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[Steve Crump]

And I'm taking this from another Danley spec, and Ivan's previous post to hart. "Please note “Continuous” does not mean “forever”!" . I.e. music with ebb and flow vs ..well, not. :>)

I am a weekend warrior, definitely have a lot of knowledge to gain. Most of my knowledge I have gathered from trial and error, (lots of error) and reading info on this forum, or reading articles and manuals. But, it is sinking in...lol.

When I read the post here it started me second guessing my setup. I haven’t lost any drivers due to overheating and would rather not, but I really want to get the most of the system when I am working outdoors. That is the reason for my questions. I assume continuous and long term are basically the same, I just wanted to make sure that there wasn’t a difference that I wasn’t aware of. Long term may be a little more relevant because it doesn’t imply forever. I completely understand that some types of shows push the system harder than others. I think what is relevant to me is the statement Tim made in this post, live music has a fairly low duty cycle and that probably is why I have had no issues.

The Crown amp manual that I have states to enter the long term rating of the driver into the RMS Power Limiter value. I think it is just a question at this point if I am willing to accept a higher level of risk, based on which factor I decide to enter into the amp’s limiter. I will say after reading all this it will make me more cautious if I ever do any other type of show or material.

Back to your original post. I think you will be fine with the XLS2500 based on my experience with those amps. I have (4) and have used them for (7) years. About a year ago I lost one at a show running monitors. It blew before the show.

[Frank Koenig]

Frank and or Ivan,

At the risk of hijacking this post, is “continuous” and “long term” speaker rating considered the same? I am reading the manual on the Crown Macro Tech I series that I am using and Crown uses the term “long term” and the manufacture of the speaker states “continuous” and I just want to make sure I have an understanding.

Thanks,

Steve

I'll take a crack at this mostly by summarizing stuff I've learned on this forum. There are folks here vastly more experienced than I so I ask them to comment on and correct the following.
 
AES Power

"AES Power" is a standard for speaker input power rating. It was taken up by ANSI, too. It says nothing about how a speaker sounds at high power, it only represents conditions under which immediate destruction will not occur. In a nutshell, it is the maximum mean-square voltage divided by the speaker's minimum impedance, of 6 dB crest-factor pink noise band-limited to one octave that the speaker can withstand for 2 hours without certain physical parameters changing by more than 10%. The octave band is chosen to be within the normal operating frequency range of the speaker. It's a pretty brutal test and is sometimes referred to as "continuous power".

Amplifier Sizing

A rule-of-thumb for the minimum amplifier power to fully utilize the capability of a speaker is that the amplifier should be capable of sufficient voltage and current, at least short term, to drive the speaker to the peak of a sine wave of twice the AES power (not that you would want actually to run a sine wave at this power very long). This sometimes is referred to as "program power". For certain speakers and high crest factor program (hf bands) it may be advantageous to have even a little more headroom -- it's just a rule-of-thumb.

Limiter Settings

The best limiter settings are likely the ones baked into a powered speaker or integrated system by a major manufacturer with heavy R&D. When left to my own devices, I follow the Powersoft guidance which has us set the average power limiter to 1/3 AES power and the peak voltage limiter to the peak voltage of a sine wave of 2 x AES power -- same as minimum amplifier power.

The average power limiter serves to prevent smoking the voice coil, for which it should do a pretty good job assuming the time constants are chosen accurately to model the thermal behavior. But there are variables that are not accounted for and perhaps some real speaker designers can elucidate. On the other hand, I'm guessing the actual volume, in dB, left on the table by not having a fancy thermal model does not amount to much. Just get more rig. It will sound better anyway. 

The peak voltage limiter serves as a proxy for an excursion limiter and, in its simplest, frequency-blind form, does a lousy job. The problem is that excursion generally goes up with decreasing frequency and gets complicated around the box resonance frequency of a bass-reflex speaker. If we open up the limiter to get the full capability at high frequencies we run the risk of over-excursion at low frequencies. If we protect from over-excursion at low frequencies (around the upper impedance peak of a bass-reflex speaker, for example) then we're not fully utilizing the speaker at high frequencies. Some limiters allow for frequency-dependent peak limiting but I don't have any advice on how to set those up -- yet.

--Frank

[Ivan Beaver]

It came to me a little later, how on earth did I (we?) ever make it through the last 40 years in audio with w/o limiters?
:>)

Because we used to actually PAY ATTENTION to the amps and how hard the sound system was pushed.

Sadly today more people either don't understand or simply don't care, or don't know enough.

People are often looking for the "magic bullet", instead of being responsible.

[Ivan Beaver]

Frank and or Ivan,

At the risk of hijacking this post, is “continuous” and “long term” speaker rating considered the same? I am reading the manual on the Crown Macro Tech I series that I am using and Crown uses the term “long term” and the manufacture of the speaker states “continuous” and I just want to make sure I have an understanding.

Thanks,

Steve

A lot of it is a matter of terminology and different people have different ideas of the same thing.

Of course this is a reason you should use the recommended amplifiers and not try to figure out what other manufacturers are saying.

Also remember that different limiters (especially thermal or heat limiters), can react very differently.

Sometimes the "automatic" limiters can act weird or not as expected.

[Steve Crump]

Thank you Frank for all your input and I think I am going to re-think my setup based on your info.

Thanks, Steve

[Steve Crump]

Of course this is a reason you should use the recommended amplifiers and not try to figure out what other manufacturers are saying.

Ivan,

Thanks for your input, it is appreciated and valued.

[ProSoundWeb Community]