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post #1 of 19 Old 08-08-2012, 09:50 PM - Thread Starter
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Hello Forum,

I'm new with all this audio systems and would like if someone can help me to clear some issues i've got reading from all the webs and wiki.

Essentially, i really want to understand the specs of a speaker and what it means for example:

Focal Sib loudspeaker

Type 2-way compact bass-reflex speaker
Finish Jet Black, Pearl White
Drivers 13cm Polyflex mid-bass 3/4"(19mm) mylar tweeter dome
Frequency response (+or-3dB) 75Hz - 20kHz
Low frequency point 69Hz
Sensitivity (2,83 V/1 m) 90dB
Nominal impedance 8 Ohms
Minimum impedance 4 Ohms
Crossover frequency 3 500Hz
Recommended amplifier power 15 - 75W
Dimensions (HxWxD) 10-3/4 x 5-9/16 x 6-7/16"
Net weight 4.6Ibs (2.1kg)


The sensitivity doubt:

2.83V/1m 90dB
Reaserching, i have read that the sensitivity is the efficiency of the speaker to convert power to audio signals. The tendency is more dB, better speaker. What i really don't understand is the explanation:

2.83V with a 8ohm speaker turns into 1watt.
I follow this webpage:
http://www.the-home-cinema-guide.com/speaker-sensitivity.html#axzz22vTATavE

So with the Sib speaker i understand:
when the amplifier sends 2.83V it generates a 90dB SPL (sound pressure level). is this for real? because at the wiki :

http://es.wikipedia.org/wiki/Decibelio
in spanish sorry about my reference, saids that aproximately a 80dB is equal to the SPL of a train!!! So i imagine 90dB with only 2.83V???? I know i'm misunderstanding something here.

And by the way, when i connect my speaker to my avr receiver and pump up the volume, just at -7dB it's really loudy!!! so how can i compare this value (90dB at 2.83V/1m) with the one displayed at my receiver (volume).

Please any repply would be great, as i mentioned before im a newbie at all this audio and avr systems and would like to understand really what means all this specs.

Thanks for all again i know it's a really long thread.

Cheers!
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post #2 of 19 Old 08-09-2012, 01:18 AM
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The thing to remeber is the speaker spec is given at 1 meter. So yes, you get 90dB with 1 watt, at 1 meter.

Typical listening position is at least 3 meters away. For every doubling of distance from the speaker, you lose 6dB. So a single speaker at 1 meter is 90 db, 2 meters is 84dB and 4 meters is 78dB.

The sensitivity and power ratings together help to determine the SPL available to the listener their listening distance.
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Originally Posted by franciscom View Post

And by the way, when i connect my speaker to my avr receiver and pump up the volume, just at -7dB it's really loudy!!! so how can i compare this value (90dB at 2.83V/1m) with the one displayed at my receiver (volume).

With a properly calibrated system, -7dB on your receiver should be about 78dB average at your listening position (0dB on the receiver is considered reference level and should be 85 dB at your listening position).

Does your AVR have a calibration mode, and have you used it?
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post #3 of 19 Old 08-09-2012, 02:06 AM
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Quote:
Originally Posted by franciscom View Post


And by the way, when i connect my speaker to my avr receiver and pump up the volume, just at -7dB it's really loudy!!!
Cheers!
Really loudy?tongue.gif

Dumb enough to spend lots of cash on this junk!
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post #4 of 19 Old 08-09-2012, 09:45 AM
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That "minus 7db" number is pretty much meaningless. What that number translates to, in actual room sound level, depends on the speaker sensitivity and room acoustics, to name only two of several variables that the receiver cannot possibly be preset for.

What it means is that there is a setting that is more or less ARBITRARILY selected as 0 db for THAT UNIT (at the factory), for reference purposes, and that you are 7 db below that level.

This has nothing to do with the actual sound pressure levels produced by the speakers. 90 dbA is a fairly loud average sound level for listening to music, but not deafening or anything....just fairly loud. 100 dbA is getting pretty damn loud, and 110 dbA is really really loud (unpleasantly loud for sane people).

Of course, playing at an average SPL of 90 dbA will quite possibly result in some momentary peak levels of over 100 dbA, depending on how much the music varies at peak times. Playing at an average level of one watt quite often means there can be peaks 20 db higher, which will momentarily require 100 watts of power from the amplifier.

And by the way; the 2.83 volts only produces 1 watt of speaker power input IF the speaker is exactly 8.00 ohms at the test frequency used! If your test frequency is 1 Khz, you need to look at a graph of impedance versus frequency for YOUR SPEAKER to find out what the actual impedance of your speaker is at that frequency.

If the speaker is 6 ohms at the test frequency, for example, the speaker terminal voltage needs to be set to 2.45 volts to put in 1 watt. If the speaker is 4.00 ohms, the voltage for one watt is 2.00 volts (for one watt of power, the voltage is the square root of the impedance).

And a freight train's engines, travelling at 40 MPH on level ground, will produce a SPL of around 110-120 dbA at 20 feet away....not 80 dbA. I have measured it with an SPL meter.
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post #5 of 19 Old 08-09-2012, 07:13 PM - Thread Starter
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thanks the son for the repply, pretty clear but one question. How do calculate this:

With a properly calibrated system, -7dB on your receiver should be about 78dB average at your listening position (0dB on the receiver is considered reference level and should be 85 dB at your listening position).

or is it just an example if my receiver is calibrated.

Thanks!
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post #6 of 19 Old 08-09-2012, 07:17 PM - Thread Starter
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commysman,

thanks for all your explanation, pretty clear and indeed now i can understand the sensibility with tables frequency vs impedance. what i learned from your explanation is that a speaker with more sensitivity would be able to give me the spl or volume i need to an specific distance from it. So the higher sensitivity, better speaker for sure.

thanks for your help really appreciatte it.
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post #7 of 19 Old 08-09-2012, 07:32 PM
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Quote:
Originally Posted by franciscom View Post

thanks the son for the repply, pretty clear but one question. How do calculate this:
With a properly calibrated system, -7dB on your receiver should be about 78dB average at your listening position (0dB on the receiver is considered reference level and should be 85 dB at your listening position).
or is it just an example if my receiver is calibrated.
Thanks!

It's for a calibrated system. What receiver are you using? A receiver with auto-calibration (properly used) should set up the speakers for an average of 85dB at the listening position. Only then will the volume dial tell you anything about the SPL, but it's still not necessarily accurate because movies/tv are really dynamic and may be louder or quieter throughout the movie/show, or even between 2 different movies/shows.

The number on the volume control really only gives you a visual reference. Like commsysman said, it's pretty meaningless - if the system isn't calibrated. It provides the user with a visual representation of where the volume control is set.
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post #8 of 19 Old 08-09-2012, 08:59 PM
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Quote:
Originally Posted by commsysman View Post

That "minus 7db" number is pretty much meaningless. What that number translates to, in actual room sound level, depends on the speaker sensitivity and room acoustics, to name only two of several variables that the receiver cannot possibly be preset for.
What it means is that there is a setting that is more or less ARBITRARILY selected as 0 db for THAT UNIT (at the factory), for reference purposes, and that you are 7 db below that level.
This has nothing to do with the actual sound pressure levels produced by the speakers. 90 dbA is a fairly loud average sound level for listening to music, but not deafening or anything....just fairly loud. 100 dbA is getting pretty damn loud, and 110 dbA is really really loud (unpleasantly loud for sane people).

As usual, you have no clue about the functioning of a modern receiver. If the receiver uses a "relative" volume scale, and the receiver is properly calibrated for the speakers, then the *system* (receiver + speakers) will output exactly 105 dB from each speaker as measured at the listening position, and 115 dB from the subwoofer. This assumes the Master Volume Control, (MVC), setting is set to "0". At any setting below "0", (i.e., -7 or -15, etc.), the volume will be *exactly* the number of decibels below Reference Level, (RL), as specified by the MVC.

To calibrate a system for the relative volume scale, you play a broadband noise tone that is 30 dB below Reference Level, (105 dB - 30 dB = 75 dB.) Then you set the speaker trim so the SPL measures 75 dB at the Listening Position, (LP.) This process accounts for the sensitivity of the speakers and the frequency response anomalies of the speaker/room combination. Once calibrated, the system will track the exact level from Reference 105 dB to whatever the MVC is set to below 105 dB. For example, if the MVC is set to -20, then the peak levels will be 85 db at the LP, (105 - 20 = 85 dB). However, remember that this is the output for each individual channel. The combined response of all the channels plus subwoofer will be significantly higher than that. A full 5.1 system playing back at full Reference Level will hit peaks of 120 to 121 dB. This includes 5 speakers at 105 dB plus the subwoofer(s) at 115 dB. The sum of all those speakers and sub(s) will hit 120-121 dB. Of course, that is "peak" SPL, and it is very rare for recordings to have full RL peaks in all channels at the the same time. You will virtually never experience those peak levels in your system.

So why is this important? Because movies are recorded at these calibrated settings. Movie mixing stages are calibrated to these levels. If you want to reproduce the sound exactly as recorded by the sound mixer/recording engineer, you need a system calibrated the same way as the sound mixing/recording stage.

Frankly, many systems are not capable of these levels. They may get "very loud", but they may not have the ability to recreate full Reference Level. Low sensitivity speakers will have a much harder time reproducing full RL, and they'll need more amplifier power to have any chance to do it. They also need to have high "power handling" to be able to do it. That's a relatively rare combination; low sensitivity AND high power handling. High sensitivity speakers will have a much better chance of getting to full RL because they more efficiently use the power sent to them.

Auto-setup/calibration systems such as Audyssey, MCACC, YPAO, Anthem ARC, etc., all use the relative scale, and they all set the system up so "0" on the MVC equals 105 dB from each speaker and 115 dB from the sub(s). Of course, they don't use 105/115 dB signals to set the levels. They use -30 dB signals to set the levels. Remember that 30 below RL is 75 dB. They use 75 dB test tones to set the levels.

Many users prefer to listen at well below RL. A setting of -10 or even -15 is still plenty loud for many people. However, it is 10 to 15 dB below the level the sound was recorded at.

Quote:
Originally Posted by commsysman View Post

What it means is that there is a setting that is more or less ARBITRARILY selected as 0 db for THAT UNIT (at the factory), for reference purposes, and that you are 7 db below that level.
When using the relative scale, if set up *correctly*, it's not ARBITRARY AT ALL. It's specifically defined as above.

Perhaps you are confusing this with a receiver that uses an "absolute" MVC scale. In that type of scale the MVC starts at "0" and ends at "99." In that type of scale, higher positive numbers reflect higher SPL's, and "Reference Level" is set at some arbitrary number. Of course, the OP was not using the absolute scale because he quoted negative volume settings. The absolute scale doesn't use any negative numbers. Only the relative scale uses negative numbers to describe the level below RL.

Craig

Lombardi said it:
Perfection is not attainable, but if we chase perfection we can catch excellence."

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post #9 of 19 Old 08-09-2012, 11:06 PM
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Quote:
Originally Posted by franciscom View Post

commysman,
thanks for all your explanation, pretty clear and indeed now i can understand the sensibility with tables frequency vs impedance. what i learned from your explanation is that a speaker with more sensitivity would be able to give me the spl or volume i need to an specific distance from it. So the higher sensitivity, better speaker for sure.
thanks for your help really appreciatte it.
Be careful of advice from that guy. He thinks he knows it all and gives quite a bit of bad advice as evidenced above.

A more sensitive speaker is not automatically better. However, it will generally give more output for the same amount of power input as a less sensitive speaker.

Very dynamic speakers are generally the best for movies. They can handle the large differences in volume that movies have without compressing or distorting. Music usually doesn't have the range movies do. There is some out there that does but usually music is much more constant in output.


As far as the sound of a freight train goes if you are standing right next to it I'm sure it would be louder than 80 dB. That must be bad info on wiki.

Dumb enough to spend lots of cash on this junk!
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post #10 of 19 Old 08-09-2012, 11:28 PM
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redface.gif

I posted some not-technically-accurate info with regard to reference level. Thanks craig john for reminding me.

redface.gif


Yes, reference is 105dB peaks. If that really works out to 85 dB average....I'm not positive, but on my system I recall 85dB with 105dB peaks. Of course, that further explains my statement that the average level will vary based on content.

I promise to speak of reference level in a technical sense of 105dB peak from now on, since average level means squat in a calibrated system and varies greatly with source material.
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post #11 of 19 Old 08-09-2012, 11:34 PM
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Oh, and it doesn't look like the wiki page specifies the train characteristic that is 80dB. My guess is it is the typical SPL a passenger experiences while riding on a train.
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post #12 of 19 Old 08-10-2012, 12:08 AM
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To give a better idea of the scale of sounds here's a list that's not too bad, altho may of the AVS forum members' home theater setups could probably be listed at the upper end of the scale...http://www.dangerousdecibels.org/education/information-center/decibel-exposure-time-guidelines/

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post #13 of 19 Old 08-10-2012, 01:12 AM
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One thing the OP might like too know, is that the decibel scale is logarithmic and not linear. So the energy contained in 90 dB is not 50% more than 60 dB. It is many times that.

Dumb enough to spend lots of cash on this junk!
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post #14 of 19 Old 08-10-2012, 07:41 AM
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Rough rules of thumb in most acoustics texts:
A 1 dB increase is about the limit at which most people can tell a difference if you nudge the volume control and requires 1.26 times the power
A 3 dB increase what most of us perceive as a slight incresae in volume and requires 2x the power.
A 10 dB increase in the midrange sounds twice as loud (not ten times as loud) and requires 10x the power. (20 dB = 100x, and so forth.)

Note in testing 0.1 dB (1.023x the power) is the accepted threshold for level matching to ensure volume differences do not affect the results (at least back when I did them, back in the 80's and 90's).

Put another way, a speaker that is 3 dB more sensitive than another will sound just as loud with 1/2 the power.

Some of the most highly-regarded speakers, and best-measuring, are not the most efficient. Efficiency is but one parameter in a rather large trade space.

HTH - Don

p.s. I did not wade through the whole thread, but doesn't THX spec a 105 dB max SPL at the listening position? Not sure, but that is about the limit my system can do anyway... Not sure I'd want to be in the room at that level; I need my ears!

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #15 of 19 Old 08-10-2012, 09:46 AM
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Quote:
Originally Posted by DonH50 View Post

p.s. I did not wade through the whole thread, but doesn't THX spec a 105 dB max SPL at the listening position? Not sure, but that is about the limit my system can do anyway... Not sure I'd want to be in the room at that level; I need my ears!

I thought the 105/115db specs were also about max peaks...

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post #16 of 19 Old 08-10-2012, 09:56 AM
 
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Quote:
Originally Posted by lovinthehd View Post

I thought the 105/115db specs were also about max peaks...

If you're a THX specification.

85 dB is reference.

105 dB is headroom

115 dB is the world of the subwoofer

And if the wife's ears are present, do you really want to go there?

confused.gif

With the addition of a proper speaker/Amp combination and sufficient subwoofers, THX is an easily achieved standard.

confused.gif

As far as our ears are concerned, isn't that a virtue we lose in a properly calibrated theater?

-
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post #17 of 19 Old 08-10-2012, 11:57 AM
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Quote:
Originally Posted by DonH50 View Post

Rough rules of thumb in most acoustics texts:
A 1 dB increase is about the limit at which most people can tell a difference if you nudge the volume control and requires 1.26 times the power
A 3 dB increase what most of us perceive as a slight incresae in volume and requires 2x the power.
A 10 dB increase in the midrange sounds twice as loud (not ten times as loud) and requires 10x the power. (20 dB = 100x, and so forth.)
Note in testing 0.1 dB (1.023x the power) is the accepted threshold for level matching to ensure volume differences do not affect the results (at least back when I did them, back in the 80's and 90's).
Put another way, a speaker that is 3 dB more sensitive than another will sound just as loud with 1/2 the power.
Some of the most highly-regarded speakers, and best-measuring, are not the most efficient. Efficiency is but one parameter in a rather large trade space.
HTH - Don
All good stuff, Don.

Quote:
Originally Posted by DonH50 View Post

p.s. I did not wade through the whole thread, but doesn't THX spec a 105 dB max SPL at the listening position? Not sure, but that is about the limit my system can do anyway... Not sure I'd want to be in the room at that level; I need my ears!

Quote:
Originally Posted by lovinthehd View Post

I thought the 105/115db specs were also about max peaks...

Quote:
Originally Posted by BeeMan458 View Post

If you're a THX specification.
85 dB is reference.
105 dB is headroom
115 dB is the world of the subwoofer
No, that is not how it works. 85 dB is NOT "reference" and 105 dB is not "headroom". 105 dB is "Full Scale" Reference level, and that is the full scale output level for each individual speaker. The combined output of all the speakers and sub(s) is far higher than that. It's more like 120 to 121 dB if all the speakers ans sub(s) are outputting a full scale signal, (which virtually never happens in an HT environment.)

When you calibrate a recording/mixing studio, you use a -20 dB noise signal. The levels are then set to 85 dB, or (105 dB - 20 dB = 85 dB). So 85 dB is not "Reference Level", it is the level used to calibrate for Reference level. This is for a professional studio.

In a home environment, the test iis slightly different for calibration, but th end result is the same. At home, we use a -30 dB test signal and we set the levels to 75 dB. This results in the exact same settings as the studio calibration, and Full Scale Reference level ends up being 105 dB for each speaker and 115 dB for each sub.

I explained in Post #8 above why this is important. It is equally important to use the terminology correctly as misuse of the terminology leads to confusion.

Craig

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post #18 of 19 Old 08-10-2012, 12:11 PM
 
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In the simple, yes, that's how it works.
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post #19 of 19 Old 08-10-2012, 01:30 PM
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Hey Craig,

Thanks for that! I admit to profound laziness; do you have a link to the THX specs? The link I had seems broken... Figured we might as well post it here.

Thanks,
Don

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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