Back Up Sound Systems

[andyw 0]

ok when we go to gigs we always take back up amp/mixer and cd decks.after our recent expirience with speakers(see other thread)its got us thinking about our sound back u.if we lose a speaker on the night we would have to run off a mono set up not ideal but at least we could get through the night.but what if we had a gig the next day copuldnt really go with 1 set of speakers,so should we have a set home here spare ,should we carry spare speakers.what have you got in place to deal with such events

[Andy Westcott 0]

I haven't got a spare speaker for my main setup, although everything but the bass driver is doubled anyhow.

 

If using active speakers, the best bet seems to be to buy three of them and rotate amongst your bookings - that way if one goes down, you have a spare of identical specification to carry on with.

 

That's the way I'd do it if I could persuade the wife to sanction some spending. It's OK for her - she doesn't have to cart my monsters about....

[andyw 0]

If using active speakers, the best bet seems to be to buy three of them and rotate amongst your bookings

 

 

we are thinking of getting a spare top and the same amp and rotating them

[Andy Westcott 0]

Andy, I'm not familiar with your gear - what have you got in use currently? I take it you don't use active speakers.

 

If you use one amp, then a second is pretty much essential. No matter how reliable your amp might be, a well-aimed pint of lager can do a lot of damage..... Take a spare, as I think you do anyhow.

 

As for speakers, if you have the room, take a spare along with you.

My thinking on speakers (not intending to turn this into yet another dicussion on speaker/amp matching) is that the speakers should be able to take a far higher RMS power than the amp can put out, then you are fairly safe from overload related failures, making backup speakers all but unnecessary.

 

I practice what I preach - 600 watt bass drivers powered by a 300 watt amp.

[TonyB 0]

I always have a bi amped system so if one amp fails, I can run of just one amp if needed. As far as the speakers are concerned, the tweeter horn is usually the weakest component so I carry a couple of tweeter boxes for emergencies as they don't take up much room and I couldn't fit a spare speaker in the car.

[HalfPint 0]

Suggestion and recomendation on why not to use Powered speakers !

 

And to consider going back to conventional Amplifiers and Speakers

 

Powered Speakers:

 

1. If they fail you loose amp and speaker while it's repaired.

 

2. It harder to trouble shoot a powered speaker. Is it the Driver / Amplifier / internal leads?

 

2. They limit your ability to grow the system into a professional active system.

 

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However:

 

If you have seperate pieces of gear, the system can grow like this:

 

This is how a system could be bought and developed:

 

start with :

 

1 x Amp and 2 x Top (full range) speakers

 

You should buy at least 1 horn diaphragm with the speakers. (these can normally be replaced in 30 mins and are the most common item to fail in this type of speaker). When we sell systems to PA companies they normal buy one HF unit. the cost can be as little as £20.00.

 

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Add 1 or two Bass bins to above ( driving all 4 speakers off 1 amp) until you can afford.....

 

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Add 2nd Amplifier. Then to make the system sound better and distribute the power correctly and not through the built in passive crossovers in the bass bins, which soak up power.......

 

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Add active Crossover to split the mixer output frequency to TOP & BASS. This will make the system sound better and be more efficient.

 

Add spare driver (not speaker) for Bass bin and tops and within 24 your system should always be working.

 

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This configeration would be flexible enough to be used as a small system for Pubs (tops only) or used together. A Mix and match system for all occassions.

 

In the event of a failure then you have all kinds of options to carry on. With the spare parts suggested you are also up and running the next day.

 

 

If you do want to use Active speakers make sure they can be either used without the amplifiers. That is, they will accept a power source from an external amplifier.

 

 

Everyone has a view... This is just one...

 

My summary:

Powered speakers are smaller and lighter than the rig suggestion.....

Everything will be great with a powered speaker until one fails.

High cost of having a third powered speaker. Better to have spare kit that can be used to increase the show rather than as a spare.

Powered speakers require less knowledge than a full active crossover system.

 

 

[UKHero 0]

Andy, I'm not familiar with your gear - what have you got in use currently? I take it you don't use active speakers.

 

If you use one amp, then a second is pretty much essential. No matter how reliable your amp might be, a well-aimed pint of lager can do a lot of damage..... Take a spare, as I think you do anyhow.

 

As for speakers, if you have the room, take a spare along with you.

My thinking on speakers (not intending to turn this into yet another dicussion on speaker/amp matching) is that the speakers should be able to take a far higher RMS power than the amp can put out, then you are fairly safe from overload related failures, making backup speakers all but unnecessary.

 

I practice what I preach - 600 watt bass drivers powered by a 300 watt amp.

 

 

I used to practice this theory ntill I started working in the industry and was told that a distorted or cliping amp can do more damage to a speaker than an amp a few watts over the speaker rating and have followed this... I am not an engineer and so would pass this over to the technical guys who will I am sure put us straight one way or another...

 

 

Nik

 

[spinner 0]

Andy, I'm not familiar with your gear - what have you got in use currently? I take it you don't use active speakers.

 

If you use one amp, then a second is pretty much essential. No matter how reliable your amp might be, a well-aimed pint of lager can do a lot of damage..... Take a spare, as I think you do anyhow.

 

As for speakers, if you have the room, take a spare along with you.

My thinking on speakers (not intending to turn this into yet another dicussion on speaker/amp matching) is that the speakers should be able to take a far higher RMS power than the amp can put out, then you are fairly safe from overload related failures, making backup speakers all but unnecessary.

 

I practice what I preach - 600 watt bass drivers powered by a 300 watt amp.

 

 

I used to practice this theory ntill I started working in the industry and was told that a distorted or cliping amp can do more damage to a speaker than an amp a few watts over the speaker rating and have followed this... I am not an engineer and so would pass this over to the technical guys who will I am sure put us straight one way or another...

 

 

Nik

 

 

 

Most professional speaker cabinet manufacturers will recommend an amp with a greater rms output than the driver's rms rated input.

 

[Kingy 0]

ACTIVE! ACTIVE! ACTIVE!

 

Depends on what you buy though.............

[TonyB 0]

 

Most professional speaker cabinet manufacturers will recommend an amp with a greater rms output than the driver's rms rated input.

 

I'm sure that this is an urban myth that has propagated from somewhere! 300 watt rms speakers are designed to be used with an amp giving out 300 watts rms. If you have to run the amp into clipping then you should replace both the amp and speakers. Thats one reason why it is best to have speakers rated at a higher RMS than the amp because it would be cheaper to just replace the amp.

 

Speakers are driven by the amp so if your amp had a 600 watt output and the speakers were 300 watt, the speakers will most probably be damaged by over driving.

 

It is easy to keep an amp out of clipping because there are usually clipping warning lights and you can hear when the sound gets distorted. There are no warnings to tell how many watts an amp is outputting.

 

I've not seen any speaker manufacturers recommend using a higher powered amp than the speaker rating. It would open them up to giving negligent advice if the speakers blew and make them liable for repairs.

 

I have seen retailers giving this advice though.

 

Would you use a 120v appliance with a 240v mains supply?

 

I have seen it mentioned that the amp should be higher powered than the speakers to give "headroom". The headroom should be in both the speakers and amp i.e. If you need a system putting out 300 watts then 500 watt amp and 500 watt speakers will give you 200 watts of headroom that will not cause any damage if you have to use the full 500 watts.

 

A 500 watt amp with 300 watt speakers will sound clear and not give you any warning that they are being overdriven until the tweeters stop working and possibly the cones are damaged.

[HalfPint 0]

Amps should be more or at least equal to speakers.

 

Thats it !.

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Reasons are~

 

Its all a question of the damage caused by overdriving. either amp or speaker.

 

If an amplifier is more powerful and it drives a speaker that is the same size (RMS) the speaker may and probably will survive because of the headroom or peak power it can take.

 

If an amplifier is over driven and goes off its power rails it just immediately dumps a DC spike down to the speaker and blows the drivers.

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Also a more powerful amplifier will also sound bettter, deeper, solid, tighter bass, more punch etc etc.

 

500 RMS Amplifier / 500 RMS speaker which is probably 1000 Peak power.

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The whole problem is when people buy cheap "peak power equipment" If you marry up a RMS amplifier to a peak power speaker watch out!

 

Somebody commented it was a retailer thing:

 

However lets look at the Martin Audio website:

 

Martin Audio Blackline speakers are designed to be used with amplifiers capable of producing

 

F12 400-650 into 4 Ohms

 

F15 400-850 into 4 Ohms

 

Warning: care should be taken to avoid amplifier clipping. It is important to understand that a low power amplifier is more lickely to damage a loudspeaker than a high power amplifier ...... etc etc...

 

end of web copy:

 

 

Please note

 

Martin F12 is rated at 300 RMS

 

and the Martin F15 is rated at 400 watts.

 

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[ChrisPointon 0]

For larger gigs its also advisable to have two medium power amplifiers and run them at say 60% of their capacity, than to have 1 high power amplifier running at 100% of its capacity .

 

The logic is simple. The more power an amplifier produces, the more heat that it has to dissipate (sp) and there is one thing that electrical components and transistors hate, it is prolonged excessive heat build up which can shorten their useful life.

 

I think I also read somewhere that MOSFETs also protect themselves from overheating by reducing the gain / power output internally? Maybe Kevin can confirm?.

 

So for example running a 500W RMS Amplifier flat out into 500W RMS Speakers will be okay, however remember that in doing so, you will have zero headroom left in both the Speakers and Amplifier and the higher the output levels the more distortion it introduces into the chain. Usually running an amplifier flat out will also increase the risk of clipping and overdriving, especially during loud bass passages or vocal peaks, and overdriving the amp and speakers through clipping is more likely to lead to premature or even instant failure of delicate coils.

 

Probably the best advice, then for larger gigs is to use two or more amplifiers at nominal power levels each driving their own speakers, rather than trying to rely on one single power amplifier running flat out for hours on end. This would mean that the amplifiers are doing less work, running cooler and producing slightly lower distortion levels and that there is plenty of headroom available if required.

 

When choosing amplifier(s) and Speakers, always go for the biggest that you can afford, and try and get more power than you actually need, as this allows more headroom and less strain on the components in normal everyday use.

 

Again there is more to consider than wattage alone which is the brawn, the other important areas to consider are the brains, which is in the speaker design and choosing one with decent SPL levels, but that is for another topic!.

[DJ Ben 0]

I practice what I preach - 600 watt bass drivers powered by a 300 watt amp.

 

AFAIK, It's better to rate the amp higher than the speakers (RMS Rating only) This gives you headroom, and because the speakers will have a Max power rating, you can afford to pump slightly more into them.

 

I think 10-50% extra in the amp is the norm (thats what I've been told by a few people.. so thats what I go with)

[Andy Westcott 0]

This idea of a weak amp damaging higher powered speakers is a load of utter rubbish, but it gets perpetuated on many audio forums by people who know little about it. Can we put a stop to it here please??

(Come on SuperStar, back me up!!)

 

If an amplifier is over driven and goes off its power rails it just immediately dumps a DC spike down to the speaker and blows the drivers.

Wrong, I'm afraid. All it does is produce a flat-topped waveform - no spikes, no DC, no drama.

 

Also a more powerful amplifier will also sound bettter, deeper, solid, tighter bass, more punch etc etc.

No, it won't sound any different at all - it'll just go louder, assuming it is of a comparable quality.

 

OK;

A speaker's rated RMS power is the highest continuous power it can dissipate; A higher continuous power will overheat it. A lower continuous power won't. Simple as that.

 

It is possible to run with a higher rated amp and get away with it simply because you rarely run it at full output - but if you do run it flat out, you're in trouble.

 

A lower powered amp is unlikely to do any damage unless you run it at a stupidly distorted level - under these conditions it can output far more than it's rated RMS power which could be above the speaker's rating, which is when and how damage occurs. No other reason.

 

There is no magic or unfathomable technology going on here, just simple power levels.

 

If you can afford to, use speakers rated somewhat higher than the amp, and then you will be better protected against those 'accidental' incidents where the output suddenly increases, such as feedback of over-enthusiastic punters getting a finger on the slider.

 

Reliability is of the utmost importance in our business, so why gamble that on buying speakers which are unable to accept the full output of your amplifier? Penny pinching or misinformation has to be the reason.

[TonyB 0]

I totally agree with Andy and is the way I have always understood it to be. As I said, having the amp higher powered than the speakers is an urban myth and usually ends up in broken speakers!

 

It is true that more expensive speakers are more tolerant of being overdriven but even they will have a shorter life span if you consistently do it.

 

 

Somebody commented it was a retailer thing:

 

However lets look at the Martin Audio website:

 

Martin Audio Blackline speakers are designed to be used with amplifiers capable of producing

 

F12 400-650 into 4 Ohms

 

F15 400-850 into 4 Ohms

 

Warning: care should be taken to avoid amplifier clipping. It is important to understand that a low power amplifier is more lickely to damage a loudspeaker than a high power amplifier ...... etc etc...

 

end of web copy:

 

 

Please note

 

Martin F12 is rated at 300 RMS

 

and the Martin F15 is rated at 400 watts.

 

---

 

I just looked at the Martin Website for the F12's and it says the speakers are 300w AES and 1200w peak. Not sure what AES is - Audio Engineering Standard perhaps? - but Peak is usually around double the RMS so I would say that they are around 500w - 600w RMS. Also the power of the speakers is quoted at 8 Ohms whereas the recommended amp power is quoted at 4 Ohms. 4 ohms power rating would be higher than 8 ohms. 650 watts into 4 Ohms is going to be around 450 - 500 watts into 8 Ohms.

 

Confusion marketing at its best I would say!

[Andy Westcott 0]

The A.E.S. standard (Audio Engineering Society) dictates that a driver should be able to withstand 'X' amount of power for 2 hours continuous, and that input is in the form of filtered white noise representative of the frequencies that particular driver is expected to deal with.

 

Far more meaningful than a simple RMS rating, as with this there is no stipulation for how long a driver has to stand it for.

 

Therefore if a certain driver had a signal fed to it at a power level of 800 watts for 5 seconds, the company could in theory advertise it with a rating of 800 watts - a pretty meaningless rating, which was why the A.E.S. standard was created.

 

If a driver can stand a certain power level for two hours, then it deserves that rating - real life conditions.

 

A.E.S. standard is the one to look at when comparing speakers - accept no imitations! smile icon

[norty303 0]

Edit: took so long to type some of the stuff has been covered since i managed to post the bloody thing!!! :)

 

Andy has pretty much hit it all, however the playing it safe option doesn't work in all arenas. Sometimes the outright power level is what is needed and so running as loud as possible is the goal (not in mobile DJ'ing though for most of the time i suspect)

 

Also a more powerful amplifier will also sound bettter, deeper, solid, tighter bass, more punch etc etc.

No, it won't sound any different at all - it'll just go louder, assuming it is of a comparable quality.

 

I will contest this point, but only from an outright power perspective. The fact that the bigger amp has more headroom means that when those fast transients hit the amp it is better able to respond than a smaller amp, giving output for very short periods that is greater than that of the smaller amp is capable of. Any amp when run to the limit on subbass will be getting close to running out of steam due to the large output requirements. Some amps very noticeably take on a breathless quality due to the lack of power available to the output stages. All this adds up to a difference in the listening experience. But as you say, its simply a factor of it being a bigger amp.

 

The 'urban myth' being talked about here is founded on well thought out theory and practise over many years.

 

There is enough behind this to write a textbook which people can go and find if they are really interested, however, a short synopsis is below...

 

The reason why a smaller amp overdriven can be more damaging is because the clipped waveform causes the cone to move in a non-linear fashion causing heating of the voicecoil beyond that of a higher amplitude waveform of a non-clipped variety. Cheaper amps limit in funny ways too, introducing distortion of the waveform sooner.

 

RMS is a standard where drive units are tested, using sine waves for extended periods without breakage. AES is a variation on this, usually resulting in values around 100watts higher for a typical 600wrms driver.

 

An amp that is rated at 600w a channel can only ever give 600w max (amp power is generally quoted by a frequency range and % of total harmonic distortion, not RMS) with limiters in use. Every amp can give massively greater outputs than quoted but at significantly higher distortion levels which is why their outputs are quoted at the most accepted levels (and what has become industry standards of measurement e.g. 0.05% THD at 20hz - 20khz for example).

 

Music is a dynamic format, with peaks and troughs, whereby the average level is somewhere between the lowest peak and highest trough, but with todays heavily compressed music, is somewhere around 2/3rds of the peak (ballpark figure). So putting 1000w of amp onto a 600w speaker and running it flat out (but not clipping/limiting) with material that is fairly well compressed means the speaker is getting about 600wrms, and may see peaks equal to, but not exceeding 1000w (the max power of the amp). As most 600wrms rated speakers will have a peak rating of 1200w you can see this is within specified tolerances. Even though the amp power is greater than the RMS rating of the speaker, this is not being 'overdriven' yet. Playing a sine wave at full power would be.

 

The '2x amp power' rule comes more from a live environment, where music is less compressed and has far greater dynamics, meaning that the average level is closer to half the total peak output. For pre-recored music, 1.5x is a better bet.

 

Of course, if you abuse the amp and drive it hard into clip/limit, you will probably break things sooner with a larger amp, but thats user error, rather than poor rating of amp/speaker. Its being used outside of the operating guidlines.

 

Other factors also come into play, such as hornloading changing the impedance of the driver significantly in some cases, reflex and bandpass boxes also having different characteristics but thats another book in itself.

 

These are not my opinions, these are methods and theories known the world over, and practised by thousands of sound people. If you have the stomach for it, visit prosoundweb forum and read some of the study hall information.

 

 

Be interesting to hear your thoughts/perceptions on that?

[Andy Westcott 0]

I excercise my right to reply........

Thankyou - I'll be looking at the site you mentioned; Looks interesting. smile icon

 

However, I differ on this:

"RMS is a standard where drive units are tested, using sine waves for extended periods without breakage."

 

RMS is simply a mathematical way of averaging a sine wave which produces a figure, which if applied as a steady DC voltage across a pure resistance, would result in the same power dissipation - it has nothing to do with duration, wheras the A.E.S. test does, and involves noise, which is why it represents a truer to life rating.

 

RMS values are wide open to abuse, as I mentioned, simply because no duration is specified - it could be as short as a second if the manufacturers wanted, although any reputable manufacturer wouldn't dare to fake the figures this way, although cheap imported stuff might be rated this way - beware!

 

Now this:

"The reason why a smaller amp overdriven can be more damaging is because the clipped waveform causes the cone to move in a non-linear fashion causing heating of the voicecoil beyond that of a higher amplitude waveform of a non-clipped variety."

 

This isn't due to the voice coil movement being non-linear and for some strange reason generating heat; It is simply because there is more electrical energy contained within a clipped waveform - a square wave being the most extreme example of this. If that contained energy is greater than the driver can handle, it will overheat, and this can]/i] occur with a lower rated amp, as I mentioned earlier, but the problem is a lot more serious and likely if the amp is rated higher than the speaker. Any distortion at all under these conditions signifies that you are running the speaker above it's limit, and to prepare to deploy your backup.....

 

I'll leave it at that - we may well continue to disagree on the odd finer point, but I'm happy with that.

[HalfPint 0]

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All I can say is have a evening with 2 amps of the same make, but different power.

 

run the first amp to about 80% of its rating, measure the SPL coming out of the Speaker.

 

Use the same speaker, same location, in fact eberything the same but.....

 

Play the same track with the bigger amp and run the amp up to the same SPL level.

 

Then listen.

 

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[HalfPint 0]

I am pleased that Andy knows more than Martin Audio!

 

Quote:

This idea of a weak amp damaging higher powered speakers is a load of utter rubbish, but it gets perpetuated on many audio forums by people who know little about it. Can we put a stop to it here please??

 

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If Martin Audio are so confident that they place a warning on their website about small amplifiers then that as good as it gets!

 

 

[Andy Westcott 0]

They are trying to sell more expensive components, I'm not. Who has the hidden agenda?

Also, I specifically mentioned audio forums....

 

Regarding this:

"Play the same track with the bigger amp and run the amp up to the same SPL level. "

Of course it will sound different - the bigger amp is running at a far smaller percentage of it's output capacity.

For this experiment to have any meaning, you need to run each amp at the same percentage of it's maximum output.

 

I love a good argument!

[norty303 0]

This isn't due to the voice coil movement being non-linear and for some strange reason generating heat; It is simply because there is more electrical energy contained within a clipped waveform - a square wave being the most extreme example of this. If that contained energy is greater than the driver can handle, it will overheat, and this can]/i] occur with a lower rated amp, as I mentioned earlier, but the problem is a lot more serious and likely if the amp is rated higher than the speaker. Any distortion at all under these conditions signifies that you are running the speaker above it's limit, and to prepare to deploy your backup.....

 

hehe, i like these sorts of discussions....

 

The way i understand it, the speaker cone attempts (under control of the amp, to a greater or lesser degree, depending on things like damping, offset, etc)) to track the waveform presented to it.

 

In a situation where the waveform is hard limited and starts to become square, the cone is trying to track the plateau at the extremes of the wave. For short periods each cycle the amp is attempting to hold the cone on this plateau, effectively a constant voltage, which is where i think the DC quote comes from that people like to mention (which i don't like incidentally). Its only for short periods but compared to a perfectly oscillating sine (and i'm using a simple sine as an example as its easier to visualise, other musical factors no doubt have an influence) the difference is fairly large in terms of heating the coil like an element. The snap back to the opposite value must also happen fairly suddenly (in true square wave there is no time element between the +ve and -ve so it s like a switch) which must also take its toll.

 

I'd love to get a signal processor which can be swept from pure sine to pure square and and measure the impedance changes and temp that occur as the waveform changes, you'd likely be able to sense the power compression from the heat in the impedance chart (as i think thats how Nexo use their sense lines)

 

As for the RMS thing, i always thought that it had a time element to it, as i'm sure it does for most driver manufacturers who will rate like this, but as you say, its not a specification for a standard as AES is. you live and learn... :)

 

 

 

From personal experience i can say that i have only EVER blown 2 bass drivers (bloody expensive Beyma ones at that!) They were run in a double bandpass enclosure (known for giving probably the least mechanical resistance of any of the common formats of cabs bar free air) and rated at 700w AES (600wrms) each. They were being driven with a bridged QSC RMX2450 (~2300w at the passband of the cab) and had been run flat out on many occasions like that. The time when they went was the one time when they were run into the limiter on the LMS, with likely one going, followed shortly by the other due to the drastically changed environment the single driver was then running in. It simply went outside of its operating parameters with expectant results.

 

Conversely i run most of my gigs hard (as there is a need for it, hence the mainly horn loading) particularly the tops, comprising Beyma CP550 2" compression drivers and Fane slots totalling about 325wrms a box. These are fed with 700w of power and sound fantastic and unstrained. Good gain control and running within limits is the key i feel. Fast CLEAN peak limiting is one of things thats essential in high power applications.

[HalfPint 0]

But......

 

It was said the amps would all sound the same! big or small!

 

Who is trying to sell anything? I certainly do not sell Martin Audio kit.

 

In fact when ever I post, I actually remove all mention of our product names as we sell exclusively to the trade and through a specific network of dealers.

 

Apart from all the aurguments that we all have posted. the smaller amp system is more expensive.

 

Speakers are generall more expensive watt for watt than amplifiers and here is another argument why you should use amps matched to Speakers

 

using your arguement:

 

250 Watt RMS Amplifier in your argument should drive 500 watt RMS Speakers.

 

Retail price of an Amp £250 - Retail price of a budget 500 watt 15" + Horn £500 (Pair)

 

Total cost for a 250 watt system £750.00 and £1500 for a 500 watt system

 

 

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Using my Argument ( and Martin Audios!)

 

500 Watt RMS Amplifier (at least) should drive 500 watt RMS Speakers.

 

Retail price of an Amp £330 - Retail price of same 500 15" + Horn £500 (Pair)

 

Total cost for a budget 500 watt system £830.00

 

Better still buy "REAL" Pro gear and have a real high end 500 watt system for under £1500 !

 

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So, what would you rather have a 500 watt system that you can use at half power and sounds great or a 250 watt system that runs out of steam! The Bigger you go the better the gear is, especially at the budget end of the market.

 

Your agrument just does not make any commercial sense.

 

ps prices taken from MusicMart adverts.

 

 

 

[norty303 0]

As i said in my posts, if making the utmost amount of sound is not a requirement then using smaller amps will suffice, and may well be safer if not overdriven.

 

However thats not most applications, otherwise we'd be all using 90db sensitivity reflex boxes, running at half volume off 50w amps.

 

My current buying practise is to buy/build the most sensitive box i can with the highest power handling, and then put the biggest amp i can on it up to about 2 times the rms rating.

 

However i think Tony Andrews (of Funktion1) has the perfect solution, by building boxes with very high sensitivity but with the LOWEST power handling for that output, meaning you can achieve monster outputs using less amp power, meaning cheaper amplification costs and weight and everything else that comes with that.

 

Some of his cabs are 10db louder at 1w input than many of the current budget and midrange speakers. Thats twice as loud for the same input. Ok, lets put that in perspective, at full whack with your current cabs (say 500w input power) which is quite loud, the FK1 cabs are not just a bit louder, but TWICE as loud! That is absolutley incredible once you scale it up. What that means in real terms is that you can achieve the same output levels with only a fraction of the power.

 

Practical example, a reflex cab with 99db sensitivity against a horn of 108db sensitivity.

 

The reflex cab can hit nearly 126db with 500w input

The horn can hit 126db with only 64watts

 

Taking them to the upper limits, the horn can hit 138db with 1000w of power.

The reflex cab would hit (if it could withstand the heat/forces, which it couldn't) the same with a staggering 10k+ of power.

 

 

10k amps are expensive. 1000w ones are not.

 

108db sensitive speakers can be had for ~£1600 new. A decent 500wrms reflex cab with 99db sensitivity (thats good for a reflex cab, most will be lower than this) will set you back £500 at least.

 

but how does this relate to a mobile market? I'm not sure it does as requirements and are different, as is budget.

[TonyB 0]

Having done a bit of research, including reading through some of the ProSoundWeb Forum, my conclusions are:

 

1) If the sound equipment is being used for live music, then the amp rating can safely be double the speaker handling power. The suggested formula is to double the speaker wattage and multiply by 0.8 and 1.25 to give an amplifier power range that the speakers can handle. e.g. a 500 watt speaker can be used with an amplifier from 800 watts to 1250 watts. The exceptions are certain signals from instruments like synthesizers or highly processed electric guitars where the amp power should not be more than the handling capacity of the speakers.

 

The sound wave from live music has lots of peaks and troughs and averages out at a lower point.

 

2) For recorded music such as CD's, the amp power should not exceed the power handling capacity of the speakers. CD's are very heavily compressed and any power from the amp above the handling capacity of the speakers is likely to damage the speakers.

 

Sound engineers heavily compress recorded music which produces an almost square wave. I read an interesting article which stated that in the last 5 years the amount of compression has increased for CD's to the point that it is no longer pleasurable to listen to them. With vinyl, such heavy compression couldn't be used because the stylus would of jumped out of the groove. This limitation doesn't apply to CD's and the quiet parts are made to sound louder so that the music "leaps out" from the speakers.

 

3) You will not damage speakers by using an amplifier that has a lower output than the speaker handling. The only time damage will occur is if you go into clipping.

 

4) There is not a lot of difference in volume when you double the amplifier power. The difference is about 2db which is virtually undetectable by the human ear. The difference is if you use a higher powered amp and drive it into clipping, it will destroy your speakers quicker because of the extra power.

 

5) It doesn't matter if you are using, for example, a 500 watt speaker with a 250 watt or a 500 watt amp, if you have to drive it into clipping it means that your set up is not powerful enough for the venue. The best solution is to use a second amp with a second set of speakers.

 

6) Having an amplifier with a greater power handling capacity than the speakers is very likely to damage the speakers, tweeter failure being the most common failure (but see 7).

 

7) Irrespective of the speaker/amp power ratio, the most common cause of failure is caused by operative error. Inexperienced users pushing the system too hard, loaning your equipment to another user or not setting it up correctly are most likely to cause failure.

 

All above ratings are RMS at the same impedance.