Watts per channel: Are they not created equal?

[Spiralout]

I've always correlated WPC with the overall ability to get loud. More watts...more boom. Right?

I've heard things like double the power, gain 3db. 10 times the power doubles the perceived loudness. yada yada.

I've also heard people driving large speakers with tiny 25 WPC amps. I've seen people post comments about you're not going to get the full effect if you don't drive them with Xhundred watts per channel.

I always thought that the receiver/amp was only using enough power to generate the desired volume level. So wouldn't a 25 or 50 watt amp drive the speakers the same at normal listening levels as a 200 watt amp driving at the same dB level?

In other words, at a low volume level, what difference does it make between 25 total watts and 200?

(This question is completely barring the fudging factor by certain manufacturers. I mean when they state 100 watts per channel, but don't mean when all channels driven, so you may only be getting 30 or 40.)

[billnchristy]

It all comes down to headroom and dynamics really.

If you are cruising around the 1w zone (which most likely, you are) when listening to music at a normal level, you will have so much in reserve. Using the double the power, gain 3dB theory, we can look at it this way:

8w amp:

1w baseline
2w +3dB
4w +6dB
8w +9dB

This amp has 9dB of headroom, so if you are listening to classical and there is 15dB of dynamics up ahead, you are in danger of clipping the amp because it is going to run out of juice at 9dB.

50w amp:

1w baseline
2w +3
4w +6
8w +9
16w +12
32w +15
64w +18

This amp will make it...just barely.

[Spiralout]

So when someone says "using an x WPC amp will really open them up," they're referring to their ability to grow and shrink with the music's needs?

What does clipping an amp (vs clipping a speaker) sound like?

[billnchristy]

Depends on the type of amp.

Tube amps flatten the clip so it smooths over so it just starts sounding saturated instead of harsh.

SS amps generally get really harsh, especially on the high end, clipping is like a saw-tooth wave and not pleasant.

digital amps are even somewhat worse.

It is said that you don't hear it until around 10% but you can hear the onset of it probably a lot sooner.

At low frequencies it is even harder to hear and you can easily exceed 10%.

[m-fine]

Also speakers are not all created equal.

One speaker might put out 85 db at 1 watt measured at a distance of 1 meter, while another speaker might put out 95 db and another 105 db.

Obviously if you have the 105 db "sensitive" speakers you can get decent dynamics with an 8 watt amp. If you start with 85 db speakers, you would need about 500 watts to get to the same levels.

Finally there is distance. Subtract 6 db for every doubling of the distance from the speaker, so 2 meters subtract 6 db, 4 meters subtract 12 db.

So, with a lower sensitivity speaker in a large room (you sit far back) you may find 2000 watts is not enough, whereas in a smaller room with sensitive speakers someone else may find 8 watts plenty.

[skullguise]

And then there's speaker impedance, and an amp's ability to drive that impedance well (or not).....

[Spiralout]

Yep, I know. This thread was started with only WPC in mind.

[Stereodude]

A watt is a watt is a watt. :stirthepot:

[CloudStrife]

What about the difference between tube watts and SS watts, if there is such a thing?

Isn't saying a watt is a watt is a watt the same as saying a wave is a wave is a wave?

[Superior Audio]

1 watt of energy is only 1 watt of energy no matter what is producing that 1 watt of energy. Now the way that 1 watt of energy is produced can take different forms but the end result is still only 1 watt of energy.

To put it in simpler terms, 1 watt of energy generated by a nuclear power plant is still only 1 watt. And 1 watt of energy produced by a coal fired steam power plant also is still only 1 watt.:scratchchin:

[Mark Seaton]

A watt is a watt is a watt. :stirthepot:

While that is true, we don't drive speakers with watts, we drive them with Volts. For a variety of reasons we quantify the output in terms of approximate watts, but what really matters is how well the amplifier can deliver an accurately scaled version of the input signal to the loudspeaker.

[mojave]

A watt is a watt is a watt. :stirthepot:

Watts love - a second hand emotion :D

[m-fine]

A singnal is in Volts (V). The resistence or impedance (R) of the speaker and the voltage desired determine the current required from the amp to maintain the desired voltage. ( V= IR or I = V/R)

Current times voltage is power or watts.

If your amp can not output enough current or watts (since they are directly tied) then the voltage of the signal becomes clipped. IMHO most of the difference people hear between amps is how they behave when pushed too hard, even briefly. There is a big difference on how a tube vs solid state A/B vs solid state class A vs class H etc etc. behave and therefore sound when they are asked to dish out more current/watts than they are rated for.

[m-fine]

While that is true, we don't drive speakers with watts, we drive them with Volts. For a variety of reasons we quantify the output in terms of approximate watts, but what really matters is how well the amplifier can deliver an accurately scaled version of the input signal to the loudspeaker.

Technically we drive speakers with current ;)

[CloudStrife]

So what is harder to drive - 4 ohm or 8 ohm?