[atledreier]

I've read alot about power compression and how it can affect transients and stuff.

How would you go about measuring your system to see if it compresses?

I tried running sweeps at different levels, but I got a linear progression up to reference level. Granted, my speakers are very sensitive and maybe they just don't compress at such 'low' levels?

 

[Moonfly]

You would have to run the drivers at considerable power so as to heat up the VC. If you only want to measure the driver then you will need a powerful amp that wont stress as well. You would need to use RTA and watch the various measurable aspects of the driver and observe how they change as the driver begins to work hard and near its limits. If you want to see the effect it has on spl you will need to take a lot of measurements right upto the limits of the sub, and re-run the mic cal routine each time to ensure accuracy of the measurements.

You would also have to be careful, people have killed drivers that way.

 

[atledreier]

well, my speakers have a 102dB/2,83V/m sensitivity, so I rarely stress drivers or amps. Rarely near or at reference, so I'm good I think. Just thought it'd be fun to observe some compression figures, is all.

I run them on an EP4000 each, btw

 

[Moonfly]

Well, first off, have a read of this:

http://www.s10forum.com/all_about_power_compression

 

[atledreier]

I did read that, and it pretty much confirmed what I already knew about power compression.

If you look at my graph you will see that there is a -0,2dB difference in the 100dB run compared to the 70dB one. I didn't go higher and the sweep was literally hurting my ears at that point. But according to simulations I was inputting somewhere in the order of 5-10W to my speakers at that point.

 

[Moonfly]

That would suggest your sub wasnt being driven that hard, so your not likely to see much there. Ive done such tests before and when you start getting up and over 110db the low frequencies start to alter and the overall response will begin to become less even.

 

[atledreier]

Yes, my subs will really struggle to reach reference, I think. The above graph was my left front speaker, which is why I didn't bother to go higher than 100dB which is most they will see in most cases.

Subs reaching 125dB with any headroom? Unlikely, even if they are big and powerful.
(my subs, I know many here have subs that reach reference with ease)

 

[atledreier]

Had a go with my subs for a laugh.

Running sweeps at this level was scary! My house sounded like it was ready to fall down, walls were rattling and subs were jumping around on the floor. All this makes me think that maybe my levels aren't calibrated properly, because it felt VERY loud even though the curve says I peaked at 101dB. I can't imagine another 20dB.