital AM system by switching to the


I would like to know what everyone thinks of Lenny Kahn's AM digital
system.

He says that his system won't have the hash on the sidebands that
interferes with first-channel stations and won't compromise the fidelity
of the existing analog audio.

And that it will make the station sound better (rather than worse) on
existing radio sets.

Comments? I'm really interested in this system but considering the
"muscle" behind Ibiquity's HD-Radio system, I think Kahn's system is bound
for the wastebasket of electronic history.

--
Sven Weil
New York City, U.S.A.

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Old October 3rd 03, 04:34 AM
Robert Orban
 
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Since the HDC codec provides 15 kHz bandwidth in stereo, while analog AM
stereo is limited to perhaps 9.5 kHz (given an ideal receiver and
understanding the absolute need for a 10 kHz carrier-beat filter), the
digital signal will sound far better to anyone whose hearing acuity
extends to 15 kHz, which is the bandwidth commonly accepted as being
necessary for an impression of high fidelity.

The digital signal will also have a noise floor in excess of 90 dB below
100% modulation, making it immune to the static and manmade noise that
has caused so many problems on the band in the last few decades.

Even disregarding the subtleties (of which there are many), these two
factors alone make HD AM dramatically superior to analog AM stereo.

In article , says...


After universal complaints about horrendously poor audio quality,
iBiquity has revamped their IBOC digital AM system by switching to the
"HDC" codec -- a slightly warmed-over version of AAC Plus, as used by
Digital Radio Mondial (DRM).

iBiquity claims a large improvement in quality -- but can IBOC, now
with HDC, even match up to the quality that analog AM Stereo has
offered for decades? Listen, compare, and judge for yourself:

http://www.geocities.com/kevtronics



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Old October 9th 03, 09:25 PM
David Robinson
 
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(Robert Orban) wrote in message ...
Since the HDC codec provides 15 kHz bandwidth in stereo, while analog AM
stereo is limited to perhaps 9.5 kHz (given an ideal receiver and
understanding the absolute need for a 10 kHz carrier-beat filter), the
digital signal will sound far better to anyone whose hearing acuity
extends to 15 kHz, which is the bandwidth commonly accepted as being
necessary for an impression of high fidelity.


Judging by the samples on...
http://www.wor710.com/Engineering/ib...io_samples.htm

....and from current tends in audio coding, it's almost certain that
the HDC codec is using spectral band replication. In which case, all
that bandwidth up to 15kHz is fake. There's a genuine 5kHz or 7.5kHz
audio bandwidth, and the rest is synthesised. Quite badly, to my ears.

The digital signal will also have a noise floor in excess of 90 dB below
100% modulation, making it immune to the static and manmade noise that
has caused so many problems on the band in the last few decades.


The fact that silence is silence will please some people, as will the
lack of crackle and hiss. But the (hopefully inaudible) coding noise
is only 20-30dB below the signal in a good, high bitrate
psychoacoustic codec. Things will be even worse in low bitrate digital
AM. I didn't know a 90dB dynamic range was part of Orban's business
plan? ;-)

Even disregarding the subtleties (of which there are many), these two
factors alone make HD AM dramatically superior to analog AM stereo.


Some people may be superficially pleased with the silence moments, and
bright sound. However, listening to the samples, it sounds really
quite nasty. IME, people can be very unforgiving of that kind of
artificial, metallic, "computer" sound.


btw - I'm in Europe, so can't listen to AM stereo, or IBOC HD radio
off air. Our digital AM plans, if any, seem to be based on DRM. I
doubt we'll see IBOC over here. It's sad that the world's radio
standards will probably be split in the same way that the world's TV
has been. That's if any consumers actually want digital radio at all.

Cheers,
David.


In article , says...
http://www.geocities.com/kevtronics


  #5   Report Post  
Old October 9th 03, 09:26 PM
WBRW
 
Posts: n/a
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Even disregarding the subtleties (of which there are many), these two
factors alone make HD AM dramatically superior to analog AM stereo.


If IBOC were running pure compressed digital audio, that would be
true!! However, IBOC on AM is only 36 kbps, and only maintains
accurate frequency response up to _5 kHz_ -- all audio above that
point is "spectrally replicated", i.e. "faked" based on harmonics of
lower frequencies. To my ears, it sounds like the treble has been run
through a cheese grater!

Analog AM may have a more limited high frequency response, but at
least it is ACCURATE treble response -- not screechy, gritty, heavily
artifacted treble that is about as pleasing to the ears as fingernails
scratching on a chalkboard.

A new comparison between analog AM Stereo and digital IBOC/"HD Radio"
AM can be found on this site:

http://www.geocities.com/kevtronics

Download the audio samples of both, and compare!

p.s. One thing I can say, however, is that your Optimod 9100-B2 is the
best-sounding analog AM audio processor that has ever been built --
and, of course, it really shines with AM Stereo. Stations which just
want to be LOUD use the 9200... but stations which want to be both
loud AND good-sounding almost universally use the 9100.



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Old October 9th 03, 09:27 PM
Diphthong
 
Posts: n/a
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(Robert Orban) wrote in message ...
Since the HDC codec provides 15 kHz bandwidth in stereo, while analog AM
stereo is limited to perhaps 9.5 kHz (given an ideal receiver and
understanding the absolute need for a 10 kHz carrier-beat filter), the
digital signal will sound far better to anyone whose hearing acuity
extends to 15 kHz, which is the bandwidth commonly accepted as being
necessary for an impression of high fidelity.

The digital signal will also have a noise floor in excess of 90 dB below
100% modulation, making it immune to the static and manmade noise that
has caused so many problems on the band in the last few decades.

Even disregarding the subtleties (of which there are many), these two
factors alone make HD AM dramatically superior to analog AM stereo.


I'd rather put up with some noise and limited bandwidth so long as the
program sounds RIGHT and natural... rather than a strange unnatural
swishing
sound that just happens to have wide bandwidth and low noise floor.

The brain filters out noise and ignores lack of 'highs'.. but when the
whole
sound of the thing is as if it's all come through a satellite
videophone.. yuk!
I've given up on broadcasting as a source of good audio, the only way
to get
good sound is to buy music. And, since I refuse to pay a penny to the
record
companies unless I really can't help myself, this means things have
gotten depressingly limited. Modern life is indeed rubbish.

  #7   Report Post  
Old October 10th 03, 05:03 AM
Bob Haberkost
 
Posts: n/a
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There's no doubt in my mind that IBOC on AM is, at best, a con. If it works at all,
it will be only in the metro coverage, as the digital sidebands, down 39db from
carrier if I read the document linked below correctly.

FM won't be much better. If your digital stream is in the noise, it won't be
available to the receiver.

It's fairly apparent that most decisionmakers in radio these days don't know what to
listen for (otherwise radio would sound better), so when they hear "digital" or
"high-definition" (a misnomer if there ever was one) they're all ears and wallets.

Barnum was right. A shame, really. The Canadians have a better way to do it, and it
ain't IBOC.

And for what it's worth, so was Nyquist. You can't get 15kHz through a channel only
designed to properly sample 5kHz.

For your reading pleasure.....
AM IBOC Standards: http://hraunfoss.fcc.gov/edocs_publi...C-02-286A3.pdf
FM IBOC Standards: http://hraunfoss.fcc.gov/edocs_publi...C-02-286A2.pdf


"WBRW" wrote in message ...
Even disregarding the subtleties (of which there are many), these two
factors alone make HD AM dramatically superior to analog AM stereo.


If IBOC were running pure compressed digital audio, that would be
true!! However, IBOC on AM is only 36 kbps, and only maintains
accurate frequency response up to _5 kHz_ -- all audio above that
point is "spectrally replicated", i.e. "faked" based on harmonics of
lower frequencies. To my ears, it sounds like the treble has been run
through a cheese grater!

Analog AM may have a more limited high frequency response, but at
least it is ACCURATE treble response -- not screechy, gritty, heavily
artifacted treble that is about as pleasing to the ears as fingernails
scratching on a chalkboard.

A new comparison between analog AM Stereo and digital IBOC/"HD Radio"
AM can be found on this site:

http://www.geocities.com/kevtronics

Download the audio samples of both, and compare!

p.s. One thing I can say, however, is that your Optimod 9100-B2 is the
best-sounding analog AM audio processor that has ever been built --
and, of course, it really shines with AM Stereo. Stations which just
want to be LOUD use the 9200... but stations which want to be both
loud AND good-sounding almost universally use the 9100.



  #8   Report Post  
Old October 10th 03, 05:03 AM
RobH
 
Posts: n/a
Default


"Diphthong" wrote in message
...
(Robert Orban) wrote in message

...
Since the HDC codec provides 15 kHz bandwidth in stereo, while

analog AM
stereo is limited to perhaps 9.5 kHz (given an ideal receiver and
understanding the absolute need for a 10 kHz carrier-beat filter),

the
digital signal will sound far better to anyone whose hearing acuity
extends to 15 kHz, which is the bandwidth commonly accepted as being
necessary for an impression of high fidelity.

The digital signal will also have a noise floor in excess of 90 dB

below
100% modulation, making it immune to the static and manmade noise

that
has caused so many problems on the band in the last few decades.

Even disregarding the subtleties (of which there are many), these

two
factors alone make HD AM dramatically superior to analog AM stereo.


I'd rather put up with some noise and limited bandwidth so long as the
program sounds RIGHT and natural... rather than a strange unnatural
swishing
sound that just happens to have wide bandwidth and low noise floor.

The brain filters out noise and ignores lack of 'highs'.. but when the
whole
sound of the thing is as if it's all come through a satellite
videophone.. yuk!
I've given up on broadcasting as a source of good audio, the only way
to get
good sound is to buy music. And, since I refuse to pay a penny to the
record
companies unless I really can't help myself, this means things have
gotten depressingly limited. Modern life is indeed rubbish.


Learn to play an instrument or go to live performance.


--
RobH
The future's dim, the future's mono.





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Old October 10th 03, 05:04 AM
Ty Ford
 
Posts: n/a
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Private owner, current software, 52 minutes of RAM, SCSI card and cable,
digital and analog I/Os, 25 foot extension cables for monitor, keyboard and
console, all disks and full manual. $8.5K

Regards,

Ty Ford


**Until the worm goes away, I have put "not" in front of my email address.
Please remove it if you want to email me directly.
For Ty Ford V/O demos, audio services and equipment reviews,
click on http://www.jagunet.com/~tford


  #10   Report Post  
Old October 10th 03, 03:36 PM
Diphthong
 
Posts: n/a
Default

"RobH" wrote in message ...

I've given up on broadcasting as a source of good audio, the only way
to get
good sound is to buy music. And, since I refuse to pay a penny to the
record
companies unless I really can't help myself, this means things have
gotten depressingly limited. Modern life is indeed rubbish.


Learn to play an instrument or go to live performance.


very practical while driving, I'm sure



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