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Pairing 1000W amp with 400W cab

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#61
agedhorse said:
My experience is that many players do not have reasonable expectations and often damage speakers when powered beyond their ratings and even in some cases where they think they are within the ratings. Then there are the unfortunate accidents where something gets unplugged or causes loud pops and/or noises. With a speaker that's connected to a larger amp, the opportunity for damage is much higher.

This is my experience across many brands over several decades in this industry, which is why I am generally more conservative than others in my recommendations.
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makes sense.

My takeaway: If idiotproofing is at all a concern, use more conservative advice.
 
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#67
while I wouldn't want to market a product to the masses encouraging them to use higher power amplifiers and the requisite appropriate caution (for what I would consider markedly improved results), this TB thread is not a product manual, and I dont see the problem with explaining to people the potential benefits as well as the potential drawbacks of such a setup. I totally get that from a manufacturers perspective, its problematic to recommend doing this. but in the context of an individual dialog with a user, it seems helpful to point out.
 
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#69
joeko said:
So I have a Hartke 4x10 amp <cab> rated at 400W @ 8ohms.
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My limited experience with Hartke 410 cabs is they are very prone to overexcursion damage - but that's quite possibly because I've seen them run with amps that lack any HPF. In any case I'm uncomfortable with running a cab from an amp capable of much more than 1/2 the cab's rated power. The Peavey MiniMax would be a decent choice for that cab - I use mine into a pair of 400w 12's.
 
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#71
You would have to squeeze every volt and ampere out of a typical 15a circuit and then some just to get the OUTPUT power of 1875w, never mind the actual power draw to to get that much output. 20a circuits I believe have the little extra blade on the plug, so if yours doesn't have that (gonna take a guess that it doesn't), it's only designed and rated for a 15a circuit. Meaning maximum power draw at 120v is 1800w, meaning maximum amplifier output would be some portion of that (depending on amplifier efficiency). In the old days, half of power draw was a good rule of thumb for output, which would imply that you've got a 900w amp. Any electrical engineers can feel free to correct any of that, but I think it's all more or less right.
 
#72
Omega Monkey said:
You would have to squeeze every volt and ampere out of a typical 15a circuit and then some just to get the OUTPUT power of 1875w, never mind the actual power draw to to get that much output. 20a circuits I believe have the little extra blade on the plug, so if yours doesn't have that (gonna take a guess that it doesn't), it's only designed and rated for a 15a circuit. Meaning maximum power draw at 120v is 1800w, meaning maximum amplifier output would be some portion of that (depending on amplifier efficiency). In the old days, half of power draw was a good rule of thumb for output, which would imply that you've got a 900w amp. Any electrical engineers can feel free to correct any of that, but I think it's all more or less right.
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I'm not a EE, not even close, but I think you have to consider the intended duty cycle.
 
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#73
It all get weird when you start looking a power amps that have rms ratings above 120V times 15A. I seem to remember one power amp I have that is spec'd at 62 amps peak draw from its 15 amp power cord. It's all about crest factor them (sortof like duty cycle but not LOL).
 
#74
I don't think duty cycle really gets around the problem of trying to get 1875w of water (and really, even more than that) through an 1800w hose. Maybe I'm wrong, but that's why we have circuit breakers, to prevent just such a thing. RMS power is basically supposed to be "constant", that's the whole point. "Program" is a little more variable, and then "peak" is more about instantaneous power that might sneak past a circuit breaker without tripping it (maybe, I don't know). Real world, unless you're playing a raw oscillator of a sine wave, you're not really going to be generating anything similar to RMS, but the rating system is the rating system. B word Industries can't just say "Our ruler is a foot. Well, it's 9.5 inches, because nobody ever really needs TWELVE whole inches all at the same time. You use 3 here, 6 there, sometimes 7 or 8. But almost never 12." But I'm buying it (or not) based on the fact that it will measure 12 inches, even if I only ever measure stuff as big as 7 or 8 or whatever. It's a standard. And that's ignoring the fact that the amp is referred to as a 3000w amp, the owner is calling it 1875, and it's really probably about 900. We shouldn't even have to be aruging the 900 vs 1875, let alone 1875 vs 3000.
 
#75
Duty cycle had everything to do with it. Look at the QSC PLX-3400 manual as an example, all the power draw data is right there. 3400 watts RMS bridged into a 4 ohm bridged load yet operates safely and UL listed to operate from a 15 amp (iirc) 120V circuit. Class D amps are even easier to accomplish this with.

Every single amp's power draw is rated this way, the minimum duty cycle allowed is 12.5% (the value most commonly used), I typically use 33% or sometimes even more depending on the application.
 
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#76
Well once you realize that those high power amps are measured in rms with the circuit breaker and power cord bypassed it's all smoke and mirrors for all the manufacturers. OTOH AFAIK most all the bass amps under 1200(?) watts can do their thing with a sine wave continuously. I'm usually running at least a mild OD so have to worry if the amp can do twice its rated power continuously - many can't. OTOH my TH-350 seems to have no problem outputting close to 700 watt square-ish waves - I wish the other manufactures published their square wave RMS output specs instead of "cheating" by using puny sine waves LOL.
 
#77
agedhorse said:
Every single amp's power draw is rated this way, the minimum duty cycle allowed is 12.5% (the value most commonly used), I typically use 33% or sometimes even more depending on the application.
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Yes, 33% for subs and bass is great for "clean" applications :) . Remember the bad old days when reggae was using square waves into scoops because the amps weren't big enough :wideyed: ? Them old Peavey CS800's had a defeat switch for the limiter :nailbiting:.
 
#79
RoadRanger said:
Yes, 33% for subs and bass is great for "clean" applications :) . Remember the bad old days when reggae was using square waves into scoops because the amps weren't big enough :wideyed: ? Them old Peavey CS800's had a defeat switch for the limiter :nailbiting:.
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Amps have gotten much more powerful, therefore this kind of operation is not often encountered these days. If they were, even more speakers would end up at the BBQ party.
 
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