I've noticed that a lot of audio receivers rate themselves as like "500 watts" with 100 watts per speaker (this is average, not peak too), but if you do the math on the power specs of the electronics, they normally are far below that, as far as wattage. Like they will draw (obviously) 120VAC at 2amps for 240Watts power usage.

http://www.sonystyle.com/is-bin/INTERSHOP.enfinity/eCS/Store/en/-/USD/SY_DisplayProductInformation-Start?CategoryName=hav_HiFiComponents_Receivers_HiFiReceivers&ProductSKU=STRDE698%2fB&Dept=tvvideo&INT=sstyle-tvvideo-deptfeature-STRDE698%2fB|sstyle:sy_dept_content_b:tvvideo

For example, that one is 90watts/channel X 7 channels, but if you click on the tab for the power usage, it pulls 220 watts. Isn't the power suppose to be conserved?

How are they calculating the power going to each speaker? Is it just the Vrms going to each speaker, with the R being the speaker impedance (so V^2/R=90w then 90 *7)?

[Edited on March 21, 2006 at 10:28 PM. Reason : link]

3/21/2006 10:28:04 PM

keep in mind they are telling you the peak power, so look at the rms power
also a more sensitive speaker requires a lot less power (its a log scale)

so dont become too distracted be the power they have on the box

3/21/2006 10:32:19 PM

There you go talking out your ass again about something you only vaguely know about.

3/21/2006 10:43:55 PM

The sony description is missing 3 key words... All channels driven.

If you hook one speak up at a time it might do 90W per channel.

Now compare Sony's specs to an amp that "only" provides 65W per channel:
http://www.outlawaudio.com/products/1070.html

Quote :

" Output Power (FTC): 65 watts per channel, 8 ohms, 20 Hz - 20kHz,<0.08%THD, all channels driven Power Consumption Standby Power Off : 1.9W Standby Power On : 37W 7 CH Load @ 65W Output Power : 855W "

Huge difference eh? Also keep in mind 7x65W= 455W so this amp is only roughly 50% efficient. Now compare back to the Sony number.

Another rule of thumb you will see a lot is to look at how much an item weighs to help guage quality. Notice the "weaker" amp is twice as heavy.

3/21/2006 10:45:27 PM

Quote :

"There you go talking out your ass again about something you only vaguely know about."

did i say anything wrong?

3/21/2006 10:54:34 PM

Quote :

"keep in mind they are telling you the peak power, so look at the rms power"

For one, he already addressed this:

Quote :

"with 100 watts per speaker (this is average, not peak too)"

Quote :

"also a more sensitive speaker requires a lot less power (its a log scale)"

It doesn't matter what sensitivity a speaker is, his question is speaker independent.

Quote :

"so dont become too distracted be the power they have on the box"

This shows you didn't even read his post apparently.

He is specifically confused about how they RMS rate them for 500w, yet it doesn't even draw that much power, phelps answered it beautifully. Stop feeling compelled to always add your 2 cents to each and every worthwhile thread on this entire fucking site, because it seems 25-33.3% of the time it is as much harmful as it is helpful.

3/21/2006 11:05:06 PM

yeah im doing 3 things at once, sue me

3/21/2006 11:09:01 PM

[Edited on March 21, 2006 at 11:14 PM. Reason : RMS pisses me off ]

3/21/2006 11:13:29 PM

So basically, if Sony were to advertise that as a 630watt system, they would be lying?

Thanks for the clarifications too.

3/22/2006 12:15:41 AM

you'd have to look at the impedances at which they are rating the power. i.e. 500w x 1 @ 1 ohm may be listed. the actual output to the speaker will somewhat vary depending on your impedances, but it won't make too much of a difference. also, they won't be lying if they are rating under optimal conditions for the circuitry (temperature, input signal strength, etc.) which will most likely not be achieved with normal installations. if you had a lawsuit planned for false advertising, i'd hold off on it...they have alotta tricks up their sleeves.

3/22/2006 3:10:59 AM

Even under optimal conditions though, the power output for all the speakers can't exceed the power input can it?

I have no purpose planned for this... I was just wondering is all.

3/22/2006 8:14:58 AM

Quote :

"Even under optimal conditions though, the power output for all the speakers can't exceed the power input can it?"

in an absolute sense, you're right, but marketing can always report power input differently from power output to make it appear that you're wrong.

3/22/2006 8:20:29 AM