Thanks, Mesch. Regards to you as well :-)

I second Larry's comments, except that his last sentence might be taken to mean that speakers ALWAYS "present an inductive load," which of course is not the case. Speaker impedance will usually be inductive at some frequencies, to some degree, capacitive at other frequencies, to some degree, and purely resistive at a few frequencies, where it transitions from inductive to capacitive or vice versa.

But first, it should be made clear that in this context "phase shift of a speaker" does not refer to phase shifts that may be produced in the acoustic output of a speaker, which is a whole different subject. What you are referring to is the "phase angle" of the impedance of a speaker. Impedance consisting of a magnitude, measured in ohms, and a phase angle, measured in degrees.

If a sine wave at a single given frequency is applied to a hypothetical ideal resistor (having no inductive or capacitive component), voltage and current will be in phase with each other, meaning that both will reach their maximum, minimum, and corresponding intermediate values at the same time. If that signal is applied to a hypothetical ideal inductor (having no resistive or capacitive component), current will lag voltage by 90 degrees, or 1/4 of a cycle of the sine wave. If that signal is applied to a hypothetical ideal capacitor (having no resistive or inductive component) voltage will lag current by 90 degrees.

Inductive and capacitive loads are collectively referred to as reactive loads, as opposed to purely resistive loads.

The phase angle of the impedance of a speaker, at a given frequency, is the angle of the "vector sum" of the magnitudes of the resistive, inductive, and capacitive components of the impedance. If the three components were plotted on a graph, by convention the inductive component would be represented as a positive number along the y (vertical) axis, the capacitive component would be represented as a negative number along the y axis, and the resistive component would be represented as a positive number along the x axis. So an inductive phase angle will be a positive number of degrees; a capacitive phase angle will be a negative number of degrees; and a resistive phase angle will be zero degrees. The larger the number of degrees in the positive direction, up to a maximum of 90, the more purely inductive the impedance is. The larger the number of degrees in the negative direction, down to -90, the more purely capacitive the impedance is. Phase angles for most speakers at most frequencies tend to fall somewhere within a range of perhaps +/- 45 degrees or so.

Most of the speaker reviews in Stereophile, which can be found at their website, include measurements taken by John Atkinson of impedance magnitude (ohms) and phase angle, and some good associated commentary.

As Larry indicated, if a speaker load is significantly reactive its efficiency (acoustic power out vs. electrical power in) will be lower than if it were purely resistive, everything else being equal. Hypothetically speaking, if a speaker had an impedance of + or - 90 degrees at some frequency, it would be unable to produce any output at that frequency, as all of the power it received at that frequency would be returned to the source, and none would be absorbed and converted into sound.

Severely capacitive phase angles, especially if they occur at frequencies for which the impedance magnitude (the number of ohms) is low, are particularly demanding on the amplifier. In part because reactive phase angles lower efficiency, as was mentioned. And also because the current drawn by a capacitor increases in proportion to the rate of change of applied voltage, which results in larger demands for current when fast transients occur than would otherwise be the case. The current drawn by an inductor, on the other hand, varies in proportion to the "integral" of applied voltage, which is not as challenging to the amplifier.

Regards once again :-)

-- Al

I second Larry's comments, except that his last sentence might be taken to mean that speakers ALWAYS "present an inductive load," which of course is not the case. Speaker impedance will usually be inductive at some frequencies, to some degree, capacitive at other frequencies, to some degree, and purely resistive at a few frequencies, where it transitions from inductive to capacitive or vice versa.

Does the phase shift of a speaker (resulting in Capacitance) refer to a lag of current behind voltage? Or is this too simple of an explanation?Actually it's the other way around, with voltage lagging current for a capacitive load. Current lags voltage for an inductive load.

But first, it should be made clear that in this context "phase shift of a speaker" does not refer to phase shifts that may be produced in the acoustic output of a speaker, which is a whole different subject. What you are referring to is the "phase angle" of the impedance of a speaker. Impedance consisting of a magnitude, measured in ohms, and a phase angle, measured in degrees.

If a sine wave at a single given frequency is applied to a hypothetical ideal resistor (having no inductive or capacitive component), voltage and current will be in phase with each other, meaning that both will reach their maximum, minimum, and corresponding intermediate values at the same time. If that signal is applied to a hypothetical ideal inductor (having no resistive or capacitive component), current will lag voltage by 90 degrees, or 1/4 of a cycle of the sine wave. If that signal is applied to a hypothetical ideal capacitor (having no resistive or inductive component) voltage will lag current by 90 degrees.

Inductive and capacitive loads are collectively referred to as reactive loads, as opposed to purely resistive loads.

The phase angle of the impedance of a speaker, at a given frequency, is the angle of the "vector sum" of the magnitudes of the resistive, inductive, and capacitive components of the impedance. If the three components were plotted on a graph, by convention the inductive component would be represented as a positive number along the y (vertical) axis, the capacitive component would be represented as a negative number along the y axis, and the resistive component would be represented as a positive number along the x axis. So an inductive phase angle will be a positive number of degrees; a capacitive phase angle will be a negative number of degrees; and a resistive phase angle will be zero degrees. The larger the number of degrees in the positive direction, up to a maximum of 90, the more purely inductive the impedance is. The larger the number of degrees in the negative direction, down to -90, the more purely capacitive the impedance is. Phase angles for most speakers at most frequencies tend to fall somewhere within a range of perhaps +/- 45 degrees or so.

Most of the speaker reviews in Stereophile, which can be found at their website, include measurements taken by John Atkinson of impedance magnitude (ohms) and phase angle, and some good associated commentary.

As Larry indicated, if a speaker load is significantly reactive its efficiency (acoustic power out vs. electrical power in) will be lower than if it were purely resistive, everything else being equal. Hypothetically speaking, if a speaker had an impedance of + or - 90 degrees at some frequency, it would be unable to produce any output at that frequency, as all of the power it received at that frequency would be returned to the source, and none would be absorbed and converted into sound.

Severely capacitive phase angles, especially if they occur at frequencies for which the impedance magnitude (the number of ohms) is low, are particularly demanding on the amplifier. In part because reactive phase angles lower efficiency, as was mentioned. And also because the current drawn by a capacitor increases in proportion to the rate of change of applied voltage, which results in larger demands for current when fast transients occur than would otherwise be the case. The current drawn by an inductor, on the other hand, varies in proportion to the "integral" of applied voltage, which is not as challenging to the amplifier.

Regards once again :-)

-- Al