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

Thanks Erik.  But I'm still not sure I understand and maybe I won't.  Are you saying that driving a high efficiency low impedance mid/tweeter section will be no easier for the amplifier than driving a full range lower efficiency speaker that dips to a similarly low impedance in the bass?  (assume we're talking about cone/dome speakers, not ESLs/panels etc)

OK. I understand that speaker impedance fluctuates with frequency.  I think what you're pointing out is that a low dip in a speaker's impedance (no matter at which frequency) is going to present a problem for a typical amplifier to track a flat frequency response because most amps cannot double their current when dropping from 4 to a 2ohm load (and tube amps halve their current).  And that a low impedance can blow up an amplifier even if it's not playing current demanding material (bass), correct?  I also didn't know that an amplifier's output impedance fluctuates with frequency response... 

I understand that the lower the load the more heat has to be dissipated, therefore the more output devices and heatsinking.  I just thought that it was low frequencies that were responsible for the majority of this demand, not higher midrange and up.  

And yeah the amplifier doesn't care about the SPL rating but it does care how hard it has to work.  And a high sensitivity speaker makes it work less hard for the same SPL.  No?

Lol MillerCarbon.  

Erik, I've looked at a bunch of other stereophile measurements of amps.  They all fluctuate in impedance but but it's not by very much, at least most of them.  I guess you would need an amplifier with an output impedance of less the .2 ohms across the spectrum and a beefy power supply/enough output deviced to drive a 2 ohm load safely.  

Erik,

Ok that makes sense.

Ralph,

That is what I needed to know, and then some! Thank you!! 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?

MC, 

I didn't just laugh at your post.  I definitely get what you're saying.  To a large degree I agree with you.  If it won't blow up and it sounds great then that's all I care about.  I know the principle behind Tekton and why people like them.  If you want to tell me more though I'd be happy to hear what you have to say.  

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.

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! 

Audioman58, 

I've never listened to a Coda amp but would love to!

Ralph, 

I should say the main reason I want to use two midrange drivers is to match their output level to the tweeter for the same given power input.  But I'm going by the notion that two drivers in parallel will result in a 6db boost in output.  That is 3db from the doubling of drivers and 3db from the doubling of power.  From my understanding two drivers in series will result in the same output as one because voltage for each will be cut in half (-3db) and the doubling of drivers will bring it back up again by 3db.  I also don't know the exact explanation between efficiency and sensitivity other than one is expressed in percentage and the other in SPL/power/distance. 

Either way, last night I modeled the drivers in a typical parallel crossover and it turns out the lowest they dip is 3 ohms.  Not as bad as I thought.