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What kills speakers? What kills amps? |
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bin juice24 
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Joined: 07 February 2020 Location: Here Status: Offline Points: 209 |
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 Topic: What kills speakers? What kills amps?Posted: 12 August 2020 at 11:47pm |
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Thought this would be useful for anyone starting out like myself.
If those generous enough, could explain the common causes, (and how to avoid?) that’d be ace and massively beneficial. Hope this question isn’t too lazy.
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markie
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Joined: 31 October 2005 Location: Sunny Liskeard. Status: Offline Points: 4570 |
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Posted: 13 August 2020 at 12:12am |
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Probably the most common cause of killing speakers is overdriving amps. If you have a decent quality amp (say 1000 watts), it's usually fine to drive a 500 watt speaker at full power (500w), or even a bit more.
Ifyou have a cheap amp that's rated at say 200 watts and you drive it at full power or even into clip that is actually more likely to kill the speaker. Even though you're only putting say 300 watts into a 500 watt speaker it's not clean power. As soon as the amp goes into clip the signal goes "square wave", which generates excess heat. In turn this excess heat makes the voice coil expand.... it starts to foul in the gap and the next thing you know the speaker is blown. Keep the amp power clean and avoid clipping. I probably didn't explain that very well but doubtless an adult will be along soon and explain it better.
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If it's got wheels or tits it's gonna cost a fortune
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Conanski
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Joined: 26 January 2006 Location: Ottawa, Canada Status: Offline Points: 2545 |
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Posted: 13 August 2020 at 1:37am |
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Oh for the love of gasoline and horsepower.... oops.. wrong forum LOL.
What kills speakers... overpowering. What kills amplifiers... idiot operators.
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Conanski
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Posted: 13 August 2020 at 2:55am |
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Was that last answer too lazy?
Ok here is one with a bit more effort. There are all kinds of ways to blow speakers, too big an amp, too small an amp, drop a mic, a feedback squeal, disconnect a piece of equipment in the signal chain while the amp is still on, a power bump that reset the LMS but nothing else, playing D&B... lol. OK maybe not just because it's D&B but playing anything with low crest factor(not much dynamics) for hours on end could overheat and blow drivers. Drivers are pretty resilient devices but they have limits and there are two main ways they can be broken, too much power for too long which blows the voice coil, or a big power spike that physically damages the voice coil, the driver suspension or cone. Cone failure are more common with horn loaded speakers due to the high pressures the cone experiences. A voice coils power limits are usually specified at least a couple ways, the long term average(usually hours) power rating sometimes referred to as RMS or AES these days, and the short term peak(often miliseconds) power handling. A voice coil depends upon the movement of the cone to force air over it for cooling, so program material that has low dynamics is usually harder on drivers. Power amp are designed to a spec, x watts into Y load at Z distortion. They can often produce a bit more power than rated if you don't mind higher levels of distortion but pushing the limits is where operators often get into trouble. An audio amplifier is really a voltage multiplier, it takes the 0.5-2v output of a preamp/mixer and boosts it up to 50v, 100v, or 150v depending on the model. The amount of power developed is really a side effect and it totally depends on the impedance of the connected speakers. The power supply inside an amp is what determines how much current it can supply, and power delivered is a mathematical function of voltage and current into the speaker load. Cheaper amps typically have smaller less capable power supplies while more expensive amps are better designed. Every amp will have a rated minimum load impedance that is determined by the above factors. If the operator ignores this and tries to make an amp rated for 4ohms min drive 4 8ohm boxes wired in parallel(a 2 ohm load) it's not going to be happy. If the amp has sufficient protection it will shut down when it gets hot which will be very quickly, if not the magic smoke gets let out. That's one way to kill and amp, another is to just keep pushing it harder and hard ignoring the clipping indicators, some amps can tolerate this abuse, some with built-in dsp may be able to survive this indefinitely but a more basic amp will give up sooner or later. Another way to kill an amp is to connect 2 or more to the same speakers(shorts the outputs together), or one of my favorites is daisy chaining amps... when the speaker outputs of one are fed to the inputs of another. Of course the genius operator thinks this will make more sound but it's just going to blow up one or both amps.
Edited by Conanski - 13 August 2020 at 3:15am |
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Chris Grimshaw
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Posted: 13 August 2020 at 8:12am |
A common myth. Clipping, in an of itself, doesn't kill speakers. Guitar speakers are often fed signals in excess of 100% THD for hours at a time - they don't die as soon as the first chord is struck. Clipping generates tiny amounts of HF harmonics, while putting a hard limit on the peak signal levels. What actually kills your speakers is not the chopping off of the occasional peak, but the increase in average power levels. Chris
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Quality sound from Sheffield
www.grimshawaudio.com |
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cravings
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Joined: 30 January 2007 Location: Ireland Status: Offline Points: 7442 |
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Posted: 13 August 2020 at 8:16am |
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for an absolute beginner... red lights mean stop.
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madboffin
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Posted: 14 August 2020 at 11:52am |
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As above, too much power kills speakers - either by overheating the voice coil or damaging the moving parts due to over-excursion.
It's very difficult to give a definitive maximum power rating for a speaker because the average (heating) power of music signals is very hard to predict. It depends on the genre of the music, the way the speaker is used, etc etc. And very much on the expertise of the users. Overdriving a lower powered amplifier can be problematic in a system with passive crossovers. The effect of overdriving is a combination of compression and clipping, which increases the average power to more than might be expected. The tweeters are only rated for a small proportion of the speaker's overall power handling spec, which is perfectly OK in normal use. But the combination of higher overall average power, plus a bit more HF due to harmonics, is more likely to break the tweeter than the LF driver. An example would be the old Martin CX2, popular in the 1980's in small club and bar installations, mobile disco's etc. Thrashing these badly with a heavily-clipping amplifer that was rated (undistorted) for a bit less than the speaker's maximum power rating would burn out the 25 Watt resistors in the crossover pad but do no damage to either the LF or HF voice coils. I had the resistors uprated to 50W. After that, the HF voice coil would burn out instead, but after labour costs were accounted for it was cheaper and easier (from the end user's point of view) to replace the HF diaphragm than to have somebody take the crossover to bits and repair it. Of course, the users would still complain that their amplifier shouldn't have been powerful enough to break the speaker! Thrashing the speakers with a much higher powered amplifier would of course blow up the LF voice coil first, as one would expect. Edited by madboffin - 14 August 2020 at 11:56am |
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4D
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Posted: 15 August 2020 at 9:19am |
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I have met the enemy. It was me...
In my experience the biggest killer of loudspeakers is gravity magnets shifting after mishandling.
Amplifiers: poor power supply, soft start goes pop, compromised airflow, coats & bags stuffed behind the rack or build up of dust & fluff. mechanical failures from excessive vibration, boards & ribbon cables shaking loose, components falling off boards, More rarely component failure. Nearly all things that can be managed with awareness, a service schedule & a commitment to caring for one's equipment. |
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DMZ. "The bass was intense. Girls were literally running up to stand next to the subs"
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Boxes-R-Blue
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Posted: 19 August 2020 at 11:33pm |
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Crappy Mains....
Just as an Example, QSC built an Amp called the PL 9.0, great amp worked well, on tour... Smaller gigs that don't have 120mm camlok feeding the PA they seemed to blow up a lot.. get a solid mains feed (over 1000A PSC) to your rig and you can push hard and long with no issue. A crappy little Genset or a too skinny mains feeder and you will take apart the best amps in no time. Whilst old school copper iron amps are a bit more tolerant they still loose definition and detail on poor power systems, newer SMPSU amps HATE crap mains you can't drive 2.66r loads off an amp delivering near to mains voltage on the outputs off 50M of 2.5mm2, your supply impendance is near that of the bloody load! Add to that current distortion, harmonics and power factor drift that all shoot through the roof when the mains is too "soft" you can't be surprised when the PSU gives up the ghost... Also if you must run 2r, don't daisy chain boxes, build a patch panel and use a "star" topology, 4 2.5 cables, one to each 8r driver is better than one 4mm daisy chained, use your kit in best possible scenario... |
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Kinda Been there, Kinda done that, YOU COULDN'T handle my bar bill!
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RobinMatrix
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Joined: 23 August 2013 Location: Kidderminster Status: Offline Points: 567 |
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Posted: 20 August 2020 at 1:01am |
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Over the years, I have seen far more speakers killed by too small amps than by too big. Take a typical 500W AES 8 Ohm driver ... it will be rated as follows: 500W AES (continuous) 1000W Programme/Music 2000W Peak A good choice of amp is one that will deliver 1000W into 8 Ohms, per channel. That is the "programme" (ie music) rating of the speaker ... so that amp will be 2000W into 4 Ohms ... and with 2 channels in the amp, most people would call that a "4kw amplifier" They should run nicely on that amp ... no need to push it flat out, nice peaks just touching the clippers. What some people do is go "500W speakers? I'll get a 1000W amp" ... but, as you can see from above, that is really only 1/4 of the required size ... then the rig isn't as loud as they had hoped so they push everything into the red, and that's when it all goes wrong. Edited by RobinMatrix - 20 August 2020 at 1:02am |
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Matrix Pro Audio ::http://matrixproaudio.com/"
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John C
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Posted: 07 September 2020 at 12:34pm |
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As a newbie this is very interesting, thanks for your advice everyone
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JonB67
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Posted: 07 September 2020 at 7:55pm |
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What kills speakers? Most of the time not turning up with enough rig for the gig!
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markie wrote: