Silas Pradetto |
500W never clipped is safer. |
Duncan McLennan wrote on Fri, 12 June 2009 15:13 |
Answer seems simple enough to me. You asked if you will be safer underpowering the speaker, and you say you will not clip anything. So in either case nothing will get clipped, therefore the lower power is 'safer'. |
Stephen Dranger wrote on Fri, 12 June 2009 16:15 |
I just noticed the amp has a clip light on it. I guess I just have to make sure not to set that off? Thanks everyone for your help! |
Stephen Dranger wrote on Fri, 12 June 2009 17:15 |
I just noticed the amp has a clip light on it. I guess I just have to make sure not to set that off? Thanks everyone for your help! |
Chris Strack wrote on Mon, 15 June 2009 15:42 |
Ok I have to say that most of the responses to the original posted question here have me confused. I have always read and understood that it is always recommended that your amplifier provide 1.5 to 2X the Continous/RMS rating of the speaker. So if his speakers are rated ay 600W RMS/1200W Program, most of the recommendation here are run them underpowered (which in his case is 450-500W with his amp) which is the opposite of what I have ever read before. WHAT GIVES ????? |
Chris Strack wrote on Mon, 15 June 2009 13:42 |
Ok I have to say that most of the responses to the original posted question here have me confused. I have always read and understood that it is always recommended that your amplifier provide 1.5 to 2X the Continous/RMS rating of the speaker. So if his speakers are rated ay 600W RMS/1200W Program, most of the recommendation here are run them underpowered (which in his case is 450-500W with his amp) which is the opposite of what I have ever read before. WHAT GIVES ????? |
Bob Leonard wrote on Mon, 15 June 2009 16:11 |
OP, I've been following this post and I have to say that some of the advice you've been given is as bad as I've read in a long time. Be aware that although heat is the real danger here that heat has to come from somewhere and it's not the sun in this case. The temperature of the voice coil is a result of the voltages and current put through the voice coil by the amplifier. Just like a light bulb, too much voltage and the voice coil will burn itself out. Many manufacturers address the issue of heat using voice coil materials and venting schemes which dissipate the heat or are impervious to the heat. Kapton is one of these materials which holds up to heat very well and is often used as a material for forming voice coils. The problem will be that although the Kapton can withstand extremely high temperatures, the voice coil wire coating and adhesives used to hold the wire to the Kapton usually fail first. Operating your speakers using the proper voltages, amplifier output results in less heat. That's a no brainer. The problem is that many people don't understand that even a very small amplifier is capable of generating enough voltage to destroy a voice coil. Voice coils that are very susceptible to this type damage are the voice coils of your compression drivers. Ever wonder why the person who shuts down his board before his amplifiers and then brings the system back up has all of a sudden lost output from the cabinet horns? It's because that "snap" he heard destroyed the voice coils in his drivers. My take in the past 40 or so years has been to never under power a cabinet unless there is no other way. 1.5 - 2x the drivers long term rating is the way to go. And NEVER an amplifier that delivers less than the long term rating of the speaker. And let's be honest here. I don't know of any NUG who hasn't wanted more output at some time or another. The odds are stacked against you. Small amp, larger than normal crowd, I'll just push it into clip for a little while. And then you wake up the next morning to drivers that are useless. Limiters, compressors, etc. are a crutch. Power the speakers properly set the gain properly, balance the board and you won't need them. Here's an old paper from JBL that's every bit as good today as it was the day it was written; http://www.jblpro.com/catalog/support/getfile.aspx?docid=290 &doctype=3 http://www.jblpro.com/catalog/support/getfile.aspx?docid=246 &doctype=3 Edit: When I re-read Bennett's response I see that we are almost aligned with one exception. The clip light is not meaningless. It should be used as a guide, a reference point, and it should never be ignored. |
Stephen Dranger wrote on Fri, 12 June 2009 14:10 |
I have a conundrum: I am stuck with a Behringer EP2500 amp and a 6925 Tapco Dual 15" speaker. The Tapco is rated 600W RMS/1200W Program and is 8 Ohms. The EP2500 gives 450-500W at 8ohms per channel and 1300-1500W at 8 ohms bridged. |
Stephen Dranger wrote on Mon, 15 June 2009 14:24 |
A Tapco guy said to me that the reason underpowering is bad is because you want to get a louder signal out of it, and therefore you end up sending a clipped signal to the amp -- clipped = direct current = broken speaker, no matter what the wattage is. |
Bob Leonard wrote on Mon, 15 June 2009 14:11 |
Limiters, compressors, etc. are a crutch. Power the speakers properly set the gain properly, balance the board and you won't need them. |
Stephen Dranger wrote on Mon, 15 June 2009 16:12 |
There's another question which would clear up a lot of things for me: does the wattage of the speaker alter how the amp works? Because if I'm not sending the amp a clipped signal, what I'm reading says that I can still clip the amp by cranking the volume. But why wouldn't an amp that's rated higher (and 1.5x RMS wattage rating) also start clipping if you cranked the volume on the same signal? Because what I'm hearing is that even if you gave the amp a signal that wasn't clipped, that volume knob is going to push the amp past its distortion level at some point no matter what amp you have. |
Stephen Dranger wrote on Mon, 15 June 2009 15:12 |
There's another question which would clear up a lot of things for me: does the wattage of the speaker alter how the amp works? |
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Because if I'm not sending the amp a clipped signal, what I'm reading says that I can still clip the amp by cranking the volume. |
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But why wouldn't an amp that's rated higher (and 1.5x RMS wattage rating) also start clipping if you cranked the volume on the same signal? Because what I'm hearing is that even if you gave the amp a signal that wasn't clipped, that volume knob is going to push the amp past its distortion level at some point no matter what amp you have. |
Andy Peters wrote on Mon, 15 June 2009 16:59 |
If the input signal times the amp gain (which is what you set with that big knob) exceeds what the amp can deal with, then you will clip the amp. So that clean input signal at 1.23 Vrms (which is what your mixer outputs when its meter reads 0 dB) will clip an amp with a 1 Vrms input sensitivity when the gain control is all the way up. |
Andy Peters wrote on Mon, 15 June 2009 18:59 |
I suppose I should ask: "Crank the volume WHERE?" Do you mean crank the level going TO the amp, or crank the amp's gain control? Actually, it doesn't matter. If the input signal times the amp gain (which is what you set with that big knob) exceeds what the amp can deal with, then you will clip the amp. So that clean input signal at 1.23 Vrms (which is what your mixer outputs when its meter reads 0 dB) will clip an amp with a 1 Vrms input sensitivity when the gain control is all the way up. If you turn that gain control down 6 dB, then you need 2 Vrms to clip the amp and your 1.23 Vrms signal is fine. The whole point here is that you NEVER want to clip your amp. Why? Because when in clipping, the amp's output can easily be double that of its unclipped state. So your clean 500 W amp can put out 1000 W when clipped, and if your speakers are rated only for 750 W, you are in trouble. Does this help, even just a little bit? -a |
Stephen Dranger wrote on Mon, 15 June 2009 17:26 |
My mixer is a Carvin, and I will definitely take the time to look up its specs. |
Bob Leonard wrote on Mon, 15 June 2009 17:11 |
Limiters, compressors, etc. are a crutch. |
Bennett Prescott wrote on Mon, 15 June 2009 18:02 |
Now fast, "peak" limiters... those cause more harm than good. |
Bennett Prescott wrote on Mon, 15 June 2009 21:02 | ||
This is where we disagree. Ideally a system will never be pushed into limit, but properly set RMS limiters can allow a system to achieve its maximum performance nearly regardless of input signal by keeping the heat generating RMS level of the waveform below what the loudspeaker can handle, while maintaining most of the integrity of the dynamics. It's like insurance for your car... no crutch, but a prudent safety margin for that unexpectedly loud show or when you hand the keys to your nephew so he can do a supermarket run. Now fast, "peak" limiters... those cause more harm than good. |
Stephen Dranger wrote on Mon, 15 June 2009 17:24 |
I guess it's not surprising that I wasn't able to find easy information from anywhere! I keep getting mixed signals; in fact two different Tapco tech support guys gave me two different answers! Sending power to speakers seems to be pretty contentious. I guess what I don't understand is that if underpowering speakers is bad, should you never ever lower the volume on your amplifier if it's running at ideal voltages? What if you are sending a quiet signal? What's the difference between sending a quiet signal to a sufficiently powered amp and sending a loud (but not clipped) signal to a slightly underpowered amp? A Tapco guy said to me that the reason underpowering is bad is because you want to get a louder signal out of it, and therefore you end up sending a clipped signal to the amp -- clipped = direct current = broken speaker, no matter what the wattage is. Things are not easy for a newbie... |
Greg Cameron wrote on Mon, 15 June 2009 20:15 |
It really depends on the quality of the limiter. There are some really cruddy sounding peak limiters for sure. But there are peak limiters that sound pretty good. Of course, that quality of limiter comes at a premium. Only the most expensive DSPs seem to have ones that are relatively transparent and don't get crunchy. There are some good sounding analog ones as well, though they're not very common these days. The peak limiters that KT used in their older analog DN800 crossover worked very well and let the system get really loud and clean when they were engaging. I have yet to find a low to mid cost DSP that I can say the same about. For subs, I'm using an old Symetrix 501 peak limiter on subs that can hit up to 45dB of gain reduction before it starts sounding ugly. I usually don't hit it that hard but when it's active it actually sounds pretty good. Greg |
John Roberts {JR} wrote on Mon, 15 June 2009 21:27 |
At the risk of stating the obvious, clip limiters built in most power amps are in fact very fast attack/release peak limiters. These are pretty transparent (IMO). The only criticism they usually get is that the amp doesn't get as loud as when defeated. JR |
Greg Cameron wrote on Mon, 15 June 2009 21:15 | ||
It really depends on the quality of the limiter. There are some really cruddy sounding peak limiters for sure. But there are peak limiters that sound pretty good. Of course, that quality of limiter comes at a premium. Only the most expensive DSPs seem to have ones that are relatively transparent and don't get crunchy. There are some good sounding analog ones as well, though they're not very common these days. The peak limiters that KT used in their older analog DN800 crossover worked very well and let the system get really loud and clean when they were engaging. I have yet to find a low to mid cost DSP that I can say the same about. For subs, I'm using an old Symetrix 501 peak limiter on subs that can hit up to 45dB of gain reduction before it starts sounding ugly. I usually don't hit it that hard but when it's active it actually sounds pretty good. Greg |
Bob Leonard wrote on Mon, 15 June 2009 21:24 |
Steve, The key point here is that quiet or loud the amplifier doesn't clip. Setting the gain structure for your system properly should allow allow full output at 0db. Full output would be ideal if the speaker handled 500 watts and the amplifier was putting out no more than 500 watts - EVER. Less power would be fine because once again the amplifier is not clipping. That also answers the reason for the x2 recommendations. It's not only possible, but depending on the type music being played, probable that your amplifier will be called on to produce output levels that actually exceed the long term rating of the speaker. This figure is usually referred to as the "program power rating" and it is a figure that reliable manufacturers use to let you know the speaker is capable of handling those short term peaks. Having the additional power available to handle those short term peaks almost eliminates the possibility that your amplifier will clip and damage the speaker. That power is held in reserve until needed by the system, so once again, the overall system gain will determine the final output from the amplifier which in almost every case should not be more than the LONG TERM power rating of the speaker. Here's a thought. Draw a straight line across a piece of paper. On the left side write the number 100. Call that the power output of a 200 watt amplifier producing a steady 100 watt sine wave. Your speakers are rated for 200 watts "program power" 100 watts long term. Push that sine wave to the speaker for 4 hours and you're still OK. Draw a vertical spike on the line anywhere you want and call it +3db. That equals 200 watts output from the amplifier. Did the amp clip? No, because it didn't exceed it's power output rating. If you clip the amp you can easily double the output. How long will your 100 watt speakers last?? |
Bennett Prescott wrote on Mon, 15 June 2009 21:25 |
A peak limiter sounds somewhat better than clipping sometimes, and that's great, but a peak limiter cannot control voice coil heating without drastic sonic consequences and loss of performance. The two concepts are opposite. Peak limiters can be used to control overexcursion, sometimes, but everyone is setting their limiter thresholds and seemingly ignoring attack and release. |
Bennett Prescott wrote on Mon, 15 June 2009 23:25 |
I don't care how good they sound... a loudspeaker is not a recording, where there is a set level beyond which catastrophic failure occurs. Clipping does not hurt loudspeakers, amplifiers, mixing consoles, or anything. A peak limiter sounds somewhat better than clipping sometimes, and that's great, but a peak limiter cannot control voice coil heating without drastic sonic consequences and loss of performance. The two concepts are opposite. Peak limiters can be used to control overexcursion, sometimes, but everyone is setting their limiter thresholds and seemingly ignoring attack and release. |
Bennett Prescott wrote on Mon, 15 June 2009 21:25 |
Peak limiters can be used to control overexcursion, sometimes, |
Chris Tate wrote on Tue, 16 June 2009 09:34 |
Man....this thread is three pages long.....I can't even be arsed reading through every reply..... Has anyone pointed out Bennett's article on the main page of PSW? He is 100% correct....if you don't understand it, read it again....and then again....it well and truly nails the lid on this thread in my humble opinion.. |
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Bob Leonard Wrote: The key point here is that quiet or loud the amplifier doesn't clip. Setting the gain structure for your system properly should allow allow full output at 0db. Full output would be ideal if the speaker handled 500 watts and the amplifier was putting out no more than 500 watts - EVER. Less power would be fine because once again the amplifier is not clipping. That also answers the reason for the x2 recommendations. It's not only possible, but depending on the type music being played, probable that your amplifier will be called on to produce output levels that actually exceed the long term rating of the speaker. This figure is usually referred to as the "program power rating" and it is a figure that reliable manufacturers use to let you know the speaker is capable of handling those short term peaks. Having the additional power available to handle those short term peaks almost eliminates the possibility that your amplifier will clip and damage the speaker. That power is held in reserve until needed by the system, so once again, the overall system gain will determine the final output from the amplifier which in almost every case should not be more than the LONG TERM power rating of the speaker. |
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Bennett Prescott Wrote: The issue with overdriving an amplifier is, an amplifier that can cleanly supply 500 watts can be severely overdriven and provide 1,000 watts. It will sound horrible, there will be no dynamic range, it will be severely distorted, but the amplifier will do it. That dense, high-RMS-value signal can then destroy a loudspeaker that can only handle 500 watts. However, if your loudspeaker can handle 1,000 watts (and it's really not this simple, but let's pretend it is to keep the discussion on one path) then that severely distorted signal from the 500 watt amp is probably fine. It will just sound terrible, because you've run out of amplifier long before you've run out of loudspeaker. You'd be much better off using a 1,000 or even 2,000 watt amplifier and not clipping it. The loudspeaker will see basically the same heat from the signal but, assuming you haven't reached the excursion limits of any drivers, it will obviously sound a lot better. Side note: That severely clipped signal actually has more RMS heat value than the same signal cleanly reproduced by an amplifier 2 or 4x the size, because all of that clipping generates significant energy in the higher frequencies (clipping = higher order harmonics). In a biamped system this is of little concern, but in a passive solution all that extra high frequency energy is going right into your tweeters. It's basically wasted power that you're throwing away from the low frequencies and dumping into the highs. The moral of the story is: Use an amplifier that has enough power to drive your loudspeaker to its peak capabilities (which are almost never listed, unfortunately) and then use an RMS limiter to keep the signal from overheating the drivers (one limiter per passband). This will result in maximum performance and fidelity, and is the reason why we (ADRaudio) feed 500+ watts into compression drivers rated for 100. |
Chris Tate wrote on Tue, 16 June 2009 10:34 |
Has anyone pointed out Bennett's article on the main page of PSW? |
Bennett Prescott wrote on Tue, 16 June 2009 00:46 |
... and then use an RMS limiter to keep the signal from overheating the drivers (one limiter per passband). |
Adam Schaible wrote on Tue, 16 June 2009 15:00 |
My amps have this built in - not sure what your budget is, but they are I-Tech HD's |
Phil Lewandowski wrote on Tue, 16 June 2009 14:51 |
Any suggestions on a limiter or device to do just this? I have been searching for a long time and all I have found is finding a limiter that has a long enough attack and release times to achieve this. |
Chris Strack wrote on Tue, 16 June 2009 12:46 |
My only additional advise to Stephen Dranger who started this thread is "Gain Structure". It took me some time to understand this concept but it is really important that you read all you can on setting up the proper gain structure for your mixer/amps/speakers. By doing this you will be able to get the most headroom out of your PA system and run it the safest way possible. Turning up the gain control as high as it can go on your amp does not give you the most head room, having a proper gain structure set up between you mixer and amps does. Proper Gain structure also helps you protect your amps from clipping. So if you haven't read about this concept, you need to before you just use your amp bridged and then turn the amp all the way up. |
Bennett Prescott wrote on Tue, 16 June 2009 15:07 | ||
Try using a compressor instead of a "limiter". Any of the quality units should do it, or any DSP that lets you really slow down the limiter. Getting that time constant correct can be the difference of a few dB in output capability. |
Stephen Dranger wrote on Tue, 16 June 2009 12:18 |
What I'm not getting is that even with proper gain structure, how can I make sure I don't overheat the speakers if I'm pumping 1300W into 600W RMS speakers, especially since some of my inputs are going to be sine-wave-like? |
Art Welter wrote on Tue, 16 June 2009 14:26 |
Stephen, If your hearing ability is like your reading comprehension, then no, there is nothing you can listen for. Smoke 'em if you got 'em. |
Greg Cameron wrote on Tue, 16 June 2009 14:37 |
Stephen, if you know for a fact that you're going to be running true sine wave signals through your amp for extended periods, get an amp that has a continuous output rating that is equal to or less than the rms rating of the speakers rather than one that is 2x the rms rating and never hit the clip lights on the amps. This is the only way without an rms limiter that you can ensure you won't cook your speakers. Also be aware that a lot of amps don't like running full power sine waves for extended periods of time and will ramp the output down if you're running full tilt. This is especially true with the newer class D style amps and low impedance loads. Older designs will tend to just overheat or pop their internal breaker if you're running low impedance loads with full power sine waves. Greg |
Stephen Dranger wrote on Tue, 16 June 2009 14:50 |
Please, point me to the post in this thread where this answer was given to me. I know I didn't see it. |
Phil Lewandowski wrote on Tue, 16 June 2009 15:28 |
What slow attack and release times do you think are good points to start with? |
Art Welter wrote on Tue, 16 June 2009 17:33 |
If I would have turned that speaker up slowly, (and had not been doing tests while drunk) I would have noticed the distortion well before I had exceeded the power level by six dB. |
Art Welter wrote on Tue, 16 June 2009 17:33 |
You will probably be quite surprised how much peak power a speaker will take before it finally burns up if the music has reasonable dynamics. |
Bennett Prescott wrote on Tue, 16 June 2009 17:38 | ||
This is not a simple issue, and it is difficult to give an accurate answer without knowing a lot about the box, its application, and the drivers. The frequency range being worked with, driver loading, driver capabilities, and excursion can all be an issue. For instance, it is perfectly possible to have a loudspeaker that is excursion, rather than thermally, limited... i.e. (usually at lower frequencies) the driver runs out of excursion before it will ever overheat. That said, and please be aware that to really get this right takes a lot of almost certainly destructive testing, the best guess for attack and release times for a low frequency driver that I have are on the order of 5-10 dB per second attack, and .5-1 dB per second release. That should be a good starting point, adjust more or less within that range until it is inaudible. Driver overheating generally occurs on the order of 30+ seconds, so these times can be very slow because of that... but too slow and it's too audible, and too fast and it's too audible. We're talking about really very small reductions in SPL here, compared to what we normally nail compressors with. Maybe 3-6 dB, maybe as high as 9 for a really big amp and really abusive source material, but the amp's rail voltage will become the limiting factor again very quickly. Good luck! |
Art Welter wrote on Tue, 16 June 2009 16:33 |
I have moderately clipped a 400 watt amp into eight 4” speakers rated 5 watts RMS apiece, 40 watts RMS total, with no problem. The musical peaks were 10 times the speaker RMS level. Same ratio as 5000 watts into a 500 watt RMS speaker. I have also (by accident) burned up a 100 watt RMS speaker in approximately one second with a 400 watt 200 HZ sine wave. If I would have turned that speaker up slowly, (and had not been doing tests while drunk) I would have noticed the distortion well before I had exceeded the power level by six dB. I was reading a dB meter set on “A” instead of “C”, so it read about 6 dB SPL low, using my eyes instead of my ears... You will probably be quite surprised how much peak power a speaker will take before it finally burns up if the music has reasonable dynamics. Art Welter |
Stephen Dranger wrote on Tue, 16 June 2009 13:09 |
How does one figure out how far they can push their speakers if you're giving them 2x their RMS rating? |
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that causes clipping and speaker failure... |