When will doubling the power really add 3dB?

[newusername 10+ year member]

So, let em get this straight (I never really understood the effects of power compression) that power compression reduces the gains in output from a sub past certain power levels, and may actually reduce output?

Just in case you haven't read it (and just so I can ***** myself out a little bit more):

http://www.soundsolutionsaudio.com/forum/index.php?showtopic=7112

If you still have questions, ask away. They are more likely to get answered over there, though. //content.invisioncic.com/y282845/emoticons/graduate.gif.d982460be9f153bb54e5d4cb744f6ae8.gif

 

[phantom240 5,000+ posts]

Yeah, I read it, but it seems like you wrote it assuming we know how power compression affects output, and explains the causes and the technical details of power compression.

 

[newusername 10+ year member]

Yeah, I read it, but it seems like you wrote it assuming we know how power compression affects output, and explains the causes and the technical details of power compression.

Lol, maybe I should re-read it and make sure it's clear for those who are newer.

Power compression does take output. An increase in resistance is bad for output, a decrease in BL or Cms is bad for output as well. I'll take a look and see what I can change to make that more clear; my apologies.

 

[phantom240 5,000+ posts]

Lol, maybe I should re-read it and make sure it's clear for those who are newer.
Power compression does take output. An increase in resistance is bad for output, a decrease in BL or Cms is bad for output as well. I'll take a look and see what I can change to make that more clear; my apologies.

hmm... seems like amybe thats whats getting to my buddy's comp 12's. Maybe theyre having massive power compression. They weren't really meant to be put on my amp.

 

[ghart999 10+ year member]

I actually emailed Mike from SoundSplinter. This is what he had to say.

"When factoring in power compression, you probably won't gain an entire 3dB of output across the board, but you will gain some, when doubling the power per driver from 500 to 1000 watts. 1000 watts, used responsibly, should not push the drivers past their limits, so long as you aren't crankin' your EQ and Gain to the max and letting it play for an extended amount of time. Most music doesn't carry sustained heavy bass, so you wouldn't be feeding the drivers a full 1000 watts continuously.

Of course, as it sounds you are into SPL competition, you would be more likely to stress the drivers by intending to push them to their limits for example, by using a test tone. So know this, 1000 watts should gain you some output and in fact most people these days on the RL-p do use a full 1000 watts on their drivers... but if you are careless and accidently clip your amp or simply run it at full power for too long of a period of time, you will be putting the drivers at risk.

Yes, you would gain some output - perhaps not a full 3 dB.. but you will need to be that much more careful when wielding the extra power!"

 

[dipitydoo 10+ year member]

3db is doubling of sound pressure. 10db is doubling of loudness to the human ear. 6db is a result of doubling cone area and power.

Power compression and cabin leakage can result in a reduced level of increase in output for a given increase in power. For small to moderate systems, these factors won't be as prevalent.

If you were to compare 1 sub at 800w vs. 2 subs at 400w each, you will get close to a 3db increase in output with the 2 sub setup. Remember, doubling power gets you 3db increase. Doubling cone area (and of course adding same power to the 2nd sub) results in a 6db increase. This results in twice the displacement. It takes 4 times the power to double excursion (or displacement), so if you wanted a 6db increase in output with one sub, you would need to quadruple the power (assuming no losses from power compression).

 

[AlStar250 10+ year member]

my .02 worth is that the size of the enclosure will play a relevant role. According to my sub manufacturer, going from a .8^tf3 sealed enclosure to a 1.5^ft3 sealed enclosure creates a +3db @ 25Hz...so maybe just go with a more efficient (bigger) enclosure

 

[jeremiah 10+ year member]

my sub has a 12mm excursion with about 120Wrms (it's a 600Wrms sub) it's at about 5/6mm peak to peak excursion win I get a 500Wrms amp do you think that I will get that 3db gain maybe more?

 

[lilmaniac2 5,000+ posts]

i doubled power and gained 4.2 db //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[AlStar250 10+ year member]

the 2-12's will hit deeper in a sealed enclosure if you were talkin about a hatch id shoot for the single 12 if you want it louder port the enclosure.

So would you rec 1 12" sealed in my hatch? (Jeep GC)

 

[AudioAnonymous 10+ year member]

Your not gonna gain no 3db from twice the power.

 

[squeak9798 5,000+ posts]

So, let em get this straight (I never really understood the effects of power compression) that power compression reduces the gains in output from a sub past certain power levels, and may actually reduce output?

Here is a relatively decent real-world example of the effects of power compression;

http://www.soundsolutionsaudio.com/forum/index.php?showtopic=7897

17.7 watts @ 133.2 dB

33.9 watts @ 135.9 dB

66.5 watts @ 138.8 dB

120.4 watts @ 141.3 dB

--- All of the above are pretty close to what we would expect to see in a driver that hasn't reached any real levels of power compression. In the above, he is just about doubling the power and gaining just under 3db. Pretty much what we would expect from "theory"

The below is where is starts to become interesting;

236.7 watts @ 143.7 dB

448 watts @ 145.1 dB

765 watts @ 146.2 dB

999 watts @ 146.3 dB

1399 watts @ 147.2 dB

1886 watts @ 147.2 dB

Notice how as he increases power, the increase in output consistently decreases...so much so that the last increase in power doesn't result in any increase in output.

The power level increases almost 8 fold from 236 to 1886. From theory we would expect that increase to result in a 9db increase in output [10*log(8/1) = 9.03]. Yet in reality he only gained around 3.5db by increasing power from 236w to 1886w

He may have reached the mechanical limit of the driver aswell (and I'm not sure if that technically falls into the realm of "power compression")....but you can bet power compression played a large roll in the above numbers.

 

[newusername 10+ year member]

(and I'm not sure if that technically falls into the realm of "power compression").

My interpretation, and supported by many, is that power compression relates to DC Re, BL, and Cms, so approaching mechanical limits would certainly be an example of power compression.

 

[phantom240 5,000+ posts]

Would it be possible to put enough power to a woofer so that it reaches its SPL output limit without reaching mechanical limits? Like how you increased the power and didn't see any gain in output? But without reaching its mechanical limits.

 

[cotjones 10+ year member]

i haven't even looked at anything but the original post, but imo... it's heavily install dependant but if you double the wattage you should get 50% more volume, because as the exursion gets higher, it gets harder to get higher again... it's kind of exponential, like DB's.... every time you go up a db it is 10 times harder to go up another

if that doesn't make sence....

doubleing the power won't double the excursion, it takes closer to 4x the power to double the excursion, so to make that sub twice as loud, you are looking at giving it 2000 watts