Here is a real stupid question,but I got to ask.

[dincz]

Hey, lets all talk about typical duty cycles and crest factor now ; }

Let's do that! What happens to the calculations if I play with a bow?

 

[greenboy]

German or French?

 

[agedhorse]

and totally disrupt the industry

 

[seamonkey]

"RMS" power has for 20 years or more been taken to mean power based on RMS voltage. "RMS" power can be continuous, or burst depending on the need of the application.

Continuous or burst, ...

Step right up FTC to protect consumers for home audio, but ignore MI amps.

P-real = V-RMS * I-RMS
"Real" needs to be equated to real world so amp to amp can be compared. I'd like to see all manufacturers consider FTC to be real, and use FTC standards to figure out real.

 

[ButtUglyJeff]

Good job Fred. Not only were you wrong about having to worry about feeling stupid, but you have all of TalkBass up in a tissy....

 

[agedhorse]

Continuous or burst, ...

Step right up FTC to protect consumers for home audio, but ignore MI amps.

P-real = V-RMS * I-RMS
"Real" needs to be equated to real world so amp to amp can be compared. I'd like to see all manufacturers consider FTC to be real, and use FTC standards to figure out real.

It's more complicated than this, Hitachi really twirled the home audio world in ~1983 with the introduction of class G in their amps, the high rails were not designed for continuous operation, but they were capable of effectively doubling the amp's power for a short time which worked very well. The amps performed exactly like an amp with double the power for the intended (home) use. Bob Carver did something very similar, but in two different ways. He was a leader in dynamic headroom, using a power supply with stored energy that carried the peak voltage through like a bigger amp but without the size/weight/heat penalty of maintaining this on a continuous basis. I remember the tussles between the FTC and the industry about how to measure and explain this stuff, Hitachi spent a lot of money trying to explain a complex subject to retail consumers and it was a huge waste of effort. All the customer wanted was a single marketing number. Sound familiar???

Currently, there is another situation that has been ongoing for a few years, the use of non-continuous power ratings in the really large class D amps by companies like PowerSoft, Crown, QSC, etc. There is absolutely not use or need for 8000 watts continuous, but if you look closely at the way the power managment is done, these amps autmatically limit back to about 1/2 this amount over time, and also limit back even more above a specific frequency spectrum because in the real world, power density versus musical spectrum plays a big part in what an amp must deliver. Again, explaining this to the average user (granted these amps are not targeted towards the average user but they shure have an opinion on this for some reason) has created more confusion than clarity, yet these amps are at the very top of the food chain and perform at high levels night after night on the top tours globally without any worry about burst versus continuous power issues. It's just that the time constants and approach to power management were done in a way that suits our (pro audio) specific industry.

 

[seamonkey]

Oh it's not too complicated. Crown, Powersoft, et. al. are smart enough not to use "RMS" as a rating.
PowerSoft is showing EIAJ ratings.
Just pick a ratings from a standards organization and stick with it.
On top of it you can market why your amp exceeds what the required standards in certain situation. And if enough manufacturers feel the standards don't fit their special cases, then they can lobby to adjust or enhance the standards.
FTC, EIA, or EIAJ - pick one. Anything else has no foundation. No repeatable results between manufacturers.
You can add special pleading on top of publish standards.

 

[agedhorse]

If you wish to simplify it down to relatively meaningless numbers then you are right, it's not too complicated.

All of the older companies did use the term "RMS" power because that was the EXACT term used by the standards organization at the time, based on the RMS voltage and a resistive load. P(RMS)=V(RMS)squared/R, leaving the terms Watts and RMS in the units. This was a somewhat simplistic use of untis, but served to characterize that the power was based on RMS measurements and not peak or average. Here is an example of the required marking (including the term RMS) by the CEA: Invalid Link Removed (from the new mobile audio standard book). This term was also required IIRC by the FTC.

Note that my involvement in this industry goes back to 1978, when "RMS power" was indeed interchangable (and required to be used) with "continuous average power", as are companies such as Crown, QSC, etc. There have been a lot of different regulations passed around between the different markets (mobile audio, consumer, MI, pro audio) trying to address this, and each market has ended up with what "works" (yes, a loose definition) for them

Over a period of time, the convention "RMS Power" was taken to be based on RMS voltage and current measurements and the term "average power", and "contnuous average power" began to replace RMS except where required by law. Now the term continuous has taken on different meanings at it is a number that means different things to different markets and applications. For an application that has high dynamics (say a full range signal), the peak to average ratio of a reasonable and typical signal is what resulted in the 1/8-power testing that has been almost universally adopted by all national standards (UL, IEC, FCC, etc.) and an amplifier must be capable of continuous operation at 1/8 of it's rated power (based on RMS voltage), so an amp that has say a 100 watt 1/8-power certification is presumed to be also rated at 800 watts continuous average power based on RMS voltage. This may or may not be accurate depending entirely on the peak to average ratio of the typical signal being used in the marketplace and the true load impedance. My feelings are that for a full range signal, or the mid and HF sections of pro audio it's pretty reasonable until you get to pretty heavily compressed program material, but for low frequency sections which are often more compressed by their nature, and for bass guitar applications 1/8-power is inadequate and a more rigerous value should be used (which I do) based on this market's specific signal profile and needs.

Here's a brief look at the topic: Invalid Link Removed

 

[Lynoon]

Is it not all theoretical power in the end? And to what end do manufacturers stand behind their listed ratings when it comes to guarantees / warranties etc?
Let's say I buy a Little Mark 800 and run it through a Markbass 104hf 4 ohm cab. Theoretically this cab will pull the full 800 watts listed and the 800 watt cab should handle it. Given they are the same manufacturer, surely there has to be some consistency and value in their listed ratings, otherwise you run the risk of over cooking your amp or blowing your speakers. I'm not an electronics guy so I know I'm missing other factors, but isn't that the point of listing watt ratings, so nuffies like me can make a simple decision?

 

[okcrum]

No, it's real power. Hook a 100 watt (RMS) light bulb (or bank of them if you have a Real Big Amp) to the amp and drive it to full brightness with a sine wave, using a (auto)transformer if needed to raise the voltage. You can then verify empirically the power is real by holding the bulb(s) in your hand.

Sort of the poor man's calorimeter...

 

[BluesBear]

Is it not all theoretical power in the end? And to what end do manufacturers stand behind their listed ratings when it comes to guarantees / warranties etc? ...

They stand just about where General Motors (and other automobile manufacturers) does on their claims of horsepower and torque ratings. While they will specify an average rating of horsepower and torque for their vehicles, they will not guarantee that your new Camaro will achieve XXX miles per hour.

... I'm not an electronics guy so I know I'm missing other factors, but isn't that the point of listing watt ratings, so nuffies like me can make a simple decision?

You can look at it that way. But that's really an over simplification. While the wattage output ratings can help us decide if an amp will be loud enough (or too loud) for our use, or to compare it to another amplifier, there are many variables to consider.

Mostly it depends on the speaker system it's connected to.

The voltage of the signal input to the amp/preamp as well as the preamp's tone control settings will have a noticable effect on the output power.

For a fixed voltage (amp output) you will get a wide variation in acoustic output (sound pressure levels) depending on the sensitivity of the speaker(s), the number of speakers, cabinet resonance, frequency response of the cabinet, total impedence, etc.

Even the dampening factor of the amp can change the percieved loudness/tonality of the system.

 

[seamonkey]

US Cars have SAE Certification for horsepower.
SI would be better.

Bass amps, and MI amps still just have excuses
Maybe manufacturers could use horsepower ratings as measured in Real Watts.

 

[Calaverasgrande]

Honestly the reason I fled to tube amp land had less to do with the "tone" of tube amps and more to do with my continued disillusionment with a long series of "300 watt" solid state amps that couldnt get nearly loud enough to keep up with a moderately loud drummer and a 50 watt (through 2x12) Mesa.
Ampeg, Carvin, Peavey etc all were found lacking.
Well I hope things have changed in the last 10 years because I am going amp shopping in the next month or so. I hope I will be pleasantly surprised by how things have progressed. But I doubt it.
It's way too easy for amp builders to claim whatever they think will sell more amps.

 

[Fred Mott]

thanks everyone i have a better idea now