Reviews like these are why I was thinking the RC70s would be a big upgrade over the RC30s.
From the 2006 Sound and Vision review:
To reverse that old audiophile cliché, the RC-70s were not ruthlessly revealing, but they were revealing enough to discern differences in the equipment driving them—including the subtle high frequency variations heard when comparing the digital outputs of several DVD players. And while I heard an occasional trace of metallic flavoring from the speaker's aluminum-dome tweeter, at its best the top end of the RC-70 is as open, airy, and as detailed as you could wish for.
The midrange was clear and free of the usual suspects—boxiness, nasality, and other nasty, artificial-sounding colorations that are particularly distracting with human voices. Voices were, in fact, beautifully served by the RC-70, with soaring female voices and male vocals that were rich and full-bodied. The RC-70s sounded neither "in your face" forward nor recessed, and produced a detailed, well-focused soundstage
From the 2006 Soundstage review:
The RC-70s did right by the celebration, and they raised a question in my mind: "How much more money would I need to spend to find a speaker I prefer substantially more?" I suspect it would be far more than Mozart was paid for his composition, adjusted for inflation, of course. The RC-70s are that kind of good.
I said it earlier, but it deserves repeating: The Energy RC-70s are special speakers. They perform well with all types of music, and they never really add themselves to the sound. Good recordings sound good, bad ones sound bad -- like it or not.
Because I thought the RC-70s performed to such a high standard, I decided to compare them to my own PSB Platinum M2s ($2500/pair), a minimonitor with some guts. I went back to the same Mozart overture in Die Zauberflöte and noted a bigger -- though not as crystal clear -- sound through the Energy speakers. Their low frequencies were far more extended than those of the PSBs, and this had the effect of adding space to the recital hall where the recording was made. Obviously the RC-70s should have more bass because the PSBs are minimonitors, but this is still worth noting if you are in the market for speakers and need (or don't need) deep bass.
If I had never heard the PSB Platinum M2 tweeter, I'd say that the RC-70 produced the best high-frequency performance I'd ever heard. It never errs on the bright side (unless the music is inherently bright) and it exhibits excellent detail. Still, when I switched over to the M2s, I found the tweeter even smoother, with more detail and what I can only describe as a very tidy sound. The M2s sound very clean, and reproduce vocals better than any speaker I've heard. While the RC-70s create well-focused images, with the M2s these images are razor sharp and give a better sense of space around each instrument.
But -- and it's a big "but" -- the M2s cost $2500, 25% more than the RC-70s, and they're minimonitors! At that price, I would expect outstanding performance from them. The fact that I thought the RC-70s deserved comparison with one of PSB's flagship Platinum-series speakers should say something about how highly I regarded the RC-70s' performance.
In my introduction I asked whether the RC-70 might set a new sonic standard at their price. More specifically, I wondered if $2000 really is the point of diminishing returns for a pair of floorstanding speakers. Although the RC-70s are wonderful, I still think that this honor is reserved for speakers that cost closer to $5000, where the competition is especially fierce. Many companies offer models around this figure, and I've heard some I liked more than the RC-70s. However, that the RC-70s get very close to the quality of these considerably more expensive designs is an important point. Their sound is extremely satisfying in so many regards, and they are such highly resolving and refined transducers that I can imagine many music lovers (myself included) living happily with them for a very long time.
My advice to potential buyers of the RC-70s would be to spend money on quality electronics to extract everything they have to offer. They can sound very good with budget gear, but their performance was elevated as the quality of the upstream components improved. The RC-70s are certainly revealing. When fed a signal that is as refined as they are, the result is so impressive that one might forget all about upgrading and simply get on with just listening to music. If this isn't the point of being an audiophile, I don't know what is.