Dukk

"Program" makes the most sense as it is theoretically the power handling with actual music input. JL used to have a dealer binder that had power ratings based on the type of customer. If I recall right they were something like, audiophile, average, and bass monster.

At the end of the day, the marketing department has more of a say in what number goes on the box than the engineering department

footballdad

How i understand it is RMS (aka. thermal power handling) is the max wattage that the speaker can take for extended periods without blowing. And peak is the max wattage during a short spike in input (big bass hit, loud something). But it differs between manufacturers. Kicker L7 8" is rated at 450rms, but looking @ the manual as soon as you enclose it that number is f'd (200w sealed, 375w ported, etc.). Cerwin-vega manual says box design doesnt affect power handling, maybe because their gear is better Box design, signal strength and clarity, proper crossover points all make a difference. It's confusing as #@$% for noobs like me. Feel free to correct me if i'm way off on something. Cheers yall.


Dads need solid bass too!
P.S. Kelowna rocks

zoomer

iTrader: (3)

speakers have 2 limits on power handling:
1: thermal limit: how much power a speaker can take before the voice coil insulation overheats and shorts or wire melts.
2: mechanical limit: how much power it can handle before something breaks due to overexcursion.

having said that I agree with the posts that there is no standard specification on this.

Generally the rms rating of a speaker is the thermal limit for continuous input at a frequency that generates enough voice coil movement for cooling airflow but not enough to cause physical dammage. For a sub this would be above the free air resonant frequency and is independant of box. It would be the power where the thermal properties of the design allow for heat transfer out of the voicecoil at a rate equal to the power dissipated by the resistive losses. I am presuming that all the power is dissipated as resistive loses. Of course the surround will warm up also as it is defoemed just like a tire does when rolling but I presume that this is very small. One normally does not expect a surround to get warm to the touch! And some power is dissipated as acoustic power in the sound waves, but as we know speakers are very inefficient converters of electrical energy to sound energy, so again this is negligible. Your walls dont get hot do they?

The peak power is a short burst that again probably does not cause overexcursion of the vc but is an arbitrary (no standards) short burst that the vc can handle without overheating. The heat is absorbed by the heat capacity of the copper and vc structure.

Now comes the more difficult one: Max power for mechanical damage: going way beyond the linear limit of Xmax and damaging the spider or surround or bottoming out (voice coil former hitting the back of the magnet structure) or comming out of the magnetic gap and getting stuck. Also voice coils detach from cones, spiders detach etc.. This is not specified as it totaly depends on the box design and frequency. It is more problematic in vented designs as a simple ported box has no loading below the vent frequency and the sub can easily exceed its excursion limits with very little power. This sub excursion power vs frequency limit is calulated by sub design software and is surprisingly low often a quarter of the RMS limit depending on frequency.

for midranges and tweeters it is usually the thermal limit that is of concern because they are usually not used below resonant frequency.

Program power is the total power delivered to the speaker using music over the designed frequency range of operation of the driver. This would be an average power plus peeks. I think it is a good measure. But remember it also depends on the type of music and the frequency content of it. Classical music, jazz, techno, rap, hip hop etc all have different frequency distribution of the music. Be carefull: a tweeter may handle 100 watts of program power, but I dont think any *non pro sound reenforcement* tweeter can handle 100 watts rms of power.. there is no way that the physical structure can transfer the amount of heat as is generated by a 100 watt bulb.. are your tweeters ever as hot as a 100 watt bulb? NO! what it means is that the tweeter can handle program power of 100 watts, which, when crossed over at the recomended crossover frequency of say 3500Hz, may result in only 20 watts or less going to the tweeter.. (can someone corroborate this?)

for example: you really think these tweets can handle 350 watts of sine wave at 10Khz?
http://cgi.ebay.ca/ORICA-1-4OHM-350WATT-TWEETER-PAIR-BRAND-NEW-/320586003540?pt=Car_Speakers&hash=item4aa46a3454


think of it.. what happens to a 100 watt light bulb? it gets so hot that it glows. The filament dissipates 100 watts of heat into the vacuum around it via light and infrared energy. It hits the glass bulb and dissipates into the air. If you get a voltage surge what happens? more current passes thru, it heats up more, and if the heat cannot escape from the fillament fast enough it will heat up and melt. Imagine your tweeter...Do you really think that the tweeter can dissipate 100 watts of heat? if it could it would probably burn your fingers if you touched the magnet just as you burn your fingers if you touch a light bulb!

Hope this helps

kevmurray

Agreed and I'll add: at the vent tuning frequency the excursion is very low which can lead to thermal damage. Usually only a problem with test tones since music is dynamic.
True though most software does not calculate the mechanical limits but rather the maximum displacement before non-linear distortion becomes significant. Reputable manufacturers list xmax as the distance before the windings leave the gap, not the actual suspension limit. The major contributor to non-linear distortion is the voice coil windings leaving the magnetic gap and therefore losing strength (Bl modulation).

Exactly
Good post Zoomer

RomanticMoments

First off, awesome post! Agree with everything except (just being picky here lol) the lightbulb theory... Tungsten is typically used for it's extremely high melting point... In other words, the filiment is designed to heat up, however, heat from voice coils is simply a biproduct, not the purpose. The program measurement does seem to be the most accurate option, so I agree there as well. Nice write up

zoomer

iTrader: (3)

I was trying to get people to think a bit of common sense. Regardless of the material whether it is the tungsten glowing bright in a 100 watt bulb or the voicecoil warming up due to a 100 watt signal, it is still the resistance of the wire that is drawing the power. It creates the same amount of heat and has to go somewhere. In both cases it ultimately dissipates into the air around it.
In the bulb it goes thru the rather large area of glass. If the glass was perfectly conductive to visible light and infrared light it would not get hot. In a tweeter it has to go from the coil/former thru air to the ouside via some venting and via conduction thru the magnet. Yea, I could analize it more but the 100 watts of power gets converted into heat and has to go somewere.

and I must dissagree: the heat generated as infrared radiation in the tungsten filament is also a byproduct of generating light! Thats why incadescent bulbs are so inefficient. The same is for speakers...most of the power goes into heat and mechanical losses and very little into acoustic power.

Thanks for the compliments

AAAAAAA

iTrader: (7)

Yeah good stuff zoomer.

RomanticMoments

Hehehe... We are having a slight disagreement over a light bulb... I love it LOL Please, look up incandescent (not to be rude)... The filament is heated to incandescence. The filament is heated for the purpose of light. Can't argue with the resistance comment though, you are completely right there, and your analogy is great, I'm just playing devil's advocate with intelligent person

zoomer

iTrader: (3)

The wikipedia entry for incadescent light bulb is actually quite interesting

what exactly are we dissagreeing on? I say that light bulbs are not efficient, that most of the energy is converted into heat instead of visible light just as a speaker converts most of the electrical energy into heat rather than acoustic energy.

RomanticMoments

I haven't read the wikipedia entry, but I'm sure it is entertaining. I was only nit-picking the filament example. It's all good bro, you aren't really wrong about anything, just trying to make conversation. You obviously have some brains, so exploring the inter-workings of a lightbulb and how it relates to a speaker's operation is obviously within your mental capacity. It's refreshing to find on a forum