Ultimately, it is the quality of the mics and their spread that defines the sound. No amp/mixer/speaker combination can make mics that make your accordion sound thin and tiinny very good. You want mics that have the proper dynamics, full low end, rich middle and clean highs. The second most important trait is as you mention, an even spread of sound. In my case, with the Free Bass, I was thinking that 10 is better than 3, without any real proof, of course, just thinking that the even spread is much better in 10 than 3 and my sound is spread out in over as wide an area on the left hand as is the right. I have no idea or proof if this is fact or not
A local accordion vendor called me here saying that Sennheiser stopped making a specific mic that was one of their best mics for the accordion application, and they are now importing an equivalent replacement from China that has the same quality and acoustic traits, but the landed price was just a touch higher. Damn, I wish I could recall the brand name he mentioned, it really bothers me that I cannot recall that.
My opinion on external mics... not my favorite for a couple of reasons:
- easy to break off
- they ruin the look of the front of the accordion
- makes them that much easier to pick up external sounds/voices
- more prone to feedback easier than mics hidden away
Again, just a bunch of opinions.