Perhaps you gathered that dialling in this bass can be a bit daunting.
I'd agree. Hopefully my personal odyssey will become a shortcut for others. One thing I can say for certain is that you'll need an amp with good grip/damping as well as fairly high power. Robert Bastanis does not recommend digital amps. The Dayton A500 plate amps get the job done but Robert insists that better amps will improve the bass further. He recommends audiophile-quality linear amps. I would add that a minimum of 200wpc into 8Ω seems advisable. The Bastanis Ultimate woofer is a recent upgrade for the open-baffle bass cab and truthfully, Robert and Mark are still working on a turnkey amplifier/xover recommendation. Robert wants an amp solution that also works for 220V customers. Rather than go right into critical listening mode with LPs, I took a slow approach and played a few CDs I'd recently purchased from the estate of a fellow Connecticut Audio Society member and devoted jazz lover. The digital side of my system is not up to the quality of my LP playback. I am pretty much a vinyl guy but do plan to upgrade my digital front end soon. In preparation, I sold off my Vecteur D2 transport and Audio Note 1.2 DAC to press into intermediate service a CAL Alpha transport and Delta DAC I had in reserve. My digital front end has been improved with a proprietary impedance interface developed by a fellow member of the Connecticut Audio Society. This is a small box with coax i/o and goes between transport and DAC, taking performance up a full notch with more dimensionality, tighter bass and better extension in the high frequencies. I am not at liberty to discuss further details.

I can't get enough of Sonny Rollins so immediately grabbed Newk's Time [Blue Note CDP 7 840012]. My first impression rang true with what Robert Bastanis had promised. The midrange was noticeably fuller and the twin widebanders pressurized the room to a greater degree than the single widebander in my Prometheus. The fuller midrange was definitely welcome on Sonny's saxophone, making the timbre more correct. I would not call the Prometheus lean but the Mandala definitely produced richer more fleshed-out tone that was ultimately more satisfying. On "Blues for Philly Joe", the system was really swinging. One strengths of the Bastanis speakers in general has been their ability to sound live. They have great dynamics and pace. Having owned or listened to four different models (Prometheus MkII, Apollo, Wildhorn, Mandala), I will also caution that they are so revealing as to, without careful matching of associated equipment, easily get too forward. I am sure that some prospective buyers heard them like it and were put off. I'm not talking about the Lowther shout but rather about an upfront super-direct sound. Careful component and cable matching is critical and prospective buyers are well advised to heed the recommendations of a dealer. This is especially true for the amplifier. At 100dB for the baffles, most owners opt for SET amps. My own 10wpc Tron 211 really made the speakers come alive but there are sweeter SET amps that others might prefer. The 211 is akin to lightning in a bottle and not as forgiving as the typical 300B or 45 SET.

Bill Demars uses a Tube Guru 6C33C SET that is a particularly good match. Bill brought it down once and we tried it on the Bastanis Wildhorn. This amp provided excellent tonal balance and a wide open soundstage. This was true also of the Allnic A5000 DHT 300B monos I was able to try when visited by dealer Sunil Lekhi. Its overall presentation was more laid back and of richer timbre than my Tron. On the other hand, the Tron rules on resolution, transparency, nuance and dynamics. I also heard that Bastanis speakers mate well, perhaps with somewhat less dynamic prowess, to 2A3, 45 and 50 SET. By word of mouth, I learnt from other owners of an occasional good match with a push-pull tube amp (e.g. the Audio Tekne 6AS7G amp) and even a Sugden A21 transistor integrated. Robert claims he even has customers using inexpensive Tripath amps. Personally, I favour a SET. After all, there are not a lot of speakers efficient enough to be driven by this class of tube amp.

Moving on to LP, I could now take the speakers' full measure. One of my favorite jazz LP for testing a system is Count Basie's Basie Jam [Pablo 2310 718]. This is a superbly natural recording with some of the best jazz musicians of the time: Count Basie, Louie Bellson, Ray Brown, Irving Ashby, J.J. Johnson, Harry Edison, Eddie Davis and Zoot Sims. While Pablo Records are not valued as highly by collectors as are the more glorified jazz labels, it's hard to argue with their generally excellent sonics. This album is a standout among them (I have three copies). Ray Brown's stalwart bass came through with excellent pitch and drive. Obviously I had the woofer settings well in place. The variety of solo performances on this Count Basie album provide excellent opportunity to judge the timbre of a number of instruments like the trombone, trumpet, saxophone, piano, organ, bass and drums. On the second cut of side 1, Harry Edison's trumpet projected well out of the left speaker with great realism and full tone. Solos often lept out of the speaker and soared into the room, grabbing my attention like at a live performance. The revealing nature of the Mandala was well demonstrated on Harry Edison's solos. All of the subtle pressure nuances that he uses on his saxophone's reed to express himself artistically were easily heard. This enabled me to more fully appreciate the range of what the musician was trying to communicate. Of course, the rest of your system must be up to the task. 

Never having heard an open-baffle woofer in my home before, I was enjoying to get to know its special qualities. I had been quite happy with the sealed 12-inchers of my Prometheus MkII. The most striking aspect to me was hearing how the Mandala bass blended better with the mids and highs. Open-baffle bass seemed to spatially energize the room in the same way as the widebanders and tweeters. There was a continuity of the soundfield up and down the bandwidth. More specifically, soundstage depth as provided by the open baffle mids and highs was matched by the woofers. One did not stand out from the other. If I had one quibble, I would say that the sealed woofers had more slam on the attack. I called a friend who has been using the Linkwitz NaO open-baffle speakers with matching open-baffle woofers for years. He agreed with my positive observations on open-baffle bass but did feel that sealed woofers may have the advantage in sheer visceral impact. [Again, that is due to how a sealed box pressurizes inside to damp the driver's inward stroke. By removing this pressure behind an OB woofer, punchiness reduces but so does box boom and ringing. Plus, the figure-eight radiation of dipole bass creates less interaction with the side walls by making the bass more directional – Ed.] Louie Bellson's drum solo toward the end of "Red Bank Blues" showed how the Ultimate woofers could put powerful deep bass energy into the room. In fact, they could shake the room. I found the Ultimate open-baffle woofers superior to the smaller sealed-box woofers in every way except for possibly that leading edge. There is no way I would go back though.

A great live recording like Asleep at the Wheel's Served Live [Capitol ST-11945] could become downright exhilarating with the Tron and Mandala team. Playing the crowd favorite "Miles and Miles of Texas", I felt at the concert. Toward the end of the song, the band takes a break and lets the audience sing the refrain. All of the voices were laid out in deep panorama and I was able to pick out individuals and follow them with great intelligibility. Still, the sound was not as relaxed as I would have liked. Unlike many reviewers, I believe in tube rolling to address sonic issues during a review. I recalled that I had compared 5U4GB rectifiers in the Tron before and then preferred the RCA black plates on my former WLM LaScala speakers. The TungSol 5U4GB is a smoother rectifier however which proved to be just the ticket with the Mandala. Swapping to the TungSol allowed me to play a much wider selection of albums without edginess in the upper midrange and highs. Up until this point, I had all of my components plugged into a Triangle Art RA-6 power conditioner with a Nordost Frey 2 power cord to the wall. Robert Bastanis sent along a new conditioner called the Afterburner which is designed to replace the power cord to the wall, with the female end plugged into a power component like the Nordost QB8. I had a QB8 on loan so was able to try it out. At first I was not impressed. However, Robert said that it needed at least 50 hours of break-in so I persevered.

"The Afterburner will have a retail price of €1'200 but has not officially launched yet. This design doesn't break the A/C power connection so there is no limitation of dynamics or max current. The Afterburner helps to feed the power supplies of the connected electronics so there are no more gaps. It has a similar effect to an expensive choke power supply. The Afterburner doesn't increase the voltage. It influences only the phase [suggesting power factor correction – Ed]. The power supplies of connected electronics produce small voltage gaps on any impulse. It doesn't matter if small or high wattages are to be delivered. This is audible as a more diffuse thinned response and limited transients. With the Afterburner, all of these problems are gone. The transient response is much better, the sound is much more substantial and realistic. Fine detail increases and imaging becomes much better and more three-dimensional." Post break-in, I did hear these positive effects as described. However, dynamics and bass impact were still better when I used the Afterburner between wall socket and Triangle Art RA-6. If you do not have a power conditioner, the Afterburner alone will be a nice upgrade at a lower cost than the $3'000 Triangle Art. Robert countered that the Afterburner is meant to be used directly in front of the components and that being followed by the Triangle Art RA-6 "reduced the positive effects a bit."