Thiel CS2 loudspeaker Measurements
Fig.1 shows the plot of impedance with frequency for the Thiel loudspeakers. It agrees with the appropriate specified impedance in the "Specifications" sidebar, but it is noteworthy how little change there is. Obvious features can be distinguished, such as the port tuning for the CS2, but I would conjecture that Jim Thiel has used some form of conjugate load system in his crossover design to give such flat curves with frequency. (This is where elements are added to the crossover to compensate for phase and impedance changes to result in a simple resistive load.) I would suggest, therefore, that the CS2 should be easy to drive.
Fig.1 Thiel CS2, electrical impedance (2 ohms/vertical div.).
Moving on to the in-room, spatially averaged response (see my review of four loudspeakers elsewhere in this issue for the details concerning how and why this test is performed), fig.2 shows that obtained for the CS2 with its grille on. The in-room response for the CS2 looks worse in the bass than that for the CS1.2, but this is my fault. I was only able to carry out measurements on one speaker of the pair in one position; the elimination of low-frequency room effects by averaging is thus much less efficient than with the CS1.2s, where both speakers were measured. For some reason, the lower-midrange depression is deeper with the CS2 than its is with the CS1.2; I suspect that the proximity of the woofer-to-midrange crossover frequencies to this room phenomenon may be responsible. The CS2 shows a typical reflex LF roll-off—I measured its nearfield –6dB point around 43Hz, not including the port output—while the upper midrange and low treble are quite smooth. The peak in-room at 12.5kHz was audible, however, and results both from a slight excess of energy on-axis and from a wider dispersion off-axis in this frequency region compared with the octave or so below.—John Atkinson
Fig.2 Thiel CS2, spatially averaged 1/3-octave response in JA's listening room.