Originally posted by: Woody419
We will take this one small step at a time.
Originally posted by: tronester1
Im still not quite sure I understand what you are saying. As for the "power envelope" technology, I have NEVER heard of that?
NAD stopped using its well-known peak output power promoting technologies like Power Envelope and Extended Dynamic Power.
The (NAD)2400...Power Envelope circuitry produces 370-440 watts per channel of tone-burst power for music.
The impedance of the speaker does not correlate directly to the efficiency. If that were the case, why would we not be using 1ohm loudspeakers instead of 8ohms?
When an amp is used to drive low impedance loads (1-2 ohms) you may stress it beyond its design capacity. The lower the impedance the more amps a circuit is required to deliver causing the transistors to overheat (
Ohm's Law) and it is more expensive to design an amp to handle low impedances. Remember Apogee electrostatic speakers? They had a very low impedance and had an annoying habit of eating amps, only a few high end amps could handle the load.
The distortion levels have no correlation to how much power the speaker can handle. A speaker sees power as power, it does not matter if it is distorted or not. You could even feed a speaker a straight DC current. The distortion does not destroy the speaker, it is the increased power level that comes with it that does.
Actually an amp that is over driven and distorting will destroy a speaker a lot quicker than a clean amp. In other words, a 25 watt amp driven into distortion will destroy a speaker while a clean 100 watt amp will drive the speaker to a louder dBA without harming it. And as for straight DC, a battery is an excellent way to test the polarity of a multiple speaker setup, just don't use a car battery.
I checked out that Nad website regarding the "Power Envelope". I see several problems with this. First, the dynamic power does not give any indication of how long the amplifier can output that much power before clipping. A gunshot or explosion is not nescesarily going to fit inside that "peak" window. I would assume the continous rating would allow for constant non stop power output. The amplifier is PROBABLY power supply limited, and the filter capacitors in the power supply probably sustain enough charge for a fraction of a second to allow the massive current draw needed for the "peak power operation". I do not see what else would be allowing brief peaks of such a magnitude over the normal output power, other than possibly the heat disapation of the heatsink on the output transistors. But typically the power supply is the weakest link (prolly from the expensive transformer) so I do not know why any manufacturer would have a power supply that would supply more current than the output transistors could handle.
You still are not understanding what I am saying. I never said that you should try and run 1ohm speakers off an amplifier that is not stable down to that impedence. I know Ohms law, but it has nothing to do with loudspeaker sensitivity in the sense I am talking. At the same VOLTAGE, yes lower impedence speakers would be louder, but spl is typically measured at 1w, quite frankly I only think the rating sensitivity at a given voltage is only good when designing xover networks and such, not when comparing two speakers to see which will be louder. I mean come on, what kind of comparison is this: Loudspeaker A has an impedence of 16ohm and a sensitivity of 100dB 2.83v/1m while Loudspeaker B has an impedence of 2ohm and a sensitivity of 101dB 2.83v/1m. When both fed the same amount of POWER, not voltage, which is going to get louder?
As for the clipping destroying loudspeakers, still that is wrong. A 25 watt amplifier has a maximum rail voltage. This rail voltage will not be surpased when the amplifier is driven into clipping. HOWEVER, the current can effectivly be doubled. Look at a sinusoial wave with a square wave with the same peak voltages superimposed over it. They both have the same maximum voltage, but the current delievered by the square wave is approximatly 2 times that of the sinusodial. The reason for this is because the square wave stays at the voltage peaks for much longer than the sine. So, your amplifier of 25 watts can only output 50 total. Your "clean" 100 watts would destroy the speaker quicker than the dirty distorted 25w amplifier could. This is of course assuming the amplifiers rated at 25 and 100 watts put out their respective power.
I already spent mucho time arguing this in the technical section of anandtech: check it out:
http://forums.anandtech.com/messageview.cfm?catid=50&threadid=833797&highlight_key=y
. (I didn't have any money back then but yea..) If they had it for $200 right now i'd get out there and buy myself a pair 
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