With the Mandala, Robert still let users source their own amps to drive the 18-inch dipole woofers. With the introduction of the Sagarmatha, Robert now offers dedicated solid-state amps for the bass. These are made by Abacus of Germany to Robert's specs and include simple crossover adjustments. The new woofer amps mean to offer seamless integration and control of the big 18" drivers. The crossover is below 80Hz and the settings are easy.
The prices for the current Bastanis speakers have increased as a result of these upgrades but the new approach improved both sonics and appearance for a better fit into typical homeowner decors. The past kit designs were more utilitarian in appearance although many ownewrs were successful in designing more attractive kit-built baffles based on photos I saw on the Internet. I find my own kit-built pair to be attractive. I modeled their appearance after the
Zugspitz Anmut Duett which use Robert's drivers.
Extra care must be given in placing any dipole in your room. In addition to the normal considerations, additional attention is needed to what's behind the speakers. Hard reflective surfaces like glass will either need to be a good distance away or be addressed with other methods like the Acoustic System International resonators and sugar cubes used by Marja and Henk in their Sagarmatha Duo
review. When I tried my Prometheus MkII in my living room with glass windows about five feet behind the baffles and no acoustic treatments, I had that upper midrange hardness and glare typical of glass reflections.
My upstairs room has standard wallboard about 7 feet behind the speakers which provides an ideal backdrop. This setup allows excellent portrayal of the rear stage from the driver back wave and causes no objectionable frequency response anomalies. Soundstage depth is one of the distinguishing aspects of Bastanis speakers and other dipoles which I have come to value.
With typical box speakers, the information and energy from the rear wave is purposely suppressed/absorbed and thereby lost. Many speaker manufacturers go to great lengths to absorb and/or dissipate this rear energy. I am not saying this is wrong. Rather, I am pointing out the difference. Of course there are many dipole and omnidirectional speakers on the market but to my knowledge, none of such high efficiency as the Bastanis.
[Right: With Prometheus era yellow Kevlar tweeter diaphragm.]