From Stereophile review of Triangle Magellan Concerto:
"The impedance magnitude remains between 2 and 4 ohms over almost the entire audioband, and there is an amplifier-punishing combination of 3.7 ohms and a 44° capacitive phase angle at 78Hz. An amplifier capable of hefty current delivery is going to be a must with this loudspeaker.
In the time domain, the Magellan's step response indicates that all the drive-units are connected with the same positive acoustic polarity, the step of each blending smoothly into that of the next lower in frequencybut the ringing from the horn-loaded tweeter is very much in evidence.
Some things the Triangle Magellan Concerto does very wellthe high sensitivity and dynamic range, the well-controlled treble dispersion, the optimally aligned bass tuning, the overall in-room response flatness. But its impedance will make significant demands for current on the partnering amplifier, and I don't like to see the resonant energy in the presence region and the top octave."
And from Stereophile review of the Thiel 2.4
"...despite Wes Phillips' conjecture that this speaker is not too hard to drive, its impedance plot (fig.1) indicates that the CS2.4 demands a lot of current from amplifiers. Not only does its impedance drop to 2.73 ohms at 600Hz, but it stays significantly below 4 ohms from 100Hz to 50kHz, and there is a difficult combination of 4.5 ohms magnitude and 45° electrical phase angle at 80Hz. Thiel CS2.4 owners should make sure they have a good 4 ohmrated amplifier to drive this speaker.
The CS2.4's step response (fig.6) has almost a perfect right-triangle shape with just a small amount of leading-edge overshoot apparent, this correlating with the shelved-up top octaves seen in the frequency response.
Overall, the Thiel CS2.4 offers pretty good measured performance, its few idiosyncrasies resulting from the designer's use of a first-order crossover between the woofer and midrange unit."
Both require good amps to drive effectively. The accuracy in the time domain means that harmonic content is better preserved with the Thiel.