[pjchappy]

Say you have an amp with a power rating of 250 Watts into 8 Ohms / 500 Watts into 4 Ohms.  You then use that amp to power 87dB efficient monitors, with a max rating of 150 Watts.

Now, would the speakers be the determining factor into how much power the amp is actually putting out?  In other words, would the amp be able to drive the speakers to the "loudest" they could handle and still not actually be putting out 500 Watts of power? (not considering transient, or whatever, outputs here and there)

Thanks!


Paul

(corrected transposed power ratings)

[Niteshade]

The amp will power them until the voice coil opens or shorts out. The speakers do not dictate how much power an amp puts out, just how much they can absorb. Your loudest before distortion should be at 150 watts.

[pjchappy]

My question is definitely a bit poorly worded, then.  Basically, under "normal" listening conditions of high volume and low distortion, the amp would only have to output 150 watts max to reach these levels?  In other words, it would never output, say 400 Watts, to push a speaker (as mentioned in my first post) to such "normal" listening levels?  Hopefully these questions are clear enough.


Paul

[srb]

The speaker manufacturer is saying that 150W is the maximum average power the speaker can take before you reach thermal or mechanical excursion limits for any of the drivers, whether you have a 200W or 2000W amplifier.
 
Steve

[*Scotty*]

Paul, think of it this way if 1 watt gives you 87dB,10watts will give you 97dB, 100watts 107dB,150watts 107 plus a fraction of a db. If you had 200watts you would see 110dB SPL or a 3dB increase in loudness over 107dB. If this is a maximum continuous input and not an instantaneous maximum limit you might be able to hit higher peak SPLs over the short term where you would more closely approach the 500watt output capability of the amplifier.
Hope this info helps.
Scotty

[pjchappy]

Yep, makes sense and was basically what I figured.  So, I could have a billion Watt amp and push the speakers to the loudest they could physically handle. . .and the amp, for all intents and purposes, would have only output 150 Watts or so, max.

[*Scotty*]

You might ask Danny how much power the speaker can take before audible distortion sets in. This may occur long before the maximum thermal limits of the drivers are approached.
Scotty

[macrojack]

Speaker manufacturers do not want to have to do warranty work on their speakers and likewise don't want to have to explain this to people who have already done damage. Therefore, they assign a safe and somewhat arbitrary power handling limit in the usually vain hope that people will take heed and behave sensibly. In the real world it makes no sense to talk about speaker watts.

[pjchappy]

I understand that.  I wasn't necessarily talking about my particular set-up.  Appreciate it, though.

I didn't think it was the case, buy my main question/concern was that a high power amp was going to put out more power at a given volume level vs. a lower power amp, into the same speakers.  Just wanted to make sure. . .thanks again.  The way I just worded that probably would have been the best way to word my original question.



Paul

[smk]

I think it depends on the output voltage of the preamp, input voltage of the amp. There's more to it than that, but that will get you started.

[werd]

Hi

My quote buggy right now so just replied.

I think more power is evident and can be heard in the soundstage with better sense of ease. Also it can translate into better imaging and prat... ime. That is at  the same volume of lower powered amps.  So having more power is beneficial i found.,

the louder you go the harder it becomes for the speakers crossovers and driver voice coils  to cool. And it becomes more dangerous with bigger power.

.02

[werd]

^^^^^^ That is from an SS perspective...

[NagysAudio]

All the responses are wrong. This is a significantly complicated issue and you need to learn electronics before you understand it. Here's a few out of a hundred things to consider:

Most cheap speakers and audiophile speakers don't have Zobel networks, therefore their impedance can vary from 3-16 ohms (or so) in the 20Hz-20,000Hz frequency band. Power(watts)=V(voltage)2(squared)/R(resistance). So what happens to power if a speaker dips to 3 ohms @ 40Hz? What if it dips below 1 ohm?

Also, speakers can handle significant peak power. Many times more than 150 watts.

And it goes on and on and on...

[werd]

All the responses are wrong. This is a significantly complicated issue and you need to learn electronics before you understand it. Here's a few out of a hundred things to consider:

Most cheap speakers and audiophile speakers don't have Zobel networks, therefore their impedance can vary from 3-16 ohms (or so) in the 20Hz-20,000Hz frequency band. Power(watts)=V(voltage)2(squared)/R(resistance). So what happens to power if a speaker dips to 3 ohms @ 40Hz? What if it dips below 1 ohm?

Also, speakers can handle significant peak power. Many times more than 150 watts.

And it goes on and on and on...

Not sure how your response disqualifies everyone elses but ok, you go hoss you tell em like it is.

[srb]

NagysAudio tries to come across as the world's most knowledgeable expert on every entity that has moving electrons.  His posts are full of words like "Wrong!", "Nonsense!" and "Ignorance!".  His inability to even partially concede any point even when wrong, combined with gaps in his knowledge, clearly demonstrates to everyone that he is not an expert.
 
There are two sides to most coins, but not for NagysAudio, where his one-sided boorish behaviour proclaims "My way or the highway".
 
Steve

[MaxCast]

I think Nagy's response is right on.
If the impedance drops too low and the amp is outputting it's full power (say 150w @ 8ohm) then the amp will try to deliver more power maybe causing distortion and frying the voice coil.  Or the amp may double it's power into 4 ohms which may be over the rating of the speaker causing damage.

Paul, an amp will provide the power it is rated for.  The speaker will not stop the power if you continue to raise the volume.  What damages speakers most is distortion when an amp is driven beyond its rated power causing distortion being sent to the voice coil.  And yes too much power can burn up a speaker or break a cone as well.  When the music gets grainy or distorted it is time to back off on the volume.  Or you hear a voice coil bottom out.

What are you trying to do?  Get louder music?

[MaxCast]

I didn't think it was the case, buy my main question/concern was that a high power amp was going to put out more power at a given volume level vs. a lower power amp, into the same speakers. 

Paul

At a given volume level both amps should be outputting the same watts.  A higher wattage amp should handle transients, peaks, and bass better.  Especially if the volume is such that the lower wattage amp is at its rated output.

[JohnR]

I didn't think it was the case, buy my main question/concern was that a high power amp was going to put out more power at a given volume level vs. a lower power amp, into the same speakers.

Assuming that the lower-power amp isn't being driven into clipping, the answer to your question is "no." However, unless you're actually monitoring the output power, this is a technical answer and mostly devoid of practical use...

Bear in mind that most loudspeakers have multiple drivers. The power generated by the amp is split up (more or less) to be sent to each driver. Each driver has two limits: thermal i.e. how much power can you put into it before it melts, and excursion i.e. how much power can you put into it before it hits some mechanical limit. The fun part about this is that neither of these are constant, but in particular excursion varies with frequency, with lower frequencies demanding more excursion than higher. What the driver does when it is driven with more power at a given frequency than it can generate within it's linear excursion depends on the driver.

The power rating of a loudspeaker is, it turns out, not all that useful if you need to ask questions like this. Feed 150W into any speaker rated at 150W, with less than a 12" woofer, at any frequency below around 50Hz, and it will most likely be excursion limited and not deliver the promised output. Feed 150W into any speaker rated at 150W at a frequency handled only by the tweeter, and you will most likely fry the tweeter instantly.

The other element here is that music is not a constant power but has a very high transient-to-average ratio. You can be well within the thermal power limits of a driver, but still be excursion-limited on peaks.

[srb]

Bear in mind that most loudspeakers have multiple drivers. The power generated by the amp is split up (more or less) to be sent to each driver. Each driver has two limits: thermal i.e. how much power can you put into it before it melts, and excursion i.e. how much power can you put into it before it hits some mechanical limit.

The other element here is that music is not a constant power but has a very high transient-to-average ratio. You can be well within the thermal power limits of a driver, but still be excursion-limited on peaks.

 
When I spoke of average power and reaching either thermal or mechanical excursion limits, I guess I wasn't totally wrong after all.
 

The speaker manufacturer is saying that 150W is the maximum average power the speaker can take before you reach thermal or mechanical excursion limits for any of the drivers, whether you have a 200W or 2000W amplifier.

Although it is a complex subject with many variables, and some of the responses, including mine, were more general, it would seem that music listeners tend to view amplifiers and speakers as reproducing a broad spectrum of frequencies simultaneously, whereas more technical types are sometimes all too often focused on the reproduction of single frequency sine waves.
 
Steve

[werd]

I think Nagy's response is right on.
If the impedance drops too low and the amp is outputting it's full power (say 150w @ 8ohm) then the amp will try to deliver more power maybe causing distortion and frying the voice coil.  Or the amp may double it's power into 4 ohms which may be over the rating of the speaker causing damage.

Paul, an amp will provide the power it is rated for.  The speaker will not stop the power if you continue to raise the volume.  What damages speakers most is distortion when an amp is driven beyond its rated power causing distortion being sent to the voice coil.  And yes too much power can burn up a speaker or break a cone as well.  When the music gets grainy or distorted it is time to back off on the volume.  Or you hear a voice coil bottom out.

What are you trying to do?  Get louder music?

Well according to Nagy you are dead wrong because thats pretty much what i said. Everything you said all ends up driving the devices into overheat which basically causes breakdown.