Members dboomer Posted February 9, 2007 Members Share Posted February 9, 2007 Let's start a new thread so it will be easier to search for later ... Ok, so the JBL spec "is what it is" - I'll buy that... but Don, what about QSC's statement on their website that we should use an amp w/ 1.5 to 2x's the amount of rated power than the speakers are rated for? You are assuming that if you hook up an amp that "can" deliver double the continuous power a speaker can handle that it "will" deliver that power. Plain and simple ... it won't ever happen ... not "continuously" (barring being struck by lightning ). Most people don't think it through ... but ... the clip lights (or DDT lights in our case) come on when the "peak" power has been achieved. when that happen the average or continuous power is probably 10 dB down from there. You simply deduct the dynamic range from the peak power. Here's an example ... if you fire the peakLED on a 1000W amp and have a 10 dB dynamic range your average continuous power at that point is only 100 W and your peak power is 1000W. Even if you are playing highly compressed rave material you probably have at a minimum 3 dB of dynamic range. If that's the case your amp is hitting a 1000W peak and delivering 333W average to the speaker. You'll just never deliver the continuous rating of the amp to the speaker. Manufacturers came up with this "Program" rating (realize there is no such thing as "program watts") as an easy way to say that it makes sense (not that it "guarantees" anything) to run an amp that is double the continuous rating of their speaker. So get this ... by doing so we really don't expect that you'll ever apply even half of the continuous power to the speaker. That's assuming you operate your system in an informed and responsible manner. Trouble is ... every time we make stuff more idiot proof they just make better idiots. A big look at this and remember here ... the above discussion is limited to "Thermal" power limitations. It's far more common that exceeding mechanical/excursion limits will blow up woofers. Again ... for the four hundredth time ... there is a more technical discussion of this on the tech support/white paper section of our website. Look up "How much powr for my speakers" and "The loudspeaker Spec Game". JBL also has some papers on their site about power handling based on the kind of material you put into the system. Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 9, 2007 Members Share Posted February 9, 2007 Yes, JBL also discusses the derating of their recommendations for average applications. Remember that a 750 watt amplifier delivers almost 1 horsepower to the speaker. Link to comment Share on other sites More sharing options...
Members dboomer Posted February 9, 2007 Author Members Share Posted February 9, 2007 "can" deliver Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 9, 2007 Members Share Posted February 9, 2007 "can" deliver At rated power of course;) Link to comment Share on other sites More sharing options...
Members Alan Roberts Posted February 9, 2007 Members Share Posted February 9, 2007 So, with all that being said, is there a simple "rule of thumb" for buyers trying to match up amps and speakers? Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 9, 2007 Members Share Posted February 9, 2007 Safely, somewhere between RMS/continuous and "Program". It all depends on how conservative you want to be. Note that you will not gain the full benefit of increasing power as you increase towards the upper end of a driver's capacity due to the effects of power compression. This is why at some point it's almost diminishing returns but with increased risk of damage. Link to comment Share on other sites More sharing options...
Members Alan Roberts Posted February 9, 2007 Members Share Posted February 9, 2007 So if my cabs are rated at 600 watts continuous @ 8 ohms, I should try to run an amp that's as close to 600 watts at 8 ohms into them as I possibly can, right? Link to comment Share on other sites More sharing options...
Members twostone Posted February 9, 2007 Members Share Posted February 9, 2007 Well isn't the RMS rating the safe zone meaning it will power that speaker for the life of that said speaker. But programmed:confused: is were it can cause damage in the wrong hands of an idiot like myself. I've been here going on 2 years and still confused most of the time:eek: maybe some day they will make an accurate amp to match the accurate speaker like they do with powered speakers and add a no fault switch or easy button. But guess if they did that you guys wouldn't have nothing to help out with. Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 9, 2007 Members Share Posted February 9, 2007 So if my cabs are rated at 600 watts continuous @ 8 ohms, I should try to run an amp that's as close to 600 watts at 8 ohms into them as I possibly can, right? That's a good starting point, and if you choose to increase beyond this, you may start reducing the long term reliability... or short term in the case of an "unfortunate accident". It's not a hard and fast rule, but a generalization. Link to comment Share on other sites More sharing options...
Members Alan Roberts Posted February 9, 2007 Members Share Posted February 9, 2007 So why do people make this overly complicated and confusing? It all seems like common sense to me. If I run an amp that's too small and push it into clipping,I run the strong risk of damaging something. If I run an amp that is capable of supplying too much power, I also have the potential of damaging the speakers and horns by overdriving them beyond their capabilities. Am I still on the right track? Link to comment Share on other sites More sharing options...
Members twostone Posted February 9, 2007 Members Share Posted February 9, 2007 Because most companies inflate their ratings just like estimates on MPG on a car. Higher number seems to always sale better. Check out Al's post he couldn't get a straight answer from York on their site. Link to comment Share on other sites More sharing options...
Members Dark Ice Posted February 10, 2007 Members Share Posted February 10, 2007 If I run an amp that's too small and push it into clipping,I run the strong risk of damaging something. If I run an amp that is capable of supplying too much power, I also have the potential of damaging the speakers and horns by overdriving them beyond their capabilities. I've read almost every discussion/arguement on this board over this topic over the last two years. And those are some long (and repetitive!) threads... After considering everything, I've basically come to the same conclusion as you. I stress though, it doesn't mean I'm right Steve. Link to comment Share on other sites More sharing options...
Members 6Imzadi Posted February 10, 2007 Members Share Posted February 10, 2007 If I run an amp that's too small and push it into clipping,I run the strong risk of damaging something. If I run an amp that is capable of supplying too much power, I also have the potential of damaging the speakers and horns by overdriving them beyond their capabilities. Herein lies the "holy grail" of the sound industry. This is what myself and others that visit this site are looking to find the answer to.Your statement is correct. note: The safest way to design a particular system is to choose the speakers you like and power them with (RMS+PROGRAM)/2 amplifiers. If this does not get the SPL you need, you must add speaker/amplifier sets. This would be the safest way to get maximum speaker life and audio quality. This is usually not what people like to hear since this will increase their investment by twice as much or more. Link to comment Share on other sites More sharing options...
Members agedhorse Posted February 10, 2007 Members Share Posted February 10, 2007 Just like how you drive the car will affect the MPG (or KPL for you metric folks), so will how you operate your PA system. Link to comment Share on other sites More sharing options...
Members W. M. Hellinger Posted February 10, 2007 Members Share Posted February 10, 2007 Just like how you drive the car will affect the MPG (or KPL for you metric folks), so will how you operate your PA system. Also, how much power the motor produces along with how you drive your car will effect the lifespan of the entire drive train. Case in point (this might be kind-of long winded): I own a 1994 Chevy 1 ton van, powered with a 350 cid motor. This van has a little less than 1/3 of a million miles on it, and to my knowledge has never had any major repairs outside of what I would consider to be routine maintenance. I religiously change the motor oil in this van every... oh... 5,000 miles or so. I religiously change the tranny oil and rear end oil every 100,000 miles or so... along with the brake shoes, serpentine belt, and other general maintenance items. This fall I purchase a "new to me" Ford 1 ton van... 'cause I wanted to have a back-up plan. The new Ford was purchased at a municipal auction (ex city fire dept personnel van). The new Ford van had really low miles on it... by my standards... approx 90K. The new Ford van appeared to be in excellent condition with full maintenance records. Only after I purchased this Ford van at the auction, I discovered the motor is a high-output 460. Shortly there-after, I discovered that the rear-end and transmission were both completely wore-out, along with a lot of other problems with the drive train. So... how is it that one van only has a 350 motor and runs for hundreds of thousands of miles, while another very similar van has a 460 motor and is completely wore out in less than 100,000 miles Link to comment Share on other sites More sharing options...
Members gearmike Posted February 10, 2007 Members Share Posted February 10, 2007 The safest way to design a particular system is to choose the speakers you like and power them with (RMS+PROGRAM)/2 amplifiers.. Where did this equation come from? Link to comment Share on other sites More sharing options...
Members preacherman672 Posted February 10, 2007 Members Share Posted February 10, 2007 The problem I have with the "power your speakers with the RMS ratings" is this: If you put 600 RMS watts into a 600 watt RMS speaker with live music which will have at least 6db peaks, then you are only running 150watts continuous into the speaker with 600 watt peaks. I assumed this was the reason for the RMS/Program/Peak ratings in the first place. Program to my understanding = highly compressed program music (modern cd)Peak = rating of less compressed music (live music) If you power with the RMS rating and keep it out of clip you surely won't blow a speaker, but you also will not reach full potential. If we like car analogies so well it would be like buying a 'Vette and putting a 3000 RPM governor in it. Sure it would last forever, but who would want it? Les Link to comment Share on other sites More sharing options...
Members W. M. Hellinger Posted February 10, 2007 Members Share Posted February 10, 2007 If you power with the RMS rating and keep it out of clip you surely won't blow a speaker, but you also will not reach full potential. If we like car analogies so well it would be like buying a 'Vette and putting a 3000 RPM governor in it. Sure it would last forever, but who would want it? Les Good example. Most of us don't own a Vette without a governor and a 7K tach. Why? Cause it costs too much money to buy, and it costs too much money to maintain, and many don't have the chops to safely operate the machine to it's capacity anyway... therefore many of the Vettes on the road are diven fairly conservatively by reasonably conservative people. The rest of us own Chevy vans and the like, and probably don't drive our Chevy vans any more conservatively than most Vettes (I distinctly remember passing a string of Vettes in my Chevy van on I-5 headed south at about Kettleman City, CA about a month ago). I used to own a '65 fuelie Corvette Roadster, and a '69 big block Roadster, and a 71 Monte SS454, and a 69 SS396 El Camino.... and those were "fun"... I guess... but I've had a lot more pure fun over the years in Chevy vans. Link to comment Share on other sites More sharing options...
Members Alan Roberts Posted February 10, 2007 Members Share Posted February 10, 2007 Just like how you drive the car will affect the MPG (or KPL for you metric folks), so will how you operate your PA system. OK. So if we use that analogy, at what point do you get the most efficient performance from amps and speakers? Do amps and speakers run most efficiently when ran to their full potential? Do they suffer if not ran at a certain minimum. Does this change from mfg. to mfg. (as I would suspect)?I know the definition of "pro level gear" varies depending on who you ask, but using that term for lack of a better one, does most pro gear like to be ran somewhere near it's full potential in order to be most efficient or is there a point at which you start to lose efficiency? Link to comment Share on other sites More sharing options...
Members solomaniac17 Posted February 10, 2007 Members Share Posted February 10, 2007 So... how is it that one van only has a 350 motor and runs for hundreds of thousands of miles, while another very similar van has a 460 motor and is completely wore out in less than 100,000 miles Link to comment Share on other sites More sharing options...
Members dboomer Posted February 10, 2007 Author Members Share Posted February 10, 2007 at what point do you get the most efficient performance from amps and speakers? With speakers the most "efficient" range is near the bottom of their power handling (low power). There is less distortion and lower heating losses (power compression) ... of course there is also less sound. With amps it varies a lot more ... mainly with the class AB, H, D etc. For the most part amps are more thermally efficient when you drive them to full rated output (or you turn them off) Link to comment Share on other sites More sharing options...
Members dboomer Posted February 10, 2007 Author Members Share Posted February 10, 2007 So if my cabs are rated at 600 watts continuous @ 8 ohms By what method are they rated? 600W continuous means different things to different manufacturers ... as it does with amps too Link to comment Share on other sites More sharing options...
Members 6Imzadi Posted February 10, 2007 Members Share Posted February 10, 2007 at what point do you get the most efficient performance from amps and speakers? With speakers the most "efficient" range is near the bottom of their power handling (low power). There is less distortion and lower heating losses (power compression) ... of course there is also less sound. This leads me back to my point of having a "safe" and conservative sound system. See my post above. I'm not a design engineer, but I am a thinker. Link to comment Share on other sites More sharing options...
Members preacherman672 Posted February 10, 2007 Members Share Posted February 10, 2007 I don't think the above car analogy is accurate for anything except for a powered speaker. The Corvette has obviously been designed and engineered to perform the way it does. It is self contained like a powered speaker. A better match in analogy might be if you were designing a race car: How big an engine for this powertrain? The 'Vette is "designed and engineered" to redline at 7 grand and the speaker is "designed and engineered" to "redline" at 600 watts RMS. If you power a speaker with 600 watts RMS and the musical peaks are 6db, the actual continuous power to the speakers is around 150 watts if you run right to the edge of clip. So it's like putting a 3000 RPM governor on the 'Vette. I have no clue what you are referring to with "self contained" comment. Maybe you could enlighten me? Les Link to comment Share on other sites More sharing options...
Members W. M. Hellinger Posted February 10, 2007 Members Share Posted February 10, 2007 It is self contained like a powered speaker. And... looking at what sized amplifier a manufacture powers a powered speaker with could give a person a pretty good indication of what size amplifier to use on an unpowered version of the same basic speaker. Link to comment Share on other sites More sharing options...
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