@chungjh, ... if that Q is directed to me, the only brand I know about is Atmasphere OTLs. I suggest that you make a call to Sound Labs. They know what electronics are the best fit for their products.
Ironically, most dynamic speakers on the market have fluctuating impedance and phase angle curves, ... but are voiced to be driven by SS amps having near zero output impedances. Fortunately, most ARC amps have "low'ish" (but not zero) output impedances and mate, for the most part, pretty well with most speakers that have moderate to high sensitivity levels.
The impedance curve of my speakers fluctuates between a low of 4 ohms in the bass region and have an impedance peak in the high-teens/low 20s in the 2200 kHz mid/tweeter cross-over point. Because I use my amp's 4 ohm taps, I calculate (as echoed by John Atkinson in his review of the Ref 150) that the SPL delta between the high and low impedance points of my speaker is roughly between .8 to .9 db. Not too bad for a tube amp.
I would call Sound Labs.
Ironically, most dynamic speakers on the market have fluctuating impedance and phase angle curves, ... but are voiced to be driven by SS amps having near zero output impedances. Fortunately, most ARC amps have "low'ish" (but not zero) output impedances and mate, for the most part, pretty well with most speakers that have moderate to high sensitivity levels.
The impedance curve of my speakers fluctuates between a low of 4 ohms in the bass region and have an impedance peak in the high-teens/low 20s in the 2200 kHz mid/tweeter cross-over point. Because I use my amp's 4 ohm taps, I calculate (as echoed by John Atkinson in his review of the Ref 150) that the SPL delta between the high and low impedance points of my speaker is roughly between .8 to .9 db. Not too bad for a tube amp.
I would call Sound Labs.
