#71 by ddff_lv
February 2nd, 2010, 5:14 pm
It's not very common to have such thing as major PA systems don't have feedback from amps to DSP, so there are used Peak or Voltage limiters. They're very detailed and often described along with formulas to calculate these limiters for each speaker system.

Powersoft has the ability to monitor output and therefore offers more control over the speaker, however there still is a lack of information or missing piece of theory how TruePower (or maybe we should call them long term or slow attack) limiters have to be used. There are several sentences arround the web - like 250W for 4" coil, attack 2 sec., release 4 sec. etc. But there is no formulas or explanations where these numbers come from. So it's a bit mystery still for me. Anyone care to explain?

thanks, ddff
#72 by ThomasM
February 2nd, 2010, 8:43 pm
Hi ddff_lv,

You're right, having this exact "view" of the load ay the amps' outputs is still a bit unusual these days, and most every user requires a bit more detailed information, if not a "formula" or at least practical examples, to use it properly in real life.

Now, we're holding it not back, and it's not that the information is not available!

Here you go:
If you are using the K Series DSP (aka KDSP), I'd assume you have taken a look at the KDSP user's manual. If not yet, it's available at http://www.powersoft-audio.com/en/download-document/104-kdsp_userguide_en.html
Go to the bottom of page 10, and there it is - because it is a DSP function for which Armonía is a comfortable GUI, so to speak.*

You'll see, there is quite a bit of background explanation as well as examples for various drivers as you' find them in the market. Naturally, each driver is different from another, so we can't list them all (and some driver manufacturers are also strangely secretive about exact specifications...).
However, assuming general understanding of the nature on the user's side, this should give you plenty of information to work from and find your correct settings.

By the way, you might notice that TruePower limiter thresholds are fairly low. Well, as our chief engineer and developer would put it when asked: "You want to be really careful with the TruePower values. Think true power, that's the real power which a driver gets to see, not some mathematically derived value that is far from reality! Then 200-250W is a lot even for a 18" subwoofer with 4" voice coil!"
So, rather stay on the conservative side with these values, otherwise the TruePower Limiter's threshold will be far too high, and the whole amazing concept remains useless, resulting in your valuable drivers going to pieces...

Hope it helps,
cheers,
Thomas

* = A user's manual for Armonía is in the works, in addition to the help system built into the software. With the TruePower Limiter being a DSP function, the Armonía manual will also refer to the KDSP manual for further explanation.
#375 by SOUNDSTORMPRO
January 14th, 2011, 9:35 am
Can you help me out with my limiter settings for my K20. Unfortunantly I have all ready blown 8x21"eighteensound NLW9600 DRIVERS and I don't want it to happen again the dsp I was using is unable to give me the appropriate information to set up limiters properly http://www.eaw.com/products/SB2001.html http://www.eighteensound.com/index.aspx ... ct&pid=286 I have posted two links in antiserpation that you will be able to assist me.
#376 by lawrence
January 14th, 2011, 11:59 am
Powersoft K amps (with DSP onboard) has many kind of limiters (peak, rms, true power).
About the true power limiters of the K amps, this limiter measure the real power delivered to the driver, this means that the DSP is capable of measuring the power dissipation of cables and components.
Now the question is: What's the correct real power that can be dissipate safely by the driver?
And as consequence: what's the attack time that we can use to avoid decreasing performance (like pump effects) ?
This is a problem of driver manufacturer and typically there's not information about power limiting. :D

What i can suggest, for my use experience, is:
1/3 of AES Power is a safe parameters but about the constant time this is more difficult (esotheric), beccause depends on many factors correlated to the material and dimensions of the coil.
i can suggest you to start from this data (for peak limiters)

0-31 Hz Attack time 45 ms
31 -63 Hz Attack time 16 ms
63 - 125 Hz Attack time 8 ms

I suggest a factor between 50 and 150, ( you have to ask, what's the aut-aut you can accept between sound quality and power protection?)

0-31 Hz Attack time 2.5/4 sec
31 -63 Hz Attack time 1/2.5 sec
63 - 125 Hz Attack time 750ms/1.5 sec

The release time i suggest you is between X2 or X4 times the attack time.

For your specific case i suggest you a limiting power of 1800/3= 600 W.
It's a 21" driver, 2 secs attack and 4 secs of release.
If you drive more components you have to multiply this number for the number of components.

And remember the peak limiter, that is needed to protect the maximum displacement of the diaphgram, keep in mind that a Kseries amplifier has a very high output voltage, (k20 has 220 peak output Voltage!!).
The peak limiter has to be set with the formula P=V^2/R, then V=sqrt(P*R), in your case i suggest to use the Program Power, then the result is 170 V with attack time of 16ms and release of 256 ms.
The above parameters are to be intended as indicative, and from datasheet of the driver i suppose they are a little bit protective.

Hope this clarify
#379 by SOUNDSTORMPRO
January 25th, 2011, 6:35 am
THANKS for the quick reply.
was this in relation to the high pass filter settings
0-31 Hz Attack time 45 ms
31 -63 Hz Attack time 16 ms
63 - 125 Hz Attack time 8 ms

I suggest a factor between 50 and 150, ( you have to ask, what's the aut-aut you can accept between sound quality and power protection?)

0-31 Hz Attack time 2.5/4 sec
31 -63 Hz Attack time 1/2.5 sec
63 - 125 Hz Attack time 750ms/1.5 sec

And I'm also not 100 percent clear you mean to multiply the attack release
(For your specific case i suggest you a limiting power of 1800/3= 600 W.
It's a 21" driver, 2 secs attack and 4 secs of release)
If you drive more components you have to multiply this number for the number of components.

(Edited by Admin: Quote marks added.)
#383 by lawrence
January 26th, 2011, 2:15 pm
As usually it's an aut-aut between quality and protection.
If you look only at quality you are right: you should keep the HP filter. On the contrary if you wish to be protective you need to look at LP filter. The suggestion could be to use the logaritmic center frequency. For example on a LF driver from 20 to 90 hz the center frequency it's near to 42.4 hz (f0=sqrt(f1*f2) where f0 is the center frequency and f1 and f2 the lower and higher limits of the bandwidth). In this case the attack time is 16 ms

THANKS for the quick reply.
was this in relation to the high pass filter settings

0-31 Hz Attack time 45 ms
31 -63 Hz Attack time 16 ms
63 - 125 Hz Attack time 8 ms

I suggest a factor between 50 and 150, ( you have to ask, what's the aut-aut you can accept between sound quality and power protection?)

0-31 Hz Attack time 2.5/4 sec
31 -63 Hz Attack time 1/2.5 sec
63 - 125 Hz Attack time 750ms/1.5 sec







Sorry my mistake, it's not clear. The power has to be multiplied for the number of components, the attack and release time remain the same.

And I'm also not 100 percent clear you mean to multiply the attack release

(For your specific case i suggest you a limiting power of 1800/3= 600 W.
It's a 21" driver, 2 secs attack and 4 secs of release)
If you drive more components you have to multiply this number for the number of components.
#1729 by elecor
November 21st, 2014, 11:17 am
I've just read this topic and I want to clear one thing for myself.

For example I have 18" woofer 1kW AES.
So I set 333W truepower limiter threshold.
But when I'll have 4 same woofers connected in parallel, I need to multiply 333 by 4??

So with 2 woofers I need to set 667W and with 4 - 1333W. Right??

Thanks.
#2830 by Sobhana123
February 14th, 2018, 7:06 am
hello. In this true Power limiter is the limiter that modulate the gain tracking the impedance curve allowing to control the real output power and thus the temperature of the voice coil controlling the voice coil resistive component thanks for sharing this topic.
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