What is "power compression"?

[psycho72 10+ year member]

Just like the title says. A guy here recommended power compression. I did a search and found a couple of pages of nothing, so here I am. Can someone explain what this is?

Click to read more...

 

[InhumanAcura 5,000+ posts]

Say you throw 2K at a sub and put up a #....You throw 4K (doubling power) and you only gain 1.4 (where you should have theoritically gained 3) you have now reached power compression...Its when the coils heat up so much that the impendance will shoot so high the sub wont see the gain in power...

Here's a better explaination...

"First some basic concepts:

1) When current flows through a voice coil, it heats the wire.

2) The hotter the wire gets, the higher its DC resistance becomes.

3) If the speaker design is not capable of dissipating the heat, the DC resistance increase leads to an increase in impedance and shifts in the speaker's parameters.

4) This rise in impedance reduces the effective power driving the voice coil, which leads to non-linear behavior (a loss of output over what would be predicted at that power with a cold speaker).

In other words, your "4 ohm" speaker becomes a 6, 7 or 8 ohm speaker when the coil gets hot resulting in less power for a given voltage driving the speaker.

Let's say we design a speaker which is capable of dissipating the heat of 100 watts very effectively but is in significant compression at 200 watts. Let's also say this speaker is 4 ohms nominal.

If we run 25 watts (based on voltage^2 / 4 ohms) we actually get 25 watts into the coil and let's say we read 110dB SPL of output. Now we increase the power by a factor of 2 to 50 watts (again assuming voltage^2 / 4 ohms) and get a predictable 3dB increase (113dB) because the speaker is not in compression. Now we double the power again to 100 watts and get 116 dB... the speaker is still not in compression.

Next we double the power to "200 watts" and we only read 117.5 dB... Whoa? shouldn't we have read 119 dB? What happened? The speaker is no longer a "4 ohm" load... it is now a 6-7 ohm load and even though we thought we doubled power (because we increased voltage by a factor of 1.4), the impedance rise caused by heat ****** up some of the power increase, leading to less than 3dB gain.

That, in a nutshell, is power compression.

At some point we reach infinite power compression, which occurs when the coil gets hot enough to fuse itself into a blob of metal. ;-)"

 

[TeamPwnage 10+ year member]

Say you throw 2K at a sub and put up a #....You throw 4K (doubling power) and you only gain 1.4 (where you should have theoritically gained 3) you have now reached power compression...Its when the coils heat up so much that the impendance will shoot so high the sub wont see the gain in power...
Here's a better explaination...

"First some basic concepts:

1) When current flows through a voice coil, it heats the wire.

2) The hotter the wire gets, the higher its DC resistance becomes.

3) If the speaker design is not capable of dissipating the heat, the DC resistance increase leads to an increase in impedance and shifts in the speaker's parameters.

4) This rise in impedance reduces the effective power driving the voice coil, which leads to non-linear behavior (a loss of output over what would be predicted at that power with a cold speaker).

In other words, your "4 ohm" speaker becomes a 6, 7 or 8 ohm speaker when the coil gets hot resulting in less power for a given voltage driving the speaker.

Let's say we design a speaker which is capable of dissipating the heat of 100 watts very effectively but is in significant compression at 200 watts. Let's also say this speaker is 4 ohms nominal.

If we run 25 watts (based on voltage^2 / 4 ohms) we actually get 25 watts into the coil and let's say we read 110dB SPL of output. Now we increase the power by a factor of 2 to 50 watts (again assuming voltage^2 / 4 ohms) and get a predictable 3dB increase (113dB) because the speaker is not in compression. Now we double the power again to 100 watts and get 116 dB... the speaker is still not in compression.

Next we double the power to "200 watts" and we only read 117.5 dB... Whoa? shouldn't we have read 119 dB? What happened? The speaker is no longer a "4 ohm" load... it is now a 6-7 ohm load and even though we thought we doubled power (because we increased voltage by a factor of 1.4), the impedance rise caused by heat ****** up some of the power increase, leading to less than 3dB gain.

That, in a nutshell, is power compression.

At some point we reach infinite power compression, which occurs when the coil gets hot enough to fuse itself into a blob of metal. ;-)"

You have no idea what you speak of //content.invisioncic.com/y282845/emoticons/boring.gif.42c69fa49b1e73e6332d62b462a2a4b3.gif n00b

 

[generalGOTCHA 10+ year member]

Team Ownage //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

He is actually , very very correct ! NOOB !

2 subs , face this issue less than one sub does ! this was in regards to another post concearning "Two subs better than one sub" . I failed to go into detail because Im lazy and dont wish to have ******** like yourself bombart a nice detail simple explination for those who are willing to lend an open ear wishing to educate themselfs more on audio.

I felt, as fragile as he could in explaining such a complex phenomina ...Acura did a mother f*cking great job to help those understand. I dont think personally, with my understanding to that theory in its fullest.. would have nor could have put it in a more easier way to understand.

most these people want boom and bang, some want BOOM, and want their drivers to BOOM BOOOOOOOOOM BOOOOOOOOOOOOOOM when they turn that **** knob up ... because they get grace from achieving such audible quality and learn why a cheap sub sounds like ****, and what to look for in a subwoofer. and more so WHY THINGS Do what they DO.

Obviously , you need to educate yourself alott more on this theory , or argue your point so we can see you education behind it and compare the two arguements.

**grabs audio theory book and waits to catch someone in 10" of bull shiiiit**

Acura , very well done sir ! I appreciate the patience you and the genious which you explained it.

some wont grasp it at all, or dont understand how you go from 93db /1w/1m - 140DB's or more wihtout reaching a barrier, and why efficiancy is a must for competing where this nature plays a big role , or physical attributes of a driver that says 1000watts cheaply made , compared to a DD , or Incriminator etc.. that says 1000watts etc..

We know where you were going with it. ALthough I fully understand the logic/ theory behind it.. in a persons shoes who doesnt ... i THINK YOU GREATLY HELPED THEM TO SPEED.

People like you are appreciated !

 

[LBX2G 10+ year member]

inhumanacra what book did u read on this.

 

[TeamPwnage 10+ year member]

I/InhumanAcura didnt write the second part....Someone from JL Audio is responsible for that. Thanks though, glad you get it now

 

[generalGOTCHA 10+ year member]

No diss on you TEAM .. Just I admire those who spend their time to educate someone. Whether he copied it or not, he posted the answer ! And you downed on his efforts to help someone. This was my cross with you , and because you didnt state your arguement behind the theory with your very own answer , I sass'd your voice in this post .

I dont know your profound knowledge or proefficiancy with audio , but you neglected to tell him where he was wrong ! and why he was a NOOB . So , I tookit as a demeanor towards an educator. Teachers dont make their own theories to teach.. they use it from an establish factorial source , which he may or may have not done from the JL audio site you claim.

Why not post the link to the site that has the explination behind it. Either way, it was wrong for you degrading his efforts to educate.

 

[InhumanAcura 5,000+ posts]

No diss on you TEAM .. Just I admire those who spend their time to educate someone. Whether he copied it or not, he posted the answer ! And you downed on his efforts to help someone. This was my cross with you , and because you didnt state your arguement behind the theory with your very own answer , I sass'd your voice in this post .

I dont know your profound knowledge or proefficiancy with audio , but you neglected to tell him where he was wrong ! and why he was a NOOB . So , I tookit as a demeanor towards an educator. Teachers dont make their own theories to teach.. they use it from an establish factorial source , which he may or may have not done from the JL audio site you claim.

Why not post the link to the site that has the explination behind it. Either way, it was wrong for you degrading his efforts to educate.

lol, dont worry about him...

 

[NDMstang65 10+ year member]

suspension also power compresses as well..

but that's another ballpark //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[psycho72 10+ year member]

Thanks Inhuman, that was a great explanation. Can I ask you to further explain general's comment that "2 subs , face this issue less than one sub does", how would two woofers lessen this effect, if at all?

From your explanation it would seem to me that it would be better to optimize my box to reach full excursion at 6-700 watts as opposed to just dumping 1200watts into a speaker.

**edit**ohh crap NV so then acheiving full excursion is also a bad thing?

 

[NDMstang65 10+ year member]

once a pistonic woofer reaches its peak and the soft parts will not move anymore and are on the verge of breaking, you are not going to gain any more output....that is what power compression is

Like InhumanAcura said - If you do not gain 3dB you are either a) powercompressing the soft parts of the woofers or b) have an inferior design that does not control the woofer as well and will not allow it to get the full potential or 3dB out of doubling power.

Btw..why or better yet how would 2 woofers be more prone to power compression then 1 woofer if they are on the same circuit? And are also the same exact woofer...

 

[psycho72 10+ year member]

Btw..why or better yet how would 2 woofers be more prone to power compression then 1 woofer if they are on the same circuit? And are also the same exact woofer...

Yeah that was my thought too but I don't know my shyt and general was gracious enough to help. I don't like to kick a helping hand in the mouth so I shutup and ask.

And as far as pistonic compression is concerned then just optimizing a box for full excursion at X watts is not gonna cause it, so I don't really have to worry about it unless I srew something up or decide to go isobaric, right? Maybe?

 

[NDMstang65 10+ year member]

Yeah that was my thought too but I don't know my shyt and general was gracious enough to help. I don't like to kick a helping hand in the mouth so I shutup and ask.

I just want to know the theory behind this...i have NEVER heard anything such as that...or even remotely close to it...

 

[NDMstang65 10+ year member]

And as far as pistonic compression is concerned then just optimizing a box for full excursion at X watts is not gonna cause it, so I don't really have to worry about it unless I srew something up or decide to go isobaric, right? Maybe?

Honestly man - If you plan on just daily driving and listening to music, you really do not need to worry about this //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif...otherwise it envolves a lot of math and a whole bunch of trial and error

 

[InhumanAcura 5,000+ posts]

Thanks Inhuman, that was a great explanation. Can I ask you to further explain general's comment that "2 subs , face this issue less than one sub does", how would two woofers lessen this effect, if at all?
From your explanation it would seem to me that it would be better to optimize my box to reach full excursion at 6-700 watts as opposed to just dumping 1200watts into a speaker.

**edit**ohh crap NV so then acheiving full excursion is also a bad thing?

You shouldnt have to worry about power compression when it comes to a "normal" install. Its a big factor when your trying to get as much out of your amps as possible for that one note. You have to play with the volume and port of the box till the impendance is at its lowest. Even the box positioning becomes a factor, you can move the box an inch one way and have the impendance rise .1x...

As far as 2 subs being more/less prone to p.c., Its all about the enclosure....You want to optimize your box and install for the vehicle. So, yes you would want the box to be optimal for the wattage you plan on sending it. But, plugging t/s parameters into a program isnt going to take into play the bizzilion variables putting the box in the vehicle provides..

Getting on a mic is the best way to learn..

EDIT : ^^^beat me to it...