Amp - Speaker Ratio

[High Fidelity 0]

We've been down this road before, but just thought I'd see how the views are balanced up.

 

I am a firm believer that your speakers should have an RMS rating at least equal to, and preferably more than the power of your amp.

 

You have an amp capable of pushing out 250watt.

 

If your speakers are 200watt rms, you have no way of knowing when you've reached the power handling capacity of your speakers. (Apart from them distorting/smoking/packing in http://www.dj-forum.co.uk/html//emoticons/fear.gif )

 

If your speakers are 250watt or more rms, then if the amp starts peaking, you know you've reached your limit and providing you back off a little so that you don't send distorted signal to your speakers, your speakers are quite safe.

 

Which camp are you in?

 

 

[ChrisPointon 0]

I don't agree with trying to force 350W RMS into a speaker rated 250W RMS - if it was designed to handle those levels for long periods it would be sold as a 350W Speaker http://www.dj-forum.co.uk/html//emoticons/smile.gif . i.e You can't get 2 gallons of water into a 1 gallon jug.

 

However, it's preferable to have an amplifier which can deliver your speakers RMS power rating without running at 100% of its capacity, and this is where a compressor limiter is a good investment. http://www.dj-forum.co.uk/html//emoticons/smile.gif

 

On the subject of RMS, there is a good comparison between RMS figures and PMPO figures explained Here

[DJ Marky Marc 0]

speaker RMS is not where it stops...

 

a set of good speakers with a 500w RMS rating will have 1000w music and 2000w peak output...

 

if your amp runs out of puff at 500w's then what are you going to do about the rest of the head room in the speakers...

 

when the amp is running flat out you will get clipping.. this is what kills speakers not the over power from an amp of lets say 600w on your 500w speakers...

 

If you read any of the pro speaker makers web sites to see what amps you they recomend for there speakers you will find that any of the speakers require amps upto 2 times the RMS rating of the speakers...

 

my JBLs are 500w RMS each I run amps that push 960w RMS into them.. they never run out of power what ever style of music I play

[Gary 0]

I work on the idea that the amp should be capable of producing more/twice as much RMS as the speakers (at the same impedence) eg: 8 ohms.

 

BUT...

 

Should deliver less than the speakers RMS rating into the speakers.

 

 

EG: If you've got a speaker that is rated at 300watts RMS (at 8ohms), then power it using a 700watt RMS (at 8ohms) amplifier BUT ensure that the amp is simply "ticking over" at half output.

 

You've normally got a few options of how to ensure only half output escapes the amp, eg: turn the controls on the amp down (not always linear scaled), send less signal to the amp from the piece of equipment infront of it eg: Mixer, equaliser, crossover etc.

[DJ Marky Marc 0]

ok have a read of these two things..

 

AMP and Speaker FAQ?

 

Low power PDF

[RichardP 0]

Ah well done Marc, I was ferreting around trying to find that very same JBL FAQ page.

[ChrisPointon 0]

Manufacturers, like sound engineers have always given conflicting opinions. Just because one manufacturer recommends that their products be used in a certain way, doesn't mean that all of the other manufacturers speakers will work in a similar configuration.

 

Maybe we should get one of the forum retailers to test the same principle on their products http://www.dj-forum.co.uk/html//emoticons/221.gif

 

http://www.dj-forum.co.uk/html//emoticons/071.gif

 

If JBL's advice is the norm, then that means the design of most active speakers is also questionable, since most active speakers are advertised as containing amplifiers which match the speakers' specification. Given this policy, all 400W RMS active speakes should contain a 800W Rms Amplifier.

 

If you search on goggle for this subject, you'll get more than several conflicting opinions http://www.dj-forum.co.uk/html//emoticons/wacko.gif , everybody professes to have used their system in a certain way which differs from the other persons, and if their speakers are still alive then each method is just as valid as the next. http://www.dj-forum.co.uk/html//emoticons/533.gif

 

Since loudspeaker designs do vary as do the quality of system components Perhaps it should be case of buyer beware and maybe "Contact your speakers manufacturer for advice if in doubt' would be the best advice.

[Jimbo55 0]

More than but only with a limiter.

 

Jimbo

[superstardeejay 0]

I'm sort of with both Gary and Chris on this one.

 

If you have access to a limiter (most nightclub installs) then go for a bigger amp throttled down to drive your speakers lazily. And choose the speakers to have plenty of headroom with regard to the maximum volume you require.

 

Driving speakers with 'too high a wattage' will lead to over-excursion of the cones. This means the cones come out of the magnet too far, where the magnetic field strength is weaker. This causes the coils to act more like an 8-ohm coil of wire rather than an 8-ohm nominal impedance inductor and this is where your amp's energy is turned to heat rather than kinetic energy (sound).

 

If you intend to 'fly by the seat of your pants' and simply keep an eye on the clip LEDs on your amp (not easy) then obviously a much larger amp will overload your speakers way before they even flicker the clip LEDs....you wont know till the morning when the molten varnish in your speaker voicecoils sets rock hard and jams the cone. (easily done with modern, compressed bass-heavy club music).

 

If the amp is smaller than the speakers, then running the amp taking care not to clip will certainly not overload your speakers, but can you afford to risk it, especially if you have vocalists or are prone to accidents with the mic..?

 

Whatever you do, buy bigger than you need and keep it down! Headroom all the way!!!

 

 

 

 

 

 

 

 

 

[norty303 0]

Generally 1.5 to 2x the RMS rating of the speaker, but only with good quality speakers.

 

This is why people have problems, they ask pro sound guys for opinions, then apply it to their Gemini/Skytec/Soundlab/[insert 'DJ' market manufacturer here] cabs which are frequently not up to the job.

 

Lets get this in perspective though - RMS is based on power handling for a continuous tone, so therefore your cabs should hold up to a sine wave continuously at the max volume (before clipping) of your amp if the cabs are rated the same as your amps.

 

Music doesn't ever get close to this, even with sinusoidal bass tones in DnB and other experimental music. Therefore peaks of 2x the RMS rating are fine as they don't heat the VC for very long. A speaker that has burnt it's voice coil is down to rubbing (mechanical/poor quality failure) or high average power for too long (such as may be caused by using very heavy compression).

 

Any other sort of failure from too much power is down to bad quality speaker design, poor implementation on the part of the user, or using beyond specified boundaries.

 

Remember that most reflex and bandpass subs (and full range cabs) are tuned to a specific frequency for the bottom end. Once a frequency below this goes thru them they are 'unloaded' (the loading from the port gives no suspension to the cone) and they start to go into massive overexcursion. You should always use a high pass filter on your rig if you are going to push high power into it, most decent company spec sheets will advise what this should be.

[Andy Westcott 0]

I've gone for the amp having a lower rating than the speaker, but it's not as simple as that.

 

If you never run such an amp/speaker configuration at clip level, you will never damage your speakers - simple as that.

 

The problem is, we have monkeys who will push an amp to clipping whether it is rated at 100 watts or 500, so with these people nothing is safe, but the lower powered amp configuration has a better chance of not burning the speakers.

 

Another fly in the ointment is that an amp rated at 100 watts RMS at, say, 0.1 % distortion will pump out rather more than this when pushed well into clipping, so the rating shouldn't be taken as an absolute maximum output.

 

In sensible hands, an amp could be rated 4 times the speaker rating, and the speaker could survive, simply because of the nature of the energy contained in the waveform. The beats could be just pushing the +3dB level, but the average power level of the music, which is what ultimately heats the speaker, could be only one quarter of this.

 

Just as an example of my situation, I'm currently using a 300 watt amp (one of 4 amps) feeding a 600 watt RMS speaker, but I am planning to upgrade at some point to a 900 watt amp. I consider this safe as long as I don't push the amp to clipping.

 

Ultimately it all depends on the volume you want to play at, and the kind of music you wish to play.

[Jimbo55 0]

Here is another Manufacturers Guide to setting up up your PA system.

 

SET UP

 

More from Crown Audio (Excellent Tech advice)

 

Here

 

More (interesting table on SPL)

 

Here

 

Sorry for the edits

 

Jimbo

[Jimbo55 0]

Sorry but the edit button decided to kick me out

 

in the crown link you will find a table that allows you to enter the values speaker spl and the level of sound that you wish to hear. I put in the 85db proposed Noise levels at work and the figures are alarming. http://www.dj-forum.co.uk/html//emoticons/fear.gif

 

Max of 20w amp allowing a 3db headroom

 

Still......... save money on the amp

 

Try it for yourself

 

Jimbo

 

 

[YourBigEvent 0]

A few weeks ago I have 3000w of amps going into 1200w of speakers, much prefer to have the amp ticking over than running hard.

[Kingy 0]

QUOTE (ADS Entertainments @ Feb 18 2006, 09:04 AM)

A few weeks ago I have 3000w of amps going into 1200w of speakers, much prefer to have the amp ticking over than running hard.

Me too.

 

However, I am in the active camp!

[Andy Westcott 0]

I prefer to have an adequately rated amp, and have the speakers ticking over. http://www.dj-forum.co.uk/html//emoticons/smile.gif

 

Possibly the more expensive option, I admit........

[superstardeejay 0]

QUOTE

I prefer to have an adequately rated amp, and have the speakers ticking over.

 

Sensible boy!

 

 

[norty303 0]

QUOTE

I prefer to have an adequately rated amp, and have the speakers ticking over.

 

Not always an option if you're required to produce a specified SPL for a gig.