New bass drivers for KEF Concords

Finally got round to ordering some better bass drivers for the KEF Concord III conversion at the very high end price of £19 each.

They’re Skytronic 902.208 8″ polypropylene drivers, and as you can see, they’re quite a bit beefier magnet-wise than the Peerless SKO200.

There seems to be some confusion about the Thiele Small parameters for this driver. As far as I can tell, the ones here are correct. It probably works out that the 30l KEF cabinets are too small, and we end up with a Q of 0.97. No matter.

I have measured the driver in the cabinet in the nearfield, and attempted to correct it for phase and amplitude, and then modified the filter to give me a driver with 38 Hz corner frequency and a roll-off at 12dB per octave. The cones move quite a lot sometimes, but the sound is good.

IMG_0208

902.208 mounted in place on the KEF III. The diameter of this driver rim is smaller than both the originals and the previous Peerless replacements, hence the need to clamp the driver as there isn’t sufficient wood to screw into.

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