Loudspeakers

Focal's familiar recipe is to create high sensitivity loudspeakers with the help of low impedance, and the Chora 826 fits that norm. However, we couldn't substantiate its claimed sensitivity of 91.5dB as our pink noise and music results of 89.8dB and 89.5dB (1m for 2.83V input), respectively, suggest that 90dB is more representative. Low impedance helps achieve this by drawing more current from the amplifier, and while Focal specifies a nominal 8ohm impedance for the 826 this is incompatible with the 2.9ohm minimum that it also quotes. In fact that's a little low even for a 4ohm nominal rating. We measured a slightly lower minimum modulus of 2.8ohm/120Hz

and a large impedance phase angle of –65o at 72Hz, the two combining in a low minimum EPDR (equivalent peak dissipation resistance) of 1.1ohm/92Hz. Elsewhere in the audible frequency range the minimum is 2.3ohm/35Hz. So the 826 is a tough load to drive at LF – not ideal for a loudspeaker likely to be partnered with inexpensive amplification.

The forward frequency responses, measured at 1m on the tweeter axis, show a wide dip in output between 1.5kHz-4kHz, but the trend is otherwise fairly flat before output begins to rise above 14kHz on the way to a very high-Q tweeter resonance at 23kHz, where the response tops out at ~103dB [see Graph 1]. The response errors are quite high at ±4.5dB and ±5.4dB (200Hz-20kHz), but these drop to about ±3.5dB below 17kHz. Pair matching over the same frequency range is ±1.1dB but this reduces to ±0.7dB if a narrowband disparity at 2.7kHz is ignored. Bass extension is fine at 41Hz (–6dB re. 200Hz), while the CSD waterfall [Graph 2, below] reveals a few treble resonances. KH