peak or continuous?

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dj Vecchio

New Member
hello every 1
I am in need of some clarification.
I read specs on speakers and always see something like
500 watts peak and 3000 continuous.
what does this mean?
I would appreciate any help

here is the exact line on a speaker i came across

"Powered 18" Portable Subwoofer system includes a
built-in amplifier with 500W peak and 300W continuous power. "


ty
 

NickyB

Gear and Equipment Moderator
Continuous power refers to the available amp power for a full range audio signal (i.e. from 20hz - 20Khz). Peak power refers to the available amp power when delivering a "spike" in the audio signal (i..e. like a cymbal crash by a drummer). The magic number for calculating the Peak power is 1.707 x the continuous power rating. Always use the continuous rating when comparing specs as it is normally required when the Federal Trade Commission (FTC) bench tests an amp for full audio range signal delivery.
 

Conanski

Active Member
The specs you listed at essentially meaningless because there is no qualifying data.. meaning they don't mention at what frequencies or for how long the amp is capable of generating those power numbers. And you can't assume that because this is a powered subwoofer that the test frequencies were within the typical subwoofer range(less that 100hz) or that the amp can produce that power indefinitely, in most cases amplifier test are done at 1khz and measurement durations can be exceedingly short both of which will exagerate potential output.

For speakers and amplifiers there are 3 common measurements used, RMS, Program, and Peak. RMS was traditionally executed with a sine wave which has no dynamic peak value, Program was 2times RMS and Peak was 4 times. These days some creative manufacturers often start with an "RMS" test signal that has a 6db peak so by the time you get to the Peak rating the numbers have no real bearing on reality so you would be well advised to completely ignore that spec. For the most part the Program rating most closely represents what you can get from the product in real world conditions, but unless there is qualifying data published with the power specs all numbers are suspect.
 
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dboomer

Member
So the first thing is amplifiers do NOT deliver "power", they deliver "voltage". "Power" is what is developed when you apply that voltage to a load (speaker).

Continuous power (commonly but incorrectly called RMS power) is the power an amp can deliver on a continuous basis. This spec has about lost all meaning when talking about music. Amplifiers delivering music will never drive an amp to do this. And typically the only way to actually get an amp to deliver continuous power for more than one second involves re-wiring the amp.

Peak power is the instantaneous peak output of an amp. The does relate to sound quality as it is the hard limit for how much drive to a speaker.

In your case, as pointed out above, these specs are pretty much meaningless and they do not provide and qualifiers as to how they were obtained. Specs for the most part were designed for engineers to communicate but they have become selling tools used by marketing departments and they usually don't mean what people think they mean. However size and weight specs are usually correct :)
 

dj Vecchio

New Member
well these answers anr not helping... srry guys
but as u stated "these specs are pretty much meaningless and they do not provide and qualifiers as to how they were obtained."
then why do they always put them under specs on a speaker cabinet without other important info?

i guess what i am trying to understand is how to pick an amplifer that will not over power and blow my speakers.

i would like to get a pair of speakers that can handle at least 750 watts or more for my main cabinets
and then a seperate amp for a sub cabinet
I know a lot of people prefer powered speakes but for the price old school seams the better way for me
thanks for the help
 

Conanski

Active Member
i would like to get a pair of speakers that can handle at least 750 watts or more for my main cabinets
Ok lets put it this way.. here is a speaker that can handle a real 750 watts...

http://www.sweetwater.com/store/detail/STX812M/

And here is an amplifier that can generate a real 750 watts per channel....

http://www.sweetwater.com/store/detail/XTi6002/

If you spend any less than what these components cost you're not getting what you're asking for.

why do they always put them under specs on a speaker cabinet without other important info?
Questionable manufacturers don't supply any qualifying data for their specs, professional manufacturers like those above publish all the specs detail you will ever need.

i guess what i am trying to understand is how to pick an amplifer that will not over power and blow my speakers.
Well if the amplifier and speakers are from reputable manufacturers you can trust the specs and products with similar ratings will play well together. It's also helps to have an electronic protection system installed such as DSP limiters, with separate components that functionality will either be included in the amplifier or will be a separate component(DSP Processor) you will have to add and configure.
 
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dboomer

Member
Ok lets put it this way.. here is a speaker that can handle a real 750 watts...

http://www.sweetwater.com/store/detail/STX812M/
Are you sure? Reading the specs further down the page it says 1200W program which usually means the continuous rating is half of that or 600W. But which 600W would that be?

Reading from the JBL spec sheet posted on their website they claim a power handling of 800/1600/3200. But again what 800/1600/3200 are they referring to? Well JBL generally uses the EIA standard which specifies which frequencies it can handle at the rating. It's not flat, that is the most power handling centers around 300 Hz and goes down on both sides of that.

The other "professional" method of power rating speakers is the AES method. It 2 specifies what frequencies and for how long. The AES method says that the driver must pass 2 hours at the rated power while the EIA method says the driver must not fail for 8 hours. Wow, that seems easy. Certainly a speaker that can run for 8 hours as opposed to one that can only run for a quarter of that time must be stronger, right? BUT ... the speaker that only has to run for 2 hours has to run considerably deeper in frequency (much more like "real" music).

Now according to Celestion (world class driver manufacturer who supplies drivers to QSC and the like) says that a driver rated using the EIA method and rated at 800W will handle about the same power as a speaker measured using AES specs and rated at about 550W. ( http://celestion.com/replace/ ... a word about power) so back to my question ... will it really handle 750 watts?

Ain't this fun? Its very difficult to make real apples to apples comparisons without knowing all the details (which are usually pretty difficult to come by). If you would like a slightly more technical explanation please read this http://www.peavey.com/support/technotes/concepts/THE_LOUDSPEAKER_SPEC_SHEET_GAME_2005.pdf

It's not too scary.

Wanna talk about power amp ratings now ;)
 

Conanski

Active Member
Don you're 100% correct though I fear you may have taken it a little too far down the engineering rabbit hole for the OP of this thread. ;)
 
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dboomer

Member
Yeah, probably (although I think there are some reading this board that it will actually help)

to Ty

If you have no idea what any of this means then you should absolutely look into self powered speakers where all the engineering you'll need is already inside the box. They will be less expensive, more reliable and sound better than if you try doing it yourself on the outside.
 

djtunes

Checking Reality
Google says this is the speaker the OP is looking at:

For those who prefer the simplicity of a self-powered subwoofer, there's the JBL JRX118SP 18" Compact Powered Subwoofer Cabinet. JBL started with the same woofer used in the non-powered JRX118S and added a specially designed amplifier with 500W (peak) and 300W (continuous) power output. The stereo crossover network is great for systems with EON or other powered satellite speakers. Peak limiter that protects the amplifier and speaker from clipping.
 

djtunes

Checking Reality
My powered tops say they're 500w RMS and they're LOUD. (In theory that's 2000w peak.) My sub says it's 1000w and it can't keep up with just one of the tops.

Trust me when I say - You're gonna need subs that are 2 or 3 times more powerful than your tops to make you happy. Or just don't turn up the tops to their max.
 

hippydog

wuz here when it was Red.
i guess what i am trying to understand is how to pick an amplifer that will not over power and blow my speakers.
with the amount of old timers and experts in this forum..
THAT was probably the better question to lead with..

We could provide even better recommendations if you posted the make and model # of your speakers :)
and what your planning to primarily use them for..

i would like to get a pair of speakers that can handle at least 750 watts or more for my main cabinets
and then a seperate amp for a sub cabinet
I know a lot of people prefer powered speakes but for the price old school seams the better way for me
thanks for the help
QSC amp selector is pretty useful..
http://www.qscaudio.com/products/amps/advanced_amp_selector.htm

Most pro amps are pretty close in rated output.. IE: a peavey amp that states 1200 watts per channel is going to be pretty close to a QSC amp that states 1200 watts..
 

Conanski

Active Member
If you have no idea what any of this means then you should absolutely look into self powered speakers where all the engineering you'll need is already inside the box.

+1.. I made the same recommendation in another thread and it does deliver as advertised as long as you don't buy the cheapest powered box you can find. I recently started a rental business and made a decision to use powered speakers because of these advantages, but startup costs are high and initial rentals frequencies were low so I couldn't afford to start off with $1000 boxes I had settle for stuff in the $300-$500 range. As a result I have amassed a bit of data on entry level powered speakers and the bottom line is they're hit and miss.. some are pretty reliable and some aren't and some perform better than others. To get high performance and reliability you really need to step up into the next price bracket up where the JBL PRX, QSC K, Yamaha DSR/DXR, etc reside. You can match or even exceed this performance with passive speakers and seperate power amps and processing but you really have to know what you're doing or it's gonna cost you serious dollars in repairs to learn just where the speaker limits are. And you will need serious speakers to get there too like the JBL STX mentioned earlier, these things are new but they're loaded with JBLs legacy SR series drivers that have a long and proven track record, but that's what it's gonna take you're not gonna come close to this with JRX level speakers.
 

NickyB

Gear and Equipment Moderator
That's why sound contractors recommend two sub cabinets for each top cabinet in large systems.
 
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