Confusing phase and timing when we say that different size speakers together is bad?

[Stealth]

No, they don't look even like a comb, but who said they would? It's frequency dependent. That's the difference between flanging and phase shifting. Phase shifting (all pass filter) has very evenly spaced notches. Time delayed flanging doesn't. Microphone and speaker interference looks like a time delay comb filter.

I believe it's the other way around - a flanger has infinite (in an analog case) linearly spaced notches because it's generated by a feedforward or feedback loop, while a phase shifter can have as many notches as you have all-pass filters, but they're not necessarily in lock-step with their notching frequencies.

 

[Arjank]

Ah......yes it does.

Look at the second graph...the spikes look somewhat like the teeth of a comb, yes?

I'm just sayin'....

Don't know if you're jokin' but that's not a frequency-response graph......
A phase plot just looks that way, take a look at the y-axis(+/-180 degrees) and you probably understand how it works and how you have to "look" at such a graph.

Btw. it looks more like a saw-tooth to me.....

 

[1958Bassman]

It was also because they were just taking the master tapes that were mastered for vinyl and just transferring them to digital.

That generally resulted in bad sounding CDs because they didn't re-master specifically for CD but the "brick wall" filtering is really known for the harsh high end and upper mid-range. The mix and mastering for vinyl is so different and the record companies incorrectly assumed these would sound good just because it was now on a generally noise-free medium but, in the words of Marty Feldman as Igor, "They were wrong, weren't they?". I was selling audio equipment before/during/after CDs first became available and the negative comments started not long after we got the first Sony units and the second brand became available (I think it was Kyocera), which used different filters. The Sony unit had been designed and was being demo'd two years before it was released, mainly because they couldn't make the optics work properly, from what I heard and IIRC. Kyocera had the benefit of time, because they were able to make sure their version didn't have these issues.