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What does watts per chanel mean?

S

Striker2237

New Member
I'm really new to the Hi-fi segment of audio and was wondering what exactly does it mean if my amp is able to output 75watts rms at 8 ohms continuesly per channel. Does this mean that if im only using 2 of its 4 outputs I can draw 150? or still just 75? Also if im using 6 ohm speakers that are rated to draw 500 watts should I stop using them?
 
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"per channel" refers to each amplifier channel your amp has.

If you have a stereo amp, you have two channels. Even though you might have the ability to run two sets of speakers (A & B) from that stereo amp, you still only have two channels and the available power for one channel is divided between the two speakers on each channel.

If you have a 5.1 receiver, you have five channels. the "'1" refers to a line-level output for a subwoofer.
 
Welcome. It means it will drive 75 watts (power) per channel into 8 ohm loads. It may be able to drive more into a 6 ohm or 4 ohm load, but make sure it can do that safely. That info should be in the manual. More info about your equipment would help us help you.

It will not drive 150/channel. The outputs are connected to the same amplifier.

Speakers don't "draw" the rated power. Those ratings are max power that the speakers can handle. You should be fine driving them with 75 watts.
 
It measures the power of your cologne. :D

Seriously, the other posters covered it well.

I would just add that when you are looking at speaker/amp compatibility to consider also the speaker efficiency. This will have a big impact on how much power you will need to drive them.
 
"Watts per channel" is supposed to give you a feeling of how loud your amp will make your speakers sound when compared to your current "watts per channel" amplifier and speakers combination.

The problem with that is that power and perceived loudness are not linear and have an exponential relationship. It takes a doubling of the power (say 50W to 100W) to just notice an increase in loudness.

....and that's for a given speaker. If your speakers never seem to play loud and you've driven your amp into distortion, trying to make your speakers play loudly, then doubling the power on your amplifier will only make your speakers play a little bit louder. .....and that's if your speaker's woofers haven't gone into thermal compression. Speakers with low sensitivity numbers will never play loudly.

I know that a power output capability is nice to know what kind of clean power can be sourced from an amplifier's power supply. But, I like to think about amplifiers as voltage sources and would rather have the specs stated as voltages into resistive loads.
 
You are probably only using a watt or two continuously, unless you crank your tunes to ear splitting levels. For example, if your speaker sensitivity is 90 db @ 1 watt, which is fairly loud BTW, you will need 2 watts to reach 93 db. Wattage is doubled for every 3 db increment. 4 watts for 96 db, 8 watts for 99 db, etc.
 
Watts are just derived from the voltage output of a given amplifier into a specific load. For example if an amplifier is pushing 4VAC into an 8 ohm load without distortion you can use the formula VAC^2 / Load Impedance = Watts, to reach an output of 2 Watts.

I guess its not cool to measure your amp in volts since watts sounds so much cooler.
 
Watts is used because electrodynamic speakers are actually oscillating electric motors. It's a combination of current and voltage that makes a motor work. Hence watts is a more appropriate measurement.
 
Watts per channel means a manufacturer is either honestly attempting to provide you with some idea of an amplifier's output capability, or is purposely attempting to mislead you by overstating that capability. A 100wpc amp may not provide any more power into a pair of real-world speakers than a 50wpc one, and that can be true even when both specs are provided honestly. The 8-ohm spec is obtained using a dummy load, not speakers. Bottom line is that wpc specs are often useful, but not all the info is always provided, and when they sound too good to be true for the price, then they are probably untrue.

Best specs will include continuous power into 8, 4, and sometimes even 2 ohms with both channels driven across all audible frequencies (not just at 1khz, which I'm seeing more often these days with some products). Also, many folks don't really need as much power as they think. As usual, it comes down to connecting an amp to a speaker and letting your ears decide.
 
Also worth noting - or repeating - WPC is usually an average power rating. Most amps will deliver around twice that with acceptable distortion for instantaneous peaks, or bursts.

Seems the older the equipment gets, the more conservative the watt ratings too. A "classic" rated at 40wpc may indeed outperform one of the newer 1000 watt units for pure listening pleasure. Holds true in my experience anyway.
 
per channel?

I have heard that the "per channel" is loosely measured. In other words the 75 watts may not be per channel driven at the same time. It may be per channel with only one channel driven and no load or signal on the other channel. This method has been disputed from way back and very flexible. The distortion figure given is again for only that one channel at one time.
If both are driven to the max rated output the rules get shaky.
How much distortion can be maintained with both channels driven? How can the power supply drive both channels with adequate supply to keep the distortion at the advertised level?
It all comes to what is advertised and how the consumer uses it.
Reviews to equipment usually arrive at different figures. Sometimes better, sometimes worse.
The manufacturer will of course dispute poor performance citing things like line voltage, equipment temperature, speaker load, speaker lead length, speaker impedance at certain frequency, and so on. In other words a crap shoot.

Paul
 
Striker2237 said:
I'm really new to the Hi-fi segment of audio ....
Click to expand...

Just curious: How did you end-up with a set of Polk SDA's?

Those are quite nice speakers but not generally what you would expect someone new to this hobby to chose. Don't get me wrong - you chose well :yes: :thmbsp:

Welcome to AK also!
 
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