What does Current mean in a power amp???

Current is the rate at which charge passes a given point in a wire. If you were somehow able to count the charges as they went by in a wire carrying 1 ampere (1 A) of current, you would discover that every second an entire Coulomb of charge passes by.

Additionally, the "formula" provided in the first post is for a DC current. Since loudspeakers are designed to use AC current that formula will be of little use.

High current amps are typically big and heavy with large heat sinks. There are many but think Krell and Levinson.

Talk to a dealer that sells your particular speakers. He can best guide you in finding a good, quality high current amp that will satisfy your aural needs

Ohm's law has nothing to do with whether or not an amplifier can drive a speaker. While an amp may be able to sustain high power levels into low impedances, that tells you nothing about how well it deals with various amounts and types of reactance across a wide frequency spectrum. It is possible for a speaker to have sharp phase angles at several different frequencies all at the same time.

If you can picture a combination of a "slalom course" AND a "torture test" for amplifiers, that is what some speakers present. As such, you can have a speaker that is highly capacitive at treble frequencies, highly inductive at low frequencies and generates a high amount of reflected EMF ( electromotive force or "voltage" ) all at the same time. All of this can be independent of the amount of "pure" resistance that the amp sees at any given time or frequency. This is why speakers are a VERY complex load and why we don't have specific "tests" that show whether or not an amp can drive every load known to man OR maintain consistent sonic characteristics doing so.

Something else that is not commonly considered is that amplifiers produce LESS power as impedance is raised i.e. kind of the "reverse" of looking for high current into low impedances. After all, impedance raises at the point of resonance on a woofer. As such, power transfer is reduced right at the point that you need it most. Since vented systems typically have MUCH higher impedance peaks at resonance, you have even less power available to control a driver that is already lacking "damping". Even though most manufacturers do not offer power output specs into 16 and 32 ohm loads anymore, one might be able to make a more informed opinion about the overall build quality of an amp if we did know such things.

If you think that this sounds "crazy", take a look at the impedance curve of a vented speaker with a large woofer(s). It is not uncommon to see impedance peaks at resonance along the magnitude of 40 - 100 ohms. What kind of power transfer do you think an average SS amplifier is going to produce into a 50 ohm load ??? Let me tell you, not much.

Most "good" sealed designs keep the impedance of the woofers below 20 ohms, which results in much more accurate and controlled bass. This is due to the increased ability of the amp to transfer power and literally "muscle" the cone when it does not want to see any type of signal at all. After all, resonance is nothing more than the speakers' point of self oscillation. If excited at that frequency, it is literally contributing sound on its' own. It is up to the amplifier to "force feed" it at that point and damp / control the ringing that is taking place. Obviously, a lower impedance at resonance allows the amp to generate more power. This in turn can effectively work to control the speaker and produce greater accuracy.

Having said all of that, rms power ratings are WAY to easy to fudge given the way that the FTC has things set up. I think that measured power output at CLIPPING at various impedances is FAR more revealing of how "sturdy" an amplifier is. After all, this is the point of maximum long term stress for an amp. As such, it is the ultimate test in terms of how much TOTAL power the output devices can pass and how much current the power supply can sustain. If an amp can come close to "doubling down" at the point of clipping from 32 ohms down to 2 ohms, it can probably drive just about any load that you can throw at it. To do so would mean that the amp was as close to a pure "voltage source" as we are currently capable of making. Even if the amp is sturdy enough to do something like this, there is no guarantee that you will like the tonal balance or level of refinement & detail that the amplifier produces. Passing the aforementioned test simply shows that it is capable of "brute force" into just about any given load and does not necessarily mean that it will "sound good". It will however, drive the load that you connect it to. Sean
>

All of the explanations above are technically accurate, but here's a very simple way for those not versed in science or engineering to think of current vs. voltage.

Imagine a river. The amount of water that is moving downstream is analogous to the voltage -- i.e., it's a measure of the size or quantity of the flow (say, 2500 cubic feet per minute). The current, or force, behind the water (usually due to gravity) is the other measure of actual or potential energy.

A river or stream with little current does not yield much energy (or force). Similarly, you can also have a relatively wide river that is very slow moving, and it does not exert much force. (If you have ever waded a river, you know from experience that it's a lot easier to cross a very slow moving flow than one moving rapidly.)

Conversely, you can have a narrow stream of water moving at very high current, and it will produce quite a bit of energy. To carry this analogy to an extreme, think of the cutting tool known as the "Water Knife" -- it forces a very small stream of water (with an abrasive added) at high pressure (up to 50,000 psi) through a small nozzle, and the stream is capable of cutting through a variety of very hard materials (such as steel).

So, to stretch this analogy, there are two ways for an amp to drive a speaker load: high current (the force), or high voltage (the amount of electricity).

Yes, yes, I know this is a rather unsophisticated explanation from an engineering standpoint, but it has the virtue of being conceptually simple for those who didn't take physics or EE courses in school.

Nikki...,

Let me be straight forward on how good watts are different from bad ones...

If you for example take a look on professional power amps such as Carver highly regarded by DJs available at RadioShack stores, you can see and feel that it has a plenty of boost and the power(~300W/side) to any impedance load and pretty darn cheap(aka $250).

The Ohm's law mentioned up above states that ALL watts are "created" equal. The double wattage of the good amps into the lower impedance loads cannot be rated as a CONTINUES power and needs lots of lines to explain. Shortly I can say that price of an amp is not an explaination why one has a reserve power and the other one hasn't.

To increase the power you either have to increase the current or the voltage.

The main problem in this issue is our 110V wall outlet power that realy limits engineers to work on high-power-quality amps where designing a proper power supply is the most essential issue.

So to correct you in both threads I must state that the main design difference between "bad watts" and "good watts" is that the power supply is OK to handle the large current.

The quality of sonics (I must say here that it's completely different issue from wattage) is the quality of an active amplification elements(tubes, transistors, diodes) and also passive elements. The working area of an amplification elements in high quality equipment is selected so that it covers the widest-possible freequency bandwidth rather than working in the peak values. Thus more transistors or tubes is required to deliver the signal to desirable level with good output characteristics.

Ohms law is not really a good way to figure current output of an amplifier. Ohm's law works in a purely resistive DC circuit. The output of an amplifier is AC. You generally will be required to factor in inductance, capacitive reactance and pure resistance (this makes up impedence)to come up with the current output into any given load. Amps that "Double down" are always better for driving low impedence loads. However, things can happen to an amps output when the load has steep phase angles and high reactance. Look at the dbw that Stereophile uses in rating amps for some reference. The bottom line here is that each amp will behave differently into the reactive load of different speakers. A resistor on the test bench doesn't mean a lot.
With this said, current is the ability of the amp to deliver actual power expressed in watts into a given load. Power(in watts)= volts x amperage This is a simplification of a more complex calculation.