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RoadRunnersDust View Drop Down
Young Croc
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Points: 617 		Post Options Post Options   Thanks (0) Thanks(0)   Quote RoadRunnersDust Quote  Post ReplyReply Direct Link To This Post Posted: 16 April 2025 at 8:33am
2.5 is slightly excessive but not ridiculous... That suggestion usually comes with the caveat that proper limiting, etc. is in place.

2x the amplifier power is +3dB of signal.

The general rule of thumb I have seen most people work to is that the amplifier's "RMS" rating should be roughly equal to the speaker's "Program" rating. That way you can run the speaker right up to it's "peak" rating (with appropriate limiters, etc.) safely whilst not pushing the amplifier all the way to it's maximum at the same time.

The more important rule of thumb that goes along with that though is that if you need to push you speakers so hard that you're hitting peak rating or limiters then you should have taken more speakers to the show...
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Points: 156 		Post Options Post Options   Thanks (0) Thanks(0)   Quote AJ113 Quote  Post ReplyReply Direct Link To This Post Posted: 16 April 2025 at 8:42am
"The more important rule of thumb that goes along with that though is that if you need to push you speakers so hard that you're hitting peak rating or limiters then you should have taken more speakers to the show."

Yes of course. However, I'm a one-man-band with limited storage and transportation - and a limited back. So I'm trying to be as compact and efficient as possible. The key for me is not to accept gigs that my PA can't handle.
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Young Croc
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Points: 617 		Post Options Post Options   Thanks (1) Thanks(1)   Quote RoadRunnersDust Quote  Post ReplyReply Direct Link To This Post Posted: 16 April 2025 at 8:51am
Quote  The key for me is not to accept gigs that my PA can't handle.

It’s a two way street, that’s just as reasonable an interpretation of the rule as “you’ve got to take a huge system to massive gigs” Smile
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madboffin View Drop Down
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I have long retired but when I was working with large (festival and touring) systems I always set the crossover limiters just below the clip point of the amplifiers. I don't remember blowing any speakers...

If you drive a speaker with square waves from a heavily clipped amplifier it will be getting more power than you might expect from the amplifier's specified maximum output, which is for an undistorted signal.

Speaker failures are normally due to burnt out voice coils caused by excessive power, and damage due to over excursion is relatively rare.
Having said that, I once had to investigate a pile of bass bins that came back from a festival with a couple of dozen failed 15" drivers. The system tech (not me, I wasn't there) had failed to set up the limiters properly, the LF amplifiers were Macrotech 3600s, and the last act of the event was Prodigy. If you aren't old enough to have seen or "experienced"  them, well, they were notoriously loud and their music produced a lot of low end...
All the bad speakers had been driven well beyond their xmax and had crumpled coil formers and damaged neck joints. Those 3600's could produce a lot of peak power. An expensive mistake.
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Points: 156 		Post Options Post Options   Thanks (0) Thanks(0)   Quote AJ113 Quote  Post ReplyReply Direct Link To This Post Posted: 16 April 2025 at 10:40pm
"I have long retired but when I was working with large (festival and touring) systems I always set the crossover limiters just below the clip point of the amplifiers. I don't remember blowing any speakers..."

Doesn't really address the issue. The question is what should the power rating of the amp be in comparison to the rating of the speakers. An amp's limiter will kick in at the onset of clip, but if the amp's output is five times that of the rated power of the speaker it's essentially irrelevant - at least to this particular discussion.
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Young Croc
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Originally posted by madboffin madboffin wrote:

I have long retired but when I was working with large (festival and touring) systems I always set the crossover limiters just below the clip point of the amplifiers. I don't remember blowing any speakers...

That is due to crest factor. It’s 1AM so the following may be completely wrong but:

Prodigy’s music, as an example, generally has a crest factor of 4 to 10 or 12-20dB. This would mean that a Crown 3600 bridged into an 8R driver (3,140W if we believe the spec sheet) with limiters set just below clip ought to give about 4kW of peak output but when the peak limiters are just being met the RMS output would be 15-100x less than peak so only 266-40W RMS.

266W is still no inconsiderable amount of power when you consider drivers are lucky if they turn even 1% of that power into sound, the rest is turned into heat and the most important part of the music is in the peaks, they are the parts that get people dancing, etc.

For reference, you can’t hold onto a 60W lightbulb without getting burnt LOL

It also goes to explain why even with such high power amplifiers as are available now, there’s not been *that* much of an increase in blown drivers or how you can run a “600W” TSW-721 on an MC2 E90 without much concern.

The reality of crest factor of the signal means you need an amplifier with substantially higher peak output than would conventionally match with its “RMS” output. This is also why the cheaper modern Class D amplifiers still manage to perform so well when not pushed to their limits, they haven’t got the continuous power capacity of the high-end expensive touring amplifiers but as long as the crest factor of the music matches the peak and RMS capacities of amplifier they don’t run out of power. At least that’s as far as raw power goes, there’s plenty else you’re paying for with a professional amplifier!
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crest factor varies with frequency.

it is higher for tweeters and lower for subs.

especially with modern electronic music like dubstep ( not to be confused with dub ) bass is starting to turn into one continuous ( processed ) sinewave ... whereas treble remains dynamic in nature ( intermittent peaks ) 

this is happening because continuous HF energy would be fatiguing to listen to, on other hand bass subsystems are limited in output so to make best use of limited capacity bass is spread out in time to make sure you get the most bass out of whatever speakers / amps you have ...
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Yes, it does vary with frequency but due to the distribution of energy the crest factor of the low frequencies does not vary that much from the crest factor of the whole spectrum when analysing music. 


No, bass is not turning into continuous sine waves. That’s utter bullshit idiots have been repeating for the past 20-30 years. If you can’t tell the difference between a sine wave and what you hear in dubstep then you shouldn’t be commenting on anything to do with perception of low frequencies. Sinusoidal modulation ≠ sine wave signal.


Quote  so to make best use of limited capacity bass is spread out in time to make sure you get the most bass out of whatever speakers / amps you have ...

Once again, nonsensical word salad to try presenting your opinion as a fact. What else should we expect from the illustrious Line Array🙄
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Originally posted by RoadRunnersDust RoadRunnersDust wrote:

Once again, nonsensical word salad to try presenting your opinion as a fact.

do not get sad just because you will never understand anything i write.  there are probably other joys in life other than learning from the great master.  though i doubt they can compare.

now for the higher life forms reading this the point is that in the past bass used to be basically a kick drum, which was a rather impulsive sound with a high peak and short duration.

but now that bass is electronically synthesized it is less like a kick drum and more like a bass guitar note, so less peaky and more continuous.

this is happening because subwoofer / amp power is available continuously, not in separate impulses like the power of a kick drum.

in a loudness war a source that better aligns with the capability of the loudspeakers system will ultimately be louder and therefore win.

with a vented box tuned to 30 hz if you want the loudest and deepest possible bass it will need to look a lot like bass guitar / synthesizer notes that bounce around 40 hz region and are fairly continuous in nature.

although musicians do not understand the physics behind this they have ears and know what sounds rich and what sounds thin and flat.  so through trial and error they are gradually converging on the mathematical inevitability which is obvious to a genius like me.

much the same as how genetic evolution is blind and random and yet at any given time you know where it is headed.

i have been looking at the FFT of various tracks in Adobe Audition and while it may not be an exact constant 40 hz sinewave it is not that far off ...

it comes and goes, the frequency moves around from about 37 to maybe 50 hz, there is usually two or three harmonics etc. but it's definitely doing its best to minimize the crest factor ...

high frequencies are not like this.

the overall music energy is of course dominated by bass, but what does your blown tweeter care about overall music energy ?  every frequency / amplification band has to be analyzed separately.  overall music energy only matters for the circuit breaker your amps plug into.

in essence both the recording medium ( Compact Disc ) and the playback system ( PA ) have more headroom in the highs, which is why there is more dynamics and a higher crest factor in the highs.  

not much headroom in the sub range and thus a lower crest factor.

obviously it can't go down to zero or it won't be music anymore, but it will try.


Edited by Line Array - 17 April 2025 at 4:25am
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 LOL you dont listen to many genres do you...
long bass is and has been in all music of all times, or should i really point out the long bass in this picture?
Music!
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Points: 204 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Line Array Quote  Post ReplyReply Direct Link To This Post Posted: 17 April 2025 at 8:10am
only serious SPL "long bass" in music used to be the Pipe Organ

but i don't think anybody tried to record a pipe organ and then play it back through speakers at a concert 

the most powerful pipe organ in the world, coincidentally located here in New Jersey:


has blowers totaling 630 horsepower.

i don't think the pesky humans in your picture can match that.
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Originally posted by Line Array Line Array wrote:


do not get sad just because you will never understand anything i write.  there are probably other joys in life other than learning from the great master.  though i doubt they can compare.
Two words that apply to you, Pal. “Dunning” and “Kruger”.

Quote but now that bass is electronically synthesized it is less like a kick drum and more like a bass guitar note, so less peaky and more continuous.

this is happening because subwoofer / amp power is available continuously, not in separate impulses like the power of a kick drum.
That is neither an accurate description of bass nor synthesised bass. It’s also completely inaccurate bullshit about its relationship to subwoofer or amplifier capacity, if anything the peak capacity of modern equipment is far greater compared to its continuous capacity than ever before. Everything I have seen you write on this forum since you popped up screams of someone that has little to no actual experience with much beyond entry level home audio equipment.

Quote with a vented box tuned to 30 hz if you want the loudest and deepest possible bass it will need to look a lot like bass guitar / synthesizer notes that bounce around 40 hz region and are fairly continuous in nature.
Apparently you don’t understand “loudness” either. It is already well understood that if you want perceived loudness and depth for bass then the critical range for the ear is with the second harmonics. Continuous bass notes also sound substantially less “loud” to general human perception than repeated notes due to the way the brain interprets the envelope of sound well but magnitude generally very poorly.

Quote although musicians do not understand the physics behind this they have ears and know what sounds rich and what sounds thin and flat.  so through trial and error they are gradually converging on the mathematical inevitability which is obvious to a genius like me.
Despite the opposite being generally true…

Quote i have been looking at the FFT of various tracks in Adobe Audition and while it may not be an exact constant 40 hz sinewave it is not that far off ...
I’m amazed a “genius” like you managed to achieve that given how an FFT shows you spectral information and nothing about waveform shape nor *anything* in the time domain.

Quote it comes and goes, the frequency moves around from about 37 to maybe 50 hz, there is usually two or three harmonics etc. but it's definitely doing its best to minimize the crest factor ...
Harmonics have little to do with envelope and so little to do with crest factor.

Quote the overall music energy is of course dominated by bass, but what does your blown tweeter care about overall music energy ?  every frequency / amplification band has to be analyzed separately.  overall music energy only matters for the circuit breaker your amps plug into.
Completely missing the point that was clearly made. Smile
To repeat it again as you seem to need a second attempt at understanding:
Overall music energy was relevant to the conversation, before you stuck your less than informed oar in, as the difference between the full spectrum crest factor and the low end crest factor is usually insignificant. This is due to the low end of the spectrum naturally having the most significant peak and RMS amplitude of the signal. Since the mid and upper ranges of the spectrum generally don’t contribute as much to the peak amplitude or drastically change the RMS amplitude when added to the isolated low end of the spectrum it serves no purpose to obfuscate the topic of conversation by addressing it.

Quote in essence both the recording medium ( Compact Disc ) and the playback system ( PA ) have more headroom in the highs, which is why there is more dynamics and a higher crest factor in the highs.
And yet there is demonstrably greater dynamic range in the low end on in music produced for digital audio formats than there is found in any of the domestically available analogue mediums. PA systems also usually only have greater headroom in the upper range due to the nature of cabinet dispersion. It’s noticeable in the lower end of the audio industry when there is often only a single source for Mid/HF on either side that the greater system headroom is usually found in the low end.
The reason the upper registers have greater crest factor in music is and always has been due to natural energy distribution and the spectral sensitivity of the human ear. it has never been driven by the capability of the system, only the other way round.[/QUOTE]

And no, it can’t go down to zero since it is a ratio of RMS:Peak amplitude. It cannot go below 1. Surely a “genius” ought to understand that enough to not make such an inaccurate observation LOL
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