Amplifier stability with very low impedance, high efficiency mid/tweeter section???

Could you explain the part about feedback falling off in the audio band as frequency increases? I have no idea what that means.  Something to do with negative feedback diminishing and thus THD going up?

You stated it correctly here. When the distortion increases above a certain frequency, you can count on harshness as a result. Combine that with an amp that easily doubles power as the load impedance is halved, driving a speaker where the high frequency array might be only 2 Ohms... that sounds like its going to be bright and harsh to me.

The technical explanation of why the feedback reduces at high frequency is quite technical! Its related to the gain of the amp circuit (with no feedback) and also its overall bandwidth (again with no feedback). That is why its called Gain Bandwidth Product. At low frequencies almost any amp has the GBP to support its feedback and  that is one reason solid state amps tend to have good bass. But at some higher frequency the GBP falls off, preventing the feedback from being the same as it is in the bass So the distortion increases. Amp manufacturers are a bit reluctant to publish this information since it tells you a bit about how the amp might sound.

All I'm saying here is that you have to be careful about the amp you select to work with a speaker like this! Put another way if the speaker were to have the usual 8 Ohms in the MTM array it would likely sound smoother for no other reason than the amp driving it will have less distortion.

Ralph, thanks for explaining that!   This is simply for a speaker I'm thinking of making myself, not for an existing product.  Once I model it I'll have a better idea of the impedance curve.  But that certainly gives me something to think about.  Thanks again! 

fiesta75,

I quite like my YBA and haven’t heard a class D that matches it in overall tone so I’m sticking with it but I may be using ICEpower for 200hz and down.

Just have a good amp with substantial power supply and stable to 4 amp double power into lower ohms preferred 

my coda has a Massive 3kva potted transformer doubles down to 2 ohms 

and 120 amps short term take 2-16 amp slow blow fuses .

my brothers Gryphon Diablo doubles power to even under 2 ohms 

the coda is a steal at $5500 or less ,and 3 power choices  when you order 

upto 18 first watts in class A