I discovered this revelation whilst talking to the owner of my local Disco shop yesterday and it confused myself and my brother that was with me!

One of my speakers blew at an open day I did due to a loud woman shouting down the Mic (lesson learnt) so I took it in and got him to change the driver.

I told him that on my newer amp (which is pretty powerful) I normally run it at half volume to make sure they dont blow again and he said that what I am doing could damage the speakers as much as overpowering them.

He said unless I turn the amp volume to full and the Mixer volume down then I may be coming back more with blown speakers...

Can anyone else give their opinion on this?

It's the same as If you overpower a small amp, the speakers get a bad distorted signal and bloow. I thinks

i was told that if you think of the amp volume as a gate.

So if the gate is only half open but your mixer is pushing alot of sound through(mixer volume up high) your amp will not be able to let all the sound pass but your mixer is pushing more and more sound trough the gate. so it comes through your amp to your speakers in drips and drabs.

open the gate fully and it will pass through nice and easy. so your using you mixer to control all the sound and your amp will be alot happier aswell.

but remember to match the amp with the speakers you dont want to blow them because you have to much power being pushed through them.

hope this sort of explains it?

theres no right or wrong way to have your amp volume

however with the amp volume lower, your mixer volume will be higher. Many "Disco" mixers will distort when turned up too loud. A Distorted signal at any volume can and will cause damage to your speakers

So basically, by turning down your amp, your mixer is higher, so when someone shouts down the mic, the headway has already been used up, so the shouting is just distortion and damage is done!

My opinion is the disco shop man is talking total rubbish. The gains on amps are there for a reason and it so you can set up a proper gain structure. It doesn't matter if you have the gains full up or not, you can still blow a speaker depending on how strong the signal is that is input into the amp.

Amps are not "happier" with the gains full up. Applying the gate principle, the mixer acts as a gate in the same way. If you have the gains full up on the amp, you will have the gains on the mixer lower which will restrict the strength of the signal reaching the amp. The amp will also have less headroom.

There are loads of articles about gain structure on the internet. http://www.thenoizeworks.co.uk/tech2.html is one example.

You should only use an amp with an output greater than what the speakers can handle if you use a limiter/compressor. If you don't use one then you should not use an amp capable of producing more power than the speakers can handle.

Irrespective of whether the amp is more powerful than the speakers can handle, clipping will damage the speakers. A higher powered amp will just damage them quicker so whilst with a lower power amp, you would probably get away with mild clipping without any damage, with a higher powered amp you won't.

Yes thats correct, the amp should always be on full, this info was given to me last year at PRO DJ show at lancaster by a guy called CHRIS HINDS who is apparently a sound & speaker expert.

I have read several of Chris's articles and am very surprised that he would say such a thing.

I'm no expert on this sort of technical question! I've always been under the impression to turn the amp down before either plugging anything in, or switching on. With the gain settings at zero when you switch on, you're not risking amplifying any distortion or damaging your speakers.
I do the same with the Bose too.
After all thee years, have I been over cautious?!

Yu are correct that you should always turn the amp gains down to zero when switching them on. If the gains are not turned down, any "thump" or loud noise that happens could damage the speakers.

Most amps have a soft start that helps to prevent damage but if something in the chain wasn't set correctly, something went faulty or if you had an open mic plugged in that you didn't realise was next to a speaker for example, as soon as the amp powers up it could damage the speakers before you get a chance to hit the off button.

If the gain controls are set to zero, you would notice something wrong as you increased the gain before any damage happened.

The matter is largely irrelevant. It doesnt matter whether you turn the amp down and the mixer up, or the mixer down and the amp up. The results are the same! The controls on the front of the amp are attenuators..they cant actually limit what comes out of the amplifier..only a limiter will do that. The 'master' on your mixer and the 'gains' on the amp are all pretty much in the same signal chain and have the same effect. The only ramification of having the amp gains down is that you'll have to push the mixer harder to get the same volume and might possibly clip the output of the mixer before the amp reaches full power, which is certainly less dangerous than clipping the amplifier output and will sound obvious.

PS Ive just read what Tony B has said and i agree with all that as well!!!!

I always turn mine on with the gain down the turn it up to full and knock it back a couple of clicks .
Right or Wrong ?

My opinion?
The disco shop owner should perhaps get himself educated in such matters in order that he will stop giving hideously incorrect and ill-founded advice.

You can damage speakers by under-powering them, can you?
So unless I run my amps at full output all the time I may burn out my speakers...

It is as silly as it sounds, but still these obviously incorrect myths get repeated by those not in the know - I just wish they'd get on with selling stuff/playing music or whatever, rather than pretend to understand something they so obviously do not.

Sorry - rant over!

SO can somebody clarify this one way or the other?

Look at it this way if an amp is supposed to be run on full why bother with controls, a simple on off would be all that's required, however they are not built that way for a reason............

Never heard of this one, doesn't sound right though. When I sound check I set the levels on the amp to whatever sounds right for the venue. Then I set the channel level and the master level so they both illuminate the first Orange light. Everything on the mixer running at or near 0dB basically. Then at the beginning when I start I control the volume using the channel faders. As the night progresses I gently push the channel faders up until I've reached the level I set when sound checking. If that's not enough now the room's full I turn the amp up a bit.

Can I make myself look really silly here please.


I know the effect adjusting those three buttons underneath the gain control on my mixer has but don't know officially what they are called or what their function is.

Don't laugh please.....I do get by and I am 50.

guessing without looking they are the EQ !!! probably low, mid, high

as for the original question distortion does blow speakers !!!
yes you are more likely to run your mixer into distortion if your pushing it to much !!!
but not turning your amp full will not alone blow speakers

but in my opinion its easier to keep the amp up and control the soung from the mixer !

This argument has been done to death here, but I'd like to point out that this is not fact, it is Tony's opinion. The compressor will still allow the average power to rise, even though it will control the peaks.

Most pro audio manufacturers specify amps of between 1.5 and 2 times the RMS rating of their speaker cabs.

RMS rating is derived by a continuous signal being passed through the driver for a period of time with no mechanical damage occuring. This is normally due to the voice coil (VC) melting much like a heater element heats up. As music is dynamic, the VC cools between peaks. So long as the AVERAGE power is around the RMS rating you're ok (although mechanical damage from over excursion can result in badly designed cabs)

Aim for an amp of power somewhere between RMS and peak (2x RMS rating) and you'll be fine so long as you don't run it into clip/limit all the time. Obviously you need to make sure that any equipment prior to that in the chain (mixer, etc) isn't distorting as well, although this is primarily a killer of compression drivers/tweeters. I've run big 2" compression driver regularly with up to 4x the rated amp on them with no ill effect as the peaks on the top end are very short with relatively long periods of nothing between them. They also sound better with it due to the extra headroom a big amp affords.

If you are blowing stuff up regularly then you really need either more efficient speakers or simply more of them. Throwing more and more power at a speaker gains you relatively little extra, especially as power compression works on the law of diminishing returns (e.g. the hotter the VC gets, the more power input gets transferred to heat than it does to sound)

All my amps are at least one-and-a-quarter times the RMS handling of the respective speakers they power (my baby amp, for example, is rated at 390w per side running 250w Root Mean Squared tops). The input signal is correctly set to 0dB, the output on the mixer is 0dB and never red-lines, the amps never red line but frequently go close so it's a pretty certain bet that I'm "over-powering" my speakers.

No problems whatsoever, ever.

The controls on the front (or, sometimes, back) of amps aren't gains - they are attenuators.

Pretty much one and the same thing. What they aren't is outright volume/power controls.



I'd say its a pretty certain bet that you're NOT over powering your speakers unless you're running a really heavy compression on your signal or you're playing sine waves through them.


I believe that Soundforge (and some other audio analysis tools) can show average power for a given signal. Try loading up an MP3/wav into it and seeing how much lower than the peak signal the average power is. This'll give a good idea of how many percent over the RMS rating you can spec your amps.

Yeah, bad choice of language.

that's why I put "over-powering" in parenthesis!

I think that what he may bed saying is that by turning the amp down and the mixer up, you may cause clipping on the mixer, which can cause tweeters to blow. 'Better to turn the gain down on the mixer, and the amp up.

just never run anything in clip compression,signal input or final output stage.

simple.

What causes a speaker to blow is a square wave signal that is v promenant eg if the speaker is pushed and held in a certain position for long enough the coils act as a heating ellement and burn and arc so it is no longer a coil.

Paul

Its not my opinion. Its something I have been studying for the past couple of years and one day when I get time I will sit down and write down everything I have learnt.

I can say for sure though that everyone I know who has blown a speaker has done so with an amplifier that exceeds the power handling capacity of the speaker. Those that I know that use an amp with a power handling capacity equal to or less than what the speaker can handle haven't had a problem.

But there are many factors to take into account. Some budget amps will output less than what they claim so using one with double the power will actually give much less than claimed.

I've seen some independent tests made of lots of different types of amps and one Crown amp actually output less power at 2 ohms than it did at 8 ohms.

We also have the exaggerated claims of some speaker manufacturers who claim the speakers can handle more than they actually can (watts sell) whilst at the other end of the scale, some of the more expensive speakers can comfortably handle more than claimed as they are given more conservative ratings.

A lot of speaker manufacturers do not make speakers for disco use. The recommendations of 1.5 to 2 times the power is based on using them for what they were designed for which is live music.

Live music has different characteristics to compressed pre recorded music. For example, sound engineers usually go for 2X for drums, 1.5X for vocals and 1X for keyboards/synthesizers. Pre recorded compressed music can be very similar to synthesizer output i.e. putting out a constant tone as the quieter bits these days are compressed to make them louder, more so than was done in the past.

I know of two people that have blown speakers this Christmas through microphones. Both were using amps outputting more power than the speakers and neither had a limiter. The limiter if it was set correctly would have stopped the volume reaching a level where it would have damaged the speakers.

To have a more powerful amp on the pretense of "I won't use all the power" is a difficult thing to do.

Firstly you have no idea how much power is being fed to speakers as generally amplifiers don't have a meter on them saying how many watts they are outputing. The different acoustic characteristics of different venues also means that you will use more power at some venues than other to give the same perceived volume level. As the night goes on, our ears adjust to the volume level, crowds get noisier and we pump up the volume. If the power is there we will use it and if there is no limiter there to restrict it, we will push the speakers beyond their design limit and pop a tweeter or a woofer.

This is not based on opinion but fact and what I have seen and heard happen.

Not just budget - some big name amps are also optimistic in their specs, whilst there are some budget amp manufacturers out there (Matrix for one) who give real specs.



Blown speakers through microphones doing what? Because a mixer red-lining will blow a speaker whether the signal is being sent to a "too powerful" amp or one that is half the rated power of the speakers. As mentioned above, it is the square waves that kills speakers.



As this is a natural reaction, it can be said that you will do this anyway whether your amp is matched to the speakers or more powerful. If it happens with an amp that only has the rated power of the speaker, in trying to get more volume it will quickly start to clip and kill the speaker. If one is doing it with an amp that is more powerful than the rated RMS handling of the speaker, the speaker will just go louder with a clean signal until the speaker can't go any louder and then, yes, if you keep on turning it up, you start to heat the drivers which will, of course, kill them.

However, you're more likely to kill the speakers quicker with a nasty square wave

Further, disregarding the speaker issues, an amp that isn't working to it's maximum sounds better, has better response times and runs cooler. Buying a powerful amp also means you have more flexibility for the future when you want to upgrade your speakers.

Yes and no..an 80's synth emits square waves (on certain settings) and there's no evidence that 80's music blows speakers any more than any other! (most electric guitars are heavily clipped but these don't hurt amps either!).

The problem is when the output stage of an amp is clipped, this creates sustained levels of +ve and -ve DC mainly due to the bias and feedback circuits in the power stages of amps being upset or confused. You wont get this by clipping the mixer as the signal is AC coupled from the output of the mixer to the first stages of the amp so can't pass any DC to the speakers by design.

The thing with clipping is that most amps never actually 'clip' (in the true sense) because they have onboard limiters to prevent it. So the light may well be flashing, but its indicating limiting rather than clipping which is an altogether different beast. In these situations it is simply the fact that the energy in the signal is higher as the average level is higher (peaks are cut off, but the signal below threshold, where the weight of a tune is, is higher up the scale)

I agree, square waves are a bit of a misnomer, it's more likely the higher energy content present in those heavily limited signals which burns voice coils. And as i said at the top, limiters that aren't dynamic level controls will not absolutely protect speakers as they only affect the signal above the threshold. They don't prevent the signal below threshold rising to damaging levels. High transients way above the rated power of the speaker very rarely kill them, its the sustained high power of very conpressed signals which does it. For HF that's things like feedback from a mic, where the VC's overheat very quickly due to their size and ability to dissipate the heat.

I normally keep my amp on full, Only turning it down for the initial swich on of amp, Mixer ect. The Mixer gain is kept at half and if any more power is needed then I use the master. I always keep an eye on the mixer levels enshurening the levels never go into the red! If they do then thats when to start turning the mixer gains down.
On the Amp if you use a modern Peavey like mine, They have a good built in gadget called DDT protection!

This post has also inspired me!!

Thanks Rich

Yes, thats what compressors do of course, but not the type that are used by PA systems to prevent overdriving. These are compressor-limiters, and work differently to a compressor in a mic channel used to accentuate quiet voices and tame loud voices. Their release time is very short and restores unity gain inbetween individual peaks crossing the threshold....squeezing..or..compressing (!!) the signal.

A compressor-limiter for PA speaker protection will have a long release time (typically over 4 seconds) and an instant attack. Ratio is set so that crossing the threshold takes the limiter immediately into gain reduction (across the entire signal range) well below the threshold and doesn't return it for several seconds after the mixer signal has been taken back below the threshold.

This way, the speakers are protected fully, it's not simply a 'peak' limiter such as the Purple Audio, Urei, Drawmer units etc...but more like the Behringer Ultradrive, BSS Omnidrive, DBX Driverack, Formula Sound AVC etc.

Just read this again and still can't believe why they said it. If they're supposed to know what they're talking about then they'll understand about signal to noise ratio and gain structure. Turning an amplifier up full will require you to drastically reduce one of the gain levels along the way which will introduce a lot of noise to the signal.

Setting all the gains to unity (0dB) will ensure the cleanest possible signal is sent to the amp. It is then down to the amplifier to set the desired sound level in the room.

Some interesting theoretical views.

I run my amps flat out. Always have. Always will!

I am extremely careful with the gain stages throughout the chain, NEVER sending anything above Odb to the amps.

Never had any problems at all.

My advice, use your ears!!!!

Remember how I posted sometime ago about working with your speakers slightly to the back of you, that way you can use them to monitor what your playing. It always amazes me to see people with theeir speakers 4 or 5 feet infront of them and regimented in a line. How, from behind your speakers, can you honestly tell what your sound is like?? Amazing.

Definitely! Although, feedback can be a problem with them behind you and, of course, you risk more hearing damage, but that's why if you see me at a gig, I spend the first hour of a gig running round the front of the speakers to listen to what they sound like.

Shouldn't be if you know how to set the mic up properly. That is most people's problem!!

There's several reasons why this is wrong. Firstly, signal to noise ratio. If you set them to 0dB then you're getting the optimum signal to noise ratio. The more you bring it down the more noise you introduce into the signal. You're also sacrificing headroom because the signal sent to the amp is not as strong as it should be so the amp will start distorting when you turn it up high. If you turned the amp down and the mixer gains up you'd achieve a sound level increase but without the distortion.

Think about it. 0dB at every gain stage will give you the cleanest signal. The amp then amplifies the signal until the amp itself starts distorting or the speakers distort if they can't handle it. Now imagine you had set everything right on the limit. 0dB on every gain and the amp up as far as possible without distortion. Now say you turned your mixer gain meter down to half. You'd lose a substantial amount of sound but if you tried to get it back by turning the amp up the amp would start distorting so by only having your mixer up half you're sacrificing a lot of headroom.

+1

i dont understand the previous 2 posts

My "+1" was agreeing with D.X.'s post.

D.X.s post was all about setting up the correct "gain structure" for the best signal/noise ratio throughout the signal chain. You want the best signal/noise ratio in order to get the best sound.

If, for instance, the input signal from your CD (Rumours by Fleetwood Mac on CD, for instance, is recorded a lot lower than "Tango in the Night") is too low and you do not adjust the input gain, there will be a lot of noise being sent to the mixer. When you up the mixer level, you up the amount of noise and this then goes to the amp.

Its the same at the next stage - if the mixer is not putting out a good strong signal (peaking at 0dB), the signal going to the amp will be noisy. If you then amplify that signal, you will amplifying a lot of noise just to get the music part of the signal to the right level.

This is why the best way to set-up your rig is to set the input gain, then the mixer, then the processors (if you have them) and then the amp(s). You get the least amount of noise for every "bit" of music.

The amp will introduce noise too (everything does), but by making sure that everything else in the signal chain is set correctly, you make the best use of what you have.

Superstar - does this help (and please forgive me if it sounds patronising; it definitely isn't intended to).

D.X. - that is that what you meant, isn't it?!

Yep, that's spot on mate

+2

I am a little paranoid about "protection"

From the mixer, first stage is the FBQ3102 with the low cut set to 40hz and the high to 20,000hz. No point sending frequencies to the amp that the speakers can't handle.

Next in the chain is an Ecler FAP30L that is a crossover and compressor/limiter. Has a very short attack time and will instantly kill the volume on any individual channel where the signal gets too hot.

All set at 0db at max volume. Anything above 0db gets cut by the compressor/limiter. Amps are set so that 0db is comfortably below clipping point.

Neither of the amps ever flash the red clipping lights even with feedback when some bright spark points the mic at the speakers.

This way your amps will last forever (probably), the sound will be as good as the system can make it and, even better, you can chuck a hell of a lot at your speakers because the signal is clean.

I'm paranoid too - red means "STOP"!

Will it? How noisy? What mixers are that noisy?

I do know what you're suggesting but surely no mixer these days is so noisy as to be audible unless its always run flat out? As a service engineer I see each and every mixer under the sun! The noisiest are the Denon digital by far but even so it's just background hiss that's in any case generated by the master D>A section and isnt affected by the channel faders or input gains...and is masked by the quietest tracks.

As you said, there are few mixers where the noise is audible, but the point about setting up the gain structure is that you minimise the amount of noise so you get the best sound quality and the best efficiency from your equipment.

Whether or not you can hear it, the noise is there (I can't hear 18kHz, but it's there!). By having incorrect gain structure on your mixer, by the time the signal gets to the amp, the amp is amplifying "noise" rather than music, so you are, effectively, wasting the power of your amp.

If you imagine that a good signal has, for example, 80% music and 20% noise (you can find out the specific S/N ratios from manufacturer's specs), then a poor gain structure could do 75% music and 25% noise. You see that you'd have to turn the amp up to get the same volume of music.

It's the same effect as when somebody doesn't have the mic close enough to their mouth - you have to turn it up to get the right sound level and find that you are amplifying "air".

Again you're right in theory but surely no s/n ratio is so bad that we have to be concerned with its detrimental effect on its amplifier. Besides, any background noise from a mixer will be present whether there's music running through it or not. Your post suggests that all that's not music is noise and all that's not noise must be music! You can actually have nothing, y'know!

No you can't! In a specific signal going to an amp, all that is not music is unwanted noise (although some music just sounds like noise to me!).

It's not that you have to worry about loud hissing noise drowning out the music (if you have that you do need to worry!); setting the gain structure is about getting the best possible signal out of the equipment you have and maximising amount of music that gets from the CD player to the speakers.

That's right, you can't. Background noise will always be present in the signal. Achieving unity gain on all gains will minimise this. At the other end of the scale is distortion which will also be introduced into the signal if an amp is turned up full.

Amps up full and gains up half produces noise and distortion. How much of it you can hear will vary but it's definitely there.

You are basing this on what???

All this talk of hiss/noise etc etc,

Why not just set up the system with the correct gain structure from mixer to amps including everything inbetween,then turn the source volume up or down with your channel faders.

It can't be that hard can it?

That's what I've been saying!!

That it's important to set up the correct gain structure!

Real life. If you know of a mixer that can send a signal with no noise and an amp that can turn that signal into sound at full volume with zero distortion I'd love to hear about them.

Are we talking audible or on a scope? If it's the latter you are of course correct, but the former...well there are loads!!