Loudspeakers

Clearly, a flat or uniform axial response is not always critical to the ‘subjective experience’ [see Graph 1]. At the standard 1m, the C1 reveals a mode right at the top of its bass/mid driver’s range [also visible on the CSD waterfall, Graph 2] prior to a full 9dB drop in output over the subsequent 2.5kHz crossover. The latter is responsible for the high ±4.9dB and ±5.9dB response errors (re. 200Hz-20kHz) although the C1’s 1.2dB pair matching [black and red traces, Graph 1] indicates this is intentional. The isodynamic tweeter gets into its stride above 5kHz, peaking just before 20kHz, but achieving a creditable 40kHz extension (–6dB re. 10kHz). Distortion is high at ~4% (re. 90dB/1m) above 8kHz.

Of course, Børresen specifies a toe-out and here, at ±15° [blue trace, Graph 1], not only does the response become more uniform (crossover dip notwithstanding) but the step response is far better resolved [not shown here] and the 2kHz mode seen on the axial Waterfall plot almost disappears... Nevertheless, the response ‘shaping’ affects sensitivity, the C1 meeting its 87dB spec. at 87.7dB/1kHz but falling to 85.2dB from 500Hz-8kHz. Bass is also ‘shaped’, the driver dipping ~5dB in the upper bass, but peaking at 105Hz. The 43Hz tuning of the lower two ports brings the diffraction-corrected bass extension down to 55Hz (–6dB re. 200Hz) although the narrow tubes do show two strong modes at 390Hz (also seen on the impedance/phase spectra) and at 2kHz, as discussed at the top of this report.

Børresen’s >6ohm impedance rating for the C1 is met with a 6.1ohm/205Hz minimum and an ‘easy’ EPDR of 2.95ohm/128Hz, despite swings in phase angle of +51/–56° from 80-100Hz. PM