What's this peak wattage all about?

[tommyboy]

I've noticed Klipsch puts a peak wattage on their speakers. My synergy's say max input is 100 watts, peak is 400 watts. Many other speaker companies only put a recommended amp wattage on their speakers. No peak wattage. So I guess what I'm asking is what exactly does peak wattage mean? And with the whole 100 watts max input thing. My old receiver pushes I think 80 w p/c @ 8 ohms. My new one pushes 150 watts p/c @ 6 ohms, and there was a day/ night difference in sound. What's that all about?

[Guest BobG]

The maximum power handling of a speaker is determined by a number of elements. These mostly relate to thermal duty cycle.

Because speakers have very poor efficiency (conversion of electrical input to acoustic output averages well below 5%) they suffer from heating problems. Voice coil temperatures can easily hit several hundred degrees coming close to the point at which the paper, plastic, glue and other materials fail. This is the typical failure mode for speakers, though there are other mechanisms that lead to damage.

Music has constantly varying signal level which makes if tough to use a single number when rating power handling. Thus Klipsch believes we are providing greater understanding of your speaker's capability when we spec both a steady state max input (100 watts in this case) and also a peak power.

Even these guidelines are imperfect as it's possible to damage a speaker using a small amp that is being overdriven. Could you use a 400 watt RMS amp with your speakers? Yes, but you'd have the ability to smoke them. A steady hand on the volume control is always called for as is some common sense.

[wuzzzer]

Peak wattage is just that, the highest level of wattage input that a speaker can handle for short bursts of sound.

I'm assuming that your new receiver sounds louder/better to you? Since you're doubling the peak output watts you're going to typically get at least 3 decibels more sound. Also if your receiver is running in 6 ohm instead of 8 ohm it is 'working harder' because of the lower ohm rating (this will be affected by the ohm rating of your speakers as well, though). Different receiver/amp brands will have different ways they measure their peak output, too. Some will measure peak output at 1kHz which is a frequency that is pretty darn easy for any amplifier to drive so generally they can put out a lot of watts at that frequency. Typically the receivers that give you a true idea of their power capability are ones that display their highest wattage output across the 20Hz-20kHz spectrum.

[tommyboy]

thanks guys!!

[DrWho]

I'm kinda repeating what was mentioned above, but this is what I tell everyone that asks me this question:

"Max power" is the point where the speaker will start to melt if you crank it too hard.

"Peak Power" is the point where the speaker reaches its mechanical limitations.

A voice coil is in many ways just like the heating coils in your toaster. In the same way a toaster doesn't heat up instantly, a voice coil takes time to heat up. The max power rating is the level at which the temperature inside the voice coil remains below the melting point. But since it doesn't heat up instantly, you can get away with bursts of more power, which gives you the opportunity to move the diaphragm much further over very short periods of time. The idea is that you should be able to run 1000W into your speakers as long as the 1000W was only happening with periodic transients (like a kick drum). As long as the voice coil has enough time to cool down before the next one, you'll be fine.

It's really an academic concept though because no speaker in the world is going to sound good when driven near the maximum. I used to do power level testing, which meant I got to blow up a lot of speakers [] It was always the goal to launch a flaming voice coil (which meant the thermal and mechanical limits were met at the same time). Usually the speakers we were testing weren't even strong enough to run into mechanical failure...talk about boring []