[Radium]

Karl Uppiano wrote:
Are you saying that
everyone has got it wrong for lo these many years?

Not necessarily. However, most stereo-to-mono conversion involve simply
decreasing the amplitude level by 50% and then downmixing to mono. The
problem with this, is that the stuff that was identical in both
channels is much louder than the stuff that was different in each
channel.

[Karl Uppiano]

"Radium" wrote in message
oups.com...
Karl Uppiano wrote:
Are you saying that
everyone has got it wrong for lo these many years?

Not necessarily. However, most stereo-to-mono conversion involve simply
decreasing the amplitude level by 50% and then downmixing to mono. The
problem with this, is that the stuff that was identical in both
channels is much louder than the stuff that was different in each
channel.

Ok, well, have fun with your rules. I'm glad you're not running the
engineering standards group at the FCC or something where you could force
everyone to use them. Of course, it wouldn't be anything new, the government
making public policy having the force of law based on junk science.

[Eeyore]

Radium wrote:

Karl Uppiano wrote:
Are you saying that
everyone has got it wrong for lo these many years?

Not necessarily. However, most stereo-to-mono conversion involve simply
decreasing the amplitude level by 50% and then downmixing to mono. The
problem with this, is that the stuff that was identical in both
channels is much louder than the stuff that was different in each
channel.

As was intended.

Graham

[Radium]

Eeyore wrote:
As was intended.

Not if the audio I'm listening to is music

[Walt]

Eeyore wrote:
Radium wrote:
Karl Uppiano wrote:

Are you saying that
everyone has got it wrong for lo these many years?

Not necessarily. However, most stereo-to-mono conversion involve simply
decreasing the amplitude level by 50% and then downmixing to mono. The
problem with this, is that the stuff that was identical in both
channels is much louder than the stuff that was different in each
channel.

As was intended.

Sorry, but I've got to side with Radium here. The center channel
build-up when taking a mono sum is a real phenomenon, and *not*
desirable or intentional.

It happens because taking a voltage sum of two signals increases the
level by 6db, not 3 db as you might expect. For example, if the
original stereo recording has three singers at equal volume panned hard
left, hard right, and hard center, summing to mono will make the guy in
the center 3 db louder than the other two. It was always thus.

So, what we have with Radium is a guy who likes mono (for whatever
reason - I'm not sure I want to know), but doesn't like how most stereo
programs sum to mono. So far, so good. Unfortunately his technique
doesn't come close to solving this problem - he gets .725(R) - .275(L)
not anything approaching a mono sum. But his problem is an
understandable one. (well, the sum-to-mono center channel buildup
problem at least. I'll refrain from commenting on the others)

What to do? Get used to listening in stereo? Write a signal
processing algorithm to compute a mono sum without the center channel
buildup? (maybe this has already been done?) Perform a mono sum the old
fashioned way by jamming a pencil eraser into one of your ears?

The possibilities are endless.

//Walt

[Randy Yates]

Walt writes:
[...]
For example, if the original stereo recording has three singers at
equal volume panned hard left, hard right, and hard center, summing
to mono will make the guy in the center 3 db louder than the other
two.

Shouldn't he have been 3 dB softer to begin with (in the stereo mix)?
--
% Randy Yates % "The dreamer, the unwoken fool -
%% Fuquay-Varina, NC % in dreams, no pain will kiss the brow..."
%%% 919-577-9882 %
%%%% % 'Eldorado Overture', *Eldorado*, ELO
http://home.earthlink.net/~yatescr

[Walt]

Randy Yates wrote:

Walt writes:

[...]
For example, if the original stereo recording has three singers at
equal volume panned hard left, hard right, and hard center, summing
to mono will make the guy in the center 3 db louder than the other
two.

Shouldn't he have been 3 dB softer to begin with (in the stereo mix)?

Yes and no. In order to sound like they're all three at the same level,
the center guy would be -3db in the left channel and -3db in the right
channel.

Say for the sake of the argument that guys on the outside are recorded
at a signal level of 0 dbu (.775 volts), that would mean the guy in the
center is -3dbu or 0.54837 volts. Do a mono sum and the guys on the
outside are still at .775 volts but the guy in the middle is now at
1.09674 volts, or 3db louder.

This little anomaly comes about because loudness as we perceive it is
proportional to the *square* of the voltage. It's called "center
channel buildup" and has been around for as long as we've been doing stereo.


//Walt

[Randy Yates]

Walt writes:

Randy Yates wrote:

Walt writes:

[...]
For example, if the original stereo recording has three singers at
equal volume panned hard left, hard right, and hard center, summing
to mono will make the guy in the center 3 db louder than the other
two.
Shouldn't he have been 3 dB softer to begin with (in the stereo mix)?

Yes and no. In order to sound like they're all three at the same
level, the center guy would be -3db in the left channel and -3db in
the right channel.

Why is that? In order for a signal s(t) to be perceived at the same
power, it should be split into s(t)/2 for the left and s(t)/2 for
the right. Then at the listening position it combines into

l(t) = s(t)/2 + s(t)/2
= s(t)

Thus the center guy should be 6 dB down (1/2 voltage) to sound the
same at the listening position. No?
--
% Randy Yates % "And all that I can do
%% Fuquay-Varina, NC % is say I'm sorry,
%%% 919-577-9882 % that's the way it goes..."
%%%% % Getting To The Point', *Balance of Power*, ELO
http://home.earthlink.net/~yatescr

[Randy Yates]

Randy Yates writes:

Walt writes:

Randy Yates wrote:

Walt writes:

[...]
For example, if the original stereo recording has three singers at
equal volume panned hard left, hard right, and hard center, summing
to mono will make the guy in the center 3 db louder than the other
two.
Shouldn't he have been 3 dB softer to begin with (in the stereo mix)?

Yes and no. In order to sound like they're all three at the same
level, the center guy would be -3db in the left channel and -3db in
the right channel.

Why is that? In order for a signal s(t) to be perceived at the same
power, it should be split into s(t)/2 for the left and s(t)/2 for
the right. Then at the listening position it combines into

l(t) = s(t)/2 + s(t)/2
= s(t)

Thus the center guy should be 6 dB down (1/2 voltage) to sound the
same at the listening position. No?

I should add that I believe the 3 dB/6 dB issue comes up as follows.

Let the left and right channel signals be denotes l(t) and r(t),
respectively. Also assume that l(t) and r(t) are zero-mean,
stationary signals, E[l(t)] = E[r(t)] = 0. Let them also have identical
power: E[l^2(t)] = E[r^2(t)] = P.

What is the power in their sum? We simply compute it as follows:

Psum = E[(l(t) + r(t))^2]
= E[l^2(t)] + 2*E[l(t)r(t)] + E[r^2(t)]
= 2*P + 2*E[l(t)r(t)].

If the left and right signals are completely uncorrelated, then
E[l(t)r(t)] = 0, and the sum power is 3 dB higher than the individual
channels (2*P).

If the left and right signals are perfectly correlated, then

E[l(t)r(t)] = E[l^2(t)] = E[r^2(t)]
= P

and therefore

Psum = 2*P + 2*P
= 4*P.

In this case the sum power is 6 dB (4*P) higher.
--
% Randy Yates % "She's sweet on Wagner-I think she'd die for Beethoven.
%% Fuquay-Varina, NC % She love the way Puccini lays down a tune, and
%%% 919-577-9882 % Verdi's always creepin' from her room."
%%%% % "Rockaria", *A New World Record*, ELO
http://home.earthlink.net/~yatescr

[Karl Uppiano]

"Walt" wrote in message
...
Eeyore wrote:
Radium wrote:
Karl Uppiano wrote:

Are you saying that
everyone has got it wrong for lo these many years?

Not necessarily. However, most stereo-to-mono conversion involve simply
decreasing the amplitude level by 50% and then downmixing to mono. The
problem with this, is that the stuff that was identical in both
channels is much louder than the stuff that was different in each
channel.

As was intended.

Sorry, but I've got to side with Radium here. The center channel build-up
when taking a mono sum is a real phenomenon, and *not* desirable or
intentional.

It happens because taking a voltage sum of two signals increases the level
by 6db, not 3 db as you might expect. For example, if the original
stereo recording has three singers at equal volume panned hard left, hard
right, and hard center, summing to mono will make the guy in the center 3
db louder than the other two. It was always thus.

So, what we have with Radium is a guy who likes mono (for whatever
reason - I'm not sure I want to know), but doesn't like how most stereo
programs sum to mono. So far, so good. Unfortunately his technique
doesn't come close to solving this problem - he gets .725(R) - .275(L) not
anything approaching a mono sum. But his problem is an understandable
one. (well, the sum-to-mono center channel buildup problem at least.
I'll refrain from commenting on the others)

What to do? Get used to listening in stereo? Write a signal processing
algorithm to compute a mono sum without the center channel buildup? (maybe
this has already been done?) Perform a mono sum the old fashioned way by
jamming a pencil eraser into one of your ears?

The possibilities are endless.

//Walt

I was thinking about this the other day, and it occurred to me that center
channel build-up is likely to be more of a problem with "fake" stereo --
multi solo tracks panned to their apparent position in the mix. A "real"
stereo performance, recorded live, with co-incident microphones probably
would not have this problem, although the performers at the center might be
louder due to their proximity to the microphone. That's probably one of the
reasons orchestras are often arranged in a semicircle.

I cannot think of a simple algebraic means to knock down the center channel,
without causing collateral damage to the un-correlated material in the left
and right channels.

[[email protected]]

Radium's "rules" are sheer made up nonsense. He may do this stuff but
there is no reason anyone else anywhere should follow suit.

[Laurence Payne]

On 14 Nov 2006 02:14:53 -0800, wrote:

Radium's "rules" are sheer made up nonsense. He may do this stuff but
there is no reason anyone else anywhere should follow suit.


er... I think we all knew that from his first post. Some of us are
amusing ourselves by teasing him, a few others are indulging in
willie-waving regarding their knowledge of technical jargon :-)

[Eeyore]

wrote:

Radium's "rules" are sheer made up nonsense.

Radium is a babbling idiot.

See his posts in the sci hierarchy.

Graham

[Karl Uppiano]

wrote in message
ups.com...
Radium's "rules" are sheer made up nonsense. He may do this stuff but
there is no reason anyone else anywhere should follow suit.

I kind of sensed that when he posted the rules without any context or
justification. I was just trying to see if I could extract any context or
justification. He has some, but it only exists in his own private universe,
and it seems, his private universe overlaps ours only ever so slightly.

[Eeyore]

Walt wrote:

Eeyore wrote:
Radium wrote:
Karl Uppiano wrote:

Are you saying that
everyone has got it wrong for lo these many years?

Not necessarily. However, most stereo-to-mono conversion involve simply
decreasing the amplitude level by 50% and then downmixing to mono. The
problem with this, is that the stuff that was identical in both
channels is much louder than the stuff that was different in each
channel.

As was intended.

Sorry, but I've got to side with Radium here. The center channel
build-up when taking a mono sum is a real phenomenon, and *not*
desirable or intentional.

It happens because taking a voltage sum of two signals increases the
level by 6db, not 3 db as you might expect. For example, if the
original stereo recording has three singers at equal volume panned hard
left, hard right, and hard center, summing to mono will make the guy in
the center 3 db louder than the other two. It was always thus.

Blah, blah, blah blah !

Have you ever tried *listening* to the effect of traditional monoing ?

Graham

[Walt]

Eeyore wrote:
Walt wrote:


The center channel
build-up when taking a mono sum is a real phenomenon, and *not*
desirable or intentional.

It happens because taking a voltage sum of two signals increases the
level by 6db, not 3 db as you might expect. For example, if the
original stereo recording has three singers at equal volume panned hard
left, hard right, and hard center, summing to mono will make the guy in
the center 3 db louder than the other two. It was always thus.

Blah, blah, blah blah !

Have you ever tried *listening* to the effect of traditional monoing ?


Yes, every recording I have ever made, and every live broacast I've ever
engineered. (i.e. several thousand) Plus every time I've ever listened
to a mono table radio, or pressed the "mono" button on my stereo tuner.
IOW, a *lot*.

If the stereo recording is even moderately phase coherent, it'll sound
reasonable in mono. The center channel buildup is not a huge effect,
but it's not exactly subtle either. And it can actually be seen as a
positive side effect 'cause it makes things in the center pop out a
little which helps intelligibility on the table radios & mono TV sets.

//Walt

[Randy Yates]

Walt writes:

And it can actually be seen as a positive side effect 'cause it
makes things in the center pop out a little which helps
intelligibility on the table radios & mono TV sets.

Walt,

You never responded to my other post to you on this. In a nutshell, I
think the only reason we have "center-channel buildup" is because the
mastering engineer "popped out" the center channel info a bit. I.e.,
the buildup is in the mastering engineer's hands. If the levels were
mixed so that they were correct mathematically, they would not build
up and they would not pop out.

That's my prediction based on my analysis. Do you disagree? Can you
see where my analysis is invalid?
--
% Randy Yates % "She has an IQ of 1001, she has a jumpsuit
%% Fuquay-Varina, NC % on, and she's also a telephone."
%%% 919-577-9882 %
%%%% % 'Yours Truly, 2095', *Time*, ELO
http://home.earthlink.net/~yatescr

[Walt]

Randy Yates wrote:
Walt writes:

And it can actually be seen as a positive side effect 'cause it
makes things in the center pop out a little which helps
intelligibility on the table radios & mono TV sets.

Walt,

You never responded to my other post to you on this. In a nutshell, I
think the only reason we have "center-channel buildup" is because the
mastering engineer "popped out" the center channel info a bit. I.e.,
the buildup is in the mastering engineer's hands. If the levels were
mixed so that they were correct mathematically, they would not build
up and they would not pop out.

That's my prediction based on my analysis. Do you disagree? Can you
see where my analysis is invalid?

Yes, I disagree. The center channel buildup is an artifact of taking a
voltage sum instead of a power sum. It happens every time you combine
stereo to mono, unless the program material was momo in the first place.
Regardless what the mastering engineer does.

Do you understand why db is calculated as follows:

db = 10Log(P1/P2)
db = 20Log(V1/V2)

Why the factor of 20 instead of 10 when using voltages instead of power?

Understand that, and you'll understand the center channel buildup:
1 watt plus 1 watt equals 2 watts, for a gain of 3 db.
1 volt plus 1 volt equals 2 volts, for a gain of 6 db.

//Walt