how does current work in an amplifier?

The are some misconceptions about current. Here's the big one:

http://www.atma-sphere.com/papers/myth.html

Others have already touched on the serious aspect of this, the idea that for 200 watts you need 7.07 amps (if a 4 ohm load) which is not really all that much.

Another way of stating 'high current amplifier' is to say that it behaves as a nearly perfect voltage source. Confusing?? yeah. Here's how it works: if the amp makes 28 volts into 8 ohms, that is 98 watts. Now if it is a 'voltage source' it will make the same voltage into 4 ohms and that is double the power, since the current increases as the impedance decreases.

The *real* issue is, is this behavior correct for a panel speaker? For certain box speakers it certainly is, as there is a woofer in the box that has a resonant frequency and that is represented by an impedance peak. With a 'voltage source' amp, that would cause the amp to throttle back its overall power as it encounters the peak. This keeps the frequency response flat.

So is this the right response for a flat panel? The panel has an impedance curve that has nothing to do with a box, and it does have cancellation as you approach the low frequency cutoff. You might want more power, if anything, as you approach the cutoff, to maintain flat response.

Tricky.

This might be why there are so many advocates of tube amps on Magnaplanars; A tube amplifier will try to make something more like constant power into a load rather than constant voltage. This means the voltage and the current will vary with the load.

IME you don't need all that much current to make Magnaplanars sing, the amp just has to be comfortable with the load, which is not that hard. Otherwise they are fairly easy to drive.

A nice thing to do if you have Magnaplanars and tube amps is to back the amps up to the crossover and use a speaker cable that is as short as possible- 6 inches is a good length, and make the connections as tight as possible. This can have a profound effect on the bass impact!

Unsound is right, tube power is expensive relative to transistors. This has been the case since forever; in the old days when transistors were coming in, manufacturers realized that they could build a transistor amp for about 1/10th the cost of tubes, but were able to charge about 90% of the retail. There was a tremendous financial incentive!

Speaker manufacturers, seeing that SS amps could double power into 4 ohms, began producing 4 ohm speakers that had larger voice coil gaps (easier to make). This cut their driver cost by a similar factor, and again it was possible to charge nearly as much- another financial incentive! IOW, it was cost and the ability to make more money that drove the rise of transistors and low impedance speakers in the 60s and 70s.

Unsound, certainly! I think we can add to that, heat, as well (although I know of transistor amps that run as hot as tubes). We are talking about a very traditional set of tradeoffs when these aspects are brought into the conversation: convenience vs performance, an issue you see in nearly every field of endeavor.

Mapman, Of course semiconductors have improved immensely since the beginning of the art! I'm not saying there is anything wrong with 'progress' in of itself. I'm just pointing out a simple fact.

Dob, I like the idea of EPDR; like other specs it does not appear to tell the whole story, but certainly would standardize a lot of things that can be hard to winnow from the other specs you see. IME, Magnaplanars seem to have an easy EPDR rating compared to a lot of 4 ohm speakers I have seen. This would be very apparent if such a spec were commonplace.

Unsound, There has been testing in the laboratory that has quantified subjective listening objectively. What the testing has shown is that if the sound system violates human perceptual rules, the processing of the music moves from the limbic system to the cerebral cortex. Pretty interesting stuff.

Unsound, most of the studies I am aware of in this area are so new that they are not published yet. However, one of the people conducting them is a Nobel Prize neuro-chemical scientist. I understand that High Emotion Audio has based a lot of their work on his studies.

Magfan, isn't that the other way 'round? :)