MBL Radialstrahler 101 E MkII Loudspeaker Jürgen Reis

Jürgen Reis

Chief engineer and guiding light of MBL, Jürgen Reis is very relaxed about describing the polar pattern of the 101 E MkIIs. 'You can call them omnis', he says 'if you are not too picky! The horizontal dispersion is more uniform than the vertical, but we address this by engineering some notches in the response.


'Meletzky, one of the three MBL founders, was convinced that a pulsating sphere must be the perfect loudspeaker. In 1979 he began with prototypes before launching a concept speaker in 1982, which is when I joined the company.'

The mid and treble drivers were developed by Jürgen with a little inspiration from a colleague who was building carbon-fibre guitar necks! The substantial bass melon remains largely unchanged but is a complex set of moving parts. 'We buy enough material for 200-300 speakers' says Jürgen, 'but there's inevitably some variation in the exact composition of the alloy and in the mechanical properties realised from the annealing process. For each production run, we tweak the low-pass crossover for the large melon – it is around 560Hz, but the value will vary between batches of speakers'.

The sensitivity of the 101 E MkII is set by the output of the treble driver. 'The length and Young's modulus [stiffness] of the treble petals sets the balance between output and extension', confirms Jürgen, 'but we have optimised this by experimenting with the resin that holds the carbon-fibre matrix together. Different percentages of fibre to resin were explored to get the best sonic result in-room'.

MBL Akustikgeräte GmbH & Co. KG
Berlin, Germany
Supplied by: Stranger High Fidelity, Real World Studios, Wilts
07702 155847