How much power is this really? (1 Viewer)

[Haywood]

Hey guys I was wondering how much power would I really get from a receiver with theses specs
100w x 5(1 khz, 0.8%, @ 8 ohms)
Thanks Haywood

 

[Ted Lee]

that spec looks pretty good, but it doesn't tell you at what frequency range. i'd say that's kinda important. also, i think .8 is pretty high.
the only time i "trust" a wattage rating spec is when it's properly given out. it'll look something like:
105 watts x5 channels into 8 ohms from 20 Hz to 20 kHz with 0.05%thd.
that usually gives us a pretty accurate measurement. watts per channel, into how many channels, into what speaker load, across what frequency response, with what thd (total harmonic distortion).
for example, it's really easy for a company to say their receiver can go to 100 watts. yeah...that may be true, but at what frequency range? can it handle putting out a 100 watts in the extreme highs & lows? probably not...
:>)
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[Jeremy Anderson]

This means they passed a 1khz signal to each channel and got 100 watt rating at 8ohms. The reason this is kind of a useless statistic is that it doesn't take into account a channel being driven with a full range of frequencies (20hz-20khz), so you get an inflated number which looks better for the average power-hungry consumer. It also doesn't take into account more than one channel being driven. You should always look for the words ALL CHANNELS DRIVEN when you're looking at power ratings.
One good way to get an idea of a receiver's power capabilities with all channels driven 20hz-20khz is to look at the rating of the power supply. For instance... If it has a 500w power supply, divide that by 5 and you get 100w per channel. But I think you'll find (especially with stuff like Kenwood, JVC, etc.) that their power supplies simply aren't up to the task. My JVC that is supposedly 100w/ch only has a 330w power supply, which means the unit is really only potentially able to supply 60w to all channels at any given moment. Now, it CAN provide 100w to a single channel at any given time, but not if the other channels are trying to do that too.
This is why people say mid to high brands like Onkyo, Harmon Kardon, etc. are more conservatively rated. The Onkyo TX-DS595, for instance, claims to provide 75w/ch. The power supply on the 595 is rated at 380w. 380 divided by 5 gives you 76w, so Onkyo's probably being pretty truthful with their power rating. That's why they also give a dynamic power rating of 90w/ch in their spec sheet -- because if the other channels aren't using the power, another channel can.
At least, this is my understanding of how it works. Someone correct me if I'm wrong.

 

[Ted Lee]

One good way to get an idea of a receiver's power capabilities with all channels driven 20hz-20khz is to look at the rating of the power supply. For instance... If it has a 500w power supply, divide that by 5 and you get 100w per channel.

i've never heard that concept before...definitetly interesting. that'd be cool if you're right.

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[Ron Eastman]

100w x 5(1 khz, 0.8%, @ 8 ohms)
When you see a spec driving 1khz you can guess-timate that if the same amp was driving 20Hz-20kHz the rating would be somewhere from 65-75 watts. While it is a sneaky way to report amp wattage, 65-75 watts truly isn't a bad number and can drive most HT systems just fine.
As a rule, to get a doubling in loudness (10dB increase doubles loudness, so 80dB is interpreted by the brain as being twice as loud as 70dB) you must increase amp wattage by a factor of 10. In other words, a 650 watt amp has the potential to be twice as loud as a 65 watt amp. The potential peak loudness difference between a 65 watt amp and a 100 watt amp is only 2-3 dB.
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[Haywood]

Thanks for the response guys
Ron I figured that 65-75 watts was about right.
Thanks again guys
Haywood

 

[JohanK]

THD performance of .8% @ 1 kHz is awful...at 20 kHz the distortion will be much higher (by a factor of approx. 10).
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