How Far Can I Turn it Up?
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Topic: How Far Can I Turn it Up?
Posted By: Rotorbar
Subject: How Far Can I Turn it Up?
Date Posted: 07 December 2009 at 10:18pm
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We used to just turn up the PA until it was loud enough, and we occasionally blew drivers. I'm trying to bring a little science into the picture. I get asked about this, and I find I really don't know, and therefore have no good answer. Is it good enough to model your PA and then use an SPL meter to see how close you are to destroying your system as compared to that model? Is there a better way? Maybe I'm just no good at listening, but I find the ears to be pretty subjective, room to room. I also know that loudest isn't always what you want. By "model" I mean you took driver sensitivity, input watts (dB above 1w/1m), thermal and mechanical driver limits, etc. into account. Once I heard a racer asking another racer how to tell if an engine was over-revved. The second racer stood there a moment, and finally said "Connecting rods sticking out through the side of the engine block are a pretty sure sign." Regards, Rotorbar |
Replies:
Posted By: cilla.scope
Date Posted: 07 December 2009 at 10:19pm
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11
------------- My girlfriend thinks I'm a stalker. Well, she's not exactly my girlfriend yet ... |
Posted By: DjMidKnight
Date Posted: 07 December 2009 at 10:36pm
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by ear is how i roll man, of course i strive to build my system so that my amps cant kill my speakers. point and case nothing will destroy a speaker faster than amplified distortion. basically if your keeping your amp out of clipping and your not sending way to much signal to said amp(djs running the gain to high/redline mixer), you should be good to go. ------------- reality is meerly a compilation of what our limited sences precieve as being fact therefore there is no true universal reality and as such i propose that space and time can be bent twisted and altered |
Posted By: Saul
Date Posted: 07 December 2009 at 10:46pm
mine goes to 12.
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cilla.scope wrote:Posted By: thepersonunknown
Date Posted: 07 December 2009 at 11:17pm
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not a very good answer but it might help:
the manuals for your amps should quote you the relation between input and output voltages. using this you can work out the rms output of your amps at a cirtain input level with a give style of music/duty cycle. its all very ballparkish, but if you set light compression a bit higher than the point where your speakers hit their program rateing and a brick wall limiter at a point a little lower than where the speakers would be peaking, it should help a little with protecting your speakers. the ´soft knee´ function on a compressor sort of does this. the worst thing about this is that it is slightly audible even when the system is no where near its peak, but i gues thats better than fried drivers. anyway its a bit of a rubbish answer but i did warn at the top of the post. im not even sure if its a safe/correct way of limmiting but it did work for me no a systrem that was out every week end for over a year. i never blew a driver, although the main threat to the drivers in that cas acros all the bands apart from the highs was clipping/squarewave from amps. im sure theirs someone out there who could better explain how to accuratly set limiters. i for one would be most interested to learn.
Edit: the light compression can have the threshold raised when used for short term and lowered when in prolonged use.
+ bare in mind that once the compression point is passed the duty cycle/rms output of the amp will increase at a faster rate as the input gain is incresed (definetly not one for dry hires) ------------- They keep telling me life is short, but its the longest thing ive ever done!!! |
Posted By: rich_gale
Date Posted: 07 December 2009 at 11:29pm
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i try to use an amp that will deliver 1.5-2 times the power of the speaker i will be running. assuming they are good quality, under rated like PD you can run the amps until you start to see a clip light flicker now and then and then i know i dont really want to put much more into the speaker. with eminence, celestion,fane id probably follow the same system, but use an amp that is the same power as the speaker. if you are being careful and notching up gradually you end up smelling the vc glue/former/copper heating up (i love the smell). at this point you need to back down a bit. its always a lovely feeling when a room stinks of vc's and you get back worrying if you need a recone but then you check and the drivers are all fine and the worrying was all for nothing. ------------- REFLEX ALL THE WAY.... (however, im playing with horns again...) That ok Mister Valiant? :) |
Posted By: RUS
Date Posted: 07 December 2009 at 11:37pm
wrong section  |
Posted By: pfly
Date Posted: 08 December 2009 at 12:03am
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I've been doing just fine with limiters set up according to the max output of the amp in question. For example if I have a driver that could take 800W RMS, but in the box it is in, its Xmax is reached around 500 watts, and I use amp that is capable of 1100W RMS for that speaker, I check when I hit amps limits, then I may set the limiter 3dB down from that point. This way that amp should give maximum of 550 watts for that speaker and all should be well.
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Posted By: jonminns
Date Posted: 08 December 2009 at 12:07am
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if you can't do it by ear you may as well give up ------------- 4 ohms is for wimps |
Posted By: rich_gale
Date Posted: 08 December 2009 at 12:24am
why not run a speaker to just under its xlim? xmax is purely the point where its optimum excursion limit is at the point of becoming below optimum isnt it? a speaker still goes louder after going past its xmax, or thats always been my belief. ------------- REFLEX ALL THE WAY.... (however, im playing with horns again...) That ok Mister Valiant? :) |
Posted By: thepersonunknown
Date Posted: 08 December 2009 at 12:29am
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@ jonminns.
personaly i find it hard to determine what rms power is going into a speaker by ear. untill u start to hit peak values i think its almost imposible to hear. that is no problem if your only going to be running your rig a couple of hours at a time but when its going for 24 or even more hours non stop on a regular basis its quite important that the rms rateings are not passed too much. this will realy take some of the lifespan out of your drivers.
sound quality starts to drop after driver xmas as the motor starts to lose control over the cone
im sure their must be some science to doing this. wheres all the electronics techs at? ------------- They keep telling me life is short, but its the longest thing ive ever done!!! |
Posted By: Rotorbar
Date Posted: 08 December 2009 at 12:34am
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Mr. RUS, At first read, I thought "he's right, I should have posted this in the newbie section." Now I'm not so sure. Virtually every answer I've read is non-scientific. I don't mean to belittle them. They obviously seem to work for their advocates. Mr. Gale seems to enjoy using the sniff test. OK, that's fine, but my nose is poor, and I'd be better off putting a smoke detector above each PA stack. I think that most all will agree with his mentioning using at least 2X amplifier capacity. Mr. DJMK mentions not letting your system feed the speakers with distorted material. Good idea, too. Mr. Unknown mentions using compression/limiting to save drivers. Good idea, too. The trouble is, these ideas are based on good judgment, which comes from experience, which comes from bad judgment. I was hoping to quantify all that good judgment into something that might save others from paying for all that expensive experience. I think Mr. Pfly has a good point on a practical way to make sure you don't over-xmax a driver. I guess where I was going was something like: give me the types of drivers you have, and information on their horns/enclosures, crossover points, etc. and I'll tell you how much power you can feed them, and what SPL you will get from them. There may be limits based on characteristic frequency content of various music types, but the engineering behind the drivers can't be voodoo. Assuming you're going for reasonably flat response, One example might be: Highs: if you want 130 dB, and your horn driver sensitivity is 110dB at 1w/1m, then you need 20 dB (100 watts) into that driver. Mids: If you want 130dB and your mids drivers (qty 2) are 101 dB 1w/1m, then you need 26dB (400 watts) into each of the mids. 101 + 26 gets you to 127dB, and doubling the drivers gets you to 130 dB. Will they each take 400W? No. They might go thermal limit, or they might go mechanical limit, but either way, you need more mids to get where you want to go... I realize there are wild cards, like unanticipated distortion, prolonged feedback, and so on, but I hate telling someone new to the business "Oh, just smoke a few diaphrams, and you'll figure out what the tops will take." I've been there, and have the box of old voice coils to prove it. Regards, Rotorbar |
Posted By: thepersonunknown
Date Posted: 08 December 2009 at 12:48am
@ rotorbar
+ one on this being valid for the forum. i wouldnt like to debate if this is an advanced topic, or compare my knowlege with that of anyone elses, but i consider myself a resonably informed tech yet stil have no idea on the science behind protecting drivers with any precision and this seems to be the case with many acomplished system owners/operators. so come on then, whos going to be the teacher on this one? ------------- They keep telling me life is short, but its the longest thing ive ever done!!! |
Posted By: B.P.Sound
Date Posted: 08 December 2009 at 7:30am
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Trun the amps up until the speakers stop working (Blown) and then turn the amps down a bit..... Level set!!!!! ------------- http://www.londoneventrentals.co.uk/ https://www.facebook.com/LondonEventRentals |
Posted By: pfly
Date Posted: 08 December 2009 at 7:39am
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rich_gale Well you said you go ultimately by the smell  I don't want to push that far.Also isn't the linear travel the travel the engineers designed the vc/cone to be used within? without too much of compression / distortion and with cooling working like it was ment to
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Posted By: Conanski
Date Posted: 08 December 2009 at 3:53pm
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Like anything protecting drivers depends upon a lot of things, but the most relavent to protection from overpowering is what type device is in use for protection and what type source material the system is handling. If you have a soft knee type limiter like those found in most compressor/limiters then you have to account for overshoot and set the threshold lower, but a brickwall limiter like those found in a PA processor can be set higher. The source material will affect the limiter setting too, with highly compressed material you want to limit to around the drivers RMS rating because that's the power level where the voice coil begins to melt when driven with a steady state signal like a sine wave.. which roughly equates to heavily compressed music. If the source is more dynamic then the limiter can be set to the program rating or so.
So how do you determine the limiter setting? If the limiter has an accurate DB calibration you can set it to the level below 0db that corresponds to the speakers rating.. assuming the amp is capable of more output than the speaker. If not then use the formula V = Square root of (PxR) to determine the amplifier output voltage level you want to limit to, where V = amp output voltage, P = speaker RMS power rating, an R is speaker nominal impedance. What you do is setup the amp without speakers attached and drive it to just about clipping with an example of the source material it will typically see, put a true rms DMM on the outputs and then reduce the level with the limiter until you get to the number you calculated above. A regular DMM will not work as well because it displays an average voltage level, while a oscilloscope would allow you to very accurately measure rms and peak voltage so it's the best choice.
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Posted By: darkmatter
Date Posted: 08 December 2009 at 5:18pm
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Didn't reply to this yesterday because I suspected Mr. Rotorbar was already as close to the truth as I'll ever be.
No substitute for experience I reckon. If you know that the fourth DJ on will push it into the reds because you've peered over the desk of red lights last time you saw him play out, you don't whip out the calculator. You set limits conservatively and keep your fingers crossed.
We're never given full specs about thermal limits of drivers with exactly the source signal that we'll be feeding them, and not a single one of us has the time of money to exhaustively test this.
From reading opinions of people who have lots of experience, they have no desire to run their system to just before breaking point anyway. They know that amps exhibit more distortion when nearing full pelt, additional SPL is near negligible when drivers are near limits due to thermal compression and unexpected peaks (cable getting pulled loose, sleeve catching a stylus) could pop your system in an instant.
Best to play it on the safe side and bring extra speakers if you need more volume, imo. But I get the sense Rotorbar already knew that ;)
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Posted By: Plaguesguitarist
Date Posted: 08 December 2009 at 7:21pm
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It also depends on in what condition your amps and drivers are in. Like any machine with moving parts, You will be able to push a new driver better with a new amp as the parts won't be worn, creating distortion. I can run my full logic rig on 2/3rds amp volume and develop 7/8 of the spl available. That way i'm not overdriving anything to breaking point. I set limiters at a reasonable level on my sabine but it is ultimately down to the job at hand.
I've also learnt several times the hard way that if you buy cheap and run like  you buy twice...------------- Why did the lampy cross the road? To steal MY sharpie. |
Posted By: Jasonstry
Date Posted: 08 December 2009 at 7:30pm
| WTF?? |
Posted By: Plaguesguitarist
Date Posted: 08 December 2009 at 7:57pm
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Sorry... I was quite high on jibberishometer there
My previous post basically translates into english as: if you push things too hard, they break, you pay. ------------- Why did the lampy cross the road? To steal MY sharpie. |
Posted By: jonminns
Date Posted: 08 December 2009 at 11:03pm
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I've set up countless systems over the years which get abused for hours on end 6 nights a week, there is no valid scientific way of doing this because you should be able to do it by ear! I can hear when a driver is happy or on edge, be it a comp, mid or bass. Of the multiple hundreds of drivers involved in these systems i've never lost one and i don't intend to! ------------- 4 ohms is for wimps |
Posted By: cilla.scope
Date Posted: 09 December 2009 at 12:11am
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Doesn't really make sense ... drivers will (eventually) overheat and fry the voice coil if driven above their rated power ... if the driver begins to exhibit distortion before at a power level less than the maximum continous power input before thermal destruction set isn, then fair enough, setting it to a level below where it begins to sound ragged will be safe. If you happen to have speakers that have an extended dynamic range and sound clean, even when pushed briefly to a level that will (if continued) would result in them overheating and going pop ... then you are on the road to an expensive re-cone if you just turn it up until it sounds ragged .... I guess it just means you typically work with speakers that sound ragged long before they reach their rated power ... Still, if you run multiple hundreds of drivers, 6 nights a week, over a period of many years .. and have never lost one .. then fair enough, it clearly works for you, thats a very impressive record .... you must have what .. 20 or so rigs out each night? 30 at weekends? ------------- My girlfriend thinks I'm a stalker. Well, she's not exactly my girlfriend yet ... |
Posted By: thepersonunknown
Date Posted: 09 December 2009 at 1:30am
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well he does come with a warning
(4 ohms is for wimps)
  peace ------------- They keep telling me life is short, but its the longest thing ive ever done!!! |
Posted By: Jasonstry
Date Posted: 10 December 2009 at 7:24pm
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Rotorbar you are either missing the difference between theory and reality or fishing. You are ignoring power compression. So much of this stuff is play time. If you have a box that can handle 500W RMS and 1000W constant that has a sensitivity of 100 dB 1W/1M then if you chuck 2W at it you might get a theoretical 3 dB (a difference that people might notice) but if you are chucking 500W at it and then double that to 1000W then you are probably going to lose most of that to power compression and you are risking blowing drivers (and possibly your amps) to make a difference that nobody would actually hear. Why would anyone want to do that? Oh yeah.....it smells nice ;-)
Andy
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Posted By: jamwa
Date Posted: 10 December 2009 at 7:43pm
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well if it all goes quite then you have gone to far....
------------- Sound, Light, Projection, Display, Cameras and production support |
Posted By: Jasonstry
Date Posted: 10 December 2009 at 8:00pm
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what, to far away?? |
Posted By: Rotorbar
Date Posted: 10 December 2009 at 9:08pm
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Mr. Jasonstry, No, I hope I'm not divorced from reality. I have fried speakers just for the fun of it, but generally, that involved a backyard barbecue and lots of beer. Handing beer bottles over the fence kept the neighbors from getting too angry. I've been out of this business for years, and I find, among other things, that by the time you factor in loss of efficiency due to long voice coils, increased power compression, and the trend towards smaller cabinets, things aren't much better than they were in the 70's and 80's, except that the amplifiers have much higher wattage. Speaker-wise, things are better, but not by that much. A trend I noticed then was long-term overloads ripped surrounds, and short-term overloads burned voice coils, but we didn't have as much control over signal bandwith, so drivers probably unloaded a lot more, then. The difference between high SPL and higher SPL was a lot of watts, so we were aware of the concept of power compression. There weren't multi-thousand watt drivers back then, but somehow we had high SPL. So, my way of knowing if I can crank it up is I look at xmax (literally, I look at the drivers), I listen, and/or I use an RMS voltmeter on the speaker leads, since I don't have a power meter anymore. If I turn it up, and ten minutes later it seems like it's not as loud as it was, I'm just making heat, so I back down between songs. Once I've run a system a couple of times, I get a feel for it, and I find the meters on the equipment tell me enough. That's fine, but I kind of start over every time I work with a new system. As an aside, I should mention that a great many sound systems are operated nowhere near the point of component failure, and they operate for years, until someone who needs to learn good judgement comes along and fries something. By the way, power compression was mentioned earlier in this thread. The concept of decreasing gains is not restricted to loudspeakers. It occurs in devices as far removed as pumps, electric motors, and diesel engines. I recognise the vast amount of knowledge and expertise shown on this forum, but most everyone has learned all this stuff the hard way. I still dislike telling someone new to the business that they are going to have to blow up stuff to learn when it's about to blow. On the other side, I doubt that things will ever get to where you can go to a college, take classes, and come out with every bit of knowledge you need to manage a sound system. I guess I was just hoping for more than what we apparently have. In 1948, JBL came out with a speaker they called the D130. That product, with minor changes, had a 50 year production run. I don't think any other speaker has matched that record. My understanding of the history is that the way they initially rated it was they played guitar through it, measure the watts, and turned it up until it blew, and then derated it from there. There, we've re-played all the jokes posted about turning it up to 11 or 12. Regards, Rotorbar |
Posted By: DjMidKnight
Date Posted: 10 December 2009 at 9:36pm
Interestingly enough here at my local college offers a program called "The sound academy" which is a 16week course on sound engineering, and covers live sound managment, acoustic system design, studio mastering, and various other topics. ------------- reality is meerly a compilation of what our limited sences precieve as being fact therefore there is no true universal reality and as such i propose that space and time can be bent twisted and altered |
Posted By: smithers
Date Posted: 10 December 2009 at 10:41pm
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in my brief experience in the PA world i've blown 3 Fane xb's, 1 V18-1200 and 1 PD 186's, all from dubstep nights!
i do agree though, you'll never know how much is too much, until you've spanked a couple of drivers. Happily i've not blown a driver for a while now! |
Posted By: Jasonstry
Date Posted: 10 December 2009 at 10:44pm
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Mr Rotobar, wtf did that come from? Yep I was there in the 70s too. Don't know how I managed to press your buttons but was trying to be helpful rather than offensive. No attack intended. OK?
Andy
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Posted By: S DeXter
Date Posted: 10 December 2009 at 10:45pm
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Yet another bizarre thread. A speaker will break if you exceed its stated watts, as was said previously. Theres no need to make a model it is a simple fact. Most music has a maxmium crest factor of about 6db in each band so if you buy and amp which is double the rated RMS of the drivers you are using there should be, in theory, around 3db of headroom. Ensure the amplifiers do not clip and you should keep all of your drivers intact. This is the way I have done it for years and its always worked (even with DNB DJs persisant redlining of mixers). ------------- Enjoy your self...... It's later than you think....... |
Posted By: norty303
Date Posted: 10 December 2009 at 10:51pm
Because some cabs handle the excursion so well that you'll never achieve Xmax without suffering thermal damage first. I was just about to say exactly what S Dexter said. It's very simple, buy amps appropriately rated and don't clip them. By appropriate I mean 1.5x to 2x the RMS rating of a cab with good quality drivers. ------------- My laser stuff: http://www.facebook.com/SubsonicSystems" rel="nofollow - Frikkin Lasers |
Posted By: Rotorbar
Date Posted: 10 December 2009 at 10:59pm
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I'd say lets give it up. There was no insult intended to all of you who have gained your experience the hard way. My education was certainly expensive enough. I'm getting older, and I find that teaching the younger folks is more important to me than showing off what I know (or more usually, don't know). I just wanted to try to find a way to pass it on to the next generation. Mr. Jasonstry, there was no perceived attack or insult. |
Posted By: S DeXter
Date Posted: 10 December 2009 at 11:07pm
?? Read my last post. It is a method many use based on technical fact not trial and error. When manufacturers specify "Amplifier power requirements" it is nearly always 2x RMS for the above reasoning. ------------- Enjoy your self...... It's later than you think....... |
Posted By: Rotorbar
Date Posted: 10 December 2009 at 11:12pm
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Mr. SDX I think our posts got crossed. I have no argument with your statements. |
Posted By: Jasonstry
Date Posted: 10 December 2009 at 11:17pm
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Mr Rotorbar, should you ever have the misfortune to have a gig in my area I will happily buy you a beer. We all learn from each other and beer normally smooths the way.....
Andy
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Posted By: sKs01
Date Posted: 13 December 2009 at 10:34am
I always thaught that power comression would becme horrendous after the coil is no longer nominaly in the magnetic gap. Running past the xmax of a driver may give you a greater psycho acoustic effect but the actual increase in db is bugger all and the life expectancy of the driver would be greatly reduced. or am i being retarded? ------------- You're a big man, but you're in bad shape. With me it's a full time job. Now behave yourself. |
Posted By: pfly
Date Posted: 13 December 2009 at 12:47pm
| sKs01 I'm with you in this one |
Posted By: darkmatter
Date Posted: 14 December 2009 at 2:18pm
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Threads like this are interesting imo, they expose common misunderstandings about what should seemingly be a simple question. This question might have a simple response if everyone was using brickwall look-ahead limiters, transducers with a flat impedance, sealed boxes and sine waves as source signal - but they're not.
Irrespective of frequency, or duration of excess? What about claims that horn loaded speakers with a small back chamber can handle significantly more instantaneous in band power than rated?
Yeah - with your limiters, which have a certain response time before reacting to a signal over the threshold. With your amps, which may respond to clipping in a pleasant, driver friendly way. How do the clip lights on your amps register - average or peak hold? In reality, instaneous peaks going into your drivers may have been well over the stated watts. Yet the speakers remained intact - suggesting it's not quite as simple as "A speaker will break if you exceed its stated watts". Very few speakers give a max. power indication, as it wouldn't be particularly relevant.
If you've never had any problem, maybe you could have got away with slightly more volume all these years? Not saying this is wise, just that I wouldn't dismiss it as a bizarre thread.
I believe this depends on whether the driver has an underhung or overhung coil, not sure on this though. |
Posted By: jonminns
Date Posted: 14 December 2009 at 3:08pm
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I'm talking about clubs with multiple rooms that i've installed/set up where there can happily be 100 drive units over 4 rooms. It's really simple boys and girls! You set sound systems up with what listens to them, the EARS! ------------- 4 ohms is for wimps |
Posted By: cilla.scope
Date Posted: 14 December 2009 at 5:00pm
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well, I admit in a newbie to this game, so enlighten me, given an amplifier with sufficient headroom and a speaker that reaches its thermal limit before it gets to x-max or starts to sound ragged .. how exactly do you set that up by ear? Admittedly with low quality drivers in relatively large volume cabinets that begin to rag and compress long before they reach their thermal overload, if you set them to a level where they start to sound on edge, you'll be below the thermal limit ... but on a system with high quality drivers in perhaps low volume cabinets, where the thermal limit is reached before they start to sound ragged ... then what? Ears are useful, and indeed, it has to sound right to the ears ... but they are only part of the story. Getting the best out of a system needs more than just ears, it needs an appreciartion of the powerhandling capabilty and the actual power being delivered to each element of the system ... only with that information can you hope to deliver a system where no individual element is over stressed, and all elements are being driven to a useful level. If something sounds wrong, then yes, your ears are telling you that something needs changing .. .but ... its quite possible that something could sound fine and be only part driven, or overdriven ... Insisting you ONLY need ears is like a ships captain suggesting he only needs a compass. A good captian will use every source of information available to him ... personally I beleive in getting as much information as possible, from as many sources as possible and takign a wider view. YMMV. ------------- My girlfriend thinks I'm a stalker. Well, she's not exactly my girlfriend yet ... |
Posted By: norty303
Date Posted: 14 December 2009 at 5:17pm
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There are very many blown drivers from systems set up with ears to prove that ears are not a good way of deciding whether you're overpowering the drivers. Reflex boxes perhaps, but horns and bandpass cabs are very effective at filtering the nasty noises out, so you don't know you're near the limit until it all goes quiet... just ask all those people with blown Lab12's whether they thought it sounded rough just beforehand, or if it was smoothe as a baby's bum, same for X1's, 1850 horns etc, etc ------------- My laser stuff: http://www.facebook.com/SubsonicSystems" rel="nofollow - Frikkin Lasers |
Posted By: 4D
Date Posted: 14 December 2009 at 5:35pm
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The science is in matching the equipment correctly. After that setting the limiters to match spec' can be done using simple math's... Heres a snippet on the subject from www.funktion-one.com Crossover points The crossover points are an integral part of our system design and the time alignment figures are a manifestation of the relative physical location of the devices. Great care and attention has been taken in arriving at these settings with regard to alignment, phase, location and the physical parameters of the drivers and waveguides themselves. Where a delay between an enclosure and a separate Bass speaker is quoted, the figure is stated assuming that the fronts of the enclosures are aligned. System EQ? What system EQ? There are no fixed inherent EQ settings for any of the drivers as these would degrade available headroom and phase coherence. We do not believe at all in fixing the loudspeakers' response electronically; we prefer to take the time to get the speaker design right as this is in keeping with our purist approach. Frequency Band Drive Levels Relative drive levels are dependent on the amplifier's through gain. For example: If a Resolution 2 is driven by two amplifiers (one for the 15'' Bass and one for Mid-High) with the same through gain then, as you will see from the settings page, the Bass will need to be run at +8 dB relative to the Mid-Highs. In the real world however the two amplifiers may not have the same gain. For example if an amplifier with a gain of 38dB is used for Bass and another with a gain of 36dB is used for Mid-High then the Bass will need to be run at +6 dB relative to the Mid-Highs to maintain the correct ratio. Limiters Limiter settings, on the other hand, are dependent on through gain, sensitivity and the loudspeaker's power handling ability. The most important thing is that the amplifier should never be allowed to run into continuous clip. Clipping squares off the output waveform of the amp, sending distortion in the form of harmonics through to the voice coil, this creates heat which if it continues will burn out the voice coil. Effectively a small amp in clip is more likely to damage a speaker than a large amp running cleanly. To avoid this, the limiters should be set at least 1 dB below the amplifier's input sensitivity. Of course setting limiters in this way does not make allowance for the fact that the amplifiers' power capability may exceed that which the speaker can handle. A suitable starting point would be to set the Bass limiters in the above way with each successive higher band being reduced by a further 2dB (assuming equal input sensitivities and gains). Therefore on a Resolution 5 four-way system, the HF limiters would end up being set at least 6dB safer than the Bass; (of course input sensitivity and gain have to be taken into account). The other factor at play here is how many drivers are connected to each amplifier channel. The lower the impedance of the load the earlier the amplifier will clip and therefore limiters should be set for the maximum number of drivers that will be driven per channel (the lowest impedance). REMEMBER: The primary purpose of crossover band limiting is to protect the system from overdriving, sudden and unexpected high level signals and occasional larger than normal transients. It is not really intended to be used instead of compressors and therefore limit lights should not be flashing or on all the time. If a system is limiting heavily, audio quality and drive units will suffer. However, if set up carefully they can be used to ensure the system stays in its comfort zone, the frequency spectrum remains reasonably balanced and the maximum system level is controlled for aesthetic or environmental reasons. Balanced sound ''On The Limit'' Here are a couple of normal scenarios. 1. You've got your mix set up and ''in the pocket'' then the singer gets a bit excited and shouts ''Hello (insert your town here)! Are we all having a good time??!'' His vocal compressor is set at a low ratio (or there isn't one) and you're not quick enough on the fader to catch the sudden burst of level. Happily your system limiters are set a couple of dB before the clip point of the amps in accordance with the power handling of the drivers and the amps don't clip. 2. A sudden burst of feedback from a vocal mic too near a side fill and the same thing happens. 3. An inexperienced guest engineer loses control of the mix and ends up running too loud, the limiters start flashing and we ask him to back off a bit, he's surprised that it actually starts to sound louder when the masters are pulled down a little and the limiters stop pumping (how many times have I seen this). In all these cases the limiters are set for system safety and nothing gets broken, all good but what does the system actually sound like and how loud is it when the limiters come into play? Mid and HF horns are usually more efficient than low mid and bass drivers. Of course they handle less power but you can often get a situation where if everything is just set for safety the system is capable of being driven into a state of imbalance where it sounds bad and can even be way too loud for the venue and the safety of the people in it. Bass speakers these days can handle a massive amount of power (as long as it's clean) so large amps are used and limiters set to stop clip from occurring. Mid and high limiters are set progressively tighter in respect to the drivers lesser power handling. It's still a good idea to use a large amp though. Transient spikes, totally valid to the music like the hit of the snare or cymbal crashes can get past the limiters and this is good because the dynamics and excitement of the music are preserved and these transients are not long enough to overpower the driver as long as they're not clipping. So what happens as the system comes up to full power. Often the bass will limit first, then as the system is driven harder the low mid starts to limit, the hi mids are still going strong as are the highs. If the bass limits 4 dB before the mid highs this is effectively the same as turning up the mid highs by 4dB, the balance of the system is completely wrong and all the hard work of tuning and sound check is wasted. The thing to do here is to tighten the limiters still further so that the mids and highs start to limit at around the same point as the bass. This way the frequency content of the music will be maintained when in the limiters, the mids stay at a level where they still relate to the low end. The settings for this will be different for live and club systems, you will want to leave a bit more headroom for the dynamics of live music. In a night club there may be noise restrictions or the owner may have an idea of how loud he wants the system to go. The principle is the same. In both cases run the system up to the required maximum level, reduce the limiters so that the limit lights are flashing then open up a dB or so to account for when the room is warm and full of people, come back later when the venue is running and fine tune if needed. Above all, lock the system to safeguard against tampering! Your system is now not only safe against damage, its also safe against being driven out of balance and sounding really bad. Digital Crossovers Another point is that digital crossovers need to be driven at the correct level to ensure maximum use of the resolution available because at low input drive levels fewer bits are used. Signal should be clearly visible on the input meters with the -6dB light flashing to get the best from the converters. Because Funktion One equipment is so intrinsically efficient (high conversion of amplifier energy into acoustic energy) we often need to reduce amplifier gain to achieve this. Signal to noise ratio will also be improved. A suitable amplifier input sensitivity to achieve this would be +10 dBu. If amplifier gain is reduced then limiters will need to be adjusted accordingly. Many amplifiers have rear-panel or internal DIP switches to enable user-selection of input sensitivity which mean that this objective can be met whilst leaving the front panel gain control safely on maximum. A gain of 32dB is a good starting point, if you need to go for less then switch to 26dB. *Warning* If the amp front panel controls are used to reduce gain and the limiters are reset to suit then great care must be taken not to turn the front panel gain control up again without re-adjusting the limiters. Crew or other operators must be made aware of this. In a 'dry-hire' environment it is probably not advisable to send a system out like this without locking the amplifier level controls to avoid unauthorised adjustment. If this isn't possible, then the sonic advantages may have to be forgone. ------------- DMZ. "The bass was intense. Girls were literally running up to stand next to the subs" |
Posted By: thepersonunknown
Date Posted: 17 December 2009 at 10:32pm
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i find that last point about running the inputs of DSPs nice and hot very interesting. their was a thread on here a while ago and it was the first time id heard of it. iv never noticed it in any real world experience (although ive never realy tested for it), and am sort of dubious as to how much effect it actualy has, but none the less it looks like a fairly bullet proof theiory (even to a digital moron like myself) ------------- They keep telling me life is short, but its the longest thing ive ever done!!! |
Posted By: nomis
Date Posted: 18 December 2009 at 8:55am
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i was told that amps should be on full,no matter what volume required,but i m sure having a good signal everywhere is better(especially into the cross).maybee its just to prevent people turning up the amps.all other logic points to having a healthy signal throughout the chain. like smithers said a while back,if youve got plenty of headroom on the amps, and dont need the system working hard,and they are on full,the lights on a 2496 are barely flickering. |
Posted By: minaximal
Date Posted: 18 December 2009 at 12:51pm
thats because the front panel knobs on amps are just attenuation controllers, NOT gain knobs, so the amp is effectively working just as hard to amplify, whether the output signal is attenuated or not, and the risk of some cokcend turning up the attenuators and overpowering your limiter settings endangers the drivers. ------------- Subs + Barges = :) http://www.metaacoustics.com" rel="nofollow - www.metaacoustics.com |
Posted By: nomis
Date Posted: 18 December 2009 at 1:47pm
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i see.it just doesnt feel right to amplify a weak signal,but i can understand the practical advantages. i m using a slave amp on mids anyway,which has no attenuation controllers at all! |
Posted By: Jasonstry
Date Posted: 18 December 2009 at 8:29pm
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nomis, You are correct. It isn't right to amplify a weak signal as you are likely to be amplifying noise from the system as well. In a perfect world you will set up a proper gain structure. If you Google gain structure you should get some better explanations but, in short, the theory is that the output stage of every component in your system should be on the edge of clipping (providing that it isn't sending the input stage of the next component in the chain into clipping). When you get to the amplifier, turn up the "gain" until it is just gong into clipping and that is absolutely the maximum clean signal you will get from your system. The "gain" knobs on the amplifier are best thought of as controlling sensitivity, as in how powerful the input signal has to be to get the maximum output from your amp. All this assumes, of course, that your speakers can handle the output from your amps. Working with an active crossover, if you find that your subs are louder than your high/mids (or the other way around) then you turn the band that is too loud down rather than turning up the band that is too quiet.
Yes it is true that you will get idiots who will turn the amps up and that is an occupational hazard but, in fairness, they will push any fader to max and turn any control clockwise in pursuit of the goal of making people's ears bleed. Yes you have to protect your system against that but it doesn't follow that you have to do it by running your amps on full bore and wrecking your gain structure.
http://www.prosoundweb.com/article/gain_structure_basics/ - http://www.prosoundweb.com/article/gain_structure_basics/
http://www.prosoundweb.com/article/how_do_you_set_system_gain_structure/ - http://www.prosoundweb.com/article/how_do_you_set_system_gain_structure/
Hope that helps
Andy
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Posted By: nomis
Date Posted: 18 December 2009 at 10:46pm
| thanks,good reading |
Posted By: Jasonstry
Date Posted: 19 December 2009 at 3:32pm
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Another good one.
http://www.rane.com/note135.html - http://www.rane.com/note135.html
I haven't done dry hires for parties (disco's in my day) for years but, when I did, I had a lead made with a resistor so that the signal was not clipping even when into the red at the mixer. With a brickwall limiter next in the chain, a properly set up gain structure and racks with lockable and ventilated plates on the front (amps had soft start protection) it was close to foolproof.
When it came to systems I ran myself, I was taught about gain structure years ago and have never blown a driver - well just one but that is another story... The key to me is rig for the gig. If you are driving your amps and speakers close to flat out just to eke out the last dB or 2, then you don't have enough rig for the gig and have to compromise.
Again, HTH.
Andy
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Posted By: thepersonunknown
Date Posted: 20 December 2009 at 8:07pm
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tell us more about that resistior lead please andy. how did it work, was it like a standard pad or did it come into efect at a set threshhold (sorry this might be a bit basic but im no electronics tech). any undesirable effect on the signal? i imagine its good for stopping ur desk preamps from clipping, but i gues the distorsion/dirtyness from the cliping dj/"I like to play with myself" mixer output remains inevitable.
+ 1 for knowing the limits of ur rig. i have also never unintentionaly blown a speaker, although i did blow a fuse in one of the output stages of the first ´pro`amp i ever owned. nice cheap lesson that was. ------------- They keep telling me life is short, but its the longest thing ive ever done!!! |
Posted By: thepersonunknown
Date Posted: 20 December 2009 at 8:09pm
 nice filter norty
------------- They keep telling me life is short, but its the longest thing ive ever done!!! |
Posted By: Jasonstry
Date Posted: 21 December 2009 at 12:25pm
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I am no great expert on the technical side either. When I first started out we were lucky enough to link up witha couple of guys who knew a lot more than we did (which wasnt hard) and had a lot more gear than us. It was a case of us lending them our PA for bigger venues and them lending us bits and pieces when needed. I learnt a lot from them but it was set up and use rather than resistors and capacitors. They used to subhire us mixers that they had installed a pad in before the output stage so that the output wasnt clippling when driven into the red. They also made up the leads for us to use when using other people's mixers. When the pad is in a lead it obviously doesn't stop the output stage of the mixer from clipping but it does stop that from sending everything else in the signal path into clipping. I really don't know what was in it. As I recall, it didn't alter the sound but it was a long time ago (nearly 30 years) and gear has moved on quality wise since then.
Cheers.
Andy
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Posted By: thepersonunknown
Date Posted: 22 December 2009 at 5:57pm
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quote: it was a long time ago (nearly 30 years) and gear has moved on quality wise since then. very true, although interestingly (and slightly of topic), the first half decent set up i owned only 5 or 6 years ago (half decent is of course very relative), used jands j600s amps to run the mids and highs. not sure if many people will be familiar with this australian built amp, but it was designed in the 70s, and very rough and ready. it did a better all round job than anything else i checked out in that price range, including many many newer bits of kit. although i must add, i usualy dont take much notice of the weight or size of my racks when evaluating their usefullness. (the joys of near healthy youth i imagine) ------------- They keep telling me life is short, but its the longest thing ive ever done!!! |
Posted By: Jasonstry
Date Posted: 22 December 2009 at 6:31pm
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Is this the same Jands who do lighting? Cheers.
Andy
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Posted By: thepersonunknown
Date Posted: 22 December 2009 at 10:04pm
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dems the ones. they used to manufacture audio equipment as well, which in australia is great budget kit, although theise days they only make lighting kit (including varilite), snakes, rack bits and power distros/cables. i was lucky enough to work for their hire company (JPS) in 04-05. i learned more their about real world teching than all the other studdy/experience ive had combined. ------------- They keep telling me life is short, but its the longest thing ive ever done!!! |
Posted By: FUBARD303
Date Posted: 24 December 2009 at 10:30pm
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Begin 2 bit monologue: Being a newb who likes to play it on the safe side, after learning judgement at my 1st gig, I use a brick wall limiter at 0db and keep my double rated amps at two clicks below clipping. (pisses off everyone when the bass drops out) Perhaps an RMS limiter should go first. (next investment?) It's worked now on my little JBL system for three years of just a lil less than weekly play, some of which being all night long (just don't tell). I might be cutting myself short but I learned the hard way A) what that horrible smell is and, B) DJs cant be trusted and must be babysat. But the point here is; I agree. I know for a fact that analysts of things that are life and death (or just big $$$) take into account ALL SOURCES of info no mater how obscure they may seem at the time, compile them and draw conclusions based on concurrences. (conspiracy theorists too, LOL) I too believe that aside from listening for speaker pain (which I'm not experienced enough to hear yet), there are some good number crunchings to be done. What they are beats the hell outta me though. Edit = spelling and symantix ------------- "Always look on the bright side of life" -Brian |
Posted By: Steevo
Date Posted: 28 December 2009 at 12:02pm
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Been wondering the same recently....I don't do a great deal of gigs, and they are often in different venues with differing amounts of kit (partly due to buying new kit as slowly building up my rig). I wondered if it was possible to either:
a) put a resettable fuse (or something) in the speakers or amp that will trip if you draw too much load. (in same way your house consumer unit works) b) run your amps through a power meter (like http://www.biomelifestyle.com/browse/living/living-room-accessories/ecosaver-powermeter/#utm_source=googlebase&utm_medium=shopping&utm_campaign=googlebase - this ) and determine when the power reaches the RMS of your speakers
c) put a clamp meter on one of the signal wires going to your speaker to measure the power going to it.
My initial thoughts are that they won't work purely because if they did, someone would already be using them. Would find it really handy to be able to know if i'm pushing my smallish rig too far, or if i've got enough power to do larger venues but I just don't know it as I'm too cautious.
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Posted By: jacethebase
Date Posted: 28 December 2009 at 1:18pm
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I like around 40% headroom on the racks to the stacks would rather blow a driver than a amp anyday!
------------- www.wedding-production.co.uk www.stage2sound.com |
Posted By: Steevo
Date Posted: 28 December 2009 at 1:28pm
Is that saying that you'd only run max 600W rms per side (4Ohm for example) using an amp that puts out 1000W rmx at 4Ohm?
I always thought that clip limiters were designed to stop you damaging your amp if you drive higher powered speakers with a low powered amp. |
Posted By: jacethebase
Date Posted: 28 December 2009 at 4:19pm
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You got it chap ;)
You never want your amp hitting clip levels!!!!!! Maybe free party boys work this way but if you go to a event being run by a pro audio company you will find amps sitting around -6db ish. ------------- www.wedding-production.co.uk www.stage2sound.com |
Posted By: Steevo
Date Posted: 28 December 2009 at 4:25pm
Is it standard practice to have that much headroom on an amp that has clip limiters enabled?
Was considering running some 4ohm 500w RMS Peavey subs using a Numark Dimension 4 amp which puts out "660W RMS @ 4 Ohms, 1KHz, 1% THD per channel (stereo)" - is this a stupid thing to do? |
Posted By: jacethebase
Date Posted: 28 December 2009 at 4:31pm
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Yeh for instance if i phoned up one of the companys i get a gear from and asked for 20k of funktion on site i would get 20k of stacks and around 30k of racks turn up.
No thats not stupid its the right thing to do! A cool amp is a happy amp! Also always bare in mind when your quoting what k your system is, your system is only as powerfull as the amps pushing the power in to the speaker units. ------------- www.wedding-production.co.uk www.stage2sound.com |
Posted By: Steevo
Date Posted: 28 December 2009 at 4:50pm
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Now I feel even more confused.....
Earlier you were saying you would only run max 600w from an amp that had a 1000w capacity. (i.e. only using 60% of amps power.
My example of my Peavey subs, uses 75% of the amp's power - should I be aiming to use an amp with even more headroom? i.e. 850w amp (which would thus put me at 58% utilisation). As for quoting the power of the setup - I always work it out based on the RMS total of my speakers, and ignore what the amps are putting out. I've always been taught to have a bigger amp than speakers so counting my speakers RMS gives me the max I could put out. Only trouble (hence my interest in this thread) is that I'm unsure how far up I can turn the amp. I've never pushed it too far for fear of doing damage, thus I don't know what "too much" sounds like if that makes sense.
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Posted By: jacethebase
Date Posted: 28 December 2009 at 5:10pm
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You will chap trust your ears! ------------- www.wedding-production.co.uk www.stage2sound.com |
Posted By: Jasonstry
Date Posted: 29 December 2009 at 10:34am
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Steveo, most drivers or speaker cabs will have 3 power ratings. RMS, constant and peak. In general, the RMS value is the power the driver will take as a continuous sine wave in the middle of its range. Drivers hate sine waves but normal music is not a sine wave so the driver can handle more watts on average when asked to reproduce music. This is the constant rating of the driver or box. Even then, the driver can handle even higher power levels provided it is not asked to for any great length of time, think the initial impact of a kick drum. A typical arrangement would be for a driver to have an RMS handling capacity of 'x' Watts, a constant handling capaicty of 2x watts and a peak handling capacity of 4x Watts. So if you have a cab with a handling capacity of say 500W RMS, it will have a constant handling capacity of 1000W and a peak handling capacity of 2000W.
So it is quite in order to have a 1000W RMS amplifier driving a 500W RMS cab although you really need to check the specs on your cabs before you try it.
There are things that can affect the handling capacity of the speakers. Modern music tends to be quite compressed to start with and this tends to increase the average level asking more of the speakers, especially if it includes distorted sounds or electronic music which often consists of sine waves. Clipping anywhere in the system adds distortion making the system sound nasty but also increases the average level again, making the drivers work still harder, as well as adding high frequency subharmonics that can blow tweeters. However the biggest offence is driving your amplifier into clipping as, if you do, it will effectively deliver a square wave signal at about twice its rated output, which can kill drivers very quickly.
You have 3 priorities then. Your amplifiers must not be allowed to deliver more power than your drivers can handle, your amplifiers should NEVER be allowed to clip more than the very occasional flicker of the warning led and you should not allow clipping anywhere in your system. There are some links earlier in this thread about setting up a proper gain structure and other posts about setting limiters. One thing to remember is that the "gain" control on your amplifier does not control how many Watts it delivers, it controls how powerful the input signal has to be in order for the amplifer to deliver its maximum output.
Hope that helps.
Andy
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Posted By: Dislexic
Date Posted: 29 December 2009 at 1:45pm
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I only run with aproximatly anywhere typically 50% headroom on my amps....
Say for example I have a 1k box, I will run with min of 1200w amp, shove pink through the box and wait for the amp to clip, then set a compressor or the DSP limiter to cick in just before the amp say 1.5-3bd lower so the amp never clips... then I'm happy to run all night long. I know I will be driving the system with more than the speakers rated power, however (didnt read all the posts ;)) Headroom is their to absorb the peaks without compromising the clarity of your system and most any decent driver will happily absorb thumps n pop's and loud DJ's randomly throughout the evening. 1000W continuose RMS of pumping bass is not going to kill an 800w speaker as it will never see 1000w unless you clip all night long and basically throw flat lines at it(typicaly from an under powered amp or distorted program material). I always think back to the AC/DC heating effect of resistors when looking at components like speakers, it takes a lot less voltage cliped to blow a driver than some people realise, hence why an oversized amp is 99% of the time better :) you always have to take the program material into consideration. a voice coil will heat up when overworked, no doubt their, however what you have to remember is that those big "none compressed or limited" spikes normaly wont do any damage, the heating effect on the driver is tiny since its only over a brief moment in time this off course is untill you have this happening continually over an excesive period of time. The main factor is not allowing the driver to heat up so much that it distorts outof shape or expands past its airgap.
Right gear right job = no problems (except when somthing breaks lol)
Most of my work is live bands, and I will happy do anything from a 4-10 hour show with amps twice the size of my cabs with no limiters or distortion.... ohh and I have only had 1 driver fail on me in 17 years and that was not blow just fatigue of the suspension due to age :)
I think what we really have to remember with volume is the continuouse and peak SPL, start measuring that and you will know how far you can turn it up, thats after you have the right kit for the job ;-)
My 2p today off to get my hard hat....
------------- How do yo spell that? |
Posted By: Jasonstry
Date Posted: 29 December 2009 at 4:40pm
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Dislexic, you and I seem to do similar things (live bands) and I agree with almost everything you say. The difference is that I ALWAYS use a brickwall limiter at -1 dB on all outputs from the (digital) desk I use. Like you, I have only lost one driver but in my case it was because a "helper" dropped a live mic during set up..... So, after that, the limiter has always been on-line.
For me, once the desk is sorted, it is a matter of correcting the gain structure to take account of eq changes for the venue and then setting the amplifiers so that either 1) I have the desired SPLs in the desired areas or 2) one or more is clipping. As soon as I have an amplifier even remotely clipping then that is the maximum SPL of the system established. If that is not enough then I haven't brought enough rig for the gig.
Andy
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Posted By: Dislexic
Date Posted: 30 December 2009 at 10:07am
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Great minds ehh ;) and I will do the or foools bit b4 anyone else does ;P I use LS9 & TT24, still got a couple of older SC's but they gathering dust now >;) I never liked bricks because if they are set below the amps clip then some muppet will no doubt turn the rig up till it redlines all the time sounds crap & loud because of it and then pop pop pop by the end of the night or scratch scratch when your out next, but thats just my pref :) I do agree with other coments that you CAN hear when your rig is maxing out as the sound does change, the trick is to recognise it but being honest I never normaly get that far these days... I must be getting old :(Dont think anyone mentioned the "midband" most limiters actualy use either hence why I'm never overly worried if me or those I trust are out with the gear. Also to put a cat into the woods.... what about volume vs clarity.... if your rig sounds sweet next to another rig thats identical but sounds crap.... in 9 of of 10 cases which rig will sound loudest.....
One of my grudgest against (no offence to anyone intended ok!) people who have badly setup rigs. their rig sounds louder because its distorted in variouse places making it less tolerent to listen to and theirfor perseved to be louder, when infact it just sounds crap lol
------------- How do yo spell that? |