Thiel CS1.6 loudspeaker:
Measurements part 2 Fig.6, produced by averaging 120 measurements for the left and right speakers individually, shows how all this added up in my listening room. Overall, the Thiels produced an impressively flat curve. However, within that flatness it can be seen that there is a slight excess of energy in the low treble and a slight reduction in the lower midrange. The top octave is shelved down a little, as expected from the quasi-anechoic measurements—but more important, so is the entire low-frequency region. Now it's true that the speakers were positioned where I found their balance to sound the most integrated through the midrange and treble, not where they produced the most bass. And, as I've pointed out in other reviews, my room does tend to lack energy in the 63Hz 1/3-octave band when measured at the listening chair. But the relative lack of low-frequency energy in-room will exaggerate the CS1.6's tendency to sound a little treble-dominant.

Fig.6 Thiel CS1.6, spatially averaged, 1/3-octave, freefield response in JA's listening room.

In the time domain, the impulse response (fig.7) is beautifully time-coherent, and the related step response (fig.8) has an excellent right-triangle shape. A slight reflection can be seen about 2.5ms after the initial rise of the step. I have no idea what this is due to, as my measuring environment has nothing close enough to produce such a reflection.

Fig.7 Thiel CS1.6, on-axis impulse response at 50" (5ms time window, 30kHz bandwidth).

Fig.8 Thiel CS1.6, on-axis step response at 50" (5ms time window, 30kHz bandwidth).

Finally, the Thiel's waterfall plot on the tweeter axis (fig.9), calculated from the impulse response with that early reflection windowed out, shows a superbly clean initial decay, which correlates well with the grain-free sound. The notch just below 14kHz is associated with some delayed energy, which suggests it is an interference phenomenon, while some delayed energy can be seen in the low treble.

Fig.9 Thiel CS1.6, cumulative spectral-decay plot at 50" (0.15ms risetime).

All things considered, the Thiel CS1.6's measurements suggest a speaker that will not be very forgiving of ancillary components that are themselves balanced on the bright side. It will also perform best in a room that offers more midbass support than mine.—John Atkinson