Thanks for all the replies.
From the limited research I've done, these two statements sum up the effect the best.
According to this article, a high output impedance amplifier will contribute to a loudspeaker reproducing music that is out of balance across the frequency range. Frequencies in which the loudspeaker has high impedance will be proportionately louder than those frequencies in which the speaker has low impedance. Therefore, treble could be significantly louder than the midrange, etc, thus contributing to a situation where the speaker seems "bright".
Shadorne touched on the second effect of amplifier output impedance, the damping factor, which has the effect of controlling the motion of the drivers...and therefore "tighter" or "looser" bass.
The article to which I refer above states that:
Therefore, if one agrees with the author, an amplifier's output impedance must be less than 1 ohm.
I suppose that answers my question, although I'd like to hear from an expert or two who might specifically state what output impedance measurement is considered too low (X ohm - low), too high (X ohm - high), and just right (X ohm - ideal). Let's call it the Goldilocks Output Impedance Rule.
In short, an amplifier with high output impedance will be much less linear when coupled with a speaker than one with low output impedance.
Shadorne (System | Reviews | Threads | Answers)
Tube amps are notorious for having high output impedance 'curves' (one of mine has a rise to 3.5 ohms in the mid bass frequencies. The net effect of this is in the frequency where this rise occurs I will hear a corresponding rise in frequency response in the speaker.
Newbee (System | Threads | Answers)
From the limited research I've done, these two statements sum up the effect the best.
According to this article, a high output impedance amplifier will contribute to a loudspeaker reproducing music that is out of balance across the frequency range. Frequencies in which the loudspeaker has high impedance will be proportionately louder than those frequencies in which the speaker has low impedance. Therefore, treble could be significantly louder than the midrange, etc, thus contributing to a situation where the speaker seems "bright".
Shadorne touched on the second effect of amplifier output impedance, the damping factor, which has the effect of controlling the motion of the drivers...and therefore "tighter" or "looser" bass.
The article to which I refer above states that:
The lower the amplifier output impedance, the lower the speaker produced voltage is. The lower the speaker produced voltage, the less effect it has on cone motion. A good rule to follow is that amplifier output impedance must be at least ten times lower than speaker impedance for good control of cone motion. This is called damping factor. Amplifier output impedance must be less than one ohm for best performance.
Therefore, if one agrees with the author, an amplifier's output impedance must be less than 1 ohm.
I suppose that answers my question, although I'd like to hear from an expert or two who might specifically state what output impedance measurement is considered too low (X ohm - low), too high (X ohm - high), and just right (X ohm - ideal). Let's call it the Goldilocks Output Impedance Rule.