Swamp, in the beginning, most of us (I know I did anyway) conceptualized 'impedance' and 'resistance' as being essentially the same thing; because they are both expressed as ohms. and we were taught (first) that ohms are a measure of resistance. Strictly speaking, that is NOT TRUE! It is IMPEDANCE that is measured in ohms, and RESISTANCE is simply ONE KIND of impedance ;-) Impedance is indeed the better term, because it refers to any condition that IMPEDES the flow of current (resistance being just one such condition.)
So, for instance, when a manufacturer specifies their speaker is "4 ohms" that's NOT what you will read if you just put an ohm meter across the speaker terminals ;-) That 4 ohm "nominal impedance" is in fact a "weighted average" of the impedance (to current flow) that the amplifier "sees" at EACH frequency across the entire spectrum. But that speaker is by no means 4 ohms across the board!
Further, when a speaker manufacturer specifies "power handling capacity" (like, 50W - 200W) they're not just saying the minimum watts you need to 'make it play', or the maximum watts before you 'fry' your speaker ;-) What they are really getting at is the RANGE of (amplifier) power ratings in which the speaker will produce the whole frequency spectrum (and without distortion.) For example, below 50 watts, some parts of the frequency spectrum (associated with hi impedance) may not reproduce at all, or only with distortion. On the other hand, driving the speaker above 200 watts, at certain (other) parts of the frequency spectrum associated with lo-impedance, you could indeed fry something (like a dome tweeter's voice coil, or burn a hole in your electrostat's diaphragm!)
Did you know that a MartinLogan panel's IMPEDANCE can drop to less than 1 ohm at 15KHz?! So if you were using a ss amp with a rated power of say 200W/ch @ 8ohms, then @ 4 ohms (following Ohm's Law) it could deliver 400W, @ 2 ohms, 800W, and @ 1 ohm, 1600W!! But at each stage, the VOLTAGE part of those bigger watts would be increasing more and more, compared to the current part. So if you were playing a LOUD 15kHz with a solid state amp into your MartinLogan, huge voltage would build up across the air gap in the panel, and pretty soon ZAP - lightening! (better known as arc-ing) and you've burned a hole in your diaphragm!
OTOH, due to the "impedance matching" capability of transformers, a tube amp won't produce this result with an electostat (unless it's a mutha of a tube amp, and your hand slipped on the volume control!) Tubes have a high internal impedance (think of a high revving 4-cyl engine) and speakers generally have a low internal impedance. Solution for getting the power to the road? A 6-speed gear box! Better known as an output transformer. If you select the correct 2, 4, 8, 16 ohm tap (gear) then you can match the amp's power (torque) to the speaker's load (incline of the hill) for maximum power transfer! (Don't ya just love physics?!) What this means (broadly generalizing ;-) is that a tube amp can supply the same watts, comprised of the same proportion of amps and volts, into any impedance. Only one solid state amplifier I know can do this, and that is McIntosh; BECAUSE they ALSO use output transformers on their SS amps, even though they don't really have to -- but it keeps THEIR clientèle from making bad amp/speaker choices ;-) I just happen to be a McIntosh "clientèle" but not because I don't know how to select an amp! ;-)
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So, for instance, when a manufacturer specifies their speaker is "4 ohms" that's NOT what you will read if you just put an ohm meter across the speaker terminals ;-) That 4 ohm "nominal impedance" is in fact a "weighted average" of the impedance (to current flow) that the amplifier "sees" at EACH frequency across the entire spectrum. But that speaker is by no means 4 ohms across the board!
Further, when a speaker manufacturer specifies "power handling capacity" (like, 50W - 200W) they're not just saying the minimum watts you need to 'make it play', or the maximum watts before you 'fry' your speaker ;-) What they are really getting at is the RANGE of (amplifier) power ratings in which the speaker will produce the whole frequency spectrum (and without distortion.) For example, below 50 watts, some parts of the frequency spectrum (associated with hi impedance) may not reproduce at all, or only with distortion. On the other hand, driving the speaker above 200 watts, at certain (other) parts of the frequency spectrum associated with lo-impedance, you could indeed fry something (like a dome tweeter's voice coil, or burn a hole in your electrostat's diaphragm!)
Did you know that a MartinLogan panel's IMPEDANCE can drop to less than 1 ohm at 15KHz?! So if you were using a ss amp with a rated power of say 200W/ch @ 8ohms, then @ 4 ohms (following Ohm's Law) it could deliver 400W, @ 2 ohms, 800W, and @ 1 ohm, 1600W!! But at each stage, the VOLTAGE part of those bigger watts would be increasing more and more, compared to the current part. So if you were playing a LOUD 15kHz with a solid state amp into your MartinLogan, huge voltage would build up across the air gap in the panel, and pretty soon ZAP - lightening! (better known as arc-ing) and you've burned a hole in your diaphragm!
OTOH, due to the "impedance matching" capability of transformers, a tube amp won't produce this result with an electostat (unless it's a mutha of a tube amp, and your hand slipped on the volume control!) Tubes have a high internal impedance (think of a high revving 4-cyl engine) and speakers generally have a low internal impedance. Solution for getting the power to the road? A 6-speed gear box! Better known as an output transformer. If you select the correct 2, 4, 8, 16 ohm tap (gear) then you can match the amp's power (torque) to the speaker's load (incline of the hill) for maximum power transfer! (Don't ya just love physics?!) What this means (broadly generalizing ;-) is that a tube amp can supply the same watts, comprised of the same proportion of amps and volts, into any impedance. Only one solid state amplifier I know can do this, and that is McIntosh; BECAUSE they ALSO use output transformers on their SS amps, even though they don't really have to -- but it keeps THEIR clientèle from making bad amp/speaker choices ;-) I just happen to be a McIntosh "clientèle" but not because I don't know how to select an amp! ;-)
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