What exactly does recommended power amplifier power mean?

[brubacca]

I see this for several speakers:

Recommended Amplifier 40 – 250 Watts


Suggested Amplifier Power Output:
40W ‐ 300W without clipping

You get the idea. I am concerned about being on the low end of the spec here, not the high end.

Does this mean that with a good quality 40W amp I can run these speakers all day long? Does it mean that I'll be able to get the rated frequency response out of them? Or does it mean ... It will work and you will not damage the speaker, but you may not get optimum sound out of the speaker.

Thanks in advance.

[hemster]

You most certainly can run these speakers all day long with an amp rated at 40wpc at full (i.e. manufacturer's stated) frequency response. 
Optimum sound? Now that's another matter. It depends on how loud you like to listen, the music genre you prefer etc. but generally speaking, I would think you're better off with the upper end of the recommended power rating. That caters for heaps of power if you need it and won't distort the sound if you're prudent with the volume control. 

[Canuck_fr]

What is the efficiency of the speaker?

How far will you be sitting from the speakers?

From those two settings, you can elaborate how loud they will play with different power amps.

That is the only thing that really matters

[brubacca]

90db and less than 10ft. Based on that I should be able to achieve 100dB peaks with my amp, which is well above normal listening level.

[Jim]

I'm not happy unless I can replicate a jet engine.

You know. Like dangerous levels. Forget puny 100 db.

:-)

[brubacca]

I just can't wrap my head around the idea that a pair of floorstanders with 3 or 4 drivers will go louder than a standmount with just two drivers (85dB standmount, 90dB floorstander, same manufacturer, same speaker line).

I only listen to music on this one. No jet engines or explosions necessary.

[rocky500]

Mar 12, 2015 5:00:36 GMT -5 brubacca said:

I just can't wrap my head around the idea that a pair of floorstanders with 3 or 4 drivers will go louder than a standmount with just two drivers (85dB standmount, 90dB floorstander, same manufacturer, same speaker line).

I only listen to music on this one. No jet engines or explosions necessary.

Heres one for you. Check out the specs and it has 2x 12" drivers. Effecient and Recommended Amplification up to 2000 watts RMS (program)
jtrspeakers.com/home-audio/noesis-212ht-lp/

[Boomzilla]

Generally, the more drivers, and the larger the drivers, the louder a speaker can play without physical damage to the drivers themselves. Why? Because the "normal" limit on driver output (for the moment, assuming infinite power and no clipping) is the travel of the speaker diaphragm before it hits the stops. Once the driver is out of travel, it begins ripping itself from the voice coil.

For a given SPL, the larger driver travels less than a smaller one. For a given SPL, multiple drivers each travel less than a single one of the same size.

These "driver limits" can be cheated on by using a coupling device (commonly called a horn) to increase their coupling to the room air. This makes a small driver behave like a much larger one. An added benefit is reduced intermodulation distortion.

One of the lowest distortion speakers in the world is STILL the Klipschorn corner horn. It effectively uses the corner walls of the room as part of its "coupling horn." The system can produce about 103 decibels at one meter from a single watt of electrical input.

So yes, brubacca, all other things being equal, a multi-driver floor-standing speaker CAN play louder than a stand-mounted two-way.

Cheers - Boom

[lionear]

If the manufacturer says 40-250W, then I'd pay attention to the lower figure. The speakers may have a certain efficiency, and manufacturer may be concerned about a 20W amp being pushed too hard as the user cranks up the volume to a "realistic" sound level. An amp that's pushed too hard will clip, and that will result in bad sound and damage to the speaker. Of course, if your listening room is very small, you listen to very low levels, with music that doesn't have crashing crescendos, you may be fine with a 20W amp.

You can ignore the upper figure. There's no upper limit (with a caveat) for a speaker. As long as your volume level is at a reasonable level (say 70 dB), there's no problem in an amp sending a 300W or 400W signal to the speaker when playing a musical climax or an explosion. That signal will be very short in duration, and the speaker will usually be fine with it.

The caveat: When there's too much power, the drivers will not move in a smooth pistonic motion. This has been referred to as "cone break up" and the sound will be very rough and distorted. It's directly related to the volume - when you reduce the volume, the speaker will sound nice again.

I've also found that an amp that has higher power will also most likely sound more dynamic and have better bass. But this may not show up in tests.