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Sound Pressure Level Meter Weighting (SPL)



 
 
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  #1  
Old May 5th 09, 03:38 PM posted to rec.audio.high-end
ST
external usenet poster
 
Posts: 41
Default Sound Pressure Level Meter Weighting (SPL)

Hi to all,

My initial post "Is flat frequencies desirable" did not really answer
what I was looking for . Though it generates a of of interesting point
that never crossed my mind before. Keep it going.

Now perhaps,I will ask the same question from a different perspective?

According to a HIgh End magazine when setting up loudspeaker or tuning
the room it is advisable to use C-Weighting measurement in the SPL. If
my reading of weighting is correct A-weighting reflects perceived
sound more accurately.

Sound mixing engineers usually do mixing based on hearing and I doubt
they use SPL to see how loud the bass should be and etc..etc. It all
depends on what they hear. Correct?

So, initially I measure the room response level using C-weighting and
with the necessary adjustment so that gives the real measurement. But
the sound turned out to be not to my liking. Then I ignored the SPL
and setup the room and speakers placement according to my ears and I
got the sound right tome the select few who I think understand music
well.

When the measurement done using SPL and test tone it is found that the
room is now tuned to emphasize the lower frequencies.

So my question is should the room and loudspeakers tuned and placed so
that we get a flat frequencies based on A-weighting (i.e, perceived
loudness to human rather than actual loudness)? If the answer is yes
than was the High End magazine was wrong to ask us to use C-weighting?

Regards,
ST

Ads
  #2  
Old May 5th 09, 07:57 PM posted to rec.audio.high-end
TheBoss
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Posts: 1
Default Sound Pressure Level Meter Weighting (SPL)

Hi ST,


On May 5, 10:38*am, ST > wrote:
> Hi to all,
>
> My initial post "Is flat frequencies desirable" did not really answer
> what I was looking for . Though it generates a of of interesting point
> that never crossed my mind before. Keep it going.
>
> Now perhaps,I will ask the same question from a different perspective?
>
> According to a HIgh End magazine when setting up loudspeaker or tuning
> the room it is advisable to use C-Weighting measurement in the SPL. If
> my reading of weighting is correct A-weighting reflects perceived
> sound more accurately.
>


If you like the results from using A-weighting, then it must be better
for you than C-weighting.


> Sound mixing engineers usually do mixing based on hearing and I doubt
> they use SPL to see how loud the bass should be and etc..etc. It all
> depends on what they hear. Correct?
>


I wouldn't presume the methods of mix engineers. In fact, I would
believe that there are many differences in mix engineer methods.
There is likely some care taken to present the engineer with a quality
of sound in the control room that will enable valid decisions to be
made during mixing. Whether this is a flat frequency response, or a
tailored frequency response probably depends on the engineer, the
studio, the producer, etc... I have read and heard that some control
room setups are tuned to a generally typical frequency response that
the mass audience of the material will probably be listening with on
their home stereos, radios, boom boxes, and such.

> So, initially I measure the room response level using C-weighting and
> with the necessary adjustment so that gives the real measurement. But
> the sound turned out to be not to my liking. Then I ignored the SPL
> and setup the room and speakers placement according to my ears and I
> got the sound right tome the select few who I think understand music
> well.
>


Positioning the speakers, in my opinion is job 1. Finding the best
room loading position where any room modes, resonances are minimized
from muddying up the sound, and never positioning the speakers to
sacrifice good stereo imaging. It is usually a bit of compromise, but
I believe it is always worth the time for experimentation.

Job 2, in my opinion is room treatment or renovation. Adding or
subtracting sound absorbing materials like curtains, drapes, rugs,
bookcases, acoustic wall and ceiling treatments, and such. Adding or
subtracting sound reflective materials like mirror tiles, ceramics,
chandeliers, bookcases, and such.

Sometimes it may require a physical renovation, or adding traps when
dealing with especially troublesome room modes.

The time and work invested in the speaker/room setup usually minimizes
the amount of equalization required, and normally increases the
perception and location of the stereo image througout the room. By
controlling the reflective nature of the room, you also personalize
your own preference regarding realism, to your senses and
expectations.

> When the measurement done using SPL and test tone it is found that the
> room is now tuned to emphasize the lower frequencies.
>


This may be a function of your particular room, the speakers, or how
they work together. This may also be a personal expectation in
reproduced sound that you prefer, or find more pleasureable and may
seem more real to your senses.

I personally find that when I am listening to reproduced sound at less
than the original performance SPL, that I prefer some bass boost and a
little high end boost. The human ear drops response in the bass and
highs when listening at lower levels. In fact you may have some
interest in the findings of Fletcher-Munson and their "equal loudness
contours" that describes the general response variations in human
hearing at various sound pressure levels. There is further
development on this topic with an newer ISO standard as well.


> So my question is should the room and loudspeakers tuned and placed so
> that we get a flat frequencies based on A-weighting (i.e, perceived
> loudness to human rather than actual loudness)? If the answer is yes
> than was the High End magazine was wrong to ask us to use C-weighting?
>
> Regards,
> ST


It is really up to you. When evaluating the appreciation of your own
sound setup, I wouldn't dwell too long on A or C or any weighting
arrangement that is mostly used to measure spl in workplaces or
concerts to figure whether people should need to wear hearing
protection or the band may need to turn down the mains.

If you wish to be accurate to the source, then you need to be very
familiar with the source event to be able to pass even a marginal
evaluation of accuracy. It can be difficult to arrange an A-B
listening test of live sound vs reproduced sound in most people's
listening rooms. Not impossible, but very difficult for most to
arrange.

If you are listening for personal enjoyment, then I say by all means
make it so! Don't worry about conforming to engineering standards.
If you have a predisposition to enjoying your reproduced music with
some bass boost, there is nothing wrong with that. Your taste in
tonal balance may change as life goes on as well. If and when it
does, then indulge yourself. If it sounds more real to you, that is
all you need to be concerned with. When listening for pleasure, make
it pleasurable.

Don.

  #3  
Old May 5th 09, 08:55 PM posted to rec.audio.high-end
[email protected]
external usenet poster
 
Posts: 380
Default Sound Pressure Level Meter Weighting (SPL)

On May 5, 10:38*am, ST > wrote:

> So my question is should the room and loudspeakers tuned and placed so
> that we get a flat frequencies based on A-weighting (i.e, perceived
> loudness to human rather than actual loudness)? If the answer is yes
> than was the High End magazine was wrong to ask us to use C-weighting?


With respect to you, your first mistake would be to believe an
instrument over your ears. Now, I am NOT stating that instruments have
no place. What I am stating is that you might measure and equalize
your room to a fare-the-well. Put in two people, a large dog, a couple
of cats and perhaps have a fire going (if so equipped) and all that
changes significantly.

With respect to that 'high-end magazine' you need to understand why
they exist - which is to sell the technology promulgated by their
advertisers and contributors that also happens to be popular with
their audience - only after which they will provide information and
insight.

Now from a purely technical view, C-weighting (uncontoured) would more
accurately reflect the relationship of input signal to output signal.
And, after all, that is what speakers are expected to produce - the
closest possible replication of what went in at the input end at the
output end. This is amplification, not digestion, so the same thing
only more-so or less so (louder or softer), not amalgamated leavings
and a bad smell. Once that is achieved, it is up to the user to add
coloration to their own peculiar taste.

Peter Wieck
Melrose Park, PA
  #4  
Old May 6th 09, 12:10 AM posted to rec.audio.high-end
g
external usenet poster
 
Posts: 111
Default Sound Pressure Level Meter Weighting (SPL)

On May 5, 10:38*am, ST > wrote:
> Hi to all,
>
> My initial post "Is flat frequencies desirable" did not really answer
> what I was looking for . Though it generates a of of interesting point
> that never crossed my mind before. Keep it going.
>
> Now perhaps,I will ask the same question from a different perspective?
>
> According to a HIgh End magazine when setting up loudspeaker or tuning
> the room it is advisable to use C-Weighting measurement in the SPL. If
> my reading of weighting is correct A-weighting reflects perceived
> sound more accurately.
>
> Sound mixing engineers usually do mixing based on hearing and I doubt
> they use SPL to see how loud the bass should be and etc..etc. It all
> depends on what they hear. Correct?
>
> So, initially I measure the room response level using C-weighting and
> with the necessary adjustment so that gives the real measurement. But
> the sound turned out to be not to my liking. Then I ignored the SPL
> and setup the room and speakers placement according to my ears and I
> got the sound right tome the select few who I think understand music
> well.
>
> When the measurement done using SPL and test tone it is found that the
> room is now tuned to emphasize the lower frequencies.
>
> So my question is should the room and loudspeakers tuned and placed so
> that we get a flat frequencies based on A-weighting (i.e, perceived
> loudness to human rather than actual loudness)? If the answer is yes
> than was the High End magazine was wrong to ask us to use C-weighting?
>
> Regards,
> ST


If you use A, your not paying attention to the lows, and things can
get mighty bad. I other words, the bass could be much louder.
Perceived listening and room response have little in common on this
issue you brought up.

greg

  #5  
Old May 6th 09, 12:30 AM posted to rec.audio.high-end
Arny Krueger
external usenet poster
 
Posts: 17,262
Default Sound Pressure Level Meter Weighting (SPL)

"ST" > wrote in message


> According to a HIgh End magazine when setting up
> loudspeaker or tuning the room it is advisable to use
> C-Weighting measurement in the SPL.


C-weighting is almost no weighting. It's pretty much flat response.

http://en.wikipedia.org/wiki/File:Ac...ing_curves.svg

> If my reading of
> weighting is correct A-weighting reflects perceived sound
> more accurately.


How sound is perceived depends greatly on the SPL.

A-weighting is an approximation of the inverse of the Fletcher-Munson curves
for low SPLs.

> Sound mixing engineers usually do mixing based on hearing


Absolutely.

> and I doubt they use SPL to see how loud the bass should
> be and etc..etc.


Any mixing effort, whether for recording or for live sound is implicity
relevant to some preferred SPL level.

If you mix and equalize for 60 dB SPL you will have a vastly different mix
than if you mix for 100 dB SPL.

The usual modern convention for mixing would be based on some presumed SPL
for listening. Much modern thought is contained in the following.

http://www.aes.org/technical/documen...s.cfm?docID=65

 




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