Thiel CS3.5 loudspeaker Measurements
Fig.1 shows the plots of impedance with frequency for the Thiel loudspeaker. It agrees with the appropriate specified impedances in the review heading, and obvious features can be distinguished, such as the box resonance for the CS3.5 at 33Hz. I would conjecture, however, that Jim Thiel has used some form of conjugate load system in his crossover designs 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 like the CS1.2 and CS2, the Thiel CS3.5 should be easy to drive, even given its 4-ohm rating.
Fig.1 Thiel CS3.5, 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 for the CS3.5. It looks uneven in the bass, but 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 normal, where both speakers were measured. The CS3.5 can be seen to have a well-controlled HF dispersion off-axis and a smooth balance overall. The effect of the equalizer set to its 20Hz position can be seen in the very extended low-frequency response in-room, to below 25Hz, though the LF measurements can only be regarded as approximate in a smallish room such as mine. The nearfield response extended even further, at –6dB at 29Hz (40Hz setting), and –6dB at 19Hz (20Hz setting). For completeness's sake, fig.3 shows the amount of boost applied by the equalizer in each of its settings.—John Atkinson
Fig.2 Thiel CS3.5, spatially averaged 1/3-octave response in JA's listening room with equalizer set to 20Hz (red) and without equalizer (black).
Fig.3 Thiel CS3.5, boost applied by line-level equalizer set to 40Hz (red) and 20Hz (blue) (2dB/vertical div.)