Non-linearity of wattage to SPL...

JoeBob · 20th February 2002, 11:02 PM

I know as wattage increases SPL increase isn't linear, but my questions is if at 1 watt there's an SPL of say 90dB, what wattage would it takke to reach 93dB?

Also, a speaker with a sensitivity of 102dB at 1 watt, what SPL would it put out at 10w, 100w and 500w?

I just don't know what the curve for the increase in SPL looks like, and it's been bothering me that I don't know...

hifi · 20th February 2002, 11:27 PM

1W = +0db (speaker sensitvity as it is speced at one watt)
2W = +3db
4W = +6db
8W = +9db
16W = +12db
32W = +15db
64W = +18db
128W = +21db
256W = +24db
512W = +27db
1024W = +30db

hopes this helps..

JoeBob · 21st February 2002, 12:07 AM

Oh, I didn't think doubling wattage caused a 3dB increase. I don't know why, I guess I heard it somerwhere. Silly question, at least it straightened me out...

Helix · 21st February 2002, 12:38 AM

db's are simply the log of a ratio,

so a doubling of power is 2/1

and when dealing with power we mutilply by 10 hence

10*log 2 = 3db

so an increase from 2 to 16 watts is :

10*log 16/2 = 9db

When dealing with voltage then you multiply by 20. Also you have to be careful with the sign and context of where it's quoted, because you could be talking 3dbs down (attenuated) or 3 db up (gain) or even -3db down (gain!).

If i had a filter and at a particular frequancy, on the input i had 10 volts and on the output there was 5 volts, i could calculate how many db's the signal is being attenuated :
20 *log 10/5 = 6db

*LECTURE MODE OFF*

PassFan · 21st February 2002, 02:32 AM

JoeBob:
Helix is right. This is a complex subject. If you care to read more on this subject do a search on the different forumns. Theres plenty in here.

cyclotronguy · 21st February 2002, 08:47 PM

As I remember one dB is an acoustic change that is only just discernable. Hearing is non-linear, ten dB gain is perceived as twice as loud; ten dB reduction half as loud.

Cyclotronguy

20th February 2002, 11:02 PM	#1
JoeBob diyAudio Member Join Date: Nov 2001 Location: Montreal, Canada	Non-linearity of wattage to SPL... I know as wattage increases SPL increase isn't linear, but my questions is if at 1 watt there's an SPL of say 90dB, what wattage would it takke to reach 93dB? Also, a speaker with a sensitivity of 102dB at 1 watt, what SPL would it put out at 10w, 100w and 500w? I just don't know what the curve for the increase in SPL looks like, and it's been bothering me that I don't know...

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20th February 2002, 11:27 PM	#2
hifi diyAudio Member Join Date: Mar 2001 Location: sweden	1W = +0db (speaker sensitvity as it is speced at one watt) 2W = +3db 4W = +6db 8W = +9db 16W = +12db 32W = +15db 64W = +18db 128W = +21db 256W = +24db 512W = +27db 1024W = +30db hopes this helps..

21st February 2002, 12:07 AM	#3
JoeBob diyAudio Member Join Date: Nov 2001 Location: Montreal, Canada	Oh, I didn't think doubling wattage caused a 3dB increase. I don't know why, I guess I heard it somerwhere. Silly question, at least it straightened me out...

21st February 2002, 12:38 AM	#4
Helix diyAudio Member Join Date: Jul 2001 Location: UK	db's are simply the log of a ratio, so a doubling of power is 2/1 and when dealing with power we mutilply by 10 hence 10log 2 = 3db so an increase from 2 to 16 watts is : 10log 16/2 = 9db When dealing with voltage then you multiply by 20. Also you have to be careful with the sign and context of where it's quoted, because you could be talking 3dbs down (attenuated) or 3 db up (gain) or even -3db down (gain!). If i had a filter and at a particular frequancy, on the input i had 10 volts and on the output there was 5 volts, i could calculate how many db's the signal is being attenuated : 20 log 10/5 = 6db LECTURE MODE OFF*

21st February 2002, 02:32 AM	#5
PassFan diyAudio Member Join Date: Aug 2001 Location: Central FL	JoeBob: Helix is right. This is a complex subject. If you care to read more on this subject do a search on the different forumns. Theres plenty in here.

21st February 2002, 08:47 PM	#6
cyclotronguy diyAudio Member Join Date: Sep 2001 Location: Northern California	As I remember one dB is an acoustic change that is only just discernable. Hearing is non-linear, ten dB gain is perceived as twice as loud; ten dB reduction half as loud. Cyclotronguy

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