Speaker phase observation and question?

Hi Guys,  most of you know that I've been building speakers for 35 + years... Overall this is a great thread..
I noticed a couple of comments of phase angles.. Kalali mentioned that they are very different.
Phase angles show us how current rides with the voltage within the speaker... if current rides in front of or behind the voltage, you will see the large rises or dips in phase angles. So the phase angle changes how a speaker sees power...
Phase/polarity is important in the sense of keeping your individual drivers moving in unison... when a speaker is 180 degrees out of phase,  one driver has complete excursion moving outward and another driver has complete excursion moving inward. 
In theory when designing a crossover,  6db per octave gives you 90 degrees out of phase, 12db produces 180 degrees out of phase, 18db per octave produces 270 degrees out of phase and 24db per octave produces 360 degrees or full circle back in phase.
The most used crossover (which I don't use at all) is 12/12 slopes,  that means that the slopes between 2 drivers is 12db up from the woofer or mid to the tweeter and 12db down from the tweeter... Again, in theory, this is 180 degrees out of phase.  A designer can simply switch polarity and bring phase/polarity back into alignment.  A ton of things go into a design so that basic theory is not absolute,  but this is an accurate look at the theory behind speaker phase/polarity. 
I hope this little explanation helps, 
Tim

Tim, thanks for another of your always valuable inputs about speaker design.  Regarding:

In theory when designing a crossover, 6db per octave gives you 90 degrees out of phase, 12db produces 180 degrees out of phase, 18db per octave produces 270 degrees out of phase and 24db per octave produces 360 degrees or full circle back in phase.

I believe this theoretical model assumes that the impedances of the drivers themselves are purely resistive, and of course they are not.  Is that the basic reason why the phase angles of a speaker's impedance, as shown for example in John Atkinson's measurements in Stereophile, typically vary up and down over the frequency range by several tens of degrees, and swing between negative (capacitive) phase angles and positive (inductive) phase angles at various frequencies?

Thanks again.  Best regards,
-- Al
 

I really again, suggest anyone who wants to learn more would do so with the LM-1 simulation files. You can review the frequency, electrical and acoustic phase of the drivers by themselves, and then see how the crossover adds to it.

Best,


E

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