Speaker phase observation and question?

Thanks Al for your kind words,  you are always a gentleman.
Remember, I was discussing how it affects phase/polarity...
For phase angles,  an amplifier is feeding a signal to a speaker,  as you know, a speaker can vary wildly in impedance load by frequency... As the signal goes through these variances,  the current and voltage are working their way through it at different rates... If current is following behind the voltage, it will create a positive angle,  but if the current is leading the voltage, it will create a negative angle.  It is because of this, that I am a big believer in impedance compensation networks on speakers (even single cone drivers) I've never heard it adversely effect a speakers sound, but in many cases, I have heard improvement...
Next,  purely resistive speakers... I've had great luck with Ribbons,  many, even most have a load that appears purely resistive to an amplifier... Not all, big ribbons will destroy an amp. 

Hi  @almarg 

Looking at my answer, I see that I tip toed around your question, this still isn't a complete answer, but contributing...
We look at phase angles varying by impedance, so yes,  if we change crossover points or slopes,  we can affect phase angles to some degree. Anytime that voltage and current cannot travel together, they are no longer in phase themselves... A speakers impedance along with each drivers own characteristics, ie load variations, qes, voice coil induction etc causes these variations.  I hope this makes sense, 
Tim

Sorry, for those of us that are a bit slow, the phase angle of a speaker obviously changes with frequency and so does the impedance. Furthermore, it appears that a combination of a low phase angle and low impedance puts "stress" on the partnering amplifier. So, this begs the question why would a "good " speaker designer design a speaker that would create such condition. In other words, how does sound quality - whatever that means in objective terms, benefit from such design.

Tim & Erik, thanks for the excellent info and the informative link, which I’m still going through.

Kalali, first, although the term "impedance" is commonly used to simply refer to a number of ohms, to be precise a speaker’s impedance is a vector quantity, meaning that it is comprised of both a magnitude (the quantity that is measured in ohms) and a phase angle (measured in degrees). If the impedance is purely resistive at a given frequency the phase angle will be 0 degrees at that frequency; if it is purely inductive (hypothetically speaking; no speaker will have an impedance that is even close to being purely inductive at any audible frequency, or it would not be able to consume any power at that frequency) the phase angle will be +90 degrees; if it is purely capacitive (again, hypothetically speaking) the phase angle will be -90 degrees.

Also, as has been mentioned above, the phase angle of the impedance describes the amount by which voltage leads current (in the case of a positive/inductive phase angle) or voltage lags current (in the case of a negative/capacitive phase angle), at a particular frequency.

But to address your question, I suggest that you take a look at this thread. The entire thread is well worth reading, but note especially the latter part of Atmasphere’s post dated 1-9-2017 (beginning with "I feel like several points need clarification ..."). The short answer is that sound quality **does not** benefit from low impedance design, but other factors such as cost and marketability may. With those factors deriving in part from the fact that solid state amps can supply more power into low impedances (up to a point, of course) than into high impedances. The background and previous experience of the particular designer, and the kinds of designs he or she is most familiar with, also seem likely to be factors in many cases.

Best regards,
-- Al

Hi Almarg,

I am definitely on team "easy to drive speakers." Get easy to drive speakers and a lot of amps will sound really great.

Get demanding speakers, and your amp costs may go up considerably.

So make sure if your speaker is demanding that it's really worth the cost of ownership. Being able to tell amps apart is not why I buy speakers anymore. :)

Best,

E