The SP1s are quite neutrally balanced, though not entirely so. Within their essentially smooth response, there are some audible broadband trends, as there are with almost any speaker. The main issues are that the speaker is up a bit around 500Hz and down slightly just below 1kHz and then back up again. And there is a small depression around 200–300Hz that makes the sound slightly lightweight. These are small effects, but they are there. The -3dB point of the sealed-box bass is at 45Hz, with the expected slow (12dB/octave) roll-off. The bass is precise and well-defined in transient character. But on account, I think, of the lack of energy in the 100–300Hz region, the speaker does sound slightly light. EQing to sound as neutral as possible involved in this case bringing up 200-400Hz, pulling down 500Hz and upping 800Hz with some small adjustments at 2kHz and higher. This was an improvement to my ears but the change was not huge, though the lifting of the 100–300Hz region was fairly conspicuous. A lot of people would probably not bother with these adjustments. The nearly perfect consistency of response over a +/-15-degree window made this micro-adjustment of response especially rewarding, giving a close approach to neutrality over a considerable window. If you are involved in DSP adjustments, this speaker with its stable response over a variety of axes, its extremely low distortion, and its considerable dynamic range will really respond very well to such treatment.
In spite of these small deviations, the speaker’s absence of resonant coloration makes its tonal presentation uncolored-sounding. And as noted the sound has a startling purity. This is a speaker capable of producing truly beautiful sound in the strongest sense. The Carmen Intermezzo from the Telarc CD already mentioned was exquisite. And piano music was superb in its freedom from any grunge whatever and its resolution of the fine structure of piano tone. Janne Mertanen’s piano performance on his Chopin CD [Gradient] sounded superbly like the real thing. (This is one of the best piano recordings ever, and it sounded like that here!) And vocal reproduction was also excellent: Jane Monheit’s “I’ll Be Around” was even more heartbreakingly beautiful than usual, with impressive naturalness to the voice (close-up recording though it is).
The SP1s are unique among dipole electrostatics in their essentially point-source character. Only the Quad 63s and their descendants have attempted a point source, done in the Quads via wave synthesis (concentric rings with time delays). But a physically accomplished point source, or close to it, from a dipole electrostatic has never been tried before. And comparison to the Quads shows that the literal physical construction of a doubly curved electrostatic element offers some advantage over wave-synthesis with delay lines. Admirable though the Quads were and are, the SP1s seem to me to offer a more convincing version of point-source imaging. Of course, there are other speakers that also function as point sources, both single-driver speakers and those with concentric drivers. The Devialet Phantom models and their Cabasse ancestors come to mind. These image superbly well and really do sound like point sources, but they are not electrostatic. And the obvious hybrid electrostatic competition include line-source speakers as far as the electrostatic part goes, namely the Sanders 10e and the various MartinLogan models.
The Sanders is not to my mind competition as such but rather a different kind of speaker altogether. It is intended to provide—and does provide—a nearly perfect replica of its input in its direct sound to the listening position. But it is not intended as a “room filler.” With its DSP built in, the Sanders does a quite startlingly good job of being flat and neutral when one is listening in its preferred “sweet-spot” position. But the nature of its sound is quite different from that heard with the Muraudio approach. To each his own.
When both the Sanders and the Muraudio Omni appeared at the same show (T.H.E. Show in Newport Beach several years ago), I ended up splitting my “Best Sound in Show” between the two. Both were doing a superb job of what they were trying to do. The Muraudio SP1s are in the same way doing an excellent, indeed uniquely excellent, job of what they are trying to do. Whether you want the room filler with stability of imaging over a larger area, or the all-but-perfect one-point experience with minimized room contribution is up to you.
The MartinLogan approach of using a slightly curved panel line source has never really jelled for me. (This applies only to the relatively narrow-panel versions, the Montis for example, which, while balanced nicely, does not really sound completely convincing to me in comparison to actual music. I have not heard under meaningful conditions the larger-panel MartinLogan Neolith that RH reviewed in Issue 259.) If you are going to curve, it seems to me that one ought to curve a lot and use a wider panel to get meaningful dispersion over a considerable angle, as Muraudio’s doubly curved panel does.