Benchmark ABH2 compared to Merrill Element Series and other ultra high end amps
soundhound OPMost comments are BS then, as the ML’s ESL's present down to 1ohm loading and this is not nice for bridged amps, let alone good non bridged. Benchmark maintains that bridged mono’ed amps are stable into low impedances.So is a 1980’s $299 Nad 3020 receiver stable into 2ohms, doesn’t mean it will sound good Cheers George |
soundhound, My electrostatics are the Audiostatic 240 from early 1980’s. They are still the most detailed stats I have ever heard, although I admire the ML CLX as next best. My 240’s are mellowing out compared to when I got them nearly 40 years ago, so I have added the Enigmacoustics Sopranino electrostatic tweeter in parallel. This gives me SOTA HF, but the impedance combo at the highest output 8kHz setting is probably 1.5 ohms or so, with a weird phase angle, so most amps are severely limited in the power they can deliver without shutting down. I make this sacrifice in power for the glorious brilliance at lower SPL’s which is doable for most classical music I listen to. |
I am sure that the Audiostatics are great speakers and like most full range or nearly full range electrostatics they present the driving amp with a capacitive load with high to very high impedances in the bass and low to very low impedance in the mid to high treble region. The obvious exception are the Quad 2800 and 2900 series. John Atkinson measured a minimum impedance of 3.3 ohms at 10 kHz and then rising with an inductive load for the 2912's. The only impedance curve that I have seen for the CLX's was published by hifi world; the impedance for the midrange/treble panel on the Montis published by Stereophile is probably representative of what a more detailed curve would look like to the CLX midrange/treble panel. The impedance in the bass is capacitive and over 30 ohms for the CLX at 50 Hz at the lower end of its range and falls to 4 to 6 ohms in the upper midrange and lower treble. It falls to 3 ohms at 6-7 kHz and then down to 0.7 ohms at 18-20 kHz all capacitive. I suspect that the impedance in the bass is unusual due to compound bass driver in the CLX. Also the sensitivity of the CLX as estimated by British hifi mags was closer to 85 dB than the 90 dB published by Martin Logan. This long discussion likely has much to do with the difficulty many amps have in optimally driving the CLX. Since starting this thread, I tried out a single Benchmark amp. It was as advertised extremely transparent and able to resolve small details. However, it lack lower midrange to bass dynamics compared to many other amps I have had, Pass Labs 100.5's, Krell 402e, and Coda No. 40 and 15.5. It also seemed to have a lack of tonal color and density. I have spoken to knowledgable personnel at Martin Logan. They have used the Benchmark in mono'ed mode with their hybrid speakers which do have a low treble impedance without any problem; however, they did not comment on the compatibility with the CLX. Other reviewers, particularly Doug Schroeder, found the mono'ed amps to be noticeably better than a single amp. Other CLX owners have noted sonic improvement with mono'ed amps. Benchmark has told me that mono'ed AHB2's can handle the low treble impedance of Martin Logan speakers. A priori, I would not have guessed such a synergy but I have no reason to doubt the observations of several experienced reviewers and audiophiles. I remain curious to try two mono'ed AHB2's with the CLX's but am also curious as to whether I would be better served by one of the newer Merrill amps. |
I did own an AHB2 and yes, it’s very quiet, distortion free. I was happy and then a friend brought over his 30 year old Mirror Image Audio amp a to try out. This amp made the AHB2 sound thin and lifeless in comparison. I now have a Coda #8 and It is even better. The AHB2 just doesn’t have enough meat on the bones for me. |
