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Amplifier "AC power rating"


Billdar

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I've noticed that the published specs of powered speakers usually include something called "AC power rating", which is often different, and sometimes significantly different, than the "300 watts RMS" (or similar) rating that is usually given as the "maximum power" rating of the unit.

 

Might this be a better guide as to the "real" power output of the unit?

 

 

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All that tells is the amount of input power the system uses. Because an amplifier cannot be totally efficient, the rated output power will always be lower than the input. The rated output power given is the best indication of how much the amp sends to the speakers. Just remember to check the output impedence. If an amp is rated at 300 watts RMS into 4 ohm, and you connect to 8 ohm speakers, the actual output will be less, by around half. By the same token, an amp rated at 300 watts @ 8 ohm will put out more into 4-ohm. The mathmatics would say 600 watts, but that's not always the case.

 

 

"In the beginning, Adam had the blues, 'cause he was lonesome.

So God helped him and created woman.

 

Now everybody's got the blues."

 

Willie Dixon

 

 

 

 

 

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Mr. Nightime,

 

Yes, makes perfect sense, and until recently, was my understanding as well. But what might your conclusions be if the

the "Power consumption" rating was 320 watts, and the "Maximum RMS power handling" rating was 450 watts, as the Mackie SRM450 specs indicate. Here's a link:

 

http://www.mackie.com/pdf/srm450_ss.pdf

 

Also, the new Bose L1 Model II specs state that the "power consumption" is 500 watts, and on the forum site, a Bose rep states that the "wattage" of this unit is 500 watts. Here's a link:

 

http://bose.infopop.cc/eve/forums/a/tpc/f/7521050644/m/9821050644/p/2

 

What does all of this mean?

 

 

 

 

 

 

 

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Simple physics fact: An amplifier cannot output more electrical energy than it draws.

 

Furthermore, there has not been an amplifier built that can claim 100% input-output efficiency, particularly since resistance from the speakers comes into play.

 

Therefore, you can safely assume those numbers on both the Mackie and the Bose are bogus.

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Also, reactive power is not the same as true power.

 

Reminds me of Radio Shack watts. I remember a RS amplifier which was listed as 200W in their catalog often ended up being a 40W RMS one. :grin:

 

:P

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Griffinator,

 

Do I see a vague reference to something that happened in a small country in South America?

 

Well, in truth most forums have some administrative input/control, including this one. But here, I am comfortable. I really like this forum, and it's the only one that I participate in.

 

In contrast to the Model II specs, Bose's specs on the original L1 show AC power as 1400 watts, and they've stated on their forum that the output wattage is 750 watts (into 4 ohm loads). Owning one of these, and possessing a DB meter as well, that sounds about right, and appears credible.

 

 

 

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In contrast to the Model II specs, Bose's specs on the original L1 show AC power as 1400 watts, and they've stated on their forum that the output wattage is 750 watts (into 4 ohm loads). Owning one of these, and possessing a DB meter as well, that sounds about right, and appears credible.

 

Indeed, it does. 55% input-output efficiency is about average for solid-state amplifiers.

 

Of course, the operative question is, are the systems actually 4 Ohms? If not, the 4 Ohm load is a pointless piece of information.

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Well I'll be, Griffinator, I see that Bose actually corrected their specs after reading your post on the Bose forum!

 

The new L1 Model II now has an UL power rating of 1000 watts, instead of 500. (I'm guessing that UL power rating is the same as "AC power rating" and "power consumption").

 

It's fun to see all of this happening! Ha!

 

Cheers!

Bill

 

 

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Frankly I'm shocked that post ever made it up. Especially with the backhand dig on the Acoustimess....

 

I decided against exploring his statement about "not providing misleading specs" when everyone who knows audio knows output wattage is the most meaningless and misleading spec there is when it comes to powered speaker systems...

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Actually, Griff, Bose is reluctant to publish output wattage. In their specs, they only publish AC power wattage. But they have quoted output wattages on their forum, with the caveats about the figure not being that important.

 

 

 

 

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Actually, Griff, Bose is reluctant to publish output wattage. In their specs, they only publish AC power wattage. But they have quoted output wattages on their forum, with the caveats about the figure not being that important.

 

The only stats that matter on powered speakers are the max and program output in dB's and the +/-3dB frequency response.

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This has come up time and time again at my company, when our sound people (whether employees, contractors, or third parties) encounter other manufacturers' gear and are surprised at the performance vs. the published ratings.

 

For an excellent discussion of this, hopefully not too technical for most people on this forum, see the paper which we published a couple of years ago on the subject:

 

http://www.meyersound.com/support/papers/amp_power.htm

 

Eugenio Upright, 60th P-Bass, Geddy Lee J-Bass, Hofner HCT-500/7, Yamaha BBP35, Viking Bari

Select Strat, Select Tele, Am Pro JM, LP 57 Gold, G5422DC-12, T486, ES295, PM2, EXL1

XK1c, Voyager, Prophet XL

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Hi Mark - so you work for Meyersound? When I was touring in the 90's, we always prefered, and often were provided with those awesome stage monitors from you guys. I can't say now I've heard everything out there, but yours remain absolutely the best I've ever heard.
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This has come up time and time again at my company, when our sound people (whether employees, contractors, or third parties) encounter other manufacturers' gear and are surprised at the performance vs. the published ratings.

 

For an excellent discussion of this, hopefully not too technical for most people on this forum, see the paper which we published a couple of years ago on the subject:

 

http://www.meyersound.com/support/papers/amp_power.htm

 

Interesting, but most amp manufacturers publish "Program" power (your "burst") along with Peak and RMS power.

 

Still doesn't say anything about a self-powered speaker. Ultimately the speaker's maximum program output SPL is the only thing that really matters. Watts are worthless.

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Hmmm........it appears that I have to correct something that I stated in a previous post in this thread. I wrote:

 

"Well I'll be, Griffinator, I see that Bose actually corrected their specs after reading your post on the Bose forum!

 

The new L1 Model II now has an UL power rating of 1000 watts, instead of 500. (I'm guessing that UL power rating is the same as "AC power rating" and "power consumption")."

 

After re-reading the Bose rep's post on the Bose forum, I see that he was referring to the new L1 Model I, not the L1 Model II, as I indicated in my post. (Actually, the Model II was the one that I was talking about throughout this post.)

 

On the Bose site, the rep stated that BOTH the new L1 Model I and the L1 Model II put out 500 watts of power. In his correction (responding to your post, Griffinator), he said what I quoted above regarding the Model I only.

 

Checking Bose's website today, and looking at the L1 Model II specs, I still see that the "AC power rating" is 500 watts.

 

I can understand a mistake being made dispensing info on a forum, but I have to take a manufacturer's specifications as posted on their website, at least regarding "AC power rating", as being fact.

 

What a can of worms!

 

 

 

 

 

 

 

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raddtunes, thanks for the compliment. I try to avoid directly containing my employer's name in my posts, so that my strong opinions are taken as my own and not my company's. Otherwise I would never dare post, for fear of incurring lawsuits :-).

Eugenio Upright, 60th P-Bass, Geddy Lee J-Bass, Hofner HCT-500/7, Yamaha BBP35, Viking Bari

Select Strat, Select Tele, Am Pro JM, LP 57 Gold, G5422DC-12, T486, ES295, PM2, EXL1

XK1c, Voyager, Prophet XL

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