Power question? - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

Old 02-23-10, 04:20 PM
Banned!
Ryan

Join Date: Jul 2009
Location: sfsd
Posts: 1,074
Re: Power question?

Quote:
lsiberian wrote: View Post
it's twice the power to gain 3db, 10 times to gain 10 db
every time i read this...it doesnt sound right
Ryan Anderson is offline

Old 02-23-10, 04:23 PM
Banned!
Ryan

Join Date: Jul 2009
Location: sfsd
Posts: 1,074
Re: Power question?

Quote:
dyohn wrote: View Post
In general, +3db = 2X input power to the same speaker. +10db = twice as loud to our ears, and that requires 10X the power.
I agree, double the power 3dB...
double the Sd 3dB
so I think doubling driver and power 6dB?

+10dB sounds twice as loud... still seems weird to me... so when dB is doubled (3dB) we don't perceive that as twice as loud? so doubling a doubling of a doubling... 9dB... only sounds like its twice as loud? hehehehehe..... 100dB base point. 103dB is twice as loud. 106dB is 4X as loud as 100dB. 109dB is 8X as loud. so 110dB sounds twice as loud as 100dB. It's like wind chill factor and heat index. makes me laugh and I dont get it!
Ryan Anderson is offline
Old 02-23-10, 05:32 PM
Senior Shackster

David

Join Date: Apr 2008
Location: Valley of the Sun
Posts: 704
Re: Power question?

It's a logrithmic scale...

Doubling the swept volume of a subwoofer is the same as doubling the input power, so yes, if one woofer @ 100 watts produces 100db, two of the same woofers @ 100 watts to each = 106db.

dyohn is offline
Old 02-24-10, 01:03 PM
Elite Shackster

Josh

Join Date: May 2007
Location: Louisville, KY
Posts: 2,431
Re: Power question?

Think of it like this...If you have a 12" woofer moving 1" p2p and generating 100db at 25hz you will add another 6db if you push the same woofer to 2" p2p, doubling the acoustic power being radiated. You will need 4X the power to accomplish this.

The same thing can be accomplished by adding another 12" woofer displacing the same 1" p2p instead of pushing the single one to 2" p2p. The total acoustic power is the same. You do need to provide the same amount of power into the second sub to drive it though, so power is doubled. However in this case power needed is only doubled due to the extra 3db of efficiency instead of 4x in the case of driving the single even harder because it's efficiency is set. .

If you increased from 1 subwoofer to 4 identical ones you could gain that 6db without increasing power applied at all.
Ricci is offline
Old 02-24-10, 02:31 PM
Elite Shackster

Mike

Join Date: Apr 2007
Posts: 19,397
Re: Power question?

Quote:
Ryan Anderson wrote: View Post
100dB base point. 103dB is twice as loud.
No, 103 is not twice as loud, it's noticeably louder then 100 db. 106 db is noticeably louder then 103 db. By the time you get to 110 db it sounds twice as loud as 100 db.
Mike P. is offline
Old 02-24-10, 05:46 PM
Shackster

Aaron

Join Date: Jul 2007
Location: Wisonson
Posts: 49
Re: Power question?

Quote:
Ryan Anderson wrote: View Post
+10dB sounds twice as loud... still seems weird to me... so when dB is doubled (3dB) we don't perceive that as twice as loud?
Correct, it's that sticky measured difference Vs. perceived difference thing.

To make matters more confusing, because of the non-linearity of our hearing, 10dB isn't perceived as twice as loud for all frequencies... but I digress.

Our calculations are always correct, for we are gigantic brains.
no. 5 is offline
Old 02-25-10, 08:38 AM
Banned!
Ryan

Join Date: Jul 2009
Location: sfsd
Posts: 1,074
Re: Power question?

ugh. I was under the impression 3dB is a doubling. But that is only 1/2. Doubling both power (3dB) and Sd (3dB) together yield a doubling of 6dB. I guess that makes sense... adding a 2nd driver and 2nd amp.
Ryan Anderson is offline
Old 02-25-10, 10:58 AM
Shackster

Aaron

Join Date: Jul 2007
Location: Wisonson
Posts: 49
Re: Power question?

Quote:
Ryan Anderson wrote: View Post
I was under the impression 3dB is a doubling.
It depends on what you are doubling. Twice the power is: 10Log10*2 = 3dB. Twice the pressure is: 20Log10*2 = 6dB.

In other words, going from a 100 Watt amp to a 200 Watt amp doubles the power giving you 3dB more output, but adding another (co-located!) subwoofer doubles the pressure, giving you 6dB more output.

Interestingly, some people who have experimented with the topic of what twice as loud measures have said that 6dB (double the pressure) is more correctly 'twice as loud' than 10dB.

Our calculations are always correct, for we are gigantic brains.

Last edited by no. 5; 02-25-10 at 11:05 AM. Reason: add some stuff
no. 5 is offline
Old 02-25-10, 12:12 PM
Banned!
Ryan

Join Date: Jul 2009
Location: sfsd
Posts: 1,074
Re: Power question?

this hobby we are in... it drives me nuts sometimes. ya know?
Ryan Anderson is offline
Old 02-25-10, 12:16 PM
Shackster

Aaron

Join Date: Jul 2007
Location: Wisonson
Posts: 49
Re: Power question?

Quote:
Ryan Anderson wrote: View Post
this hobby we are in... it drives me nuts sometimes. ya know?
LOL, when I feel that way, I like to blame the math.

Our calculations are always correct, for we are gigantic brains.
no. 5 is offline

 Bookmarks

 Tags power , question?

Message:
Options

## Register Now

Random Question
Random Question #2

User Name:
OR

## Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.