Lionel wrote:

My problem Arnold is that I don't really like the sound of "modern"
speakers because I like quick and precise answer from the bass an not
this diffuse and not well defined loud bass that we can hear from a lot
of speakers and moreover from a lot of subwoofer.
In fact I just need to reproduce with the maximum fidelity the sound of
a double-bass.

Then there's really only ONE solution other than a planar speaker - look
into a dual-concentric type driver. It has a tweeter in the center of
the main driver and gives you a 2-way sound with a one-way effect.