Speaker phase observation and question?

Interesting !!! Would not know about the manufacturer's inverting phase on mids/highs, that you would have to ask or check it out with some tech guys.

The results obtained with the bass are normal, and are you absolutely sure that your ears did not trick you, since when there is less bass, the mids and highs will appear to come out more, and vice versa. Maybe you prefer and advantage these frequencies in your personal sound analysis, and it would just mean that your speakers (and/or associated amps) are not very well balanced for your ear preferences. 

Another tech reason would be that inverting the bass could be pushing /helping the midrange cone, if the later is not isolated from bass resonance in the cabinet.

I also have a pair of MA Silver 8s that I fiddled with phase for years, and was never quite happy with the results. They play loud, they play clean, but I never was completely happy with imaging, soundstaging and coherence.
Bought a pair of Vandersteen 2Cs and am loving them.
Kept the 8s for a second system. My wife likes them better. YMMV

Tom

Man, I’m sorry I have to jump in here:

In a good many speakers the phase angle is significantly different for the woofers than it is for the midrange and tweeter. If the woofer has a significant negative phase angle while the midrange and tweeter are quite positive, inverting the phase of the woofer will bring them into better coherence.

This is too confusing phase angle with polarity. The polarity is either positive or negative. Applying the (+) of a 1.5V battery to the (+) terminal of a driver will result in the driver moving OUT. Reverse the battery and the driver will go IN.

Because drivers as well as their crossovers result in phase angles that may not add up correctly, matching the drivers so their total output adds correctly across the crossover frequency often results in the need to invert the polarity of drivers.  Something else not thought about is the time. In a flat baffle, a tweeter arrives about 0.1

My guess is that 99% of two-way systems have the tweeter in negative polarity. This is a good thing, because the alternative would be a deep null.

Designers deal with driver polarity consideirng only a pair of drivers at a time. By convention, the woofer is in positive polarity. Then the woofer/midrange is considered. If necessary, the midrange will be inverted. Based on the phase angles of the midrange and tweeter the polarity of the tweeter is considered. This time the tweeter may or may not be inverted.

The size, depth, placement of the drivers, the angle of the baffle, the order of the filters (1st, 2nd, etc.) all play into whether drivers will need to be inverted.

For goodness sakes, no one should be inverting individual drivers, that way lies madness unless you have the right tools or background information.

There are designers like old Thiel and current VanDerSteen who make polarity and phase coherense an absolute priority, and then buy or have drivers made that can work well in these configurations. It is not rocket-science, but neither is it proven to be desirable above all else, and often has risks associated with it.

Best,

E

By the way, if anyone wants to learn about speaker design, and how drivers and crossovers work together I have quite a bit of documentation, including real-time simulation tools you can use to play around and look at some of these concepts.  Please visit my LM-1 design page, here:

https://speakermakersjourney.blogspot.com/2016/02/the-lm-1-bookshelf-version.html

The files and design info are 100% free for music lovers. :) Haters have to pay.