Class D

This graph https://ibb.co/MS3xC6M I have seen on other forums but I never quite understood it. Is it showing that the impedance at 20Hz is .005 Ohms which stays fairly flat to 1Khz then rises to .05 Ohm at 20 Khz? The phase shifts 70° from
.025 Ohm to .015 Ohms across the 20hz to 20 Khz? This is the electrical phase of the amp? If so did they adjust for time delay ? I don’t really understand all this but I don’t see how the electrical phase of 70° over a .10 Ohms is very relevant to how an amp deals with a speaker?

Common jonesy really!!

The "ohm" is for the blue trace showing output impedance of the amp v frequency

The red is just phase degrees v frequency
On very good "phase correct" speaker/drivers that you paid big for!! and especially ESL, you would hear upper mids and highs that are 70 degrees (almost 25%)  out of phase, compared to being in phase from below the upper-mids.
Why do you think good manufacturers strive for "time coherent speaker design", even going to the lengths of staggering the drivers mounting distance to the listeners ears.

Thanks George but perhaps someone who understands the question might answer.

You you don’t even understand what you asked, they utilized one graph instead of two just to confuse the likes of you

Well put djones51

The time coherence is w.r.t. blending drivers at the cross-over point, not across the whole output. If you ever looked at electrical phase versus acoustic phase you would see that what you describe is a rarity in speakers if at all. One simply needs to look at the impulse functions for that. However at the crossover point it is important so you don’t have peaks and valleys in the response. Turns out our ears/brain have never been shown to be that sensitive to phase, not surprising when you look at the physical structure, but I digress.

It does appears that the phase shifts almost 70 degrees, but if you understand LC filters and output impedance, you would know this would not be possible as the L would make for a very high impedance, the C a low impedance and you would get a much faster drop in the response curve. To be honest, it is not completely clear whether they are looking at the phase of the output impedance or what. I know when you look at an amp that includes a "special" 1200AS you see a pretty clean square wave at 10KHz which would be impossible if the phase response was that variable over those frequencies.


https://www.stereophile.com/content/ps-audio-stellar-m1200-monoblock-power-amplifier-measurements

and the BelCanto which I think has an older 1000AS, has a very good 1KHz square wave indicative of little phase-shift from 1Khz to 10-20KHz.
https://www.stereophile.com/content/bel-canto-ref1000m-monoblock-power-amplifier-measurements


The 700AS has about 25 degrees at 20Khz, half that at 10KHz, so at cross-over frequencies fairly minimal. Just remember that people put super tweeters on top of their speakers and don’t align them to fractions of a mm .. but I digress.


https://icepower.dk/support/#download-expand