Well guys, I got a few questions for tonight.
For a speaker's sensitivity rating, they usually measure it at 1 watt/1 meter, right? And that gets you an output of so many dB's.
So if they measure a speaker this way and it is 90 dB at 1W/1M, then would that same speaker play at 45 dB with 1 watt, but at 2 meters instead of 1?
If so, would you also get that same result if you played it at 1/2 a watt at 1 meter?
Reason I ask this is it seems that if it was 90 dB at 1W/1M, then it would be 180 dB loud with only 2 watts sitting 3 feet in front of it. That's loud! We would give it far more than that with just a head unit and only turned up half way. An amp would make it even louder. That is at only 3 feet away anyway. I know you don't sit that close to it, but your driver's side dash speaker would be that close in some cars.
Also, what is this sensitivity rating I sometimes see that is measured at like 2.83 volts instead of 1W/1M? I think I used to know this, but it's been a long time and I forgot.
Replies (14)
uochronos on 02/7/2005 19:14:50
umm the DB's dont drop in half the farther you are from it... there is a loss i'm sure but it is not double...
Chronos
PS
i well let swez or somone else explain it in more detail
cplkittle on 02/7/2005 20:26:59
The curve on a decibel increase is not directly equal to the power supplied as asked above. 10x the power is roughly a 10db increase. Therefore a subwoofer, for example, with an efficiency rating of 90db (1w/1m) would produce 100dB @ 10 watts, 110dB @ 100 watts, and 120 @ 1000 watts.
Not very impressive, huh? How then do you get 130+ dB's out of one speaker? Simple.. there are many other factors involved in the reproduction and amplification of sound. First of all, these measurements are derived from a sound lab and they are basically free air measurements. Put a speaker in a box of any type and you have significantly increased the sound pressure or dBs. As far as 1m is concerned.. that is just an industry standard for microphone placement since there would be some deviation at different distances.
Here is a fun chart to ponder over....
Weakest sound heard 1dB
Normal conversation (3-5') 60-70dB
Telephone dial tone 80dB
City Traffic (inside car) 85dB
Train whistle at 500' 90dB
Subway train at 200' 95dB
Level at which sustained exposure may result in hearing loss 90 - 95dB
Power mower 107dB
Power saw 110dB
Pain begins 125dB
Pneumatic riveter at 4' 125dB
Jet engine at 100' 140dB
Death of hearing tissue 180dB
Loudest sound possible 194dB
cplkittle on 02/7/2005 20:40:38
got me there.. I left out the 100.. will fix right now.
audeogod on 02/7/2005 21:55:26
OK, so there is a difference the farther away you are, it's just not linear like I imagined.
What about speaker sensitivities rated at the 2.83 volts instead of 1W/1M? I once heard that this measurement was deceiving and could not be trusted.
Victor on 02/8/2005 02:27:09
hey kittle.. could you tell me how did u get the
"loudest sound possible - 194dB" .. from where did u get that figure and is it proved , under what conditions,, I sorta raise my finger to oppose this statement , got nothing to back up my stance but i am sure it must just be " the loudest sound RECORDED" and not "the loudest sound POSSIBLE"
Victor...
uochronos on 02/8/2005 02:31:09
i dont know about loudest sound possible but you can only displace so much air... so i would assume there is a cap on how loud something could be..
But then again its not possible to hear something that loud you would be deaf before you knew you heard it hehe..
Chronos
uochronos on 02/8/2005 03:24:04
hmm never acurred to me that a sonic boom is the same phenomenon but it makes perfect since..
Glad you found your awnser.
Chronos
swez on 02/8/2005 08:12:19
Interesting topic here.... good research as well.
There is one question we seem to have missed. How much dB loss can we expect at a given distance from the sonic source? Am sure it's XdB rolloff per Y linear feet of distance. Don't happen to know that reference off hand.
Let's say we have a sonic level of 100dB @ 1m. (3.3 ft) What is the drop off rate as we move further away from the sound source? I believe it also is different with frequency as well. Especially with MR and highs, on axis and off axis.
About voltage used in standard industry measurements... I believe 2.83 volts is the 1 watt reference for an 8 ohm speaker. For a 4 ohm speaker, it closer to 2.0 volts. If you wish to run some numbers to verify that, use Ohm's Law: Watts = E^2/R
2.83 x 2.83 = 8.009/4 = 2.002 watts (or 1 watt @ 8 ohms
2.0 x 2.0 = 4/4 = 1 watt
Swez
Victor on 02/8/2005 14:24:43
There's the undisputed answer to the riddle..
Hope that helps..
Any point source which spreads its influence equally in all directions without a limit to its range will obey the inverse square law. This comes from strictly geometrical considerations.
The intensity of the influence at any given radius (r) is the source strength divided by the area of the sphere. Being strictly geometric in its origin, the inverse square law applies to diverse phenomena.
Point sources of gravitational force, electric field, light, sound, or radiation obey the inverse square law.
http://hyperphysics.phy-astr.gsu.edu/hbase/forces/isq.html
http://hyperphysics.phy-astr.gsu.edu/hbase/acoustic/invsqs.html#c1
A formula called the "inverse square law" tells us that when the distance from the source is doubled, the sound pressure weakens by 6 dB. Among sound engineers, there's a common saying: "6 dB per distance double."
comments...??
Victor...
MrBrownstone on 02/10/2005 21:11:12
1 watt/1m = 90db
2 watts/1m = 93db
However, it may take 100W to make 1 watt @ 1 meter, and 200 to make 2 watts at 1 meter.
The 1W/1M sensitivity rating is not really useful for speaker output or performance. You could use 5 different speaker mfr's with the same rating and get different sound.
Oh, and for you math guyz, you can't add logarithmic numbers so 3db + 3db is not 6 db. you have to return the db back into a linear number, then add. Db are 10^x power. Of course, double devil's advocate, dbWhat? dbA, dbW, doobie, doobie, doobie...
:)
Victor on 02/10/2005 22:42:16
""""""For a speaker's sensitivity rating, they usually measure it at 1 watt/1 meter, right? And that gets you an output of so many dB's.
So if they measure a speaker this way and it is 90 dB at 1W/1M, then would that same speaker play at 45 dB with 1 watt, but at 2 meters instead of 1? """"""
This was the question Mr. Brownstone..
all of us know that 5 different speaker mfr's with the same rating can sound different, but the question was never related to sound quality.
The question was related to a mathematical answer, and the "INVERSE SQUARE LAW" is based on pure physics, logic and is backed by appropriate math.
And by the way , The " dB " we are talking over here is the unit of sound pressure. hehe..doobie doobie dB.
Victor..
P.s - lol... what do you mean by this , please explain .. """However, it may take 100W to make 1 watt @ 1 meter, and 200 to make 2 watts at 1 meter."""
MrBrownstone on 02/11/2005 19:18:20
I was just adding some muck about how useless the sensitivity ratings are. I've seen 2.83 volts at 0.5 meter, 1.4W @ 1 meter, etc...and the whole conversation is just ridiculous.
Sensitivity ratings are about as useless as damping factor, s/n etc.
PS If it's not A-weighted, the meter won't reflect what your ears hear. Also, if you don't specifiy the frequency, often times they use 1kHz...which or many speakers isn't it's intended purpose.
cplkittle on 02/15/2005 17:41:11
Victor,
The loudest sound possilble or maximum of the scale is the scientific proven standard. just do a search for db chart, decible scale, etc.. you will find several charts and scales with this number being the loudest obtainable sound.
Victor on 02/17/2005 01:34:19
yeah.. i already did that kittle.. and convinced myself about it..
Thanks.
Victor...
For a speaker's sensitivity rating, they usually measure it at 1 watt/1 meter, right? And that gets you an output of so many dB's.
So if they measure a speaker this way and it is 90 dB at 1W/1M, then would that same speaker play at 45 dB with 1 watt, but at 2 meters instead of 1?
If so, would you also get that same result if you played it at 1/2 a watt at 1 meter?
Reason I ask this is it seems that if it was 90 dB at 1W/1M, then it would be 180 dB loud with only 2 watts sitting 3 feet in front of it. That's loud! We would give it far more than that with just a head unit and only turned up half way. An amp would make it even louder. That is at only 3 feet away anyway. I know you don't sit that close to it, but your driver's side dash speaker would be that close in some cars.
Also, what is this sensitivity rating I sometimes see that is measured at like 2.83 volts instead of 1W/1M? I think I used to know this, but it's been a long time and I forgot.
Replies (14)
uochronos on 02/7/2005 19:14:50
umm the DB's dont drop in half the farther you are from it... there is a loss i'm sure but it is not double...
Chronos
PS
i well let swez or somone else explain it in more detail
cplkittle on 02/7/2005 20:26:59
The curve on a decibel increase is not directly equal to the power supplied as asked above. 10x the power is roughly a 10db increase. Therefore a subwoofer, for example, with an efficiency rating of 90db (1w/1m) would produce 100dB @ 10 watts, 110dB @ 100 watts, and 120 @ 1000 watts.
Not very impressive, huh? How then do you get 130+ dB's out of one speaker? Simple.. there are many other factors involved in the reproduction and amplification of sound. First of all, these measurements are derived from a sound lab and they are basically free air measurements. Put a speaker in a box of any type and you have significantly increased the sound pressure or dBs. As far as 1m is concerned.. that is just an industry standard for microphone placement since there would be some deviation at different distances.
Here is a fun chart to ponder over....
Weakest sound heard 1dB
Normal conversation (3-5') 60-70dB
Telephone dial tone 80dB
City Traffic (inside car) 85dB
Train whistle at 500' 90dB
Subway train at 200' 95dB
Level at which sustained exposure may result in hearing loss 90 - 95dB
Power mower 107dB
Power saw 110dB
Pain begins 125dB
Pneumatic riveter at 4' 125dB
Jet engine at 100' 140dB
Death of hearing tissue 180dB
Loudest sound possible 194dB
cplkittle on 02/7/2005 20:40:38
got me there.. I left out the 100.. will fix right now.
audeogod on 02/7/2005 21:55:26
OK, so there is a difference the farther away you are, it's just not linear like I imagined.
What about speaker sensitivities rated at the 2.83 volts instead of 1W/1M? I once heard that this measurement was deceiving and could not be trusted.
Victor on 02/8/2005 02:27:09
hey kittle.. could you tell me how did u get the
"loudest sound possible - 194dB" .. from where did u get that figure and is it proved , under what conditions,, I sorta raise my finger to oppose this statement , got nothing to back up my stance but i am sure it must just be " the loudest sound RECORDED" and not "the loudest sound POSSIBLE"
Victor...
uochronos on 02/8/2005 02:31:09
i dont know about loudest sound possible but you can only displace so much air... so i would assume there is a cap on how loud something could be..
But then again its not possible to hear something that loud you would be deaf before you knew you heard it hehe..
Chronos
uochronos on 02/8/2005 03:24:04
hmm never acurred to me that a sonic boom is the same phenomenon but it makes perfect since..
Glad you found your awnser.
Chronos
swez on 02/8/2005 08:12:19
Interesting topic here.... good research as well.
There is one question we seem to have missed. How much dB loss can we expect at a given distance from the sonic source? Am sure it's XdB rolloff per Y linear feet of distance. Don't happen to know that reference off hand.
Let's say we have a sonic level of 100dB @ 1m. (3.3 ft) What is the drop off rate as we move further away from the sound source? I believe it also is different with frequency as well. Especially with MR and highs, on axis and off axis.
About voltage used in standard industry measurements... I believe 2.83 volts is the 1 watt reference for an 8 ohm speaker. For a 4 ohm speaker, it closer to 2.0 volts. If you wish to run some numbers to verify that, use Ohm's Law: Watts = E^2/R
2.83 x 2.83 = 8.009/4 = 2.002 watts (or 1 watt @ 8 ohms
2.0 x 2.0 = 4/4 = 1 watt
Swez
Victor on 02/8/2005 14:24:43
There's the undisputed answer to the riddle..
Hope that helps..
Any point source which spreads its influence equally in all directions without a limit to its range will obey the inverse square law. This comes from strictly geometrical considerations.
The intensity of the influence at any given radius (r) is the source strength divided by the area of the sphere. Being strictly geometric in its origin, the inverse square law applies to diverse phenomena.
Point sources of gravitational force, electric field, light, sound, or radiation obey the inverse square law.
http://hyperphysics.phy-astr.gsu.edu/hbase/forces/isq.html
http://hyperphysics.phy-astr.gsu.edu/hbase/acoustic/invsqs.html#c1
A formula called the "inverse square law" tells us that when the distance from the source is doubled, the sound pressure weakens by 6 dB. Among sound engineers, there's a common saying: "6 dB per distance double."
comments...??
Victor...
MrBrownstone on 02/10/2005 21:11:12
1 watt/1m = 90db
2 watts/1m = 93db
However, it may take 100W to make 1 watt @ 1 meter, and 200 to make 2 watts at 1 meter.
The 1W/1M sensitivity rating is not really useful for speaker output or performance. You could use 5 different speaker mfr's with the same rating and get different sound.
Oh, and for you math guyz, you can't add logarithmic numbers so 3db + 3db is not 6 db. you have to return the db back into a linear number, then add. Db are 10^x power. Of course, double devil's advocate, dbWhat? dbA, dbW, doobie, doobie, doobie...
:)
Victor on 02/10/2005 22:42:16
""""""For a speaker's sensitivity rating, they usually measure it at 1 watt/1 meter, right? And that gets you an output of so many dB's.
So if they measure a speaker this way and it is 90 dB at 1W/1M, then would that same speaker play at 45 dB with 1 watt, but at 2 meters instead of 1? """"""
This was the question Mr. Brownstone..
all of us know that 5 different speaker mfr's with the same rating can sound different, but the question was never related to sound quality.
The question was related to a mathematical answer, and the "INVERSE SQUARE LAW" is based on pure physics, logic and is backed by appropriate math.
And by the way , The " dB " we are talking over here is the unit of sound pressure. hehe..doobie doobie dB.
Victor..
P.s - lol... what do you mean by this , please explain .. """However, it may take 100W to make 1 watt @ 1 meter, and 200 to make 2 watts at 1 meter."""
MrBrownstone on 02/11/2005 19:18:20
I was just adding some muck about how useless the sensitivity ratings are. I've seen 2.83 volts at 0.5 meter, 1.4W @ 1 meter, etc...and the whole conversation is just ridiculous.
Sensitivity ratings are about as useless as damping factor, s/n etc.
PS If it's not A-weighted, the meter won't reflect what your ears hear. Also, if you don't specifiy the frequency, often times they use 1kHz...which or many speakers isn't it's intended purpose.
cplkittle on 02/15/2005 17:41:11
Victor,
The loudest sound possilble or maximum of the scale is the scientific proven standard. just do a search for db chart, decible scale, etc.. you will find several charts and scales with this number being the loudest obtainable sound.
Victor on 02/17/2005 01:34:19
yeah.. i already did that kittle.. and convinced myself about it..
Thanks.
Victor...
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