KEF R400b Subwoofer

Subwoofer KEF R400b is, so to speak, a half of LF-section of Blade acoustics. Two absolutely identical emitters, the baskets of which are rigidly interconnected, are mounted in completely closed 22-litre body. Working in-phase and radiating in opposite directions, they create identical spurious vibrations, which are opposite in phase.

As the result, the impact of one speaker completely cancels the impact of another, and no vibration is transmitted to the body. This can be easily seen, putting a hand on running subwoofer. When it plays on such high power that you are afraid to touch jumping diffusers, the body stays absolutely motionless.

The construction of speakers also deserves a special attention. The diffuser that we see on the outside is only the part of complex mobile system. An absolutely rigid plate of the diffuser, made of composite material, is placed on the aluminum frame, which is driven by sound coil of big diameter, working in the field of powerful, ventilated magnet system. There are numerous holes, guaranteeing free air stream, in the frame, connecting the coil and diffuser. This avoids the effect of compression and improves the accuracy of emitter's work.

Amplification is provided by two 250W modules of D class. The crossover is regulated smoothly within wide limits; phase control is discrete. Also there is the possibility of additional equalizing of bass. EQ control allows to locally increase the output on the frequency of 40 Hz on 6 or 12 dB. In addition to low-level inputs there is a high-level one, which is not through and realized in the form of original connector.

We had to horse around the setting. When we tried KEF R400b to go with satellites on the frequency higher 100 Hz, the middle and upper bass becomes to dominate, thereby masking the lower frequencies. Thus, it is preferable to use this sub with system, which is able to play low frequencies confidently up to 80 Hz. Listening to how KEF R400b works in cinema mode, you understand that despite of quite small sizes exactly the lower bass is its native environment. The subwoofer elaborates LFE-channel authentically and powerfully. It is not bad in music too, but sometimes I would like to add more subtle microdynamics to clarity and cleanliness of bass. However, there is the risk to roll down to coloring and KEF can't afford it.

KEF R400b Subwoofer photo