Steve Marsh
Analog source: Nottingham Analogue Mentor turntable with 10” Ace Anna tonearm, Benz LP-S moving coil cartridge
Digital source: Accuphase DP-70 CD player with Tom Evans Audio Design reclocking board
Preamps: Doshi Alaap Purist Mk. II full-function tube preamp, Levinson 26S line stage, Klyne 7PX4 phono stage
Power amp: Tron 211 SET amp with upgraded exotic-core interstage transformers (General Electric 211 power tubes, Western Electric 417A input tubes, Tung Sol black plate 5U4GB rectifiers), Arcturus 801A SET [in for review]
Speakers: Bastanis Sagarmatha open baffle speakers with AlNiCo drivers and Gemini MkII tweeters, Bastanis 18-inch open baffle powered subwoofers
Interconnects: Audio Magic The Natural pre to amp, long Radio Shack interconnects from preamp out to Dayton A500 subwoofer plate amps
Power cords: Bastanis Epilog II on Tron amp, industrial-sourced power cord on Doshi preamp
Speaker cables: Audio Magic The Natural
Equipment rack: Adona 6-shelf, low profile isolation rack
Power line conditioning: Triangle Art RA-6 power conditioner, Bastanis Afterburner power conditioner
Sundry accessories: High End Novum PMR Premium Resonator, set of four Stein Harmonizers with Stein Magic Stones, Entreq Silver Tellus grounding box with Atlantis grounding cable, Synergistic Research FEQ, Audio Magic Room Correction Bells, Audio Prism Ground Control, three Bybee Quantum Signal Purifiers, Audio Horizons Fuse in Tron amp, AudioDesk Pro record cleaning machine
Room size:  22' long x 17' wide X 10' high, with eaves on front and back walls starting 40 inches up from floor

For owners of Bastanis Mandala open-baffle speakers like myself,
it is possible to upgrade to the new generation of drivers employed in the Sagarmatha Duo. And that's exactly what I did. Here are my impressions about upgrading a pair of Mandala speakers with the new drivers. It's been more than a decade since I first reviewed Robert Bastanis' Prometheus MkII. Over these years, the speakers were in my second upstairs system but did not see as much playing time as I would have liked due to the room's less than ideal heating and cooling. That was finally rectified. Now this larger better-sounding room has become my primary listening space. It has been treated using professional software to analyze the room and correct any acoustic problems. In 2016, I reviewed the Bastanis Mandala and gave them a Blue Moon award. About a year later, Robert Bastanis changed his business plan with a new sales model aiming for even better sound quality, improved aesthetics, overall finish and no more kit options. The general design principles of the Bastanis open baffles remain unchanged as high-efficiency speakers with separately powered woofers and passive tweeters (i.e. augmented widebanders). These have been refined over many evolutionary steps across the years and the Sagarmatha Duo mark the latest step. They employ a new generation of AlNiCo widebander where the prior Crystal units in the Mandala had ferrite motors. These drivers are sourced from a different manufacturer before Robert applies his proprietary cone treatments of lacquer coatings and baking. The Gemini compression tweeter too has been upgraded to a MkII version which features an increase in throat diameter from 1" to 1.4".

Polyester tweeter diaphragms, one treated with two more lacquer layers.

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.]